Drugmakers are racing to repurpose existing medicines to fight the novel coronavirus. Here's what you need to know about the 17 leading medications being put to the test.

Repurposed drugs are the most promising options for finding a treatment quickly for COVID-19, the disease caused by the novel coronavirus.

Dozens of clinical trials are testing drugs originally designed for other ailments, such as Ebola, HIV, malaria, and arthritis.

These potential treatments have already been tested in humans for other diseases, and some are already approved to treat other conditions. That means we already know how safe they are for people to take, and what side effects to expect. Researchers can skip some early steps and move quickly into human trials testing how well the drugs work in COVID-19. 

As cases surge in the US, some of that research into potential treatments is getting put to work with the hopes of helping more survive COVID-19. For instance, on June 16, researchers revealed that dexamethasone, a cheap, widely available steroid, managed to reduce deaths in patients with severe COVID-19

While repurposed drugs can be tested now, they aren't expected to be anything close to a panacea for the virus. The gold standard for halting infectious diseases remains vaccines, which can protect healthy people from getting infected in the first place.

Read more: There are more than 25 coronavirus vaccines set to be tested in people this year. Here are the 10 leading vaccine candidates, and what to watch for in the rest of 2020.

Vaccine research typically takes years. Even under the urgency of this pandemic, US health officials have said it will take at least a year to know if any vaccine is safe and effective.

Simultaneously, biotech and pharma companies are scrambling to craft new therapeutics. These will be tailored specifically to fighting this novel coronavirus. Even under the most aggressive timetables for clinical testing, those won't be widely available to patients until at least the fall. 

That leaves repurposed drugs as the near-term hope. Here are the top candidates and how they are being tested against COVID-19.

This article was initially published in April 2020 and has been updated. 

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On June 16, dexamethasone, a common, cheap, steroid became the first drug to reduce deaths in severely ill COVID-19 patients in a clinical trial, according to a statement released by the trial's lead investigators. 

Giving the steroid in critically ill COVID-19 patients on ventilators reduced deaths by one-third, and it reduced deaths in patients on oxygen by 20%. COVID-19 patients who didn't need help with breathing didn't benefit from the drug.

Dexamethasone is one of a number of corticosteroids, which acts on the immune system by providing relief to inflammation in the body. In critically ill COVID-19 patients, doctors have thought that it might be the body's response to the virus — rather than the virus itself — that's wreaking havoc on the body. 

The World Health Organization has previously recommended against using corticosteroids in COVID-19, particularly in treating viral pneumonia, based on a review of how well the drugs worked in past coronavirus outbreaks. One of the concerns the organization had was over whether the steroids would help keep the virus replicating, known as viral shedding. 

Major studies to watch:

  • Trials are ongoing in Spain and France to see how well the drug works in critically ill COVID-19 patients with acute respiratory distress syndrome and pneumonia, respectively. 
In this March 2020 photo provided by Gilead Sciences, a vial of the investigational drug remdesivir is visually inspected at a Gilead manufacturing site in the United States. Given through an IV, the medication is designed to interfere with an enzyme that reproduces viral genetic material. (Gilead Sciences via AP)
In this March 2020 photo provided by Gilead Sciences, a vial of the investigational drug remdesivir is visually inspected at a Gilead manufacturing site in the United States. Given through an IV, the medication is designed to interfere with an enzyme that reproduces viral genetic material. (Gilead Sciences via AP)
Associated Press

Remdesivir is an antiviral drug developed by Gilead Sciences in 2009. It was previously tested in more than 100 Ebola patients during that outbreak.

Through clinical trials and expanded access programs, thousands of COVID-19 patients have already been treated with remdesivir.

The National Institutes of Health released data showing the drug helps coronavirus patients recover more quickly from the virus. Based on that data, the FDA on May 1 issued an emergency authorization for the drug's use. While it's not an approval, it could allow for more hospitalized patients to receive the drug.

On June 1, Gilead said that remdesivir helped hospitalized patients with more moderate forms of COVID-19 recover more quickly when receiving the treatment for 5 days. The results were mixed, however, in moderately ill patients who received the treatment for 10 days. In that case, results weren't statistically significant, the company said. 

For now, the drug is authorized to be given to severely ill hospitalized patients via an intravenous infusion over the course of a five- or 10-day period.

But starting in August, Gilead is exploring how remdesivir might work in an inhaled version, which could make it more widely available for use in treating COVID-19 in patients who aren't hospitalized. 

Read more: The 3-decade rise of Gilead, from California startup to the biotech with the best chance yet at an effective coronavirus treatment

Major studies to watch:

  • Full results from Gilead's study enrolling 1,600 moderate COVID-19 patients randomized to either 5-day IV infusion of remdesivir, 10-day infusion of remdesivir, or standard of care (link)
  • A WHO trial involving over 90 countries, testing remdesivir, Kaletra, and interferon-beta-1a in COVID-19 patients (link)
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A pharmacy worker wears a protective mask shows a box of Plaquenil on March 25, 2020 in Paris, France. T
Chesnot/Getty Images

Hydroxychloroquine is a widely used medication by people with lupus or arthritis. It was first approved in the 1950s.

Early in the pandemic, the drug caught the eyes of doctors, experts, and the Trump administration as a potential coronavirus treatment. Some early, promising results regarding the drug were published in late March.

Since then, the drug has largely been written off as a potential treatment for COVID-19.

In June, the University of Minnesota released results from its randomized controlled trial testing whether hydroxychloroquine can prevent coronavirus. The first high-quality look at the medication's use to prevent COVID-19, the study found that the drug did not help prevent infections

Two observational studies, published in the New England Journal of Medicine and the Journal of the American Medical Association, found that among thousands of hospitalized coronavirus patients, those who received the antimalarial medication hydroxychloroquine didn't fare better or worse than patients who didn't receive the drug. 

In the wake of the results, a number of clinical trials have been called off. A WHO trial involving over 90 countries testing remdesivir, hydroxychloroquine, Kaletra, and interferon-beta-1a in COVID-19 patients dropped the hydroxychloroquine arm of the trial in June. 

The NIH in June also halted a trial after determining the drug is "very unlikely to be beneficial" in hospitalized patients. 

And on June 15, the FDA revoked an emergency use authorization issued early in the pandemic for the drug. The drug has not been approved by the FDA to  treat COVID-19.

Read more: The first high-quality study of malaria pill hydroxychloroquine just found it doesn't help prevent coronavirus infections

Major studies to watch: 

  • The Bill and Melinda Gates Foundation is working with the University of Washington and other partners to test 2,000 asymptomatic people who are in close contact with a COVID-19 patient. The trial randomly assigns either hydroxychloroquine or vitamin C pills as a placebo comparison (link)
  • The University of Oxford is recruiting 40,000 participants to test the malaria drug as preventive treatment for frontline healthcare workers. Volunteers will receive either hydroxychlorouqine in Europe or chloroquine in Asia and be compared against a placebo arm (link)
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Workers on the production line of Cefazolin sodium injection (for treating bacterial infections) in the Harbin Pharmaceutical Group General Pharmaceutical Factory in Harbin, northeast China's Heilongjiang Province, March 2, 2020.
Xinhua/Wang Jianwei via Getty Images

Azithromycin is a widely prescribed generic antibiotic, sometimes referred to as Z-Pak. While it's used to fight bacteria, not viruses, there is some research suggesting the drug has antiviral properties.

Pharma company Pfizer in April published a review of these antiviral characteristics seen in laboratory research and clinical tests with the intent of facilitating further research of how azithromycin works in COVID-19. 

Several trials are testing azithromycin in combination with hydroxychloroquine. An observational study published in the Journal of the American Medical Association in May found that those who received hydroxychloroquine, the antibiotic azithromycin, or both hydroxychloroquine and azithromycin didn't have meaningfully lower rate of in-hospital deaths compared to patients who didn't receive the drugs. 

One potential concern is serious heart side effects. Azithromycin drugs can cause abnormal changes in the rhythm of the heart. These can be fatal, particularly for susceptible patients who already have heart problems. Many studies are using EKG tests to closely monitor patients receiving this treatment combinations of the antibiotic and hydroxychloroquine.

Major studies to watch: 

  • Intermountain Health Care and the University of Utah will treat 300 COVID-19 patients with either azithromycin or hydroxychloroquine. (link) They are also testing 1,550 COVID-19 patients in an outpatient setting with either hydroxychloroquine or azithromycin (link)
  • Rutgers University is testing 160 COVID-19 patients with either hydroxychloroquine or hydroxychloroquine and azithromycin (link)
  • Duke University will test 500 hospitalized COVID-19 patients randomly with either standard of care or hydroxychloroquine. Those selected for hydroxychloroquine will also be randomized to either receive azithromycin in addition or just hydroxychloroquine (link)
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A medical worker treats patients suffering from coronavirus in an intensive care unit at the Oglio Po hospital in Cremona, Italy on March 19, 2020.
Reuters/Flavio Lo Scalzo

Kevzara was approved in the US in 2017 to treat rheumatoid arthritis. The biologic injection is an anti-inflammatory medication. Regeneron and Sanofi co-promote the drug. 

It may help the most severe COVID-19 patients who are suffering from an overactive immune response. This condition, known as a cytokine storm, may be the reason some patients crash. Kevzara inhibits a key cytokine called IL-6. 

In April, however, researchers narrowed a clinical trial of the drug Kevzara after an early review of how the treatment was working.

The early look at the data led researchers to focus exclusively on critically ill patients, instead of more broadly testing it on severely and critically ill patients. Critical patients are on ventilators, high-flow oxygen therapy, or they're in the intensive care unit. The study is now looking at just higher doses of the medication as well.

Read more: A potential coronavirus treatment just suffered an early setback, and researchers are now focusing their efforts on the sickest COVID-19 patients

Major studies to watch: 

  • Regeneron is running a US trial of 400 hospitalized COVID-19 patients with severe cases. It randomizes patients to a low dose, high dose, or placebo arm (link)
  • Sanofi is running a trial outside the US of 300 severe COVID-19 patients, also testing a low dose and high dose against a placebo comparison (link)
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Dr. Zhou Min, a recovered COVID-19 patient who has passed his 14-day quarantine, donates plasma in the city's blood center in Wuhan in central China's Hubei province, February 18, 2020.
Chinatopix via AP

Convalescent plasma is a century-old treatment technique that has generated encouraging — yet early — results as a COVID-19 treatment. 

The treatment requires recovered COVID-19 patients to donate blood that is rich in the antibodies that fight the virus. These are then infused into hospitalized patients with severe disease.

Japan's largest pharmaceutical company is leading a worldwide collaboration to use the blood of recovered COVID-19 patients to treat others.

While the company first planned to develop its own treatment using this approach, it started a partnership in April to work with other companies and expedite the process of collecting plasma donations. These plasma specialists will develop one unbranded medicine for patients with severe COVID-19. 

In May, the Mayo Clinic reported safety data on 5,000 hospitalized patients that received convalescent plasma in the US. Early indications suggested the treatment is safe. 

If further studies validate this approach, a critical challenge will be scaling up this treatment to address a pandemic. That requires having widespread and reliable antibody testing as well as the medical workers to collect blood and get plasma to patients in need.

Read more: A new report raises hope that the blood of recovered patients can help treat severe coronavirus cases

Major studies to watch: 

  • Netherlands researchers are recruiting 426 severe COVID-19 patients to randomly receive either convalescent plasma or just standard of care (link)
  • The Food and Drug Administration has set up a national expanded access program. As of May 11, more than 14,000 patients had enrolled and 8,900 patients had been infused with the treatment (link)
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