Before COVID-19 even had a name, George Diaz was working with other physicians and health regulators to treat the first U.S. patient with the virus with Gilead Sciences Inc.’s antiviral remdesivir.

Now the infectious disease expert is involved in three trials of Regeneron Pharmaceuticals Inc.'s antibody cocktail, joining thousands of scientists and researchers who are trying to understand how to treat people who have contracted a virus that has killed over 1.1 million people worldwide.

The World Health Organization cast doubt on the effectiveness of remdesivir for treating COVID-19 while U.S. President Donald Trump lauded Regeneron's antibody cocktail. But both therapies have shown promising results in certain people who contract the illness, Diaz said. Pinpointing who those patients are has driven his efforts for most of the year.

An infectious disease physician at Providence St. Joseph Health's Providence Regional Medical Center Everett in Washington state, Diaz treated the first U.S. COVID-19 patient in January 2020. Diaz told S&P Global Market Intelligence that while his hospital had prepared to receive highly infectious patients, little was known about how to tackle the new virus.

"There still was relatively little data coming from China even by the time the patient arrived. So, for example, the genetic sequence of COVID-19 hadn't been made available by the Chinese [government] until about Jan. 12, and our patient came in on the 20th," Diaz said.

Following the release of the genetic sequence, Diaz said the U.S. Centers for Disease Control and Prevention went to work looking for existing drugs and therapies that could be effective against COVID-19 — ultimately deciding on remdesivir. At the time the patient's condition worsened, however, the therapy had only been tested in animal models against other coronaviruses like Middle East respiratory syndrome.

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With the patient's consent, Diaz and his colleagues began treating him with remdesivir on a compassionate-use basis granted by the U.S. Food and Drug Administration.

While WHO's clinical study results, released via pre-print Oct. 15, showed that the drug had little to no effect on reducing mortality or length of hospital stay among patients with COVID-19, Diaz's patient began to feel better soon after treatment and only needed a five-day course of the drug versus the standard 10-day course.

Providence doctors would go on to treat about half a dozen more patients the same way over the next few months, according to Diaz. In March, Diaz and other researchers began a clinical trial testing the effectiveness of a five-day course of remdesivir versus a 10-day course. Results ultimately showed no significant difference between the two regimens.

Regeneron's antibody cocktail

A five-day course of remdesivir was one of the treatments Trump's doctors decided to give him in early October when the president became ill with COVID-19. In addition to the antiviral drug, Trump received Regeneron's antibody cocktail and the steroid dexamethasone.

In an Oct. 7 video, Trump said of Regeneron's REGN-COV2, "It was like unbelievable. I felt good immediately."

While the Tarrytown, N.Y.-based company is still waiting for an emergency use authorization from the FDA, Diaz and other researchers are running three clinical trials testing the efficacy of Regeneron's combination monoclonal antibodies on three different patient groups.

One study is looking at the effects of the antibody cocktail on hospitalized patients like Trump who are not sick enough to be on a ventilator and who have been ill fewer than 10 days. Diaz said the antibody cocktail is more effective earlier on in the disease.

"There's sort of a viral phase where the virus is sort of driving things and then there's an inflammatory phase where the immune system is driving things, and so we believe that reducing the virus being present is most helpful sort of earlier [in the] disease," Diaz said.

The second study looks at patients who are being treated with COVID-19 in an outpatient setting. Early results released by Regeneron showed that treated patients in this cohort had fewer symptoms and faster recovery times. Finally, the third study will measure the effects of the cocktail on exposed contacts or people who live in the same household as COVID-19 positive patients. The idea behind this study, according to Diaz, is that community spread will be decreased if they can prevent contacts from contracting the virus.

Along with its potential to positively affect multiple groups of patients, Diaz said the antibody cocktail would also be easier to manufacture than remdesivir.

"If these trials prove to be effective as a therapy for prevention of COVID, there's going to be a real possibility that this will be available for people that haven't been vaccinated yet or didn't receive the vaccinations that are available for disease prevention, so I think it's really promising in that regard."

Despite cautions surrounding these relatively new and experimental therapies, Diaz said the only way his team and other researchers have been able to get as far as they have in studying COVID-19 therapies and vaccines is because of clinical trials and the patients enrolled in those trials.

"It's not easy being a research participant. There's a lot of testing that we have to do, et cetera, and it's a commitment, but it is a way we move forward," Diaz said. "We're not there yet. There are still plenty of people that die from this disease; we can see the news every day. And to reduce mortality, we just have to have data for clinical trials."