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Experts Conclude Heritable Human Genome Editing Not Ready for Clinical Applications

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We stand at a critical juncture in the history of science. CRISPR and other innovative genome editing systems have given researchers the ability to make very precise changes in the sequence, or spelling, of the human DNA instruction book. If these tools are used to make non-heritable edits in only relevant tissues, they hold enormous potential to treat or even cure a wide range of devastating disorders, such as sickle cell disease, inherited neurologic conditions, and muscular dystrophy. But profound safety, ethical, and philosophical concerns surround the use of such technologies to make heritable changes in the human genome—changes that can be passed on to offspring and have consequences for future generations of humankind.

Such concerns are not hypothetical. Two years ago, a researcher in China took it upon himself to cross this ethical red line and conduct heritable genome editing experiments in human embryos with the aim of protecting the resulting babies against HIV infection. The medical justification was indefensible, the safety issues were inadequately considered, and the consent process was woefully inadequate. In response to this epic scientific calamity, NIH supported a call by prominent scientists for an international moratorium on human heritable, or germline, genome editing for clinical purposes.

Following on the heels of this unprecedented ethical breach, the U.S. National Academy of Sciences, U.S. National Academy of Medicine, and the U.K. Royal Society convened an international commission, sponsored by NIH, to conduct a comprehensive review of the clinical use of human germline genome editing. The 18-member panel, which represented 10 nations and four continents, included experts in genome editing technology; human genetics and genomics; psychology; reproductive, pediatric, and adult medicine; regulatory science; bioethics; and international law. Earlier this month, this commission issued its consensus study report, entitled Heritable Human Genome Editing [1].

The commission was designed to bring together thought leaders around the globe to engage in serious discussions about this highly controversial use of genome-editing technology. Among the concerns expressed by many of us was that if heritable genome editing were allowed to proceed without careful deliberation, the enormous potential of non-heritable genome editing for prevention and treatment of disease could become overshadowed by justifiable public outrage, fear, and disgust.

I’m gratified to say that in its new report, the expert panel closely examined the scientific and ethical issues, and concluded that heritable human genome editing is too technologically unreliable and unsafe to risk testing it for any clinical application in humans at the present time. The report cited the potential for unintended off-target DNA edits, which could have harmful health effects, such as cancer, later in life. Also noted was the risk of producing so-called mosaic embryos, in which the edits occur in only a subset of an embryo’s cells. This would make it very difficult for researchers to predict the clinical effects of heritable genome editing in human beings.

Among the many questions that the panel was asked to consider was: should society ever decide that heritable gene editing might be acceptable, what would be a viable framework for scientists, clinicians, and regulatory authorities to assess the potential clinical applications?

In response to that question, the experts replied: heritable gene editing, if ever permitted, should be limited initially to serious diseases that result from the mutation of one or both copies of a single gene. The first uses of these technologies should proceed incrementally and with extreme caution. Their potential medical benefits and harms should also be carefully evaluated before proceeding.

The commission went on to stress that before such an option could be on the table, all other viable reproductive possibilities to produce an embryo without a disease-causing alteration must be exhausted. That would essentially limit heritable gene editing to the exceedingly rare instance in which both parents have two copies of a recessive, disease-causing gene variant. Or another quite rare instance in which one parent has two copies of an altered gene for a dominant genetic disorder, such as Huntington’s disease.

Recognizing how unusual both scenarios would be, the commission held out the possibility that some would-be parents with less serious conditions might qualify if 25 percent or less of their embryos are free of the disease-causing gene variant. A possible example is familial hypercholesterolemia (FH), in which people carrying a mutation in the LDL receptor gene have unusually high levels of cholesterol in their blood. If both members of a couple are affected, only 25 percent of their biological children would be unaffected. FH can lead to early heart disease and death, but drug treatment is available and improving all the time, which makes this a less compelling example. Also, the commission again indicated that such individuals would need to have already traveled down all other possible reproductive avenues before considering heritable gene editing.

A thorny ethical question that was only briefly addressed in the commission’s report is the overall value to be attached to a couple’s desire to have a biological child. That desire is certainly understandable, although other options, such an adoption or in vitro fertilization with donor sperm, are available. This seems like a classic example of the tension between individual desires and societal concerns. Is the drive for a biological child in very high-risk situations such a compelling circumstance that it justifies asking society to start down a path towards modifying human germline DNA?

The commission recommended establishing an international scientific advisory board to monitor the rapidly evolving state of genome editing technologies. The board would serve as an access point for scientists, legislators, and the public to access credible information to weigh the latest progress against the concerns associated with clinical use of heritable human genome editing.

The National Academies/Royal Society report has been sent along to the World Health Organization (WHO), where it will serve as a resource for its expert advisory committee on human genome editing. The WHO committee is currently developing recommendations for appropriate governance mechanisms for both heritable and non-heritable human genome editing research and their clinical uses. That panel could issue its guidance later this year, which is sure to continue this very important conversation.


[1] Heritable Human Genome Editing, Report Summary, National Academy of Sciences, September 2020.


Heritable Genome Editing Not Yet Ready to Be Tried Safely and Effectively in Humans,” National Academies of Sciences, Engineering, and Medicine news release, Sep. 3, 2020.

International Commission on the Clinical Use of Human Germline Genome Editing (National Academies of Sciences, Engineering, and Medicine/Washington, D.C.)

Video: Report Release Webinar , International Commission on the Clinical Use of Human Germline Genome Editing (National Academies of Sciences, Engineering, and Medicine)

National Academy of Sciences (Washington, D.C.)

National Academy of Medicine (Washington, D.C.)

The Royal Society (London)

Citizen Scientists Take on the Challenge of Long-Haul COVID-19

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Woman frustrated while working
Credit: iStock/Poike

Coronaviruses are a frequent cause of the common cold. Most of us bounce back from colds without any lasting health effects. So, you might think that individuals who survive other infectious diseases caused by coronaviruses—including COVID-19—would also return to normal relatively quickly. While that can be the case for some people, others who’ve survived even relatively mild COVID-19 are experiencing health challenges that may last for weeks or even months. In fact, the situation is so common, that some of these folks have banded together and given their condition a name: the COVID “long-haulers.”

Among the many longer-term health problems that have been associated with COVID-19 are shortness of breath, fatigue, cognitive issues, erratic heartbeat, gastrointestinal issues, low-grade fever, intolerance to physical or mental activity, and muscle and joint pains. COVID-19 survivors report that these symptoms flair up unpredictably, often in different combinations, and can be debilitating for days and weeks at a time. Because COVID-19 is such a new disease, little is known about what causes the persistence of symptoms, what is impeding full recovery, or how to help the long-haulers.

More information is now emerging from the first detailed patient survey of post-COVID syndrome, also known as Long COVID [1]. What’s unique about the survey is that it has been issued by a group of individuals who are struggling with the syndrome themselves. These citizen scientists, who belong to the online Body Politic COVID-19 Support Group, decided to take matters into their own hands. They already had a pretty good grip on what sort of questions to ask, as well as online access to hundreds of long-haulers to whom they could pose the questions.

The citizen scientists’ group, known as the Patient-led Research for COVID-19, brought a lot of talent and creativity to the table. Members reside in the United States, Canada, and England, and none have ever met face to face. But, between their day jobs, managing time differences, and health challenges, each team member spends about 20 hours per week working on their patient-led research, and are now putting the final touches on a follow-up survey that will get underway in the next few weeks.

For their first survey, the group members faced the difficult decision of whom to contact. First, they needed to define long hauler. For that, they decided to target people whose symptoms persisted for more than 2 weeks after their initial recovery from COVID-19. The 640 individuals who responded to the survey were predominately white females between the ages of 30 to 49 who lived in the United States. The members said that the gender bias may stem from women being more likely to join support groups and complete surveys, though there may be a gender component to Long COVID as well. About 10 percent of respondents reported that they had ultimately recovered from this post-COVID syndrome.

Another important issue revolved around COVID-19 testing. Most long-haulers in the online group had gotten sick in March and April, but weren’t so sick that they needed to be hospitalized. Because COVID-19 testing during those months was often limited to people hospitalized with severe respiratory problems, many long-haulers with mild or moderate COVID-like symptoms weren’t tested. Others were tested relatively late in the course of their illness, which can increase the likelihood of false negatives.

The team opted to cast a wide investigative net, concluding that limiting its data to only people who tested positive for COVID-19 might lead to the loss of essential information on long-haulers. It turns out that half of the respondents hadn’t been tested for SARS-CoV-2, the virus that causes COVID-19. The other half was divided almost equally between those who tested positive and those who tested negative. Here are some highlights of the survey’s findings:

Top 10 Symptoms: Respondents were asked to rank their most common symptoms and their relative severity. From highest to lowest, they were: mild shortness of breath, mild tightness of chest, moderate fatigue, mild fatigue, chills or sweats, mild body aches, dry cough, elevated temperature (98.8-100), mild headache, and brain fog/concentration challenges. Highlighting the value of patient-led research, the team was able to assemble an initial list of 62 symptoms that long-haulers often discuss in support groups. The survey revealed common symptoms that have been greatly underreported in the media, such as neurological symptoms. These include brain fog, concentration challenges, and dizziness.

Making a Recovery: Of the 60 respondents who had recovered, the average time to recovery was 27 days. The respondents who had not recovered had managed their symptoms for 40 days on average, with most dealing with health problems for 5 to 7 weeks. The report shows that the chance of full recovery by day 50 is less than 20 percent.

Exercise Capacity: About 65 percent of respondents now consider themselves mostly sedentary. Most had been highly physically active before developing COVID-19. Many long-haulers expressed concern that overexertion causes relapses

Testing. Respondents who reported testing positive for SARS-CoV-2 were tested on average earlier in their illness (by day 10) than those who reported testing negative (by day 16). The team noted that their findings parallel those in a recent published scientific study, which found false-negative rates for current PCR-based assays rose as the time between SARS-CoV-2 infection and testing increased [2]. In that published study, by day 21, the false-negative rate reached 66 percent. Only two symptoms (loss of smell and loss of taste) occurred more frequently in respondents who tested positive; the other 60 symptoms were statistically the same between groups. The citizen scientists speculate that testing is not capturing a subset of COVID patients, and more investigation is required.

Since issuing their survey results on May 11, the team has met with staff from the Centers for Disease Control and Prevention and the World Health Organization. Their work also been mentioned in magazine articles and even cited in some papers published in scientific journals.

In their next survey, these citizen scientists hope to fill in gaps in their first report, including examining antibody testing results, neurological symptoms, and the role of mental health. To increase geographic and demographic diversity, they will also translate the survey into 10 languages. If you’re a COVID-19 long-hauler and would like to find out how to get involved, there’s still time to take part in the next survey.


[1] “What Does COVID-19 Recovery Actually Look Like?” Patient-led Research for COVID-19. May 11, 2020.

[2] Variation in False-Negative Rate of Reverse Transcriptase Polymerase Chain Reaction-Based SARS-CoV-2 Tests by Time Since Exposure. Kucirka LM, Lauer SA, Laeyendecker O, Boon D, Lessler J. Ann Intern Med. 2020 Aug 18;173(4):262-267.


Coronavirus (COVID-19) (NIH)

Patient-led Research for COVID-19

Exploring Drug Repurposing for COVID-19 Treatment

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Drug screening-High throughput robot
Caption: Robotic technology screening existing drugs for new purposes. Credit: Scripps Research

It usually takes more than a decade to develop a safe, effective anti-viral therapy. But, when it comes to coronavirus disease 2019 (COVID-19), we don’t have that kind of time. One way to speed the process may be to put some old drugs to work against this new disease threat. This is generally referred to as “drug repurposing.”

NIH has been doing everything possible to encourage screens of existing drugs that have been shown safe for human use. In a recent NIH-funded study in the journal Nature, researchers screened a chemical “library” that contained nearly 12,000 existing drug compounds for their potential activity against SARS-CoV-2, the novel coronavirus that causes COVID-19 [1]. The results? In tests in both non-human primate and human cell lines grown in laboratory conditions, 21 of these existing drugs showed potential for repurposing to thwart the novel coronavirus—13 of them at doses that likely could be safely given to people. The majority of these drugs have been tested in clinical trials for use in HIV, autoimmune diseases, osteoporosis, and other conditions.

These latest findings come from an international team led by Sumit Chanda, Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA. The researchers took advantage of a small-molecule drug library called ReFRAME [2], which was created in 2018 by Calibr, a non-profit drug discovery division of Scripps Research, La Jolla, CA.

In collaboration with Yuen Kwok-Yung’s team at the University of Hong Kong, the researchers first developed a high-throughput method that enabled them to screen rapidly each of the 11,987 drug compounds in the ReFRAME library for their potential to block SARS-CoV-2 in cells grown in the lab. The first round of testing narrowed the list of possible COVID-19 drugs to about 300. Next, using lower concentrations of the drugs in cells exposed to a second strain of SARS-CoV-2, they further narrowed the list to 100 compounds that could reliably limit growth of the coronavirus by at least 40 percent.

Generally speaking, an effective anti-viral drug is expected to show greater activity as its concentration is increased. So, Chanda’s team then tested those 100 drugs for evidence of such a dose-response relationship. Twenty-one of them passed this test. This group included remdesivir, a drug originally developed for Ebola virus disease and recently authorized by the U.S. Food and Drug Administration (FDA) for emergency use in the treatment of COVID-19. Remdesivir could now be considered a positive control.

These findings raised another intriguing question: Could any of the other drugs with a dose-response relationship work well in combination with remdesivir to block SARS-CoV-2 infection? Indeed, the researchers found that four of them could.

Further study showed that some of the most promising drugs on the list reduced the number of SARS-CoV-2 infected cells by 65 to 85 percent. The most potent of these was apilimod, a drug that has been evaluated in clinical trials for treating Crohn’s disease, rheumatoid arthritis, and other autoimmune conditions. Apilimod is now being evaluated in the clinic for its ability to prevent the progression of COVID-19. Another potential antiviral to emerge from the study is clofazimine, a 70-year old FDA-approved drug that is on the World Health Organization’s list of essential medicines for the treatment of leprosy.

Overall, the findings suggest that there may be quite a few existing drugs and/or experimental drugs fairly far along in the development pipeline that have potential to be repurposed for treating COVID-19. What’s more, some of them might also work well in combination with remdesivir, or perhaps other drugs, as treatment “cocktails,” such as those used to successfully treat HIV and hepatitis C.

This is just one of a wide variety of drug screening efforts that are underway, using different libraries and different assays to detect activity against SARS-CoV-2. The NIH’s National Center for Advancing Translational Sciences has established an open data portal to collect all of these data as quickly and openly as possible. As NIH continues its efforts to use the power of science to end the COVID-19 pandemic, it is critically important that we explore as many avenues as possible for developing diagnostics, treatments, and vaccines.


[1] Discovery of SARS-CoV-2 antiviral drugs through large-scale compound repurposing. Riva L, Yuan S, Yin X, et al. Nature. 2020 Jul 24 [published online ahead of print]

[2] The ReFRAME library as a comprehensive drug repurposing library and its application to the treatment of cryptosporidiosis. Janes J, Young ME, Chen E, et al. Proc Natl Acad Sci USA. 2018;115(42):10750-10755.


Coronavirus (COVID-19) (NIH)

ReFRAMEdb (Scripps Research, La Jolla, CA)

The Chanda Lab (Sanford Burnham Prebys Medical Discovery Institute, La Jolla, CA)

Yuen Kwok-Yung (University of Hong Kong)

OpenData|Covid-19 (National Center for Advancing Translational Sciences/NIH)

NIH Support: National Institute of Allergy and Infectious Diseases; National Institute of General Medical Sciences

New Weapon Targets Ancient Foe

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Microscopic image of a long, thin, rod-like bacteria

Colorized scanning electron micrograph of Mycobacterium tuberculosis. Source: Clifton E. Barry III, Ph.D., NIAID, NIH.

Tuberculosis is an ancient scourge that has evolved in lockstep with humans for more than ten millennia. It infected residents of ancient Egypt; remnants of Mycobacterium tuberculosis, the deadly bacterium that ravages the lungs and other organs of its victims, have been found in Egyptian mummies dating back 3,000 years. It is considered one of the world’s deadliest diseases.

I’ve had my own experience with TB. As a medical resident in the intensive care unit in North Carolina in 1977, I was exposed to the bacterium during emergency care of a young migrant worker who arrived at our hospital in extremis from internal bleeding. Only after the hemorrhaging was stopped did we discover his advanced tuberculosis. But I’m happy to say we treated him successfully with a battery of drugs, and he walked out of the hospital. My own TB skin test tested positive a few months later, and so I had to take a year’s worth of therapy with isoniazid to wipe out those little microbial invaders. That was all it took.

For the most part, TB cases have been reduced to a trickle in the Western world—thanks to antibiotics—and relegated to the history books with descriptions of ‘consumption’ in nineteen-century England and tales of jail-like sanatoria where those consumptives were quarantined and often died.