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What’s Regeneron’s antibody cocktail? Experimental Covid-19 treatment given to Trump in 'race against coronavirus'

Called REGN-COV2, it reduced viral levels and improved symptoms in non-hospitalized patients with Covid-19, shows early data on 275 people

After testing positive for the novel coronavirus, President Donald Trump has received a dose of an experimental Covid-19 treatment being developed by Regeneron. In a memo shared by the White House, Trump’s physician Dr Sean Conley said that “as a precautionary measure,” Trump was given “a single 8 gram dose of Regeneron’s polyclonal antibody cocktail.” “He completed the infusion without incident. In addition to the polyclonal antibodies, the president has been taking zinc, vitamin D, famotidine, melatonin, and a daily aspirin. As of this afternoon, the president remains fatigued but in good spirits,” said the statement issued on October 2. Shortly after the memo was released, the White House said the President was being taken to Walter Reed Medical Center “out of an abundance of caution.”

There are no approved treatments for Covid-19 currently, and in a statement, Regeneron confirmed that the antibody cocktail was provided to Trump under compassionate use request. What do we know so far about Regeneron’s antibody cocktail, which is yet to be approved for wider use?

REGN-COV2 is being evaluated for treatment and prevention of Covid-19

Regeneron’s drug, REGN-COV2, is part of a class of experimental Covid-19 drugs known as monoclonal antibodies: Lab-engineered versions of proteins made by the immune system. REGN-COV2 is a combination of two monoclonal antibodies (REGN10933 and REGN10987) and was designed specifically to block the infectivity of SARS-CoV-2, the virus that causes Covid-19. “To develop REGN-COV2, Regeneron scientists evaluated thousands of fully-human antibodies produced by the company’s VelocImmune mice, which have been genetically modified to have a human immune system, as well as antibodies identified from humans who have recovered from Covid-19,” explains the biotechnology company.

The first data on this investigational antibody cocktail reveals that it reduced viral levels and improved symptoms in non-hospitalized patients with Covid-19. REGN-COV2 also showed positive trends in reducing medical visits. The greatest improvements were seen in patients who had not mounted their effective immune response before treatment. The ongoing, randomized, double-blind trial measures the effect of adding REGN-COV2 to usual standard-of-care, compared to adding placebo to standard-of-care. It is part of a larger program that also includes studies of REGN-COV2 for the treatment of hospitalized patients, and for prevention of infection in people who have been exposed to Covid-19 patients.

“After months of incredibly hard work by our talented team, we are extremely gratified to see that Regeneron's antibody cocktail REGN-COV2 rapidly reduced viral load and associated symptoms in infected Covid-19 patients. The greatest treatment benefit was in patients who had not mounted their own effective immune response, suggesting that REGN-COV2 could provide a therapeutic substitute for the naturally-occurring immune response. These patients were less likely to clear the virus on their own, and were at greater risk for prolonged symptoms,” said Dr George D Yancopoulos, president and chief scientific officer of Regeneron in a September 29 statement.

He added, “We are highly encouraged by the robust and consistent nature of these initial data, as well as the emerging well-tolerated safety profile, and we have begun discussing our findings with regulatory authorities while continuing our ongoing trials. In addition to having positive implications for REGN-COV2 trials and those of other antibody therapies, these data also support the promise of vaccines targeting the SARS-CoV-2 spike protein.”

The analysis covers the first 275 patients enrolled in the trial, which was designed to analyze anti-viral activity with REGN-COV2 and identify patients most likely to benefit from treatment. The next cohort, which could be used to rapidly and prospectively confirm these results, has already been enrolled. Patients in the trial were randomized 1:1:1 to receive a one-time infusion of 8 grams of REGN-COV2 (high dose), 2.4 grams of REGN-COV2 (low dose), or placebo. All Covid-19 patients entering the trial were being treated in the outpatient setting.

“Patients were prospectively characterized prior to treatment by serology tests to see if they had already generated antiviral antibodies on their own and were classified as seronegative (no measurable antiviral antibodies) or seropositive (measurable antiviral antibodies). Approximately 45% of patients were seropositive, 41% were seronegative and 14% were categorized as "other" due to unclear or unknown serology status,” the findings state.

Among the first 275 patients, about 56% were Hispanic, 13% were African-Americans and 64% had one or more underlying risk factors for severe coronavirus, including obesity (more than 40%). On average, patients were 44 years of age. In total, 49% of participants were male and 51% were female.

A high dose of REGN-COV2 led levels of the virus to decrease more quickly in non-hospitalized Covid-19 patients. Patients who were seronegative and/or had higher baseline viral levels also had greater benefits in terms of symptom alleviation. Among seronegative patients, the median time to symptom alleviation (defined as symptoms becoming mild or absent) was 13 days in placebo, 8 days in high dose, and 6 days in low dose. Patients with increasing viral loads at baseline had correspondingly increasing benefit in time to symptom alleviation, suggests trial results.

According to the company, both doses were well-tolerated. However, infusion reactions were seen in four patients (two on placebo and two on REGN-COV2). Serious adverse events occurred in two placebo patients, one low dose patient, and no high dose patients. There were no deaths in the trial. “More than 2,000 people have been enrolled across the overall REGN-COV2 development program, and no unexpected safety findings have been reported by the Independent Data Monitoring Committee,” said the company.