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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.

References:

[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.

Links:

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


Encouraging News for Kids with Neurofibromatosis Type 1

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Dr. Collins with NF1 Patient
Caption: This photo goes back a few years. I’m talking to a child with neurofibromatosis type 1 during the search for the NF1 gene, which was discovered in 1990. Credit: University of Michigan Bio Med Photo Department, Ann Arbor

Amid all the headlines and uncertainty surrounding the current COVID-19 pandemic, it’s easy to overlook the important progress that biomedical research is making against other diseases. So, today, I’m pleased to share word of what promises to be the first effective treatment to help young people suffering from the consequences of a painful, often debilitating genetic disorder called neurofibromatosis type 1 (NF1).

This news is particularly meaningful to me because, 30 years ago, I led a team that discovered the gene that underlies NF1. About 1 in 3,000 babies are born with NF1. In about half of those affected, a type of tumor called a plexiform neurofibroma arises along nerves in the skin, face, and other parts of the body. While plexiform neurofibromas are not cancerous, they grow steadily and can lead to severe pain and a range of other health problems, including vision and hearing loss, hypertension, and mobility issues.

The good news is the results of a phase II clinical trial involving NF1, just published in the New England Journal of Medicine. The trial was led by Brigitte Widemann and Andrea Gross, researchers in the Center for Cancer Research at NIH’s National Cancer Institute.

The trial’s results confirm that a drug originally developed to treat cancer, called selumetinib, can shrink inoperable tumors in many children with NF1. They also establish that the drug can help affected kids make significant improvements in strength, range of motion, and quality of life. While selumetinib is not a cure, and further studies are still needed to see how well the treatment works in the long term, these results suggest that the first effective treatment for NF1 is at last within our reach.

Selumetinib blocks a protein in human cells called MEK. This protein is involved in a major cellular pathway known as RAS that can become dysregulated and give rise to various cancers. By blocking the MEK protein in animal studies and putting the brakes on the RAS pathway when it malfunctions, selumetinib showed great initial promise as a cancer drug.

Selumetinib was first tested several years ago in people with a variety of other cancers, including ovarian and non-small cell lung cancers. The clinical research looked good at first but eventually stalled, and so did much of the initial enthusiasm for selumetinib.

But the enthusiasm picked up when researchers considered repurposing the drug to treat NF1. The neurofibromas associated with the condition were known to arise from a RAS-activating loss of the NF1 gene. It made sense that blocking the MEK protein might blunt the overactive RAS signal and help to shrink these often-inoperable tumors.

An earlier phase 1 safety trial looked promising, showing for the first time that the drug could, in some cases, shrink large NF1 tumors [2]. This fueled further research, and the latest study now adds significantly to that evidence.

In the study, Widemann and colleagues enrolled 50 children with NF1, ranging in age from 3 to 17. Their tumor-related symptoms greatly affected their wellbeing and ability to thrive, including disfigurement, limited strength and motion, and pain. Children received selumetinib alone orally twice a day and went in for assessments at least every four months.

As of March 2019, 35 of the 50 children in the ongoing study had a confirmed partial response, meaning that their tumors had shrunk by more than 20 percent. Most had maintained that response for a year or more. More importantly, the kids also felt less pain and were more able to enjoy life.

It’s important to note that the treatment didn’t work for everyone. Five children stopped taking the drug due to side effects. Six others progressed while on the drug, though five of them had to reduce their dose because of side effects before progressing. Nevertheless, for kids with NF1 and their families, this is a big step forward.

Drug developer AstraZeneca, working together with the researchers, has submitted a New Drug Application to the Food and Drug Administration (FDA). While they’re eagerly awaiting the FDA’s decision, the work continues.

The researchers want to learn much more about how the drug affects the health and wellbeing of kids who take it over the long term. They’re also curious whether it could help to prevent the growth of large tumors in kids who begin taking it earlier in the course of the disease, and whether it might benefit other features of the disorder. They will continue to look ahead to other potentially promising treatments or treatment combinations that may further help, and perhaps one day even cure, kids with NF1. So, even while we cope with the COVID-19 pandemic, there are reasons to feel encouraged and grateful for continued progress made throughout biomedical research.

References:

[1] Selumitinib in children with inoperable plexiform neurofibromas. New England Journal of Medicine. Gross AM, Wolters PL, Dombi E, Baldwin A, Whitcomb P, Fisher MJ, Weiss B, Kim A, Bornhorst M, Shah AC, Martin S, Roderick MC, Pichard DC, Carbonell A, Paul SM, Therrien J, Kapustina O, Heisey K, Clapp DW, Zhang C, Peer CJ, Figg WD, Smith M, Glod J, Blakeley JO, Steinberg SM, Venzon DJ, Doyle LA, Widemann BC. 18 March 2020. N Engl J Med. 2020 Mar 18. [Epub ahead of publication.]

[2] Activity of selumetinib in neurofibromatosis type 1-related plexiform neurofibromas. Dombi E, Baldwin A, Marcus LJ, Fisher MJ, Weiss B, Kim A, Whitcomb P, Martin S, Aschbacher-Smith LE, Rizvi TA, Wu J, Ershler R, Wolters P1, Therrien J, Glod J, Belasco JB, Schorry E, Brofferio A, Starosta AJ, Gillespie A, Doyle AL, Ratner N, Widemann BC. N Engl J Med. 2016 Dec 29;375(26):2550-2560.

Links:

Neurofibromatosis Fact Sheet (National Institute of Neurological Disorders and Stroke/NIH)

Brigitte Widemann (National Cancer Institute/NIH)

Andrea Gross (National Cancer Institute/NIH)

NIH Support: National Cancer Institute


Could Repurposed Asthma Drugs Treat Parkinson’s Disease?

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Asthma medicine

Thinkstock/ia_64

I had asthma as a child, and I still occasionally develop mild wheezing from exercising in cold air or catching a bad cold. I keep an inhaler on hand for those occasions, as this is a quick and effective way to deliver a medication that opens up those constricted airways. Now, an NIH-supported team has made the surprising discovery that some asthma medicines may also hold the potential to treat or help prevent Parkinson’s disease, a chronic, progressive movement disorder that affects at least a half-million Americans.

The results, published recently in the journal Science, provide yet another example of the tremendous potential of testing drugs originally intended for treating one disease for possible use in others [1]. In this particular instance, researchers screened a library of more than 1,100 well-characterized chemical compounds—including drugs approved by the Food and Drug Administration for treating asthma—to see if they showed any activity against a molecular mechanism known to be involved in Parkinson’s disease.


Treating Zika Infection: Repurposed Drugs Show Promise

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Zika researcher

Caption: An NCATS researcher dispenses Zika virus into trays for compound screening in a lab using procedures that follow strict biosafety standards.
Credit: National Center for Advancing Translational Sciences, NIH

In response to the health threat posed by the recent outbreak of Zika virus in Latin America and its recent spread to Puerto Rico and Florida, researchers have been working at a furious pace to learn more about the mosquito-borne virus. Considerable progress has been made in understanding how Zika might cause babies to be born with unusually small heads and other abnormalities and in developing vaccines that may guard against Zika infection.

Still, there remains an urgent need to find drugs that can be used to treat people already infected with the Zika virus. A team that includes scientists at NIH’s National Center for Advancing Translational Sciences (NCATS) now has some encouraging news on this front. By testing 6,000 FDA-approved drugs and experimental chemical compounds on Zika-infected human cells in the lab, they’ve shown that some existing drugs might be repurposed to fight Zika infection and prevent the virus from harming the developing brain [1]. While additional research is needed, the new findings suggest it may be possible to speed development and approval of new treatments for Zika infection.