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Although scientists and have celebrated the for emergency use of remdesivir to treat COVID-19, a cure for the disease that has killed over remains a long way off 鈥� and might never arrive.

Hundreds of drugs are being studied around the world, but 鈥淚 don鈥檛 see a lot of home runs right now,鈥� said Dr. Carlos del Rio, a professor of infectious diseases at the Emory University Rollins School of Public Health. 鈥淚 see a lot of strikeouts.鈥�

Researchers have launched more than of COVID-19. Pharmaceutical companies are investing billions to develop and to help end the pandemic.

Dr. Anthony Fauci, director of the National Institute of Allergy and Infectious Diseases, was cautious when announcing the results of a clinical trial of remdesivir last week, noting it isn鈥檛 a 鈥渒nockout.鈥� Although remdesivir helped hospitalized COVID-19 patients , it hasn鈥檛 been proved to save lives.

鈥淭his [drug] is opening the door,鈥� Fauci said. 鈥淎s more companies and investors get involved, it鈥檚 going to get better and better.鈥�

Researchers have that they will combine remdesivir with an anti-inflammatory drug, baricitinib 鈥� now used to treat 鈥斅爄n the hope of improving results.

But COVID-19 is an elusive enemy.

Doctors treating COVID patients say they鈥檙e fighting a war on multiple fronts, battling a virus that batters organs throughout the body, causes killer blood clots and prompts an immune system overreaction called a 鈥渃ytokine storm.鈥�

With so many parts of the body under siege at once, scientists say, improving survival rates will require multiple routes of attack 鈥� and more than one drug. While some of the experimental medications target the virus, others aim to prevent the immune system from inflicting collateral damage.

鈥淭here are so many pieces of this, and they will all require different therapies,鈥� said Dr. Lewis Kaplan, president of the Society of Critical Care Medicine, whose doctors provide intensive care.

High-tech approaches include using , virus-specific and to neutralize the coronavirus.

Scientists are also taking a fresh look at that might be repurposed to fight COVID-19. These include , , and even . If repurposed drugs are successful, they could reach patients relatively quickly, because doctors are already familiar with their side effects and safety concerns.

Some doctors are skeptical that drugs for heartburn or have any chance of treating a killer like COVID-19.

Dr. Steven Nissen, chair of cardiovascular medicine at the Cleveland Clinic, said he fears that hype over unproven products will harm patients, even if it temporarily boosts company stock prices. Patients who demand antacids or antimalarial drugs being studied in COVID-19 could be harmed by side effects, for example. Those who hoard drugs 鈥� on the hope of protecting themselves from COVID-19 鈥� could deprive other patients of medications they need to stay healthy. Some people may refuse to participate in clinical trials because they fear being given a placebo.

鈥淭his rush to get every imaginable treatment into a study, it鈥檚 not prudent,鈥� Nissen said. 鈥淚t鈥檚 not good medicine. It鈥檚 an act of desperation.鈥�

Other experts say scientists should cast a wide net.

鈥淚 don鈥檛 think we want to rule anything out because it sounds out of the ordinary,鈥� said Dr. Walid Gellad, director of the Center for Pharmaceutical Policy and Prescribing at the University of Pittsburgh.

Antivirals In The Spotlight

Antivirals such as remdesivir aim to prevent viruses from replicating, said Dr. Peter Hotez, a professor at Baylor College of Medicine in Houston.

That doesn鈥檛 always work. A small Chinese study of remdesivir, published last month in , found no benefit to severely ill COVID-19 patients. Remdesivir had previously .

Antivirals tend to be most helpful in the early stages of infection, when most of the harm to the patient is caused by the virus itself, rather than the immune system, Hotez said.

Remdesivir is just one of many antivirals being tested against COVID-19.

International researchers are studying the antiviral developed to fight the flu.

The antimalarial drugs chloroquine and hydroxychloroquine 鈥� which have been 鈥� also have antiviral effects. Although the Food and Drug Administration against COVID-19, the agency later warned that they could cause

A study in the likewise found no benefit in giving two antivirals used to treat HIV 鈥昦 combination of lopinavir and ritonavir, sold as Kaletra鈥� in adults hospitalized with severe COVID-19.

Harnessing The Immune System

One of the therapies generating excitement is also one of the oldest: antibody-rich blood from COVID survivors.

The immune system produces antibodies in response to invaders such as viruses and bacteria, allowing the body to recognize and them. Antibodies also recognize and neutralize the virus the next time that person is exposed.

Doctors hope that patients who develop antibodies against the novel coronavirus , at least for a few years, although this hasn鈥檛 been proved.

Scientists developing this 鈥渃onvalescent plasma鈥� are studying whether COVID-19 survivors can share this immunity with others by donating their plasma, the liquid part of blood that contains antibodies, said Dr. Shmuel Shoham, an associate professor of medicine at the Johns Hopkins University School of Medicine.

In addition to treating people who are already sick, donated plasma could potentially prevent people exposed to the virus 鈥� such as health care workers 鈥� from developing symptoms.

Donated antibodies 鈥� and any immunity they might provide 鈥� don鈥檛 last forever, said Dr. William Schaffner, a professor at the Vanderbilt University Medical Center. The body destroys aging antibodies as part of its routine maintenance, he said. In general, half of donated antibodies are eliminated in about three weeks.

The use of convalescent plasma goes back more than a century. It was used during the and was shown during the 2009-10 H1N1 pandemic.

Doctors don鈥檛 know yet whether convalescent plasma will benefit people with COVID-19.

In general, convalescent plasma is expected to be more effective in preventing illness than in treating it. It may be less likely to help someone in intensive care, Shoham said.

Researchers are also studying the use of prepackaged plasma, called , in COVID patients. This product, known as IVIG, is taken from healthy donors in the general population and has long been used to help patients with Hospitals keep it in stock and some are already using it to treat COVID patients.

Although the antibodies in prepackaged IVIG don鈥檛 specifically target the coronavirus, researchers hope they will tamp down the immune response.

In a third form of immune therapy, researchers are trying to identify the specific antibodies that are most important for neutralizing the coronavirus, then reproduce them as drugs called monoclonal antibodies. Monoclonal antibodies are already used to treat a variety of conditions, from cancer to rheumatoid arthritis and migraines.

鈥淲hen we give people an antibody, they are immediately at least partially immune to that specific virus,鈥� said Dr. James Crowe, director of the Vanderbilt Vaccine Center, who hopes to have antibodies ready for a clinical trial in a few months. 鈥淲e鈥檙e moving the immune system from one person to another.鈥�

Ideally, doctors would develop a very potent monoclonal antibody or a cocktail of antibodies for COVID-19 patients, to ensure the best chance of success, Crowe said. But manufacturing these drugs can be complicated, expensive and time-consuming.

鈥淢aking two antibodies would be at least twice as complicated as making one,鈥� Crowe said. 鈥淎 cocktail might be preferred, but cocktails are harder to move quickly.鈥�

Calming The Immune System

In most cases of COVID-19, the immune system neutralizes the coronavirus and patients recover without going to the hospital.

For reasons that doctors don鈥檛 totally understand, the immune system of some COVID-19 patients becomes hyperactive, attacking not just the virus but the patient鈥檚 own cells. A 鈥渃ytokine storm,鈥� in which the immune system floods the body with inflammatory chemicals, can do more damage than the virus itself.

In an effort to calm the immune system, researchers are testing immune-suppressing drugs, including monoclonal antibodies already used to treat autoimmune diseases such as rheumatoid arthritis, said Dr. Amesh Adalja, a senior scholar at the Johns Hopkins Center for Health Security.

Dr. Anar Yukhayev, pictured on March 24, was hospitalized at Long Island Jewish Medical Center for COVID-19. He agreed to join a clinical trial of Kevzara, an immune suppressant.(Courtesy of Dr. Anar Yukhayev)

Health care giant Roche is conducting large clinical trials of its drug, , in the hope of preventing cytokine storms, which can cause organ failure and a life-threatening condition called sepsis. Actemra is designed to lower levels of an inflammatory chemical, interleukin-6, which has been found to be elevated in some COVID-19 patients.

Scientists are also studying similar drugs, and .

Another immune suppressant from Regeneron and Sanofi, called , has had disappointing results in clinical trials. The manufacturers plan to continue studying the drug to see if it can help certain types of patients.

a New York OB-GYN who was hospitalized with COVID-19 on March 16, agreed to join a clinical trial of Kevzara.

鈥淚 was having so much trouble breathing that I was desperate for anything to help,鈥� said Yukhayev, 31, who was treated at Long Island Jewish Medical Center.

About 36 hours after receiving an infusion, as Yukhayev was being treated in intensive care, his symptoms began to improve. He was able to avoid being put on a ventilator. Doctors didn鈥檛 tell him if he received Kevzara or a placebo, but his liver enzymes also began to rise, suggesting the organ was under stress. Elevated liver enzymes are a known side effect of Kevzara.

Yukhayev made a full recovery and went back to work full time April 13. He donated his plasma to researchers.

Until vaccines and other preventive medicines are developed, the best way to prevent coronavirus infections is to maintain social distancing, Adalja said.

鈥淪ocial distancing is a blunt tool,鈥� he said, 鈥渂ut it鈥檚 all that we have.鈥�

Dr. Anar Yukhayev donates plasma on April 18, after making a full recovery from COVID-19.(Courtesy of Dr. Anar Yukhayev)