gene editing research studies

CRISPR Clinical Trials: A 2022 Update

*See our 2023 clinical trials review here . 

The IGI has been closely tracking the development of new CRISPR-based therapies and the progress of the growing number of clinical trials. O ver the past year, trials have started in new disease areas including diabetes and HIV/AIDS. In our annual deep dive into CRISPR clinical trials, we guide you through the current landscape of clinical trials, outcomes, what we hope to learn from each trial, and what is coming next in the world of therapeutic genome editing .

CLINICAL TRIAL BASICS

In the United States, the Food and Drug Administration (FDA) assesses new disease treatments for safety and efficacy through clinical trials on patient volunteers. Early trials (phase 1) evaluate safety and treatment side effects. Later trials (phase 2 and 3) evaluate how effective treatments are and compare new therapies to standard treatments. Sometimes trial phases are combined to expedite testing a treatment. 

While the number of CRISPR clinical trials is growing each year, most of the current trials using CRISPR-based treatments are still in early stages. That means that even if the treatments are safe and effective, they’re likely still a few years away from a possible FDA approval and being available to patients in the US.

The development of CRISPR genome editing opens up new possibilities in precision medicine. Current trials are underway in seven treatment areas: blood disorders, cancers , inherited eye disease, diabetes, infectious disease, inflammatory disease, and protein-folding disorders. 

Before we dive into each treatment area, keep in mind that all current CRISPR clinical trials target specific cells or tissues in individuals without affecting sperm or eggs — that is, no DNA changes are intended to be passed onto future generations.

BLOOD DISORDERS

Disease backgrounds .

In sickle cell disease, red blood cells are misshapen. Their “sickle” or crescent shape blocks blood vessels, slowing or stopping blood flow. This causes sudden, severe pain crises. Complications of SCD include chronic pain, strokes, organ damage, and anemia. In beta thalassemia, patients do not make enough of the hemoglobin protein, leading to fatigue and anemia. In severe cases, patients suffer organ damage, especially to the bones, heart, and liver. SCD and beta thalassemia can both be fatal. 

SCD disproportionately affects certain populations. Globally, the highest level of incidence is in sub-Saharan Africa. In the United States, SCD mainly affects Black Americans. While SCD was the first identified genetic disease, it has received poor research funding and individuals with SCD tend to receive poorer care compared to individuals with other genetic diseases, like cystic fibrosis, that are more likely to affect wealthier, White individuals. New research into genomic treatments for SCD are an important step towards equity. 

There are some treatments available for SCD and beta thalassemia, but patients often have severe symptoms and complications even with treatment. Patients with more severe cases of either condition need frequent blood transfusions. Bone marrow transplant can be curative; however, this can only be done when a healthy, matching donor can be found. Bone marrow transplant is not an option for most SCD or beta thalassemia patients.

TREATMENT STRATEGIES

The approach taken to treat these blood disorders with CRISPR technology in the most advanced trial doesn’t directly correct the gene variants that cause disease. It uses a clever workaround: instead of restoring healthy adult hemoglobin, the goal is to increase levels of fetal hemoglobin. This is a form of hemoglobin that fetuses make in the womb, but children and adults don’t make. We don’t know yet why humans switch from one form of hemoglobin to the other after birth, but fetal hemoglobin is not affected by the sickle cell mutation and can take the place of defective adult hemoglobin in red blood cells. This treatment can be used for both SCD and beta thalassemia.

In individuals with SCD, symptoms start to show during infancy, after fetal hemoglobin (HbF) levels decrease. The first step of treatment is to harvest a patient’s blood stem cells directly from their blood. Next, scientists edit the genomes of these cells to turn the fetal hemoglobin gene on. Then, chemotherapy eliminates the disease-causing blood stem cells from the patient’s body. Finally, billions of genome-edited stem cells are put back into their bloodstream. These genome-edited blood stem cells are administered by IV. If it works as intended, these cells will take up residence in the bone marrow, creating a new blood stem cell population which will make edited red blood cells that produce fetal hemoglobin.

This treatment approach is called ex vivo genome editing, because the editing occurs outside of the patient’s body. The advantage of ex vivo editing is ensuring that genome-editing tools only come in contact with the right target cells. It also avoids the risk of long-term presence of CRISPR components in the body, like unwanted edits or immune reactions. 

CURRENT CRISPR CLINICAL TRIALS

In the first use of an ex vivo CRISPR-based therapy to treat a genetic disease, researchers treated an individual with beta thalassemia in Germany in 2019. CRISPR Therapeutics and Vertex Pharmaceuticals are running this trial in Europe and Canada. According to company press releases, at least 14 more individuals have since been treated and followed for at least three months, with five followed for over a year. The first individual with SCD was treated with the same therapy in Nashville, Tennessee in 2019. At least six more individuals with SCD have been treated since then and followed for at least three months, with two followed for over a year. 

So far, patient volunteers with both conditions have made remarkable recoveries. 

• Patients treated for SCD or beta thalassemia show normal to near-normal hemoglobin levels, where at least 30% (SCD) or 40% (beta thalassemia) of hemoglobin is fetal hemoglobin. 
• Patients with beta thalassemia are free from needing blood transfusions. Patients with SCD are free from transfusions and disabling pain crises.
• Molecular tests on bone marrow from each of six patients a year or more after treatment show the continued presence of genome-edited cells 
• One patient with beta thalassemia experienced serious immune reactions to treatment which have since resolved. No other serious adverse events were observed, and side effects seem to be related to chemotherapy, not the genome-editing treatment. 
• Hear directly from Victoria Gray or Jimi Olaghere , who were both treated for sickle cell disease.

CRISPR Therapeutics and Vertex Pharmaceuticals are jointly running these combined phase 1, 2, and 3 trials in the US, Canada, and Europe. In Europe and the US, this treatment has been given special status to fast-track approval.

Read more: 

• CRISPR-Cas9 Gene Editing for Sickle Cell Disease and β-Thalassemia — Frangoul et al., New England Journal of Medicine
• Vertex and CRISPR Therapeutics Present New Data in 22 Patients With Greater Than 3 Months Follow-Up Post-Treatment With Investigational CRISPR/Cas9 Gene-Editing Therapy, CTX001™ at European Hematology Association Annual Meeting — Press release from CRISPR Therapeutics

The other two trials — one from Graphite Bio, and the other from a consortium of researchers from IGI, UCSF, UCLA, and UC Berkeley — will test an alternate approach that would use CRISPR to directly repair the mutation that causes SCD, reverting it to the healthy version. Graphite has begun enrolling patients, and the UC trial will begin recruiting patients later in 2022. The UC consortium trial is the only not-for-profit trial for sickle cell disease .

WHAT TO WATCH FOR 

Over the last few years, there has been a burst of research into treatments for blood disorders. Pharma, biotech companies, and academic research institutions are working on conventional and genomic therapies. It’s too soon to say which approaches will be the safest and most effective, but patients are sure to benefit from the renewed research in these disease areas.

The initial results from Victoria Gray, Jimi Olaghere , and other patient volunteers are what genome-editors dream of. If trial data continue to be so positive, the treatment could be approved as soon as 2023. 

“Bottom line, the progress of CRISPR/Vertex is a landmark in that it’s likely to generate the first approved CRISPR-based medicine,” says Fyodor Urnov, Ph.D., IGI’s Director of Technology and Translation and a 20-year veteran of the sickle cell field. “That would be an extraordinary moment for us. And it will create a wide road for others in this space — like Beam and the UC Consortium — to rapidly follow suit.”

Long-term follow-up of these and other trial participants is crucial: they will be tracked for years to come to see if the treatment remains effective, and to look for potential long-term side effects which wouldn’t be apparent until further down the line, like cancer from unwanted changes to the DNA. It will be especially interesting to see, for instance, if there are differences in outcomes between patients who receive cells edited with conventional CRISPR versus base editing.

“The main side effects so far have been from the chemotherapy necessary to wipe out the pre-existing bone marrow cells in order for the edited cells to engraft. The chemotherapy is a huge limiting factor for these therapies,” explains Megan Hochstrasser, Ph.D., a CRISPR expert who studied with Jennifer Doudna. “If you have to be in the hospital for weeks because you are getting your bone marrow ablated with chemotherapy, which cripples your immune system, it’s risky, expensive, and time-consuming. That’s a huge barrier to scaling this and making it available widely. It’s a big hurdle that could be overcome if someone finds a way to deliver the treatment directly, without bone marrow ablation.”

Scalability — making enough of a treatment to get it to the many people who need it — will be a major challenge for CRISPR-based treatments for blood disorders, both because of the technical challenges of creating the individualized product and administering the treatment protocol, and the cost. The cost of the current CRISPR-based therapy is in the $1–2 million range, and can only be performed at a small number of medical facilities worldwide, putting it well out of reach of the vast majority of people with SCD or beta thalassemia. Research into in vivo approaches, which could eliminate the need for chemotherapy and decrease the associated risks and expenses, is in early stages, but will be a focus of researchers working to make more widely accessible CRISPR-based therapies for blood disorders in the coming years.

DISEASE BACKGROUND

Cancer refers to diseases that are caused by uncontrolled cell growth. Right now, CRISPR-based therapies are mainly aimed at treating blood cancers like leukemia and lymphoma .  

TREATMENT STRATEGY

T cells are a type of white blood cell that have a central role in immune system response. T cells are covered in receptors that recognize other cells as safe or threatening. They patrol the body, killing foreign or dangerous cells, or recruiting other cells to assist. In CAR-T immunotherapy, researchers genetically engineer an individual’s T cells to have a receptor that recognizes their cancer cells, telling the T cells to attack. 

The immune system is highly regulated to avoid attacking healthy cells. Some T cell receptors work as “checkpoints” that determine whether an immune response occurs. When a T cell PD-1 receptor comes in contact with a molecule called PD-L1 on another cell, it communicates that it is a “safe” cell and the T cell leaves it alone.

Cancer cells often cloak themselves in these safety signals, tricking the patrolling T cells into ignoring them. Researchers are using CRISPR to edit the PD-1 gene in T cells to stop them from making functional PD-1 receptors so they can’t be tricked by cancer cells. This immunotherapy approach is known as checkpoint inhibition, and it is often used in conjunction with CAR-T engineering to give T cells the greatest possible chance of eliminating cancer.

For these treatments, researchers harvest T cells from a patient’s blood and engineer them in a lab. Then, they put them back into the patient’s bloodstream by IV. Because this treatment relies on ex vivo editing, it is easy to deliver the genome-editing tools to the target cells. CAR-T therapy was approved for use in treating blood cancers in 2017.

Learn more about CAR-T: 

• CAR T-cell Therapy and Its Side Effects — The American Cancer Society
• CAR T Cells: Engineering Patients’ Immune Cells to Treat Their Cancers — National Cancer Institute 

In 2016, an individual with lung cancer became the first person in the world to be treated with a CRISPR-based therapy: this patient was injected with PD-1 edited T cells in a Chinese clinical trial. This and an American clinical trial using CRISPR-based immunotherapies for cancer have been completed. Several other clinical trials using CRISPR-based immunotherapies, mainly to treat blood cancers, are ongoing. 

In the Chinese trial, researchers at Sichuan University treated 12 patients with non-small-cell lung cancer with PD-1 edited T cells. This approach did not include CAR-T, as it is not currently an option for lung cancers. Like early stage trials in the US, the main goal was to assess safety and side effects rather than efficacy. 

In April 2020, the researchers reported that the treatment was safe to administer and had minor side effects like fever, rash, and fatigue. The intended edit was found with a low efficiency: a median of 6% of T cells/patient before infusion back into the patient. Off-target effects — unintended changes at various places in the genome — also occurred at a low frequency and were mostly in parts of the genome that don’t code for proteins. On-target effects — unintended changes at the target site — were more common (median of 1.69%). 11 out of 12 patient volunteers had edited T cells two months after the infusion, although at low levels. Patients with higher levels of edited cells had less disease progression. 

• Safety and feasibility of CRISPR-edited T cells in patients with refractory non-small-cell lung cancer — Yu et al., Nature Medicine
• First Trial of CRISPR-Edited T cells in Lung Cancer — Lacey & Fraietta, Trends in Molecular Medicine

The first CRISPR-based therapy trial in the US combined CAR-T and PD-1 immunotherapy approaches, using CRISPR to edit three genes in total. This phase 1 study, run by the University of Pennsylvania in collaboration with the Parker Institute, was completed in 2020. Like the Chinese trial, the goals were to determine if the treatment was safe and had acceptable side-effects, not to cure patients. Two patient volunteers with advanced white blood cell cancer (myeloma) and one with metastatic bone cancer (sarcoma) were treated. Researchers reported that the treatment was safe to administer and had acceptable side effects. The edited T cells took up residency in the bone marrow and remained at stable levels for the nine months of the study. Biopsies on the patient with bone cancer showed that T cells were able to find and infiltrate tumors. Off-target effects were rarely observed. However, unintended edits at the target site were observed frequently, with 70% of cells showing at least one mutation at or near the target site during the T cell manufacturing process. After infusion and over time in patients, the percentage of cells with mutations decreased. 

“A really interesting thing is that the American study did show a percentage of the large genomic rearrangements that people fear,” says Hochstrasser. “But the percentage of cells with these changes actually decreased over time. It seemed like the cells that had those types of mutations were dying or getting out-competed by the other cells. So, it seemed like the cells that you wouldn’t want in the body were not actually sticking around in the body, which was a surprise to me, and very encouraging.”

• CRISPR-engineered T cells in patients with refractory cancer — Stadtmauer et al., Science

The therapies in the two trials described above are autologous : cells are taken from each patient, edited, multiplied, and then put back into the same patient. This process is expensive, time-consuming, and few facilities can do it. Sometimes the manufacturing process — which is starting with cells from a sick patient — just doesn’t work, produces low potency cells, or individuals die of their disease while waiting for the manufacturing process to be completed. 

In October 2021, CRISPR Therapeutics announced results from their ongoing US-based Phase 1 trial for an allogeneic T cell therapy. Allogeneic therapies are made from cells from a healthy donor. These cells are edited to attack cancer cells and avoid being seen as a threat by the recipient’s immune system, and then multiplied into huge batches which can be given to large numbers of recipients. Allogeneic products reduce cost, time until treatment, and potentially provide more consistently potent cells. Allogeneic therapies are sometimes referred to as “off-the-shelf.”

The press release from CRISPR Therapeutics gave preliminary results for individuals with lymphomas who had been treated and followed for at least four weeks after treatment. Side effects were not severe, and the safety profile was superior to other CAR-T products. In these patients, almost 60% showed a positive response to treatment, with 21% showing no sign of disease for six months after a single treatment. This is similar to approved autologous CAR-T therapies made without CRISPR technology. 

Together, these studies indicate that CRISPR-engineered CAR-T therapy may be a promising line of treatment: they appear to be fairly safe, the side effects are tolerable, and the treatment does not tend to induce a strong immune reaction. 

WHAT TO WATCH FOR

The FDA has already approved CAR-T therapies and PD-1 pathway inhibitors that don’t use genome editing. In other words, the proof-of-principle work for these therapies has already been done successfully. 

The efficiency of editing — meaning, the percentage of cells that actually got edits — was poor in both autologous trials. But these trials were done using technology from 2016, and there have been significant improvements over the last six years. These trials are an important proof of concept about the immediate safety and tolerability of the treatment, but hopefully new trials will show improved editing efficiency. 

If researchers get better editing efficiency, will genetic checkpoint inhibition work as well or better than checkpoint-blocking drugs? Will PD-1 editing be as or more effective than antibody treatments that disable PD-1? Future research will have to answer these questions. And while right now CRISPR-based CAR-T does not provide an advantage over conventional CAR-T, CRISPR provides options to develop T cell therapies in ways that are not possible with conventional gene therapy . Researchers are working on CRISPR-editing T cell therapies where genes are added at specific locations in the genome, or using base editing to make changes to multiple genes at once.  

The push towards allogeneic, or off-the-shelf, treatments is particularly interesting, given the possibility for quicker and broader access. We will be sure to keep an eye on the development of this and other allogeneic cancer immunotherapy products. 

There are two more big areas where CRISPR-based immunotherapies for cancer are heading. The first is targeting solid tumors, with at least three early stage trials going on currently. Solid tumors are a tougher challenge than blood cancers. First, in blood cancers, the cancerous cells are easier for immune cells to reach. In solid tumors, immune cells have to infiltrate a solid mass that isn’t friendly to T cells. Second, scientists are still trying to find ways to send T cells specifically to solid tumors. And finally, when T cell therapy is effective, it kills cancer cells. When a high number of cells are killed at once — from a big tumor, or multiple smaller tumors — the dead cells can cause a dangerous inflammation reaction. We’ll definitely be keeping an eye out for safety and side effect data from the new trials. 

“People have been thinking of various ways to boost T cell functionality,” says Alex Marson, M.D., Ph.D., IGI’s Director of Human Health and a Professor of Medicine at UCSF. “CRISPR may be useful for adding or removing genes to make T cells more powerful in solid tumors. We’re looking for ways to enhance the functionality and persistence of T cells, and the safety of this approach.” 

The other development to keep an eye out for is moving immunotherapy beyond T cells. “Another thing coming down the road is using different cell types,” says Marson. In addition to allogeneic products from healthy donors, researchers are working on developing natural killer cells and stem cell-derived cells to target cancers. 

GENETIC BLINDNESS

Leber Congenital Amaurosis (LCA) is the most common cause of inherited childhood blindness, and LCA10 is the most common form of LCA. This disease is caused by a single nucleotide mutation in a photoreceptor gene, leading to serious vision loss or blindness within the first few months of life. 

Photoreceptor cells in the eye convert light into nerve signals that travel to the brain. In LCA10, the photoreceptor gene has a mutation, leading the cells to make a shortened, faulty version of a crucial protein. This faulty protein makes the photoreceptor cells dysfunctional. When patients with LCA10 receive light to the eye, the dysfunctional photoreceptor cells can’t send all of the  necessary messages to the brain. Without good communication between the eyes and the brain, patients experience vision loss or blindness.

TREATMENT STRATEGY 

The CRISPR treatment for LCA10 makes a change to the patient’s defective photoreceptor gene so that it makes a full-size, functional protein instead of the short, broken version of the protein. If enough cells are edited to make the healthy protein, the hope is that patients will regain vision. 

This approach is an in vivo treatment, meaning the genome editing occurs inside the patient’s body. Compared to ex vivo editing, in vivo editing has more challenges and different risks. One of the biggest risks is that viral delivery tools or genome editing components will provoke dangerous immune reactions in a patient. Another big challenge is finding ways to stop the CRISPR enzymes from sticking around for too long, since that would give them a greater chance of making unwanted cuts in the DNA.

Though needles near eyeballs makes most people a little queasy, the eye is actually an ideal organ for in vivo editing. It is small, so it only requires a single-dose, small-volume treatment. The eye has less immune reactivity than most tissues, making a dangerous immune reaction less likely. And because the eye is relatively contained, the CRISPR components aren’t likely to travel to other parts of the body, so there is a lower risk of unwanted genome editing or immune responses in other tissues. In experiments on a mouse model of LCA with the same mutation, researchers found that ~10% of cells showed the desired edit — this is thought to be the minimal percent needed to get some vision restoration. The treatment showed few side-effects in animal models, and studies in human retinal cells showed no off-target effects at over 100 sites with similar sequences. See preclinical data here . 

CURRENT CRISPR CLINICAL TRIAL

This is the first in vivo CRISPR therapy trial, meaning, the first time CRISPR is being used to edit someone’s genes within their own body. The first patient volunteer in this US-based study, sponsored by Editas Medicine, was given a low-dose of the treatment in March 2020. Dosing of two patient volunteers in the first, low-dose cohort was completed by November 2020 and dosing of four patient volunteers in an adult mid-dose cohort followed, completed by June 2021. Starting with a low dose reduces the risk of dangerous side effects throughout the trial. Enrollment for a high-dose adult cohort (four patient volunteers) and a pediatric cohort (four patients) began in June 2021, after safety was established from dosing adult patients with low and mid doses. Dosing of the new cohorts is expected to be completed by July 2022. Patients are dosed in a single eye, with the other eye serving as a control to test the vision of the treated eye against. 

No papers have been published sharing trial data, but Editas has issued press releases and presented data at two conferences in fall 2021. According to press release materials, no serious adverse events or dose-limiting toxicities had been observed. 

Efficacy is challenging to evaluate in these individuals. Because their vision is so reduced, the classic line-by-line letter reading eye test you may be familiar with cannot be used. A number of other tests, including mobility (e.g., ability to navigate around objects in one’s path) and ability to detect light were used. Researchers are still honing in on the best way to assess vision change in these patients. In two of the three mid-dose subjects who were followed for at least three months, there were improvements in some of the vision assessments. Hear directly from trial participants Carlene Knight and Michael Kalberer here . 

Learn more:  

• BRILLIANCE: A Phase 1/2 Single Ascending Dose Study of EDIT-101, an in vivo CRISPR Gene Editing Therapy in CEP290-Related Retinal Degeneration — Data presentation from Editas

The FDA is satisfied with the initial safety data, but long-term safety is unknown. Because this treatment is delivered with a viral vector, there will be ongoing expression of CRISPR-Cas components in the eye. Ongoing expression presents a higher risk of unwanted DNA edits, and, perhaps more crucially, of immune reactions to the viral vector and/or the Cas protein over the long-term. It will be necessary to follow these patient volunteers for years to come to see how they fare. 

In terms of efficiency and off-target effects, there is currently no way to directly assess what percentage of cells are being edited or whether there are unwanted edits in living patient volunteers. Inferences about the efficiency of editing can only be made relative to how much vision improvement there is among patient volunteers. Researchers are following individuals who have already been dosed to track whether improvements in vision are stable over time, improve, or are lost.

This trial came on the heels of the FDA approval of Luxturna, a gene therapy product for a different inherited retinal disease that causes vision loss. “The retina is a promising place for molecular therapies. In fact gene augmentation [for Luxturna patients] had such dramatic improvement that the FDA rapidly approved it,” says Bruce Conklin, M.D., IGI Deputy Director and Gladstone Institutes Investigator. “But LCA10 was a much tougher target, since the vision loss is so great that the brain actually loses its functional writing to the eye. So, even if the therapy is successful in the retina, the brain can not process the information.” In other words, because the extent of vision loss is more severe in LCA10 patients, and because vision loss occurs earlier in development, it is likely that the part of the brain that processes visual information has not developed all the necessary connections for vision. So, even if the retina issue is corrected, the brain of individuals with LCA10 may not have the ability to process much visual information.

The company reported their data of improvement on some measures in two patients in an optimistic light. Hear from those individuals here . That said, the reception by the scientific community was mixed. Some saw the results as a step in the right direction; others saw it as a deep disappointment. Hopefully the next steps of the trial — treating individuals with LCA10 at a younger age (pediatric cohort) and/or with higher doses (adult high-dose cohort) — will yield more dramatic and definitive improvements. Higher dose treatments may prove more effective, although they are also more likely to provoke stronger immune reactions against the treatment. In all scenarios, the surgery necessary to administer the therapy is complex and may prove to be the major risk of this approach.

DISEASE BACKGROUND 

When we eat, nutrients from our food enter our bloodstream. Insulin is the crucial molecule that ferries sugar from the bloodstream into our cells for use as energy. Beta cells in the pancreas make insulin. 

Type 1 diabetes (T1D) is an endocrine disorder that occurs when pancreatic beta cells are destroyed, usually by an autoimmune reaction. Without enough beta cells, the body cannot make enough insulin. Individuals with T1D must carefully monitor blood sugar and insulin levels for their entire lives, avoiding life-threatening blood sugar highs and lows by carefully timing meals, exercise, and self-dosing of insulin. T1D is not caused by diet, exercise, or weight, and cannot be controlled through lifestyle changes alone. Kidney damage, nerve pain, damage to blood vessels and the heart, vision loss, and limb amputation are common complications of T1D. 

Researchers have long been interested in transplanting healthy pancreatic cells into individuals with T1D. While ongoing clinical trials in this area show that pancreatic cell transplantation can greatly benefit individuals with T1D, individuals who receive conventional pancreatic cell transplants must take drugs that suppress the immune system on an ongoing basis so that their body does not attack the transplanted cells. Immunosuppressant drugs can have serious side effects, including increased risk of dangerous infections and cancers. 

In the new CRISPR treatment strategy, pancreatic cells will be made from stem cells. CRISPR will be used to edit the immune-related genes of these cells so that the patient’s immune system does not attack them. These cells will be implanted into the patient’s body in a special pouch. Blood vessels will grow along the outside of the pouch, bringing the cells oxygen and vital nutrients from the blood, and taking up insulin from the cells. The aim is for patients to have healthy new pancreas cells to help control or even cure their T1D without having to take immunosuppressants . 

CURRENT CRISPR CLINICAL TRIAL 

There is currently one clinical trial for T1D, sponsored by CRISPR Therapeutics and ViaCyte, Inc. The first patient volunteer was treated in Canada earlier this year . This is a phase 1 trial, which will assess safety, side effects, and whether the cells are able to avoid attack by the immune system. This trial represents the first use of CRISPR to treat an endocrine disease.  

Conventional pancreatic cell transplantation is already being tested in clinical trials with some strong signs of improvement in T1D patients: some are able to stop self-administering insulin altogether and those who are not still report improvement in managing blood sugar. 

There are two main differences in this trial: 1) the transplanted cells are derived from stem cells and 2) CRISPR is used to edit the cells to avoid detection by the patient’s immune system. If this works, patients could have the benefit of transplantation — improvement or even a cure for T1D — without the risks and side effects of immunosuppressants. Early data from ViaCyte’s other trials of implanted stem cells sans CRISPR edits show positive indications that the cells are safe and turn into mature insulin-producing cells. Whether the cells in this trial can successfully evade detection by the immune system will be the most crucial outcome to watch. 

If this treatment is successful, it has a scalability advantage over conventional transplants. In conventional transplants, cells come from a deceased donor on an individually-matched basis or the patient’s own cells are harvested and edited, a highly technical process that few facilities can do. In this trial, the pancreatic cells are made from a stem cell source that could be given to any patient in need. In other words, the pouch of edited cells could be an off-the-shelf type product, rather than an individually manufactured product. Off-the-shelf products are quicker, easier, and cheaper to make than personalized products and could increase the accessibility of this therapy. 

INFECTIOUS DISEASE – CHRONIC UTI 

Urinary tract infections (UTIs) are a common infection causing over 8 million visits to health care providers every year. UTIs occur when bacteria that shouldn’t be there take up residence in the bladder, kidneys, the tubes that connect the bladders to the kidneys, or the tube through which urine exits the body. E. coli , a common fecal bacteria, is usually the culprit. For anatomical reasons, UTIs are much more common in women. 

UTIs cause a burning sensation during urination and the need to urinate frequently. Beyond discomfort, they can become dangerous if they affect the kidneys or if bacteria enter the bloodstream. Most UTIs are easily treated with a short course of antibiotics, but sometimes antibiotics are ineffective or the infection keeps recurring, known as chronic UTI. 

The treatment currently in clinical trials is a cocktail of three bacteriophages combined with CRISPR- Cas3 , designed to attack the genome of the three strains of E. coli responsible for about 95% of UTIs. The destruction of the genome kills the bacteria. 

Bacteriophages, or phages for short, are viruses that attack bacteria. They usually work by injecting their genetic material into bacteria and using the bacteria as a factory to make more bacteriophages. Eventually, the bacteria will burst, dying as they release more copies of the phage. Phages are being developed for use against bacterial infections, and have gotten more attention recently as antibiotic resistance has become a major public health threat. 

In this treatment, phages have been engineered to be an even more powerful tool against E. coli . In addition to the natural action of phages that kills bacteria, these bacteriophages contain CRISPR-Cas3 in their genome. While the more-famous Cas protein Cas9 makes a precise cut at a single location, Cas3 shreds DNA at the gene regions it is targeted to find. In this treatment, the CRISPR-Cas3 system is made to target the genomes of the targeted E. coli strains and damage them by shredding stretches of DNA. In experiments on isolated cells and in animals with urinary tract and other infections, the addition of CRISPR-Cas3 makes phages much more effective at killing E. coli . Locus Biosciences delivered the treatment directly to the bladder by catheter in the phase 1 trial.  

This is the first trial using a CRISPR-based therapy to treat infection. It is also the first trial to use the Cas3 protein, which targets longer stretches of DNA for destruction, rather than Cas9, which makes a precise cut at one location. 

Phages have been considered a possible antibacterial therapy since they were first identified about 100 years ago, but the discovery of antibiotics like penicillin, as well as the difficulty of patenting phages, limited the development of phage therapies. Over the past decades, phages have occasionally been used by doctors for what is known as “compassionate treatment.” Compassionate treatment is when an unapproved drug or therapy is used to treat a seriously ill individual when no other treatments exist. At least 25 case reports of compassionate phage therapy have been published in the last 20 years. Some reports claim success at healing patients, but under compassionate treatment, clinicians use different phages in different amounts for different conditions — clinical trials are necessary to really evaluate the safety and efficacy of phage treatments. 

As resistance to traditional antibiotics like penicillin becomes an increasing public health threat, there is renewed interest in developing and testing phage therapies. Phages could in some ways even be preferable to effective antibiotics, because each phage usually only kills a specific kind of bacteria. Antibiotics are typically destructive to healthy bacteria as well, whereas phage therapy has the potential to be much more targeted and precise. In addition to innovations using CRISPR technology, this trial is significant because it is one of the first few well-controlled clinical trials for phage therapy, and the first to combine the CRISPR system with phage therapy. 

Locus Biosciences completed their US-based Phase 1b trial in February 2021. In press releases, they reported that results of the trial supported the safety and tolerability of the new therapy, with no drug-related adverse effects. No data have been published yet, but Locus says the initial results show a decrease in the level of E. coli in the bladder of patient volunteers given the CRISPR-based treatment. A representative of Locus Biosciences has confirmed that the company is moving forward with a phase 2/3 trial, expected to begin recruiting patients by June 2022. Combining phases 2 and 3 helps shorten the time until potential FDA approval for the therapy. 

The completed trial was Phase 1, which means it was designed mainly to test whether the treatment is safe and has tolerable side effects, not how effective the treatment is. However, the results from the trial indicate that the therapy can decrease the level of E. coli in the bladders of infected patients. Researchers at Locus also used this trial to do careful analysis of how quickly phages can multiply within the urinary system — this is the kind of information about phage therapies that is needed for the field to advance.  

While Cas3 can destroy longer stretches of DNA, Cas9’s ability to make double-stranded breaks could also be effective at killing bacteria, but at the moment there is no comparative data. “Perhaps Cas3 could better prevent any straggling survivors that somehow managed to repair the Cas9 cut,” says Hochstrasser. “But I’d be curious to know if there is a difference, because it’s part of a huge system that could be hard to deliver in other contexts.”

INFECTIOUS DISEASE – HIV/AIDS

Human immunodeficiency virus, commonly referred to as HIV, is a virus that attacks the body’s immune system. HIV infects CD4 T lymphocytes, a type of immune cell that is important for fighting infections. HIV makes copies of itself inside the CD4 cell and then kills the cell, releasing more copies of the virus to infect and kill other CD4 cells. If HIV is untreated, it can lead to acquired immunodeficiency syndrome (AIDS), a condition where the immune system is severely damaged and an individual can get very sick or die from common infections. Individuals with AIDS are also vulnerable to rare infections and cancers that are not seen in people with healthy immune systems. 

AIDS was first recognized in gay men in the early 1980s, and it took years of activism to combat social stigma and get significant research funding. In 1987, the first treatment that inhibits replication of HIV was approved by the FDA. There are now six types of drugs used to treat HIV/AIDS, often in combination. These drugs are remarkably effective at reducing the amount of virus an HIV positive person has, allowing many HIV positive people to live long, healthy lives. However, HIV is a retrovirus, which means it stores copies of its own genetic material within the host’s own genome in an inactive form. Even when individuals have such low levels of the virus that it is undetectable in blood tests, their own cells act as a “reservoir” from which the virus can be reactivated at any time. Because of this, it is currently not possible to eliminate HIV from the body. Antiviral treatments, which can have serious side effects over time, must be taken on an ongoing basis by the ~1 million Americans who are HIV-positive. 

TREATMENT APPROACH

This is the first trial targeting a retrovirus, and it is sponsored by Excision Biotherapeutics. It is currently open for enrollment, with an aim of enrolling ~9 patient volunteers at locations across the US. As a phase 1/2 trial, the goals are to evaluate safety and side effects, correct dosage, and efficacy of the treatment at excising the virus out of cells.  

Since researchers have learned about the HIV “reservoir,” their goal has been to eliminate it to cure patients. In terms of efficacy, we have every reason to think that CRISPR will be able to disrupt and cut the HIV genetic material in its hiding place in the human genome. But the big question is what percentage of cells will it be able to reach? Can it edit enough cells to eliminate the infection? This is a much tougher problem than treating conditions like blood disorders where getting enough cells making enough healthy protein is sufficient for a cure. Editing less than half of blood stem cells seems to be enough to effectively cure sickle cell disease or beta thalassemia. But for the HIV treatment to be curative, a CRISPR therapy needs to eliminate the HIV genetic material from almost every cell where it is hiding. Many in the field are highly skeptical that this approach can work. 

One common concern about genome-editing therapies is off-target effects: unwanted edits made by the genome-editing components. This trial is only the second systemic administration of a CRISPR treatment. In most other treatments, specific types of cells are edited outside of the body, and then put back in after editing (like treatments for blood disorders, cancer, or T1D) or genome-editing therapies are delivered to self-contained organs (like treatment for genetic blindness and chronic UTI). Systemic delivery exposes a wide variety of body tissues to genome-editing components, making the risk of off-target effects higher than for non-systemic approaches. 

“This is a viral-delivered Cas9 — a highly immunogenic protein — with what, as best as we can tell, is a ubiquitous promoter,” says Urnov. “It’s different than an in vivo editor making cuts in the eye, which is an immunoprivileged, self-contained setting.” In other words, when CRISPR-based treatments are delivered by a virus and with this particular genetic sequence, the genome-editing components can persist in many parts of the body for a long time. The longer they are in the body, and the more widely spread, the greater the opportunity for unwanted edits and immune reactions against the CRISPR components. The individuals in this trial will be followed for years to come to monitor for any long-term health effects that could be associated with unwanted changes to the DNA. 

This trial will be done on patients who are responding well to antiretroviral treatments. If this phase goes well, future trials will likely aim to take patients off of their medications and assess if the virus is able to rebound or has been eliminated from the body. 

Another area of CRISPR research that may eventually help individuals with HIV or other chronic infections is editing T cells to help control infections. For HIV, this could come in the form of editing different kinds of T cells to better eliminate the virus or to be more resistant to becoming infected. 

PROTEIN-FOLDING DISEASE – HEREDITARY TRANSTHYRETIN AMYLOIDOSIS 

When the TTR gene is mutated, it makes a protein that folds the wrong way. The incorrectly folded proteins stick together, forming clumps called amyloid fibrils, in a process called amyloidosis. The protein clumps accumulate in organs and tissues, where they interfere with normal functions. ATTR has similarities to other neurological diseases involving protein misfolding and amyloidosis including Alzheimer’s and Parkinson’s diseases. 

Individuals with ATTR first have symptoms in early or middle adulthood. Symptoms vary, but usually include severe effects on the nervous system and/or heart. Nerve pain, loss of movement control, digestive problems, vision loss, dementia, and heart failure are common in ATTR. Damage to the nervous system and/or heart eventually kills the individual.

ATTR usually occurs spontaneously, but for some individuals, the mutated gene is passed down from their parents. This leads to hereditary ATTR, or hATTR. Often, hereditary forms of neurological diseases are better understood than spontaneous cases because they are easier to study. hATTR is a rare disease, affecting about 50,000 people worldwide. 

The treatment being investigated uses CRISPR-Cas9 tools to reduce the amount of faulty TTR protein the body makes. Less faulty TTR means less protein clumps (amyloidosis). The treatment is delivered in a single dose by IV. 

The aim of this hATTR treatment isn’t to fix a gene: it’s to break the gene so that patients stop making the faulty protein altogether. The CRISPR components cut the TTR gene, creating a double-stranded break in the DNA. As the cell tries to repair the DNA without a corrected template, the repair attempts mutate the gene even more. And when a gene is too badly damaged, a cell will sometimes stop making the protein it codes for. 

Getting the CRISPR components into cells is a big challenge for in vivo genome-editing therapies. Many treatments in development use viruses to deliver the genome-editing components. This is the first clinical trial for a CRISPR-Cas9 therapy delivered in a lipid nanoparticle . The lipids, or fat molecules, surround the gene-editing components, and are able to get into the cell. 

In animal models, lipid nanoparticles have a tendency to accumulate in the liver. TTR is primarily made in the liver, so researchers are taking advantage of this to naturally get the treatment to where it is needed in the body. 

This is the first trial that uses lipid nanoparticles to deliver the genome-editing treatment. It is also the first trial to deliver genome-editing components systemically, that is, to the whole body rather than to one specific type of cell or tissue. 

The phase 1 trial is sponsored by Intellia Therapeutics in collaboration with Regeneron Pharmaceuticals. The first patient volunteer was dosed in November 2020 in the United Kingdom. In total, data has been shared on fifteen patient volunteers, who received one of four potential dosages of the gene-editing reagents. Most adverse events were mild. All patient volunteers showed a reduction in TTR protein levels, with higher doses leading to greater reductions in the protein. The protein level was reduced by an average of 87% in individuals who received the highest dose. In amyloid disorders like TTR, the level of precursor proteins is related to clinical outcomes. In other words, if the patient volunteers continue to produce less TTR protein, it is very likely that they will have less severe disease. Intellia CEO John Leonard hopes that with dramatic reductions in toxic proteins being produced, people’s bodies will be able to clear out the toxic protein and even reverse damage done by the disease, but it’s too soon to tell. Currently, more patient volunteers are being enrolled in the phase 1 study. 

• CRISPR-Cas9 In Vivo Gene Editing for Transthyretin Amyloidosis — Gillmore et al., New England Journal of Medicine

This is the first experimental CRISPR therapy to be administered systemically to edit genes inside the human body. In other treatments, specific types of cells are edited outside of the body, and then put back in after editing (like treatments for blood disorders and cancer) or genome-editing therapies are delivered to self-contained organs (like treatment for genetic blindness and chronic UTI). These strategies help ensure that only the cells or tissue of interest are edited. 

One common concern about genome-editing therapies is unwanted edits made by the genome-editing components. This is particularly a concern with CRISPR treatments delivered by viruses, since the genome-editing components may persist in the cell for a long time, giving them more opportunity to make editing errors. Avoiding systemic delivery helps reduce the overall risk. 

In this trial, risks are reduced because 1) lipid nanoparticles tend to aggregate in the liver, which is the tissue being targeted in ATTR treatment and 2) no viruses are used. In animal studies of the hATTR treatment delivered by lipid nanoparticles, the genome-editing components were cleared from the body in less than a week, dramatically reducing the chance of unwanted edits. Another risk of systemic administration of editing reagents is the potential to trigger a dangerous immune reaction: so far, the outlook is sunny as no trial participants have experienced any serious side effects. 

Efficiency — meaning, what percentage of cells are edited — is a big question. In nonhuman primates, only 35–40% of liver cells need to be edited to reduce TTR levels enough to have a therapeutic benefit. There are no reports yet on what percentage of cells are edited in these patients, but the strong reductions in TTR protein are extremely encouraging as indicators of efficiency of editing and efficacy of the treatment. We’ll be watching closely to see whether these reductions in TTR protein last over time and lead to changes in real-world outcomes for trial participants. 

The early positive indicators from this trial are encouraging for treating other disorders where editing liver tissue may be beneficial. Hear directly from Patrick Doherty , a trial participant. 

INFLAMMATORY DISEASE – HEREDITARY ANGIOEDEMA

In hereditary angioedema (HAE), an individual has severe attacks of inflammation, leading to swelling. Swelling usually happens in the arms and legs, face, intestines, or airway. Swelling of the intestines can lead to severe pain, nausea, and vomiting, and swelling of the airways can be life-threatening. Individuals with HAE usually begin to get attacks in childhood. Without treatment, attacks occur every 1–2 weeks, lasting 3–4 days each. HAE affects about 1 in every 50,000 people. 

There are three known types of HAE. Types I and II are caused by mutations in the gene that makes the C1 inhibitor protein. In healthy individuals, proteins that increase and decrease inflammation are in a careful balance, helping the body respond to threats and injuries to just the right degree. The C1 inhibitor protein helps reduce inflammation. In HAE, mutations lead to lower levels of C1 inhibitor protein. Without enough C1 inhibitor protein, the protein bradykinin accumulates in the blood. Bradykinin makes fluid leak from the blood vessels into body tissues. When this happens excessively, it leads to HAE swelling attacks. 

Current treatment options require daily pills or intravenous (IV) or injection administration as often as twice per week. Even when administered regularly, individuals with HAE may still experience occasional attacks. 

Like hATTR, angioedema can happen spontaneously, but for some individuals, the mutated gene is passed down from their biological parents. This leads to hereditary angioedema. HAE is a rare disease, affecting about 150,000 people worldwide.

The treatment that is currently in clinical trials uses CRISPR-Cas9 tools to reduce the amount of bradykinin protein the body makes. Less bradykinin means less inflammation and swelling. The treatment is delivered in a single dose by IV. As in the hATTR treatment, the aim isn’t to fix a gene, but to break a gene to stop the disease process. 

The CRISPR components cut the TTR gene, creating a double-stranded break in the DNA. As the cell tries to repair the DNA without a corrected template, the repair attempts mutate the gene even more. And when a gene is too badly damaged, a cell will sometimes stop making the protein it codes for. 

The protein prekallikrein is processed into kallikrein, which is crucial to making bradykinin. In this treatment, the aim is to make the gene that codes for prekallikrein nonfunctional (knock-out), reducing the amount of kallikrein, and ultimately reducing the amount of bradykinin. CRISPR-Cas9 is used to make a cut in the prekallikrein gene and when the body tries to repair the DNA break, it renders the gene nonfunctional. If this works as intended, it will reduce the amount of bradykinin, bringing it back into balance with C1 inhibitor protein to prevent inflammation attacks. Previous research shows how much kallikrein needs to be reduced to prevent attacks. In Intellia’s work in nonhuman primate models, a single dose of the CRISPR-based treatment can reduce kallikrein protein to this level, and the reduction was sustained for more than a year.

In this trial, the CRISPR-Cas9 reagents are delivered by lipid nanoparticles. As in hATTR, the aim is to edit cells in the liver. Lipid nanoparticles have a natural tendency to accumulate in the liver, so researchers are taking advantage of this to get the treatment to where it should be. This is an in vivo, systemic treatment, administered intravenously. 

This phase 1/2 study is being sponsored by Intellia Therapeutics, enrolling up to 55 patient volunteers in New Zealand. The first phase will test two different doses of the treatment, looking at safety and side effects. The second phase will compare the efficacy of the treatment relative to placebo.  

This trial uses the same design as Intellia’s trial for hATTR: CRISPR-Cas components packaged in lipid nanoparticles, administered by IV. The lipid nanoparticles accumulate in the liver, which is where researchers are hoping editing will occur. This is an example of a platform technology : using the same components, delivery, and administration method for a treatment, while just changing onecomponent to adapt the therapy to a different disease. For CRISPR-based treatments, the variable component is typically the guide RNA that determines where a DNA cut will be made. The early success of Intellia’s hATTR treatment at reducing the target protein is a positive indicator for the lipid nanoparticle/IV administration platform for liver editing. 

An advantage of both the hATTR trial and this trial (HAE) is that each has a helpful biomarker that can be measured. A biomarker is a molecule in the blood, urine, or other body fluid that can be measured as a diagnostic to assess how well a treatment is working. For HAE, researchers will use blood testing to see if the genome-editing components are successfully reducing the levels of proteins that cause inflammation. This is a real advantage over trials like the LCA10 trial where researchers have no direct way to assess if the successful genome editing is occurring in a living subject. In the HAE study, researchers will also track the number of inflammation attacks after treatment. 

THE BIG PICTURE 

CRISPR genome editing is only 10 years old, but we are already seeing remarkable progress. Each year, this article gets longer as more trials launch and therapies expand into new disease areas. Taken together, these CRISPR clinical trials are helping scientists learn about the types of DNA changes CRISPR enzymes make in different cells, (including unwanted off-target changes and problematic on-target changes), the way the immune system reacts to CRISPR-Cas tools, and how well different delivery and administration methods work. 

Over the past couple of years, there has been encouraging news: Victoria Gray, Jimi Olaghere, and others seem to be functionally cured of sickle cell disease or beta thalassemia, and the edited cells have taken up residence in the bone marrow, indicating the potential for a long-lasting cure. Trials for cancer immunotherapies are at early stages, but the safety and tolerability of the treatments looks promising for moving forward with more newer versions of editing technology, off-the-shelf products, for moving towards new cancer targets, and even developing new cell types for immunotherapy. The initial safety results for treating LCA10 and chronic UTI are positive and we hope to get more efficacy data over the next year. The preliminary results from the hATTR trial are particularly encouraging for this disease and a wide range of diseases with liver pathology, including the new HAE trial. New trials started this year also widen the scope of CRISPR applications to include more common diseases: HIV/AIDS and type 1 diabetes.

All of the treatments are relatively new. Positive results still require long-term follow-up to see if the treatment remains effective, whether patients suffer ill effects from unwanted edits, and whether there are immune reactions in patients with virally delivered Cas proteins. 

MORE CRISPR FIRSTS TO LOOK OUT FOR

While the current CRISPR clinical trials are exciting, they focus on the basic capabilities of CRISPR-Cas enzymes and offer only a glimpse of their therapeutic potential. Future milestones will help us learn more about CRISPR’s ability to treat or even prevent diseases: 

• A CRISPR treatment that involves inserting DNA to repair or replace a harmful DNA sequence, in essence “pasting” in new material, is still coming. The Graphite Bio sickle cell disease trial will be the first to attempt to directly correct a mutation back to the healthy variant.  
• A CRISPR therapy that edits multiple genes at the same time, also known as multiplex editing. Researchers have achieved impressive feats in isolated cells and animal models, and multiplex editing for cancer immunotherapy is currently being developed. 
• A treatment that uses base editing. Base editing uses CRISPR components to directly change single DNA letters without making double-stranded breaks in the DNA. For diseases caused by single-letter changes to DNA, base editors may be a safer editing option than conventional CRISPR. Several base-editing treatments are being developed for clinical trials, including for sickle cell disease. 
• A treatment that uses prime editing . Prime editing, like base editing, uses CRISPR components to make changes to DNA without making double-stranded breaks. Prime editors can potentially change both single bases and longer stretches of DNA, but has not yet been applied therapeutically. 
• A trial where CRISPR tools are used to turn genes on and off without changing the DNA sequence. These strategies, known as CRISPR activation and CRISPR inhibition, don’t require making breaks in a patient’s DNA, so they might be a safer option than conventional CRISPR. CRISPRi and CRISPRa may be reversible — another potential advantage for some applications. 

MORE INFO ON CRISPR CLINICAL TRIALS

If you or a loved one are interested in participating in a clinical trial, learn more about how US-based clinical trials work and where to find them on our Patients & Families page. Discuss all important medical decisions with your doctor. Keep in mind that clinical trials are the first tests of new medical treatments, so they are inherently risky and never guaranteed to be successful.

Thanks to Megan Hochstrasser, Fyodor Urnov, Matthew Kan, Bruce Conklin, Alex Marson, Melanie Ott, and John Flannery for insight and editing, and to Dave Ousterout, CSO of Locus Biosciences, for information on their phage therapy program for chronic UTI.  

Hope Henderson holds a B.A. in Biology from Brown University and a Ph.D. in Molecular & Cell Biology from the University of California, Berkeley. She joined the IGI in 2019 to work in science communication. In addition to serving as IGI’s main writer, she plans content strategy and manages IGI’s social media, illustration, and translation. 

You may also be interested in

Prioritizing Sickle Cell Patients: A Chance to Mend Broken Ties

$17 Million Will Launch Trial of CRISPR Cure for Sickle Cell

When Will CRISPR Cures Be Available?

Paying for CRISPR Cures: The Economics of Genetic Therapies

MIT Technology Review

• Newsletters

More than 200 people have been treated with experimental CRISPR therapies

But at a global genome-editing summit, exciting trial results were tempered by safety and ethical concerns.

• Jessica Hamzelou archive page

This article is from The Checkup, MIT Technology Review's weekly biotech newsletter. To receive it in your inbox every Thursday, sign up here .

I’ve spent the last few days thinking about how, when, and if we should use gene-editing tools to change the human genome. These are huge questions, and very emotive ones—especially when it comes to editing embryos.

I watched scientists, ethicists, patient advocacy groups, and others wrestle with these topics at the Third International Summit on Human Genome Editing in London earlier this week.

There’s plenty to get excited about when it comes to gene editing. In the decade since scientists found they could use CRISPR to edit cell genomes, multiple clinical trials have sprung up to test the technology’s use for serious diseases. CRISPR has already been used to save some lives and transform others.

But it hasn’t all been smooth sailing. Not all of the trials have gone to plan, and some volunteers have died. Successful treatments are likely to be expensive, and thus limited to the wealthy few. And while these trials tend to involve changes to the genes in adult body cells, some are hoping to use CRISPR and other gene-editing tools in eggs, sperm, and embryos. The specter of designer babies continues to loom over the field.

It was at the last summit, held in Hong Kong in 2018, that He Jiankui, then based at the Southern University of Science and Technology in Shenzhen, China, announced that he had used CRISPR on human embryos. The news of the first “CRISPR babies,” as they became known, caused a massive ruckus, as you might imagine. “We’ll never forget the shock,” Victor Dzau, president of the US National Academy of Medicine, told us.

He Jiankui ended up in prison and was released only last year . And while heritable genome editing was already banned in China at the time—it has been outlawed since 2003—the country has since enacted a series of additional laws designed to prevent anything like that from happening again. Today, heritable genome editing is prohibited under criminal law, Yaojin Peng of the Beijing Institute of Stem Cell and Regenerative Medicine told the audience.

There was much less drama at this year’s summit. But there was plenty of emotion. In a session about how gene editing might be used to treat sickle-cell disease, Victoria Gray, a 37-year-old survivor of the disease, took to the stage. She told the audience about how her severe symptoms had disrupted her childhood and adolescence, and scuppered her dreams of training to be a doctor. She described episodes of severe pain that left her hospitalized for months at a time. Her children were worried she might die.

But then she underwent a treatment that involved editing the genes in cells from her bone marrow. Her new “super cells,” as she calls them, have transformed her life. Within minutes of receiving her transfusion of edited cells, she felt reborn and shed tears of joy, she told us. It took seven to eight months for her to feel better, but after that point, “I really began to enjoy the life that I once felt was just passing me by,” she said. I could see the typically stoic scientists around me wiping tears from their eyes.

Victoria is one of more than 200 people who have been treated with CRISPR-based therapies in clinical trials , said David Liu of the Broad Institute of MIT and Harvard, who has led the development of new and improved forms of CRISPR . Trials are also underway for a range of other diseases, including cancers, genetic vision loss, and amyloidosis.

Liu highlighted the case of Alyssa, a teenager in the UK who was diagnosed with a form of leukemia that affects a type of white blood cells called T cells. Chemotherapy didn’t work, and neither did a bone marrow transplant. So doctors at Great Ormond Street Hospital in London tried a CRISPR-based approach.

It involved taking healthy T cells from a donor and using CRISPR to modify them. The treated cells were altered so that they wouldn’t be rejected by Alyssa’s immune system, but they would be able to track down and attack Alyssa’s own cancerous T cells. These cells were then given to Alyssa as a treatment. It seems to have worked.

“As of now, approximately 10 months after treatment, her cancer remains undetectable,” Liu said.

It really is incredible that we are hearing such success stories already. But there are concerns.

The question of equity came up again and again at the summit. Gene-editing therapies are expected to cost a lot of money—likely millions of dollars. Who will be able to afford them? Probably not the people living in low- and middle-income countries, multiple attendees worried.

For now, CRISPR therapies are still considered experimental, and none have been approved, so the only way for people to access them is through clinical trials. The majority of these are being run in the rich world. Natacha Salomé Lima, a psychologist and bioethicist at the University of Buenos Aires in Argentina, pointed out that while 70% of global cancer cases are in low- and middle-income countries, two-thirds of gene-therapy cancer trials are taking place in wealthy countries.

I could tell that the summit’s organizers had made an effort to feature speakers from all over the world, and to include people who have the disorders being targeted by gene editing. But some attendees felt that some voices were still missing from the discussion. “What about the LGBTQ community?” Marc Dusseiller of ETH Zurich in Switzerland, who describes himself as a “workshopologist” interested in biohacking and bio art, asked me.

It’s also worth pointing out that not all CRISPR treatments have been a success. Multiple researchers noted that we still don’t fully understand how the treatment works. We know we can cut DNA, and swap either DNA bases or chunks of genetic code. But we can’t be sure about unintended effects elsewhere in the genome. It’s possible that you could accidentally trigger some genetic change elsewhere—one that might have harmful consequences.

Last year, 27-year-old Terry Horgan died while participating in a clinical trial of a CRISPR treatment designed to treat his Duchenne muscular dystrophy, a fatal disease that causes muscle degeneration. The cause of his death—and whether or not it might have been related to the treatment—has not been made clear.

And there’s always a risk that rogue scientists will set up companies offering unapproved procedures to desperate individuals who are willing to pay for them, said Robin Lovell-Badge, a stem-cell biologist at the Crick Institute, where the summit took place. They might even sell unauthorized procedures designed to enhance people rather than treat them.

On the first day of the summit, a couple of protesters stood at the entrance of the venue, holding a banner reading “Stop designer babies.” This sentiment is shared by a lot of scientists. They are particularly worried about future attempts to edit the genes of eggs, sperm, or embryos.

In theory, you could change the DNA of an embryo to prevent a baby from developing a heritable disease. But research into early embryos (scientists are generally allowed to study them for only 14 days before having to destroy them) suggests that they are even more likely to be affected by unintended, potentially harmful effects of gene editing. And these changes would be passed on to the next generation, too.

Most attendees focused on technical and ethical worries, but Dusseiller had another concern. The summit was too dry, he told me; the serious issues surrounding gene editing can be addressed with some degree of humor. “We need more weirdness,” he argued. “We need more jokes .”

Read more from Tech Review's archive

There are more than 50 experimental studies underway that use gene editing in people to treat cancer, HIV, blood diseases, and more. Most of them involve CRISPR, my colleague Antonio Regalado reported earlier this week.

And last year, a volunteer in New Zealand became the first to receive an experimental CRISPR treatment to lower her cholesterol. One of the scientists behind the work thinks the approach could potentially benefit almost everyone .

CRISPR is also being explored for an inherited form of blindness. The first volunteer underwent the experimental treatment in 2020 .

He Jiankui’s work was never published. It was rejected by the leading medical journals it was submitted to. But Antonio got hold of the manuscript, and showed it to four experts . Their verdicts were damning. He’s claims were not supported by his results, the babies’ parents may have been under pressure to agree to join the experiment, and the researchers went ahead without fully understanding what they were doing.

The summit was focused on human genome editing, but CRISPR is also being explored to make farmed animals bigger and stronger . One team of scientists has put an alligator gene into catfish in an attempt to make them more resistant to disease, for example.

From around the web

A microbiologist found a forgotten beef soup at the back of her fridge had turned bright blue. So she set out on a scientific quest to find out why. ( Twitter )

Governments around the world are using algorithms to control access to various services. A system that flags people who might be committing benefits fraud in Rotterdam appears to discriminate on the basis of ethnicity and gender, according to an investigation. ( Wired )

Last year, biotech company Retro Biosciences announced its launch with $180 million in funding. It turns out that all of that is from Sam Altman, the CEO of OpenAI. ( MIT Technology Review )

Biotechnology and health

Google helped make an exquisitely detailed map of a tiny piece of the human brain.

A small brain sample was sliced into 5,000 pieces, and machine learning helped stitch it back together.

• Cassandra Willyard archive page

That viral video showing a head transplant is a fake. But it might be real someday. 

BrainBridge is best understood as the first public billboard for a hugely controversial scheme to defeat death.

• Antonio Regalado archive page

The effort to make a breakthrough cancer therapy cheaper

CAR-T cells could revolutionize the treatment of a wide variety of diseases, if only we can make them cheaper.

Beyond Neuralink: Meet the other companies developing brain-computer interfaces

Companies like Synchron, Paradromics, and Precision Neuroscience are also racing to develop brain implants

Stay connected

Get the latest updates from mit technology review.

Discover special offers, top stories, upcoming events, and more.

Thank you for submitting your email!

It looks like something went wrong.

We’re having trouble saving your preferences. Try refreshing this page and updating them one more time. If you continue to get this message, reach out to us at [email protected] with a list of newsletters you’d like to receive.

Editing without 'cutting': Molecular mechanisms of new gene-editing tool revealed

Researchers elucidate the spatial structure and molecular mechanisms of 'prime editor,' a novel gene-editing tool.

Joint research led by Yutaro Shuto, Ryoya Nakagawa, and Osamu Nureki of the University of Tokyo determined the spatial structure of various processes of a novel gene-editing tool called "prime editor." Functional analysis based on these structures also revealed how a "prime editor" could achieve reverse transcription, synthesizing DNA from RNA, without "cutting" both strands of the double helix. Clarifying these molecular mechanisms contributes greatly to designing gene-editing tools accurate enough for gene therapy treatments. The findings were published in the journal Nature .

The 2020 Nobel Prize in Chemistry was awarded to Jennifer Doudna and Emmanuelle Charpentier for developing a groundbreaking yet simple way to edit DNA, the "blueprint" of living organisms. While their discovery opened new avenues for research, the accuracy of the method and safety concerns about "cutting" both strands of DNA limited its use for gene therapy treatments. As such, research has been underway to develop tools that do not have these drawbacks.

The prime editing system is one such tool, a molecule complex consisting of two components. One component is the prime editor, which combines a SpCas9 protein, used in the first CRISPR-Cas gene editing technology, and a reverse transcriptase, an enzyme that transcribes RNA into DNA. The second component is the prime editing guide RNA (pegRNA), a modified guide RNA that identifies the target sequence within the DNA and encodes the desired edit. In this complex, the prime editor works like a "word processor," accurately replacing genomic information. The tool has already been successfully implemented in living cells of organisms such as plants, zebrafish, and mice. However, precisely how this molecule complex executes each step of the editing process has not been clear, mostly due to a lack of information on its spatial structure.

"We became curious about how the unnatural combination of proteins Cas9 and reverse transcriptase work together," says Shuto, the first author of the paper.

The research team used cryogenic electron microscopy, an imaging technique that makes observations possible at a near-atomic scale. The method required samples to be in glassy ice to protect them from the potential damage by the electron beams, posing some additional challenges.

"We found the prime editor complex to be unstable under experimental conditions," explains Shuto. "So, it was very challenging to optimize the conditions for the complex to stay stable. For a long time, we could only determine the structure of Cas9."

Finally overcoming the challenges, the researchers succeeded in determining the three-dimensional structure of the prime editor complex in multiple states during reverse transcription on the target DNA. The structures revealed that the reverse transcriptase bound to the RNA-DNA complex that formed along the "part" of the Cas9 protein associated with DNA cleavage, the splitting of a single strand of the double helix. While performing the reverse transcription, the reverse transcriptase maintained its position relative to the Cas9 protein. The structural and biochemical analyses also indicated that the reverse transcriptase could lead to additional, undesired insertions.

These findings have opened new avenues for both basic and applied research. So, Shuto lays out the next steps.

"Our structure determination strategy in this study can also be applied to prime editors composed of a different Cas9 protein and reverse transcriptase. We want to utilize the newly obtained structural information to lead to the development of improved prime editors."

• CRISPR Gene Editing
• Biotechnology
• Biochemistry Research
• Microbiology
• Organic Chemistry
• Biochemistry
• Microarrays
• Forensic Research
• Computational genomics
• Gene therapy
• Molecular biology
• Genetic code
• Bioinformatics

Story Source:

Materials provided by School of Science, The University of Tokyo . Note: Content may be edited for style and length.

Journal Reference :

• Yutaro Shuto, Ryoya Nakagawa, Shiyou Zhu, Mizuki Hoki, Satoshi N. Omura, Hisato Hirano, Yuzuru Itoh, Feng Zhang, Osamu Nureki. Structural basis for pegRNA-guided reverse transcription by a prime editor . Nature , 2024; DOI: 10.1038/s41586-024-07497-8

Cite This Page :

Explore More

• Adjusting Sunglasses for Your Windows
• Novel Gene-Editing Tool Created
• How Hummingbirds Hover With Such Accuracy
• Complete X and Y Chromosomes of Great Apes
• Moonlets Stuck Together Orbit 'Dinky' Asteroid
• Orchids Aid Seedlings Through Fungal Networks
• Precise Maps of the Moon's Surface
• Amazing Expertise of Scent Detection Dogs
• Getting to Grips With a Handy Extra Thumb
• H5N1 Bird Flu Transmitted from Cows to Humans

Trending Topics

Strange & offbeat.

• May 28, 2024 | Scientists May Have Discovered an Achilles Heel for Hepatitis B
• May 28, 2024 | Challenging Classical Physics: Surprising Properties of Elastic Turbulence Discovered
• May 28, 2024 | Johns Hopkins Scientists Solve 30-Year Biological Mystery of Night Blindness
• May 28, 2024 | Cutting-Edge Phage Research Promises New Solutions for Old Pathogens
• May 28, 2024 | Vanishing Without a Trace: Why Stars Mysteriously Disappear From the Night Sky

Gene Editing Breakthrough: CRISPR Improves Vision in Clinical Trial

By Massachusetts Eye And Ear May 13, 2024

In a recent clinical trial, CRISPR gene editing was applied to 14 patients suffering from a form of inherited blindness. The treatment proved safe and resulted in measurable vision improvements in 11 of the participants. The trial, named BRILLIANCE, signifies a significant step forward in gene therapy for ocular diseases. Credit: SciTechDaily.com

Mass Eye and Ear-led phase 1/2 trial, which included 14 participants, found that the first-of-its-kind experimental treatment was safe and efficacious.

• BRILLIANCE trial results showed 11 out of 14 treated participants experienced some improvements in vision and quality of life measures.
• CRISPR-based therapy was found safe with no dose-limiting toxicities reported.
• Mass Eye and Ear researchers say their findings support continued research and clinical trials of CRISPR therapies for inherited retinal disorders.

Results from a groundbreaking clinical trial of CRISPR gene editing in 14 individuals with a form of inherited blindness show that the treatment is safe and led to measurable improvements in 11 of the participants treated. The phase 1/2 trial called BRILLIANCE, was led by principal investigator Eric Pierce, MD, PhD, of Mass Eye and Ear, a member of the Mass General Brigham healthcare system, and sponsored by Editas Medicine, Inc. Findings are reported on May 6th in The New England Journal of Medicine .

“This research demonstrates that CRISPR gene therapy for inherited vision loss is worth continued pursuit in research and clinical trials,” said Pierce, director of Ocular Genomics Institute and Berman-Gund Laboratory for the Study of Retinal Degenerations at Mass Eye and Ear and Harvard Medical School. “While more research is needed to determine who may benefit most, we consider the early results promising. To hear from several participants how thrilled they were that they could finally see the food on their plates –that is a big deal. These were individuals who could not read any lines on an eye chart and who had no treatment options, which is the unfortunate reality for most people with inherited retinal disorders.”

Jason Comander, MD, PhD, performs the procedure to deliver the CRISPR-based medicine as part of the BRILLIANCE trial in September 2020 at Mass Eye and Ear. Credit: Mass Eye and Ear

Participant Demographics and Trial Procedures

All 14 trial participants, including 12 adults (ages 17 to 63) and two children (ages 10 and 14), were born with a form of Leber Congenital Amaurosis (LCA) caused by mutations in the centrosomal protein 290 ( CEP290 ) gene. They underwent a single injection of a CRISPR/Cas9 genome editing medicine, EDIT-101 in one eye via a specialized surgical procedure. This trial, which included the first patient to ever receive a CRISPR-based investigational medicine directly inside the body, focused primarily on safety with a secondary analysis for efficacy.

No serious treatment or procedure-related adverse events were reported, nor were there any dose-limiting toxicities. For efficacy, the researchers looked at four measures: best-corrected visual acuity (BCVA); dark-adapted full-field stimulus testing (FST), visual function navigation (VNC, as measured by a maze participants completed), and vision-related quality of life.

Eleven participants demonstrated improvements in at least one of those outcomes, while six demonstrated improvement in two or more. Four participants had clinically meaningful improvement in BCVA. Six participants experienced meaningful improvements in cone-mediated vision as indicated by FSTs, five of whom had improvements in at least one of the three other outcomes. Cone photoreceptors are used for daytime and central vision.

Infographic explaining the phase 1/2 results of the BRILLIANCE trial. Credit: Mass General Brigham

CRISPR’s Potential and Early Successes

“The results from the BRILLIANCE trial provide proof of concept and important learnings for the development of new and innovative medicines for inherited retinal diseases. We’ve demonstrated that we can safely deliver a CRISPR-based gene editing therapeutic to the retina and have clinically meaningful outcomes,” said Baisong Mei, MD, PhD, Chief Medical Officer, Editas Medicine.

Studies like this one show the promise of gene therapy for treating incurable conditions. Mass General Brigham’s Gene and Cell Therapy Institute is helping to translate scientific discoveries made by researchers into first-in-human clinical trials and, ultimately, life-changing treatments for patients.

Mutations in the CEP290 gene are the leading cause of inherited blindness taking place during the first decade of life. The mutations cause rod and cone photoceptors in the eye’s retina to function improperly, which after some time will lead to irreversible vision loss. Pierce compares it to a small part of an engine breaking down, which eventually leads the entire engine to falter.

CRISPR-Cas9 is a gene editing toolkit that acts as a GPS -guided scissor to cut a portion of the mutated genome to leave a functional gene. For inherited blindness, the goal was to inject CRISPR to reach the eye’s retina to restore the ability to produce the gene and protein responsible for light-sensing cells.

The CEP290 gene is larger than what traditional adeno-associated virus (AAV) vector gene therapies, including one FDA-approved for a different type of inherited vision loss, can accommodate. The genome editing company Editas Medicine began exploring how to tackle the CEP290 mutation in 2014, conducting preclinical studies to determine whether a gene editing approach like CRISPR-Cas9 might be feasible to target these large gene mutations. This work led to the BRILLIANCE trial, which began in mid-2019.

Jason Comander, MD, PhD, director of the Inherited Retinal Disorders Service at Mass Eye and Ear, examines the CRISPR-based medicine prior to performing a surgery of the novel treatment in September 2020, at Mass Eye and Ear in Boston. Credit: Mass Eye and Ear

Trial Outcomes and Future Directions

The first patient to receive a CRISPR treatment inside the body ( in vivo ) took place at the Casey Eye Institute at Oregon Health & Science University (OHSU), under the leadership of Mark Pennesi, MD, PhD.

“This trial shows CRISPR gene editing has exciting potential to treat inherited retinal degeneration,” Pennesi said. “There is nothing more rewarding to a physician than hearing a patient describe how their vision has improved after a treatment. One of our trial participants has shared several examples, including being able to find their phone after misplacing it and knowing that their coffee machine is working by seeing its small lights. While these types of tasks might seem trivial to those who are normally sighted, such improvements can have a huge impact on quality of life for those with low vision.”

The second patient was treated at Mass Eye and Ear in September 2020, following delays caused by the COVID-19 pandemic. Additional participants were treated across three other trial sites: Bascom Palmer Eye Institute, W.K. Kellogg Eye Center, and Scheie Eye Institute at the Children’s Hospital of Philadelphia (CHOP) and the Hospital of the University of Pennsylvania. Two adults received low-dose therapy, five received mid-dose, and another five received a high-dose treatment. Two children, treated at CHOP under the leadership of Tomas S. Aleman, MD, received a mid-dose treatment.

Principal investigator of the BRILLIANCE trial, Eric Pierce, MD, PhD, director of Ocular Genomics Institute and Berman-Gund Laboratory for the Study of Retinal Degenerations at Mass Eye and Ear and Harvard Medical School. Credit: Mass Eye and Ear

“Our patients are the first congenitally blind children to be treated with gene-editing, which significantly improved their daytime vision. Our hope is that the study will pave the road for treatments of younger children with similar conditions and further improvements in vision,” said Aleman , the Irene Heinz-Given and John LaPorte Research Professor in Ophthalmology at Penn Medicine with the Scheie Eye Institute and a pediatric ophthalmologist at CHOP who served as a site principal investigator and study co-author. “This trial represents a landmark in the treatment of genetic diseases, in specific, genetic blindness, by offering an important alternative treatment, when traditional forms of gene therapy, such as gene augmentation, are not an option.”

Participants were monitored every three months for one year, and then followed less frequently for two additional years. At visits, they would undergo a series of serum and vision tests to examine safety and efficacy outcome measures.

In November 2022, Editas paused enrollment on the BRILLIANCE trial. Pierce and colleagues are exploring working with other commercial partners to conduct additional trials, in collaboration with Editas. The researchers hope future studies can examine ideal dosing, whether a treatment effect is more pronounced in certain age groups such as younger patients, and include refined endpoints to measure the effects of improved cone function on activities of daily living.

For more on this research, see Pioneering CRISPR Gene Editing Trial: 79% of Participants See Improvement .

Reference: “Gene-editing for CEP290-associated Retinal Degeneration” by Eric A. Pierce, Tomas S. Aleman, Kanishka T. Jayasundera, Bright S. Ashimatey, Keunpyo Kim, Alia Rashid, Michael Jaskolka, Rene L. Myers, Bryon L. Lam, Steven T. Bailey, Jason I. Commander, Andreas K. Lauer, Albert M. Maguire and Mark E. Pennesi, 6 May 2024, New England Journal of Medicine . DOI: 10.1056/NEJMoa2309915

The senior corresponding author of this study was Eric A. Pierce, MD, PhD (Mass Eye and Ear), and Tomas S. Aleman, MD (CHOP) and Mark E. Pennesi, MD, PhD (OHSU) were co-corresponding authors. Additional co-authors include Kanishka T. Jayasundera, MD (Kellogg), Bright S. Ashimatey, OD, PhD (Editas), Keunpyo Kim, PhD (Editas), Alia Rashid, MD (Editas), Michael C. Jaskolka, PhD (Editas), Rene L. Myers, PhD (Editas), Byron L. Lam, MD (Bascom Palmer), Steven T. Bailey, MD (OHSU), Jason I. Comander, MD, PhD (Mass Eye and Ear), Andreas K. Lauer, MD (OHSU), Albert M. Maguire, MD (CHOP).

This research was funded by Editas medicine. This research was also supported by the National Institute of Health P30 EY014104 core grant to Mass Eye and Ear, P30 EY010572 core grant, the Malcolm M. Marquis MD Endowed Fund for Innovation, and an unrestricted grants from Research to Prevent Blindness to Casey Eye Institute and the Scheie Eye Institute. Additional support was provided by the Irene Heinz Given and John La Porte Given Endowment, and Hope for Vision.

More on SciTechDaily

AI Transforms Drug Discovery With Faster, Safer Cancer Treatments

Astronomers Reveal Previously Unknown Details About The Milky Way

New Approach to Gene Therapy: Prime Editing System Inserts Entire Genes in Human Cells

Revolutionizing Water Decontamination With Plasma Technology

Brain-Eating Amoeba Meets Its Match: Unusual Giant Virus Discovered in Austria

Unleashing Photonic Snake States: A New Era of Light Perception

MIT Scientists Find Clues to Why Fake News Snowballs on Social Media

Webb Space Telescope Captures Nearby Planetary System in Breathtaking Detail

Be the first to comment on "gene editing breakthrough: crispr improves vision in clinical trial", leave a comment cancel reply.

Email address is optional. If provided, your email will not be published or shared.

Save my name, email, and website in this browser for the next time I comment.

• Introduction to Genomics
• Educational Resources
• Policy Issues in Genomics
• The Human Genome Project
• Funding Opportunities
• Funded Programs & Projects
• Division and Program Directors
• Scientific Program Analysts
• Contact by Research Area
• News & Events
• Research Areas
• Research investigators
• Research Projects
• Clinical Research
• Data Tools & Resources
• Genomics & Medicine
• Family Health History
• For Patients & Families
• For Health Professionals
• Jobs at NHGRI
• Training at NHGRI
• Funding for Research Training
• Professional Development Programs
• NHGRI Culture
• Social Media
• Broadcast Media
• Image Gallery
• Press Resources
• Organization
• NHGRI Director
• Mission & Vision
• Policies & Guidance
• Institute Advisors
• Strategic Vision
• Leadership Initiatives
• Diversity, Equity, and Inclusion
• Partner with NHGRI
• Staff Search

What’s Happening in Genome Editing Right Now?

In the United States and around the world, scientific institutions are developing recommendations to facilitate decision-making for the responsible use of human genome-editing research.

National Academies of Sciences, Engineering and Medicine

In light of recent advances in gene-editing research and technologies, the National Academies of Sciences, Engineering, and Medicine (NASEM) launched an  initiative  in December 2015 to facilitate decision making for the responsible use of human gene-editing research. This initiative examined the clinical, ethical, legal and social implications of human gene editing. Their efforts included an  international summit , a comprehensive study with a diverse committee of experts, and a series of  public meetings  for the committee to hear from different groups including patients, community leaders and policy makers.

NHGRI uses the term "genome editing" to describe techniques used to modify DNA in the genome. Other groups also use the term "gene editing". In general, these terms are used interchangeably.

International Summit

Along with the academies, the British Royal Society and the Chinese Academy of Sciences co-hosted the  International Summit on Human Gene Editing . The summit lasted three days and included panels that touched upon a range of topics related to gene editing: the history of gene editing, the scientific background of gene editing and CRISPR in particular, the clinical applications of gene editing, germline modifications, somatic cell therapy, societal implications, international perspectives, governance, and issues related to equity and access to technology.

On February 14, 2017, the committee published a report of their study findings titled,  Human Genome Editing: Science, Ethics, and Governance . Based on input from public meetings and stakeholders in and out of the scientific community, the report identified seven overarching principles to guide the research and clinical use of genome editing technologies. Most notably, the report concluded that while current regulations are sufficient to oversee the use of genome editing in basic research and somatic therapy trials, there are still safety, technical, and ethical issues barring the wide application of this technology in germline therapy trials. The committee recommended a set of very strict criteria to permit clinical trials for germline therapy. The report stated gene therapy trials should be limited to treatment and prevention of disease or disability, but also suggested there should be more public discussion on the permissibility of gene therapy for enhancement purposes.

National Institutes of Health

The  Recombinant DNA Advisory Committee (RAC)  provides the National Institutes of Health (NIH) with recommendations on basic and clinical research involving recombinant DNA (in which genes from different sources are combined). On June 21-22, 2016, the RAC met to review a series of human gene transfer protocols. Among the protocols was one that proposed the use of CRISPR to edit the T cells (a type of immune cell) of patients suffering from some types of advanced cancers, namely myeloma, melanoma and sarcoma. It would be one of the first studies in the US to use CRISPR in humans.  1 , 2

Because CRISPR is an important tool for basic genomics research, NHGRI currently conducts and funds research that uses CRISPR technology. For instance:

• NHGRI's Embryonic Stem Cell and Transgenic Mouse Core uses CRISPR to generate laboratory mice with specific gene alterations for the study of human genetic diseases. Many NHGRI researchers take advantage of this resource.
• The Knockout Mouse Project (KOMP) is an National Institutes of Health (NIH) Common Fund initiative that NHGRI helped develop. It was designed to generate mice containing mutations in every gene of the mouse genome. For KOMP2, researchers are using CRISPR to create these mice more efficiently. Any researcher can purchase these mice for their research.
• Dr. Shawn Burgess' lab at NHGRI has developed a high-throughput pipeline that can create multiple, simultaneous gene knockouts using CRISPR/Cas9 in zebrafish (Varshney, et al., 2015). The lab has also created a database called  CRISPRz  that catalogs CRISPR targets in zebrafish. These target DNA sequences can be used by other researchers to identify areas of interest for their research.

[1] The first study to use CRISPR in humans took place in October 2016 in a clinical trial by a team from Sichuan University in China:

Cyranoski, D. CRISPR gene-editing tested in a person for the first time.  Nature , November 15, 2016. [ Full Text ]

[2] Reardon, S. First CRISPR clinical trial gets green light from US panel.  Nature News,  June 22, 2016. [ Full Text ]

Last updated: May 14, 2018

• Skip to main content
• Skip to main navigation
• Awards & Honors
• News by topic
• News archives
• E-Newsletter
• Tuesday Newsday
• UCSC Magazine
• Administrative Messages

Home / 2024 / May / Tiny target discovered on RNA to short-circuit inflammation

New study discovers tiny target on RNA to short-circuit inflammation

Paper details high-throughput process for rapid screening, identification of mysterious ‘long non-coding RNA’

May 24, 2024

By Mike Peña

UC Santa Cruz researchers have discovered a peptide in human RNA that regulates inflammation and may provide a new path for treating diseases such as arthritis and lupus. The team used a screening process based on the powerful gene-editing tool CRISPR to shed light on one of the biggest mysteries about our RNA–the molecule responsible for carrying out genetic information contained in our DNA.

This peptide originates from within a long non-coding RNA (lncRNA) called LOUP. According to the researchers, the human genome encodes over 20,000 lncRNAs, making it the largest group of genes produced from the genome. But despite this abundance, scientists know little about why lncRNAs exist or what they do. This is why lncRNA is sometimes referred to as the "dark matter of the genome."

The study , published May 23 in the Proceedings of the National Academy of Sciences (PNAS), is one of the very few in the existing literature to chip away at the mysteries of lncRNA. It also presents a new strategy for conducting high-throughput screening to rapidly identify functional lncRNAs in immune cells. The pooled-screen approach allows researchers to target thousands of genes in a single experiment, which is a much more efficient way to study uncharacterized portions of the genome than traditional experiments which focus on one gene at a time.

The research was led by immunologist Susan Carpenter, a professor and Sinsheimer Chair of UC Santa Cruz's Molecular, Cell, and Developmental Biology Department . She studies the molecular mechanisms involved in protection against infection. Specifically, she focuses on the processes that lead to inflammation to determine the role that lncRNAs play in these pathways. 

"Inflammation is a central feature of just about every disease," she said. "In this study, my lab focused on trying to determine which lncRNA genes are involved in regulating inflammation."

This meant studying lncRNAs in a type of white blood cell known as a monocyte. They used a modification of the CRISPR/Cas9 technology, called CRISPR inhibition (CRISPRi), to repress gene transcription and find out which of a monocyte's lncRNAs play a role in whether it differentiates into a macrophage—another type of white blood cell that's critical to a well-functioning immune response.

In addition, the researchers used CRISPRi to screen macrophage lncRNA for involvement in inflammation. Unexpectedly, they located a region that is multifunctional and can work as an RNA as well as containing an undiscovered peptide that regulates inflammation.

Understanding that this specific peptide regulates inflammation gives drugmakers a target to block the molecular interaction behind that response in order to suppress it, Carpenter said. "In an ideal world, you would design a small molecule to disrupt that specific interaction, instead of, say, targeting a protein that might be expressed throughout the body," she explained. "We're still a long way from targeting these pathways with that level of precision, but that’s definitely the goal. There's a lot of interest in RNA therapeutics right now."

Co-authors of the study from UC Santa Cruz include Haley Halasz, Eric Malekos, Sergio Covarrubias, Samira Yitiz, Christy Montano, Lisa Sudek, and Sol Katzman, along with researchers at UCSF and MIT. The research was supported with funding from the National Institute of General Medical Sciences (R35GM137801 to Carpenter) and the National Institute of Allergy and Infectious Diseases (F31AI179201 to Malekos).

University News

• University News Home
• Monthly Newsletter

Other News & Events

• Campus Calendars

• UCSC Chancellor
• Press Releases
• Contacts for Reporters
• Send us an email
• Report an accessibility barrier
• Land Acknowledgment
• Accreditation

Last modified: May 24, 2024 128.114.113.87

share this!

May 29, 2024

This article has been reviewed according to Science X's editorial process and policies . Editors have highlighted the following attributes while ensuring the content's credibility:

fact-checked

peer-reviewed publication

trusted source

Researchers find RNA editing sites likely play a more significant role in genetic disease

by Ellen Goldbaum, University at Buffalo

New findings by University at Buffalo researchers reveal that RNA editing may play a larger role in human biology and in the development of human disease than has generally been understood.

In an article published in Communications Biology on May 4, the study's authors conclude that the work provides evidence for a more nuanced understanding of how molecular biology works, especially in terms of how proteins and genes respond to environmental challenges .

RNA editing sites cause changes in single nucleotide polymorphisms (SNPs)—the most common type of genetic variation in humans—in transcribed genes that can lead to the coding of different proteins. The expression of these different proteins may in turn be a factor in a broad range of human diseases.

Changing biology

"External phenomena can make changes in your biology to change how you respond to challenges you're facing, whether that's infectious disease or climate change ," explains Peter L. Elkin, MD, corresponding author and professor and chair of the Department of Biomedical Informatics in the Jacobs School of Medicine and Biomedical Sciences at UB.

With these types of challenges, he continues, interferon gets upregulated, which stimulates the release of APOBEC enzymes, a family of enzymes that edit RNA.

The research focuses on this family of enzymes. Elkin's team found that 4.5% of SNPs that result in a specific type of change in DNA are probable sites for RNA editing. If this type of RNA editing occurs at even a fraction of these sites, the authors state, it could have meaningful effects on human health.

Previous work has shown some relation between APOBEC-mediated RNA editing and certain autoimmune and neurological diseases. Elkin adds that about 70% of genetic neurological diseases involve at least one RNA editing site.

"There are specific areas in the genome that we found are susceptible to these kinds of changes," he says, which suggests that RNA editing sites could therefore have a significant effect on genetic diseases.

The researchers were further intrigued when their collaborators at Roswell Park Comprehensive Cancer Center found RNA editing sites were involved in particular cancers.

"It began to occur to me that RNA editing sites could have a bigger role in disease than was previously thought," Elkin says.

To discover all RNA editing sites in the genome, the team developed a computational tool called RNAsee, which they validated with machine learning.

The tool revealed that 22.7% of the potential editing sites found by RNAsee were labeled as likely pathogenic or pathogenic, compared to only 9.2% labeled as likely benign or benign.

The authors write that this finding demonstrates that the type of RNA editing they studied "has a substantial possibility of negatively influencing human health."

"This work adds another dimension to our understanding of how our proteome develops," says Elkin, referring to the complete set of proteins that humans express.

The next step in the work, he adds, would be for researchers who are working on the genetics of specific diseases where RNA editing sites have been found to follow up on these findings.

"My hope is that researchers will follow up with basic experiments looking at genes of interest where we have found RNA editing sites," says Elkin.

Journal information: Communications Biology

Provided by University at Buffalo

Explore further

Feedback to editors

Antibiotic pollution disrupts the gut microbiome and blocks memory in aquatic snails, study finds

A new Hungarian method may aid protein research

3 hours ago

Symbiosis study exposes new 'origin' theories, identifies experimental systems for plant life

AIM algorithm enhances super-resolution microscope images in real time

Study reveals maintenance of male-related genes after loss of males in stick insects

4 hours ago

Research team shows theoretical quantum speedup with the quantum approximate optimization algorithm

New wind speed sensor uses minimal power for advanced weather tracking

New sensing techniques can detect drought tolerance in ancient crops, may inform new breeding programs

Researchers apply quantum computing methods to protein structure prediction

5 hours ago

Abandoned farmlands could play a role in fighting climate change. A study shows exactly where they are

Relevant physicsforums posts, a dna animation.

14 hours ago

Probability, genetic disorder related

May 28, 2024

Looking For Today's DNA Knowledge

May 27, 2024

Covid Vaccines Reducing Infections

Human sperm, egg cells mass-generated using ips, and now, here comes covid-19 version ba.2, ba.4, ba.5,....

May 25, 2024

More from Biology and Medical

Related Stories

Study unveils mysterious nature of RNA editing in plants

May 9, 2023

Genome-editing tool TALEN outperforms CRISPR-Cas9 in tightly packed DNA

Jan 27, 2021

Researchers identify RNA editing events that impact gene expression and phenotype

Mar 9, 2021

Researchers develop DANGER analysis tool for the safer design of gene editing

Oct 23, 2023

Geneticists develop novel base editors

Aug 29, 2023

New way to identify RNA variants could make CRISPR gene editing more effective

Jun 29, 2023

Recommended for you

Understanding plant breathing: Study identifies the key protein interplay behind rhythmic stomatal movements

8 hours ago

Scientists identify gene that could lead to resilient 'pixie' corn

9 hours ago

New antibiotic kills pathogenic bacteria, spares healthy gut microbes

10 hours ago

Let us know if there is a problem with our content

Use this form if you have come across a typo, inaccuracy or would like to send an edit request for the content on this page. For general inquiries, please use our contact form . For general feedback, use the public comments section below (please adhere to guidelines ).

Please select the most appropriate category to facilitate processing of your request

Thank you for taking time to provide your feedback to the editors.

Your feedback is important to us. However, we do not guarantee individual replies due to the high volume of messages.

E-mail the story

Your email address is used only to let the recipient know who sent the email. Neither your address nor the recipient's address will be used for any other purpose. The information you enter will appear in your e-mail message and is not retained by Phys.org in any form.

Newsletter sign up

Get weekly and/or daily updates delivered to your inbox. You can unsubscribe at any time and we'll never share your details to third parties.

More information Privacy policy

Donate and enjoy an ad-free experience

We keep our content available to everyone. Consider supporting Science X's mission by getting a premium account.

E-mail newsletter

An official website of the United States government

The .gov means it's official. Federal government websites often end in .gov or .mil. Before sharing sensitive information, make sure you're on a federal government site.

The site is secure. The https:// ensures that you are connecting to the official website and that any information you provide is encrypted and transmitted securely.

• Publications
• Account settings
• Browse Titles

NCBI Bookshelf. A service of the National Library of Medicine, National Institutes of Health.

National Academies of Sciences, Engineering, and Medicine; National Academy of Medicine; National Academy of Sciences; Committee on Human Gene Editing: Scientific, Medical, and Ethical Considerations. Human Genome Editing: Science, Ethics, and Governance. Washington (DC): National Academies Press (US); 2017 Feb 14.

Human Genome Editing: Science, Ethics, and Governance.

• Hardcopy Version at National Academies Press

3 Basic Research Using Genome Editing

The recent remarkable advances in methods for editing the DNA of genes and genomes have engendered much excitement and activity and had a major impact on many areas of both basic and applied research. It has been known for 60 years that all life on Earth is encoded in the sequence of DNA, which is inherited in each succeeding generation, but accelerating advances have greatly enhanced understanding of and the ability to manipulate DNA.

This chapter reviews the various types of and purposes for basic laboratory research involving human genome editing. It begins by describing the basic tools of genome editing and the rapid advances in genome-editing technology. The chapter then details how genome editing can be used in basic laboratory research aimed at advancing understanding of human cells and tissues; of human stem cells, diseases, and regenerative medicine; and of mammalian reproduction and development. Ethical and regulatory issues entailed in this research are then summarized. Throughout the chapter, key terms and concepts germane to basic research involving genome editing are defined; Box 3-1 defines the most foundational of these terms.

Foundational Terms.

• THE BASIC TOOLS OF GENOME EDITING

All living organisms, from bacteria to plants to humans, use similar mechanisms to encode and express genes, although the sizes of their genomes and their numbers of genes differ greatly. Hence, understanding of any form of life is immensely informative with respect to understanding all other forms, and provides insights and applications that obtain across species—a fact that has been particularly invaluable in the development of methods for editing genes and genomes.

The earliest studies in molecular biology were on bacteria and their viruses. Their relative simplicity and ease of analysis were key in establishing the basis of the genetic code and the expression of genes. Parallel research on more complex organisms built on the advances in these studies of bacteria, and by the mid-1960s, it was clear that bacteria, plants, and animals shared many fundamental molecular mechanisms. Key discoveries in bacteria uncovered some of their mechanisms for protection against viruses, including so-called restriction endonucleases, proteins bacteria use to cleave the DNA of infecting viruses and “restrict” their growth. This discovery allowed scientists to cut DNA in predictable and reproducible ways and to reassemble the cut pieces into recombinant DNA.

By the mid-1970s, it was evident that recombinant DNA offered a powerful means of combining DNA in productive ways, with promising applications in biotechnology. However, this potential also raised questions about whether the application of these novel methods might entail some risk. In light of those concerns, a group of scientists and others convened a meeting at Asilomar in 1975 to consider what precautions might be needed to oversee this new technology and established a set of guidelines to regulate the containment and conduct of the research. The descendants of those guidelines still regulate recombinant DNA research to this day, some of them incorporated into official regulatory systems. In practice, the most extreme concerns did not eventuate. Today, the use of recombinant DNA methods is widespread worldwide and has yielded enormous benefits to humankind in terms of scientific understanding and medical advances, including many valuable drugs and treatments, and the biotechnology industry is now a thriving part of the world economy.

Among methods developed through the use of recombinant DNA technology is the ability to introduce DNA into cells where it can be expressed—a so-called transgene. This method is widely used in fundamental laboratory research (see Appendix A for more detail). When such exogenous DNA is introduced into a cell, it can insert into the DNA of the cell's genome largely at random and, depending on how and where it is inserted, can be expressed as RNA and protein, although this overall process is not very efficient. A key advance was the development of techniques for generating molecular tools that could be used to cut the DNA of genes and genomes in specific places to allow targeted alterations in the DNA sequence. It was found that double-strand breaks (DSBs) could be deliberately generated by nucleases that cut DNA at defined sites ( homing nucleases , sometimes also called meganucleases , originally discovered in yeast) ( Choulika et al., 1995 ; Roux et al., 1994a , b ). In the succeeding 20 years, based on these groundbreaking discoveries, several additional types of nucleases that can be targeted to specific sites were developed and adapted for use in targeted DNA cleavage ( Carroll, 2014 ).

Such double-strand breaks also occur naturally during DNA replication or through radiation or chemical damage, and cells have evolved mechanisms for repairing them by rejoining the ends (a process known as nonhomologous end joining [NHEJ ]). However, this rejoining often is not perfect, and small insertions and deletions can be introduced during the repair. Such insertions and deletions ( indels ) can disrupt the sequence of the DNA and often inactivate the gene that was cut. This targeted cleavage and inaccurate repair through NHEJ provide a means of inactivating genes or gene-regulatory elements. Although the resulting indels are usually one or a few nucleotides long, in some cases they can consist of thousands of base pairs. Genome editing through NHEJ can also be harnessed to create defined chromosomal deletions or chromosomal translocations by simultaneously creating two double-strand breaks at different sites, followed by rejoining at those two sites. These sites can be either on the same chromosome (producing a deletion) or on different chromosomes (producing a translocation).

More precise editing can be achieved if, during the breakage-repair process in the cell, an extra piece of DNA is provided that shares sequence (i.e., is homologous) with the cleaved DNA. Such homologous repair also is used by normal cellular repair mechanisms. These mechanisms can be exploited to make precise changes. If homologous DNA slightly different in sequence from the cleaved sequence is introduced into the cell, that difference can be inserted into the sequence of the gene or genome, a process termed homology-directed repair (HDR) . HDR can also be used to insert a novel sequence (e.g., one or more genes) of variable length at a precise genomic location. In contrast to NHEJ, HDR-mediated genome editing allows scientists to predict both where the edit will occur and the size and sequence of the resulting change. Thus, HDR-mediated editing is very much like editing a document because precise changes in the characters can be made.

Two types of targeted nucleases that have been widely developed for use in editing genes and genomes are zinc finger nucleases (ZFNs) and transcription activator-like effector nucleases (TALENs) . Both rely on proteins whose normal function is to bind to specific relatively short DNA sequences. Zinc fingers are segments of proteins used by multicellular organisms to control the expression of their genes by binding to DNA (they also typically bind zinc as part of their structure; hence their name). They can be engineered by molecular biologists to recognize different short DNA sequences and can be joined to nucleases that cleave DNA. Thus, the zinc fingers target specific sequences in genes and genomes, and the attached nucleases cleave the DNA to generate a double-strand break by cleaving both strands of the DNA. ZFNs have been developed for gene editing and are in clinical trials—for example, in attempts to confer resistance to the HIV virus in AIDS patients ( Tebas et al., 2014 ). TALENs work similarly to ZFNs, also using DNA recognition proteins (transcription activator-like effectors or TALEs) originally identified in bacteria that infect plants. The DNA recognition sequences of TALE proteins are made of repeating units, each of which recognizes a single base pair in the DNA. TALEs are simpler and easier to engineer than are zinc fingers and can similarly be joined to DNA-cleaving nucleases to yield TALENs. The preclinical application of TALENs to engineer lymphocytes for the treatment of acute lymphoblastic leukemia was recently reported ( Poirot et al., 2015 ).

Thus, these tools are already well-established approaches to the use of genome editing for applications in gene therapy, and many of the associated safety and regulatory issues have already been addressed (see Chapter 4 ). However, the protein engineering required to design site-specific versions of TALENs and, even more so, of ZFNs, remains technically challenging, time-consuming, and expensive.

The past 5 years have seen the development of a completely novel system, known as CRISPR/Cas9 (CRISPR stands for clustered regularly interspaced short palindromic repeats) ( Doudna and Charpentier, 2014 ; Hsu et al., 2014 ). Short RNA sequences modeled on the CRISPR system, when paired with Cas9 (CRISPR associated protein 9, an RNA-targeted nuclease), or alternatively with other similar nucleases, can readily be programmed to edit specific segments of DNA. The CRISPR/Cas9 system is simpler, faster, and cheaper relative to earlier methods and can be highly efficient. CRISPR/Cas9, like TALEs, was originally discovered in bacteria, where it functions as part of an immunity system to protect bacteria from invading viruses ( Barrangou and Dudley, 2016 ; Doudna and Charpentier, 2014 ). The key distinguishing feature of CRISPR/Cas9 is that it uses RNA sequences instead of protein segments to recognize specific sequences in the DNA by complementary base pairing.

As first reengineered in 2012 ( Jinek et al., 2012 ), the bacterial nuclease Cas9 binds a single RNA sequence known as a guide RNA tailored to recognize any sequence of choice. This two-component system can bind to the chosen site in DNA via the guide RNA and cleave the DNA using the Cas9 nuclease. Since it is simple to synthesize RNA of any desired sequence, generation of CRISPR/Cas9 targeting nucleases is straightforward—the system is readily programmed to target any sequence in any genome. Programs exist for choosing suitable guide RNAs, and while not all guides work equally well, testing a number of guides to find effective ones is not difficult or expensive. This ease of design, together with the remarkable specificity and efficiency of CRISPR/Cas9 has revolutionized the field of genome editing and has major implications for advances in fundamental research, as well as in such applications as biotechnology, agriculture, insect control, and gene therapy.

Figure 3-1 provides a summary of the ZFN, TALEN, and CRISPR methods of genome editing. As mentioned, these genome-editing methods are being widely applied across a broad range of biological sciences, from fundamental laboratory research on cells and laboratory animals; to applications in agriculture involving improvements in crop plants and farm animals; to applications in human health, both at the research level and, increasingly, in clinical applications. Agricultural applications have been addressed in other studies by the U.S. National Academies of Sciences, Engineering, and Medicine (see Chapter 1 ) and potential clinical applications are the subject of subsequent chapters of this report. The focus in this chapter is on basic laboratory research using genome editing.

Methods of genome editing. Top: Zinc finger nucleases (ZFNs): The colored modules represent the Zn fingers, each engineered to recognize three adjacent base pairs in the DNA; these modules are coupled to a dimer of the FokI nuclease that makes a double-stranded (more...)

This research addresses fundamental questions concerning the use and optimization of genome-editing methods both in cultured cells and in experimental multicellular organisms (e.g., mice, flies, plants). Such basic discovery research is essential for improving any future applications of genome editing. Applications of genome editing in laboratory research also have added powerful new tools that are contributing greatly to understanding of basic cellular functions, metabolic processes, immunity and resistance to pathological infections, and diseases such as cancer and cardiovascular disease. These laboratory studies are overseen by standard laboratory safety mechanisms. In addition to these applications, this chapter reviews the potential for using similar approaches in basic research on human germline cells, not for the purposes of procreation but solely for laboratory research. This work will provide valuable insights into the processes of early human development and reproductive success, and could lead to clinical benefits, directly as a result of work with human embryos and germline cells or through improvements in the derivation and maintenance of stem cells in vitro.

• RAPID ADVANCES IN GENOME-EDITING TECHNOLOGY

The development of CRISPR/Cas9 has revolutionized the science of gene and genome editing, and the basic science is advancing extremely rapidly, with additional CRISPR-based systems being developed and deployed for multiple different purposes. Different species of bacteria use somewhat different CRISPR systems, and although the CRISPR/Cas9 system is currently the most widely used because of its simplicity, alternative systems being developed will provide increased flexibility in methodology ( Wright et al., 2016 ; Zetsche et al., 2015 ).

Among the issues that need to be addressed going forward are the specificity and efficiency of the DNA cleavage mediated by CRISPR-guided nucleases. While the roughly 20-base sequence recognized by the guide RNA provides a great deal of specificity (an exact match should occur by chance in approximately 1 × 10 12 base pairs—1 in a trillion—the equivalent of several hundred mammalian genomes), there is some small potential for so-called off-target events , in which the nucleases make cuts in unintended places, especially if the guide RNA binds to DNA sequences that are slightly different from the intended target. Some early experiments suggested that off-target events might occur at a significant rate, but as the methods have been improved and as their application has increasingly been in normal cells rather than cultured cell lines, the frequency of off-target cleavages appears to be very low. Advances have been achieved in the specificity of Cas9 cleavage ( Kleinstiver et al., 2016 ; Slaymaker et al., 2016 ), and methods have been developed for monitoring the frequency of off-target cleavage. (See Appendix A for more detail.)

Another significant advance has occurred in the development of methods for modifying the CRISPR/Cas9 system so that DNA cleavage is avoided. For example, the nuclease function of Cas9 can be inactivated so that a complex of guide RNA and such a “dead” Cas9 (dCas9) will target a specific site via the guide RNA but will not cleave the DNA ( Qi et al., 2013 ). By coupling other proteins with different activities to the dCas9, however, different sorts of modifications can be made to the DNA or its associated proteins. Thus, it is possible to design variants of CRISPR/Cas9, ZFN, or TALE that will turn on or turn off adjacent genes, make single-base changes, or modify the chromatin proteins that associate with DNA in chromosomes and thus modify the epigenetic regulation of genes ( Ding et al., 2016 ; Gaj et al., 2016 ; Konerman et al., 2015 ; Sander and Joung, 2014 ). All of these noncleaving variants fail to cleave DNA, thus reducing the potential for deleterious off-target events, and many other modifications are being introduced to enhance specificity and reduce off-target events (see Appendix A for further detail). Most recently, CRISPR/C2c2, a programmable RNA-guided, RNA-cleaving nuclease, has been described ( Abudayyeh et al., 2016 ; East-Seletsky et al., 2016 ) that could be used to knock down specific RNA copies of genes without affecting the gene itself. This development raises the future possibility of nonheritable or reversible editing.

As can be seen from this brief survey, the rapidly developing versatility of these RNA-guided genome-editing systems is opening up numerous means of manipulating the expression and function of genes. A recent report of methods for inducibly knocking down or knocking out genes in a multiplex fashion in many cell types, including human pluripotent stem cells, as well as in mice ( Bertero et al., 2016 ) further expands the potential of these methods. These and other advances have rapidly rendered these methods basic tools of molecular biology worldwide, adding to the existing toolkit assembled over the past 40 years. These methods are now being applied to study with unprecedented ease the functions of genes in cells and in experimental animals, such as yeast, fish, mice, and many others, to enhance understanding of life. They also are being used to investigate the derivation and differentiation of stem cells, providing fundamental insights relevant to regenerative medicine, and to develop culture models of human disease both to advance understanding of disease processes and to enable testing of drugs on human cells ex vivo.

• BASIC LABORATORY RESEARCH TO ADVANCE UNDERSTANDING OF HUMAN CELLS AND TISSUES

Basic biomedical research aimed at discovering more about the mechanisms and capabilities of genome editing offers significant opportunities to advance human medicine. Genome-editing research conducted on human cells, tissues, embryos, and gametes in the laboratory offers important avenues for learning more about human gene functions, genomic rearrangements, DNA-repair mechanisms, early human development, the links between genes and disease, and the progression of cancer and other diseases that have a strong genetic basis. Manipulation of genes and gene expression by genome editing allows one to understand the functions of genes in the behavior of human cells, including why they malfunction in disease. For example, editing of cultured human cells to model the changes that arise in cancer or in genetically inherited diseases provides culture models of those diseases with which to understand the molecular basis of the resulting defects. Such laboratory studies also allow the development of means of combating those defects, such as the testing of potential drugs in cell culture. All of those approaches are much easier now than they were just a few years ago.

Certain cells derived from an early embryo, after fertilization but prior to the developmental stage at which it would implant in a woman's uterus, are referred to as embryonic stem (ES) cells. These ES cells have scientific advantages because they can reproduce in cell culture and have the potential to form all the different body cell types while lacking the potential themselves to develop into a fetus. It is now also possible to create stem cells by manipulating adult somatic cells to convert them to a state in which they, too, have the ability to form multiple cell types, reducing the need to take stem cells from an early embryo. These are referred to as induced pluripotent stem (iPS) cells. Such pluripotent stem cells can be cultured in vitro and induced to develop into many different cell types, such as neurons, muscle or skin cells, and many others. Advances over the past several decades in understanding stem cells and how they can be used form the foundation for the field of regenerative medicine, which seeks to repair or replace damaged cells within human tissues or to generate new tissues after disease or injury. Although these are increasingly areas of clinical practice, and the application of genetically altered cells in humans is not covered in this chapter (see Chapter 4 ), there are nevertheless a number of important reasons why scientists aim to undertake basic investigations in human and animal stem cells in the laboratory.

Genome-editing methods have been extremely useful in generating a variety of genetic modifications in human ES and iPS cells. Before the advent of efficient genome-editing tools, these cells had proven resistant to genetic modification with the standard tools of homologous recombination that had been used effectively in mouse ES cells. Using those tools in human cells resulted in very low frequencies of targeted recombination. Improvements in efficiency resulting from the use of CRISPR/Cas9 have enabled rapid generation of tagged reporter cell lines, making it possible to follow differentiation pathways, look for interacting proteins, sort appropriate cell types, and investigate the functions of individual genes and pathways in cells, among many other applications ( Hockemeyer and Jaenisch, 2016 ). For example, the ability to make precisely targeted mutations or corrections in specific genes has made possible the generation of human ES lines with different specific disease alleles on the same genetic background ( Halevy et al., 2016 ) for use in research on the consequences of such disease genes. Conversely, genome editing also allows the targeted correction of disease mutations in patient-specific iPS cell lines to generate genetically matched control lines. Such modified stem cell lines are used primarily to conduct experimental and preclinical studies, to investigate specific disease processes, and to test drugs that could be used to treat such diseases. In the future, such edited stem cell lines could be used for various forms of somatic cell–based therapies (see Chapter 4 ).

• BASIC LABORATORY RESEARCH TO ADVANCE UNDERSTANDING OF MAMMALIAN REPRODUCTION AND DEVELOPMENT

Germline cells are cells with the capacity to be involved in forming a new individual and to have their genetic material passed on to a new generation. They include precursor cells that form eggs and sperm, as well as the eggs and sperm cells themselves. When fertilization occurs to create an embryo, the earliest stages of this embryo, referred to as the zygote (fertilized egg) and blastocyst, have the potential to divide and form all the cells that will make up the future individual, including somatic (body) cells and new germ cells. As the embryo continues to develop, its cells differentiate into specific cell types that become increasingly restricted in their functions (e.g., to form specialized cells such as those in the nervous system, skin, or gut).

During reproduction and development, genetic changes made directly in gametes (egg and sperm), in egg or sperm precursor cells, or in very early embryos would be propagated throughout the future cells of an organism and may therefore be heritable by subsequent generations. As emphasized above, this chapter focuses exclusively on the use of genome-editing technologies in the laboratory, and not on clinical applications in humans or in embryos for the purposes of implantation to initiate pregnancy. Nevertheless, it is important to understand which cell types are involved in human development and their functions, because this information informs researchers' decisions about how to study particular scientific questions and informs ethical, regulatory, and social discussions around when and why it may be useful to use human cells, including embryos, in basic laboratory research.

Genome Editing of Germline Stem Cells and Progenitor Cells

It is already possible in mice to genetically modify the genome in a fertilized egg (the zygote), in individual cells of the early embryo, in pluripotent ES cells, or in spermatogonial stem cells, just as in somatic cells. In all these cases, the effects of the genetic modifications can be studied directly in the embryo or in cells in culture. There are a number of ways to undertake these genetic manipulations and a number of cell types in which they can be conducted. The cell types below are all considered part of the germline or have the capacity to contribute to the germline:

• embryonic stem cells derived from normal early embryos (blastocyst stages)
• cells from early embryos produced after somatic cell nuclear transfer (SCNT) 1
• iPS cells obtained by reprogramming somatic cells into an ES celllike state

In mice, these cell types can all be manipulated experimentally through genome editing. Stem cells of the types listed above can contribute to the germline in vivo after they are introduced into mouse embryos at the morula or blastocyst stage. This process generally creates an embryo that is a chimera, in which some cells are derived from the stem cells introduced into the embryo, and some are formed from the initial embryonic cells. Mouse or rat spermatogonial stem cells can be cultured and their genomes edited, and the cells can then be introduced into recipient mouse or rat testes, where they can give rise to sperm able to fertilize oocytes, at least in vitro (see Appendix A and Chapman et al., 2015 ). In all of these cases, when the resultant embryos are transferred back into the uterus to complete pregnancy, it is possible to establish lines of mice carrying the genetic alterations. These approaches provide unprecedented opportunities to explore the functions of all the genes in the genome and to develop rodent models of human diseases. Proof-of-principle experiments also have been reported in which disease-related genetic mutations have been corrected in mouse zygotes ( Long et al., 2014 ; Wu et al., 2013 ), embryonic stem cells, or spermatogonial stem cells ( Wu et al., 2015 ) and then transmitted though the germline to produce genetically corrected mice.

The application of genome-editing technologies to the equivalent human cell types holds considerable potential value for fundamental research without any intent to use such manipulated cells for human reproductive purposes. Improved knowledge of how an early human embryo develops also is valuable in its own right, and because such knowledge can help answer questions about humans' own early development, as well as facilitate understanding and potential prevention or treatment of a wide range of clinical problems. A number of these applications are described below.

Improvements in Assisted Reproductive Technology

The success of human reproductive technologies and preimplantation genetic diagnosis (PGD) of inherited diseases has been, and continues to be, dependent on in vitro fertilization (IVF) and on culturing of human embryos from the zygote to the blastocyst stage. However, tools for ensuring that an individual embryo in culture is normal and capable of completing pregnancy remain limited. Most embryo research has been conducted on mouse embryos, which are similar to human embryos in certain respects but significantly different in others (see Box 3-2 ). Even the conditions in which human embryos are kept in culture are based largely on those established for mouse embryos. High rates of aneuploidy 2 are found in cultured human embryos relative to other species. This aneuploidy is often mosaic—that is, it varies among cells in the embryo ( Taylor et al., 2014 )—but how it arises and how it relates to in vitro culture conditions are not well understood. There is also concern that epigenetic 3 abnormalities might occur in human embryos in vitro ( Lazaraviciute et al., 2014 ), which might compromise development or health, even later in life. Research on early-stage human embryos in culture should enable scientists to better understand the cellular and molecular pathways that control early human embryo development and the conditions under which human embryos in culture can develop successfully. This knowledge could in turn help improve IVF outcomes.

Differences Between Mouse and Human Development.

All of the differences between humans and mice discussed above mean that it is not possible to accurately infer developmental events in human embryos from studying mice. This limitation has practical consequences for the development of improved IVF technologies, as well as for the ability to derive the best pluripotent or other stem cells for modeling of human disease and for future regenerative therapies. Thus, there is considerable interest in experimental investigation of preimplantation human development in culture, in jurisdictions where such research on human embryos is permitted. The goals of this work are to understand the fundamental events of fertilization, activation of the embryonic genome, cell lineage development, epigenetic events such as X-inactivation, and others, and how these events compare and contrast with what is understood from studying mice.

Similar research also could provide insights into the reasons for the high rates of early pregnancy loss in natural human pregnancies (10 to 45 percent, depending on the age of the mother), as well as the causes of infertility. Better understanding of sperm development would be crucial in addressing issues of male infertility. Pluripotent stem cells arise from the early embryo, and these cells can generate ES cells in culture. Better understanding of human embryonic development would provide insights into the origins and regulation of pluripotency and how to translate that knowledge into improved stem cells for regenerative medicine. The potential benefits of such research are not limited to embryonic stem cells. Cell types that give rise to the yolk sac and the placenta also are determined in the early embryo prior to implantation. The yolk sac and placenta establish the crucial links with the mother during pregnancy and provide nutrients and other factors that enable the embryo to survive. Defects in these tissues can compromise a pregnancy, leading to miscarriage, premature birth, or postnatal abnormalities. Better understanding of how the yolk sac and placenta originate would help in improving techniques for overcoming infertility and preventing early miscarriage, as well as understanding and preventing congenital malformations. These extraembryonic cell types also provide cues that pattern the early postimplantation embryo, although almost nothing is known about these processes in humans. These possibilities and others discussed in this chapter are summarized in Table 3-1 .

Reasons for Laboratory Studies of Human Embryos.

Understanding of Human Development

Genome editing by CRISPR/Cas9 and similar techniques has a key place in the tool set needed to undertake such experiments. CRISPR/Cas9guided activation or inactivation of specific target pathways could be used to understand overall gene regulation in development. Indeed, as the efficiency of CRISPR/Cas9 continues to increase, it should be possible to use genome editing to knock out 4 genes in zygotes and study the effects directly in genetically altered embryos. None of these experiments would involve human pregnancies, so none could result in heritable germline modifications. They would all be in vitro experiments, with results being analyzed primarily at the blastocyst stage in the first 1-6 days of development.

In some cases, there could be interest in exploring the effects of altering specific genes at the next stages of human development, notably the early stages after the embryo would implant in a uterus. At present, culture of human embryos up to the stage just prior to germ-layer formation (at 14 days after fertilization or the formation of the “primitive streak”) is permitted in many countries. Improved culture systems that allow human embryos to develop in culture during the implantation period are being developed. Recent results suggest that these systems could be used to study the elaboration of extraembryonic structures and of the epiblast into an “embryonic disc”—processes that occur in humans in ways not found in mice ( Deglincerti et al., 2016 ; Shahbazi et al., 2016 ). These improved cell culture systems, combined with better ways of analyzing gene function using genome editing, can be expected to lead to better understanding of the fundamental processes of early human development. Already at least two research groups (in the United Kingdom and Sweden) have received regulatory permission to carry out CRISPR/Cas9 experiments on human embryos, aimed at addressing these kinds of fundamental biological questions.

Knowledge gained from such studies is expected to inform and improve IVF procedures and embryo implantation rates and reduce rates of miscarriage. Conversely, the same studies may lead to novel methods of contraception. Such research also should lead to better ways of establishing and maintaining stem cells from these early embryonic stages, which could facilitate efforts to derive cell types for studies and treatments of disease and traumatic injury. Knowledge gained from these laboratory studies using genome-editing methods in early human embryos should also provide information about the suitability of these methods for any eventual potential clinical use. That is, basic research can be expected to inform an understanding of the feasibility of making heritable, and preferably non-mosaic, changes in the genome (see Chapter 5 ). Because human embryos that can be used in research are a valuable and relatively scarce resource, it will be important to ensure that the most efficient methods are used for these laboratory studies of their basic biology. Thus, it is likely that in the course of this research, various technical issues associated with improving the use of genome-editing methods in human embryos will be addressed. Relevant questions include

• the type and form of genome-editing components to be introduced;
• whether to use Cas9 or an alternative nuclease;
• what method to use to introduce the genome-editing components—for example, as DNA, mRNA, protein, or ribonucleoprotein complex;
• whether to use single guide RNAs, pairs, or multiple guide RNAs as part of the editing machinery;
• the size of the DNA template and whether such a template is required;
• the optimal timing for genome editing, that is, whether information can be obtained by using two-cell embryos, whether it is necessary to use one-cell embryos, or whether it is best to introduce the reagents along with the sperm during in vitro fertilization;
• whether mosaicism can be tolerated, keeping in mind that it may be an advantage for certain experiments, as when cell fate is to be followed, but may need to be avoided in other cases, such as when investigating a gene whose product is a secreted protein; and
• how to test and improve modified versions of nucleases such as Cas9 or inhibitors of certain repair mechanisms (e.g., an effective inhibitor of nonhomologous end joining may be needed if the experiment demands homology-directed repair [ Howden et al., 2016 ]).

Understanding of Gametogenesis and Infertility

In mice, the generation of spermatogonial stem cell (SSC) lines from the adult testes has provided a rich source of cells with which to study the process of spermatogenesis in vitro and in vivo, after regrafting to the testes. It is possible to alter these cells genetically and study the impact of the changes on the process of spermatogenesis itself or, in mice, the impact on the offspring. It is also possible to correct genetic mutations in the stem cells in vitro using CRISPR/Cas9. Proof of principle for such an approach has been published ( Wu et al., 2015 ). This work used CRISPR/Cas9 editing in mouse SSCs to correct a gene mutation that causes cataracts in mice. The edited SSCs were transferred back to mouse testes, and round spermatids were collected for intracytoplasmic sperm injection (ICSI), a form of IVF, to create embryos. Resulting offspring were correctly edited at 100 percent efficiency. Similar experiments have been conducted using SSCs from other species, including macaques ( Hermann et al., 2012 ). Stable human SSC lines have not yet been reported, but would clearly be an important tool for understanding male infertility and for exploring such issues as the higher rate of mutations associated with age. This is an active area of research because it may enable restoration of fertility in male cancer patients after radiation or chemotherapy. The ability to grow and manipulate human SSCs would, however, raise the possibility of generating human germline alterations if the cells were grafted back to the testes or used in IVF.

Related issues arise from experiments in which both oocytes and sperm progenitors have been generated from mouse ES cells. ES-derived oocytes can be fertilized by normal sperm, and ES-derived spermatids can fertilize eggs by ICSI ( Hayashi et al., 2012 ; Hikabe et al., 2016 ; Saitou and Miyauchi, 2016 ; Zhou et al., 2016 ). Human gametes have not yet been generated successfully from pluripotent stem cells, although two recent papers report the generation of early germ cell progenitors from human ES cells ( Irie et al., 2015 ; Sasaki et al., 2015 ). Through the use of genome-editing methods, this work also highlighted significant differences between mice and humans in the genes involved in specification of primordial germ cells. There is evidence as well that knowledge gained from studying later stages of spermatogenesis in mice may not always be applicable to the same process in humans. These findings reflect the role of research on human cells in answering questions about human biology. If human haploid gametes could be generated from human pluripotent cells, as they can be in mice, it would open up new avenues for understanding gametogenesis and the causes of infertility. It would also open up possibilities for using heritable genome modifications to address health problems that originate from genetic causes.

• ETHICAL AND REGULATORY ISSUES IN BASIC RESEARCH

As described in more detail in Chapter 2 , basic science research performed in the laboratory on somatic cells will be subject to regulation focused on safety for laboratory workers and the environment, including special review by institutional biosafety committees for work involving recombinant DNA. Few new ethical issues are raised, although if the cells and tissues come from identifiable living individuals, donor consent and privacy will be a concern, and in most cases the protocols will be subject to at least some review by institutional review boards.

Research with embryos is more controversial. As noted earlier, research using viable embryos is illegal in a small number of U.S. states ( NCSL, 2016 ), and while permitted in most states, research that exposes embryos to risk generally may not be funded by the U.S. Department of Health and Human Services (HHS); this is due to the Dickey-Wicker Amendment, 5 which has been adopted repeatedly since the 1990s as part of the HHS appropriations process, including in the bills introduced for 2017 funding (see Chapter 2 ). 6 It states

(a) None of the funds made available in this Act may be used for— (1) the creation of a human embryo or embryos for research purposes; or (2) research in which a human embryo or embryos are destroyed, discarded, or knowingly subjected to risk of injury or death greater than that allowed for research on fetuses in utero under 45 CFR 46.204(b) and section 498(b) of the Public Health Service Act (42 U.S.C. 289g(b)). (b) For purposes of this section, the term “human embryo or embryos” includes any organism, not protected as a human subject under 45 CFR 46 as of the date of the enactment of this Act, that is derived by fertilization, parthenogenesis, cloning, or any other means from one or more human gametes or human diploid cells.

The effect of this combination of state and federal law is to make embryo research legal in most of the United States but generally not eligible for HHS funding.

Additional, extralegal oversight of laboratory research using human embryos comes from the stem cell research oversight committees that were widely adopted pursuant to recommendations of the National Academies regarding embryonic stem cell research ( IOM, 2005 ; NRC and IOM, 2010 ). Recently, the International Society for Stem Cell Research, whose membership includes investigators from around the world as well as the United States, adopted guidelines calling for the transformation of these voluntary stem cell research oversight committees into human embryo research oversight (EMRO) committees that would oversee “all research that (a) involves preimplantation stages of human development, human embryos, or embryo-derived cells or (b) entails the production of human gametes in vitro when such gametes are tested by fertilization or used for the creation of embryos” ( ISSCR, 2016a , p. 5). The review would include details of the proposal and the credentials of the researchers under the auspices of these independent, multidisciplinary committees of scientists, ethicists, and members of the public. The proposed committees would assess research goals “within an ethical framework to ensure that research proceeds in a transparent and responsible manner. The project proposal should include a discussion of alternative methods and provide a rationale for employing the requested human materials, including justification for the numbers of preimplantation embryos to be used, the proposed methodology, and for performing the experiments in a human rather than animal model system” ( ISSCR, 2016a , p. 6).

• CONCLUSIONS AND RECOMMENDATION

Laboratory research involving human genome editing—that is, research that does not involve contact with patients—follows regulatory pathways that are the same as those for other basic laboratory in vitro research with human tissues, and raises issues already managed under existing ethical norms and regulatory regimes. This includes not only work with somatic cells, but also the donation and use of human gametes and embryos for research purposes, where this research is permitted. While there are those who disagree with the policies embodied in some of those rules, the rules continue to be in effect. Important scientific and clinical issues relevant to human fertility and reproduction require continued laboratory research on human gametes and their progenitors, human embryos, and pluripotent stem cells. This research is necessary for medical and scientific purposes that are not directed at heritable genome editing, though it will also provide valuable information and techniques that could be applied if heritable genome editing were to be attempted in the future.

RECOMMENDATION 3-1. Existing regulatory infrastructure and processes for reviewing and evaluating basic laboratory genome-editing research with human cells and tissues should be used to evaluate future basic laboratory research on human genome editing.

SCNT is a technique in which the original nucleus of an egg cell is removed and replaced with a “donor” nucleus taken from another cell (e.g., from a somatic cell that has undergone genome editing). This is the technique that was used to create Dolly, the first cloned mammal obtained from an adult cell.

Having a chromosome number that is not an exact multiple of the usual haploid number.

The term “epigenome” refers to a set of chemical modifications to the DNA of the genome and to proteins and RNAs that bind to DNA in the chromosomes to affect whether and how genes are expressed.

A gene is said to be “knocked out” when it is inactivated because the original DNA sequence has either been replaced or disrupted.

Public Law No. 114-113, Division H, Title V, § 508.

§ 508(a) in both S. 3040 and H.R. 5926.

• Cite this Page National Academies of Sciences, Engineering, and Medicine; National Academy of Medicine; National Academy of Sciences; Committee on Human Gene Editing: Scientific, Medical, and Ethical Considerations. Human Genome Editing: Science, Ethics, and Governance. Washington (DC): National Academies Press (US); 2017 Feb 14. 3, Basic Research Using Genome Editing.
• PDF version of this title (3.9M)

In this Page

Recent activity.

• Basic Research Using Genome Editing - Human Genome Editing Basic Research Using Genome Editing - Human Genome Editing

Your browsing activity is empty.

Activity recording is turned off.

Turn recording back on

Connect with NLM

National Library of Medicine 8600 Rockville Pike Bethesda, MD 20894

Web Policies FOIA HHS Vulnerability Disclosure

Help Accessibility Careers

Featured Topics

Featured series.

A series of random questions answered by Harvard experts.

Explore the Gazette

Read the latest.

Had a bad experience meditating? You’re not alone.

Rethinking life-support decisions

What to do about mental health crisis among Black males

New alzheimer’s study suggests genetic cause of specific form of disease.

Neurons with amyloid plaques.

Samantha Laine Perfas

Harvard Staff Writer

Findings eventually could pave way to earlier diagnosis, treatment, and affect search for new therapies

A recent study published in Nature Medicine offers evidence that genetics may be a direct cause of a specific form of Alzheimer’s disease and not merely a risk factor. While most patients currently do not have a clearly identified cause of this devastating illness, researchers found that people with two copies of the gene variant APOE4 are at extremely high risk of developing Alzheimer’s. The finding led them to recommend a new designation that takes this into account, which could lead to up to a fifth of Alzheimer’s patients being classified as having a genetically caused form of the disease. The shift eventually could lead to earlier diagnosis and treatment and affect the search for therapies. Reisa Sperling , a neurologist at Mass General Brigham and an author of the study, explains the importance of the findings. This interview has been edited for clarity and length.

Your study highlights a new, clearly identified genetic component to Alzheimer’s disease worthy of a new designation. Could you explain why that’s significant?

Designating this form of Alzheimer’s disease means a group of people who are extremely likely — I won’t say absolutely, but extremely likely — to develop Alzheimer’s could be treated earlier. This could really have an impact on preventing dementia.

The second thing is there’s been an ongoing debate about whether Alzheimer’s disease has anything to do with amyloid plaques or not. And in this group, they begin to have buildup of amyloid plaques and tau tangles in their late 50s and early 60s, and the likelihood that they will develop symptoms of Alzheimer’s disease is extremely high. So it creates another link in our understanding of the disease process.

And finally, this is a bridge between the rare forms of genetically determined Alzheimer’s disease that are 100 percent penetrant and often affect people in their 40s and 50s. Those cases are often considered such a rarity that they’re not representative of Alzheimer’s disease. So people with two copies of APOE4 are a bit in the middle. This new study really suggests that their biomarkers are similar to what we see in these rare autosomal dominant diseases, and over 90 percent will develop Alzheimer’s pathology in their brains. It links the rare genetic forms of Alzheimer’s to what we call sporadic late-onset Alzheimer’s disease.

Part of this new classification would also make this type of Alzheimer’s one of the most common genetic disorders in the world. Are there benefits to having it classified that way?

I don’t know that I’m the best person to opine on that, but I certainly think there may be important reasons. For example, eventually getting insurance coverage for individuals who are below the age of 65 and need rapid evaluation and treatment for Alzheimer’s disease. Alzheimer’s disease often doesn’t get diagnosed in these individuals because people think they’re too young. Additionally, they may not have insurance coverage for all of the medications required for treatment.

I do think it is important that this is recognized as one of the more common genetic links to Alzheimer’s disease and leads the way to one day being able to treat people who have a strong family history and genetic predisposition. Then we can really think about being aggressive and treating patients early.

“Somehow, we have to turn these findings to — instead of being scary for people — being a sense of hope.” Reisa Sperling

We’ve known for a long time that there is a genetic component to Alzheimer’s disease. Is this one of the first studies to show such a specific genetic link?

No. As I mentioned there are these rare genes that we’ve known for more than 20 years that are very specific and cause Alzheimer’s disease at a much younger age. But this data really suggests that people who have two copies of this particular allele, APOE4, have such a high likelihood of developing Alzheimer’s disease.

So it’s not the first genetic link, but it is the first large study that convincingly says having two copies of this gene really increases the likelihood you will have Alzheimer’s disease. And it’s a more common gene; these other known genes are very rare. But with APOE4, it’s estimated that up to 15 percent of Alzheimer’s patients carry two copies of these alleles (although I will say that estimate is a little different across studies). It is much more common than these very rare autosomal dominant forms.

How common is it in the general population to have two copies of that gene?

Estimated, about 2 percent of the population, so it’s not that common. People having at least one copy of APOE4 is fairly common. Depending on which part of the world you’re from, that can be up to 25 percent. But having two copies is still pretty rare.

There is still so much that we don’t know about Alzheimer’s, but it does seem to be fueled by both genetic and environmental factors. In what ways does this research help push our understanding of the disease overall?

That’s a great question. And for me, this research really does provide support to both camps. One, the likelihood that people with these genes will develop amyloid plaque by the time they’re age 65 is somewhere between 75 and 95 percent. To me that suggests that it is genetically driven.

But there is a variability in the range of when people develop symptoms. And that suggests that there might be environmental or lifestyle factors that can make people’s brains more resilient, or conversely, more vulnerable. This research really supports both ideas that genetics is a major driver in Alzheimer’s disease, but you can modulate your risk of showing symptoms.

Would it be beneficial for people to know early on if they are carriers of these genes?

At this moment, I do not recommend that people who don’t have symptoms get genetic testing or blood-based biomarker testing. I hope that recommendation will change greatly over the next few years.

There are large-scale clinical trials, including the one I run . We’re recruiting people who have evidence of amyloid buildup, but don’t yet have symptoms, and we’re recruiting a lot of people with a family history and have copies of APOE4. If that study and other studies like it succeed in treating people before they have symptoms, then I would recommend testing and trying to get treatment as soon as possible.

But we don’t have that available right now, and I just think we don’t yet know what to do with that information before people have symptoms.

If this new classification did occur, what areas of further research would you be most excited to pursue?

Number one for me is we need to be able to offer treatments to those patients. Right now, there’s actually a black-box warning on some currently approved Alzheimer’s treatments that cautions treating people who have two copies of APOE4 because the risk of side effects is so great. I want to redouble my efforts to make sure we can offer disease-modifying medications in a safe way.

Number two is about the environment. I’m quite interested in what it is that modulates whether people get symptoms sooner rather than later, with this buildup of amyloid that’s genetically determined. How do we understand what factors were protective? That’s a very important area of research to help us understand what can modulate people’s risk of symptoms in the setting of a very strong genetic predisposition.

We talk about this in the study, but I think it’s also important to mention that these studies mostly observed white majority populations. And one of the things we desperately need to know is whether these findings are also true in more ethnic and racially diverse populations. There is some evidence that APOE4 might have a slightly different effect on amyloid in populations who come from communities of color.

Similarly, there are slight differences in the sex effects: Women APOE4 carriers have more likelihood of developing symptoms. I think it’s really important to get more information on representative populations, especially from communities of color, and really help us develop treatments that will work best for everybody.

For people who have Alzheimer’s or loved ones with Alzheimer’s, how do these findings offer hope or shed light on the disease?

This is another tool to be able to find people who have Alzheimer’s disease at an earlier stage and treat them earlier. My dad and my grandfather died of this disease, and I’m a clinical neurologist. When I see people with symptoms, I think this is helping us learn about the underlying causes and will help us in accelerating to find good treatments.

I think it will both help the next generation of people who are likely to develop Alzheimer’s disease, but it will also help us treat people who already have Alzheimer’s disease symptoms because every little bit of information helps us develop better treatments for all.

I really hope this research doesn’t have the effect of just scaring people. I hope it will instead say, “These are important clues so that we can treat people earlier and hopefully prevent dementia.”

Somehow, we have to turn these findings to — instead of being scary for people — being a sense of hope. I hope this means we will be able to find people and treat them before they develop symptoms.

Get the best of the Gazette delivered to your inbox

By subscribing to this newsletter you’re agreeing to our privacy policy

Share this article

You might like.

Altered states of consciousness through yoga, mindfulness more common than thought and mostly beneficial, study finds — though clinicians ill-equipped to help those who struggle

Of the survivors within one study group, more than 40% recovered at least some independence.

Symposium examines thorny, multifaceted dilemma from systemic racism in policing, healthcare to stigma attached to psychotherapy in community

Six receive honorary degrees

Harvard recognizes educator, conductor, theoretical physicist, advocate for elderly, writer, and Nobel laureate

When should Harvard speak out?

Institutional Voice Working Group provides a roadmap in new report

Day to remember

One journey behind them, grads pause to reflect before starting the next

Thank you for visiting nature.com. You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

• View all journals
• Explore content
• About the journal
• Publish with us
• Sign up for alerts
• 13 March 2019

Germline gene-editing research needs rules

You have full access to this article via your institution.

The ethical and moral issues around gene editing in human embryos have become a topic of debate worldwide. Credit: Sandy Huffaker/Bloomberg/Getty

Late last month, China’s health ministry released draft guidelines aimed at stopping rogues from prematurely using new and unapproved biomedical technologies in the clinic. The regulations require that the riskiest of techniques — including human gene editing — be approved by China’s health ministry first.

Nowhere in the announcement, in the regulations or in a background document, is the name He Jiankui. But the controversy surrounding He — who last year announced the birth of gene-edited babies — was clearly the driving force behind the guidelines. China is embarrassed by He’s widely condemned work, which flouted conventions of safety and research ethics. Its latest regulations — which include threats of fines and blacklists, and references to pre-existing laws — are clearly designed to create a stronger deterrent.

Adopt a moratorium on heritable genome editing

How to stop the next gene-editing rogue is a pressing topic for researchers around the world. In Nature this week, an international group of ethicists and researchers, including some of those who originally developed CRISPR–Cas9 as a gene-editing tool, call for a moratorium on clinical use of human germline editing — introducing heritable changes to sperm, eggs or embryos — until the safety of the technique has been better investigated and acceptable uses agreed on. The US National Institutes of Health has supported the call .

Whether such a moratorium would be effective is one point being actively debated by the research community, national academies and groups such as the World Health Organization (WHO). Just as important is whether it would facilitate a deeper consideration of the ethical and moral issues surrounding clinical uses of germline editing from people with diverse perspectives. So far, there is no sign of resolution. It is a debate that requires the wider participation of society at large, especially families affected by genetic conditions. It is also unclear how a global moratorium would be enforced. China had regulations on gene editing that amounted to a national moratorium, but they clearly didn’t work.

Whether or not a moratorium receives more widespread support, several things need to be done to ensure that germline gene-editing studies, done for the purposes of research only, are on a safe and sensible path. As a starting point, proposals for all ethically vetted and approved basic research studies that use gene-editing tools in human embryos and gametes, including those aimed at assessing efficacy and safety, should be deposited in an open registry.

Second, researchers need to develop a system that allows early recognition of any research that risks overstepping predefined boundaries. A useful model to follow could be the WHO guidance for regulating research with a potential biosecurity risk. The system should include a mechanism — perhaps affiliated with the open registry — that allows researchers to flag up potentially dangerous research. Analysing whether He’s work could have been prevented will help. It’s important to hammer out whether, how and to whom scientists and ethicists who became aware of the project could have voiced their concerns — and how they could do so more easily in future. Raising the alarm would require a change of practice for researchers who, for the sake of scientific independence, often do not intervene in the choice of research projects undertaken by their peers.

Unfortunately, there will always be countries with relatively lax legal frameworks that could be exploited by would-be mavericks, so global efforts should also be aimed at developing and integrating legal strategies for the prevention and penalization of unacceptable research.

A global framework could be inspired by the UK Human Fertilisation and Embryology Authority, an independent regulator of research involving human embryos and gametes. Researchers could present to such a body proposals designed to assess the safety and feasibility of a particular genetic modification in embryos, as well as justification for the work. To be allowed to proceed, researchers could be asked to adhere to a set of principles by signing a code of conduct. Research institutions and funders, meanwhile, should define and monitor clear protocols for germline genome-editing research. Institutes must take responsibility for carefully reviewing any such studies at their inception and regularly along the way.

Journals need to agree to properly documented minimum standards for ethical conduct and reporting, to which submitted research should be held. Nature Research journals, like many others, seek ethical advice alongside scientific review when considering sensitive categories of human embryo research (see Nature 557 , 6; 2018 ).

Stakeholders must act now to reach a consensus, and the WHO is well placed to take the lead. In a welcome move, scientific academies around the world have now stated their intention to lead a commission on the scientific and ethical issues of germline gene editing .

One small contribution Nature can make is to air debate and encourage more of it. In this spirit, we welcome readers’ views (see go.nature.com/correspondence ). Could the clinical use of germline gene-editing tools one day be justifiable? If so, under what framework should this come about?

We would particularly like to hear from those whose voices have been somewhat sidelined so far. This includes patient groups and those with valuable experience in working with human embryos, embryonic stem cells and germ cells, as well as experience with related research and regulations, such as the governance of innovation, disability rights, citizen-engagement methodologies and the history and philosophy of science and dual-use technologies. The right decisions on human germline modification can be reached only through frank and open discussion, followed by swift action. With so much at stake, that must happen now.

Nature 567 , 145 (2019)

doi: https://doi.org/10.1038/d41586-019-00788-5

Reprints and permissions

Related Articles

Academies’ action plan for germline editing

NIH supports call for moratorium on clinical uses of germline gene editing

• Medical research

The complete sequence and comparative analysis of ape sex chromosomes

Article 29 MAY 24

Molecular basis for differential Igk versus Igh V(D)J joining mechanisms

The immune system can sabotage gene therapies — can scientists rein it in?

News 28 MAY 24

Innovative cancer therapies offer new hope

Outlook 29 MAY 24

Advances in highly targeted radiation treatment for cancer have ignited interest in a once obscure field

Randomized trials of cancer drugs are for yesterday

Guidelines for academics aim to lessen ethical pitfalls in generative-AI use

Nature Index 22 MAY 24

Are robots the solution to the crisis in older-person care?

Outlook 25 APR 24

Postdoctoral and Visiting Scholar positions in Immunology, Stem Cells, and Cancer

Postdoctoral Research Fellow and Visiting Scholar positions in immunology, stem cells and cancer are immediately available at UConn in USA

Storrs Mansfield, Connecticut

University of Connecticut-Lai's Lab

Zhejiang Provincial Hospital of Chinese Medicine on Open Recruitment of Medical Talents and Postdocs

Director of Clinical Department, Professor, Researcher, Post-doctor

Hangzhou, Zhejiang, China

The First Affiliated Hospital of Zhejiang Chinese Medical University

Postdoc in Biomechanical Engineering (m/f/d)

The Muskuloskelettales Universitätszentrum München (MUM) on the Campus Großhadern invites applications for the department Orthopädie

Munich (Stadt), Bayern (DE)

PWG-LMU Klinikum

Assistant, Associate or Full Professor

The McLaughlin Research Institute and Touro University – Montana campus invite applications for open rank faculty positions.

McLaughlin Research Institute

Postdoctoral Associate- Neuroscience

Houston, Texas (US)

Baylor College of Medicine (BCM)

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Quick links

• Explore articles by subject
• Guide to authors
• Editorial policies