Eastview, NY—When the FDA revised the Emergency Use Authorization (EUA) for REGEN-COV (casirivimab and imdevimab, administered together) authorizing the combination for postexposure prophylaxis, it specifically emphasized that the product was not authorized for preexposure prophylaxis to prevent COVID-19 before being exposed to the SARS-CoV-2 virus—only after exposure to the virus.

The revision was for adults and children aged 12 years or older who weigh at least 40 kg and are at high risk for progression to severe COVID-19, including hospitalization or death.

The FDA said that REGEN-COV also remains authorized for the treatment of mild-to-moderate COVID-19 in adults and pediatric patients (age 12 years and older weighing at least 40 kg) with positive results of direct SARS-CoV-2 viral testing and who are at high risk for progression to severe COVID-19, including hospitalization or death.

Regeneron Pharmaceuticals, Inc. announced recently that the investigational antibody cocktail REGN-COV2 reduced viral load and the time to alleviate symptoms in nonhospitalized patients with COVID-19 while also showing positive trends in reducing medical visits.

“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,” said George D. Yancopoulos, MD, PhD, president and chief scientific officer of Regeneron. “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. 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 descriptive analysis included the first 275 patients enrolled in the trial with the purpose of evaluating antiviral activity with REGN-COV2 and identifying patients most likely to benefit from treatment.

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 patients entering the trial had laboratory-confirmed COVID-19 that was being treated in the outpatient setting.

Prior to treatment, patients were prospectively categorized by serology tests to determine if they had already generated antiviral antibodies on their own. They were classified as seronegative (no measurable antiviral antibodies) or seropositive (measurable antiviral antibodies). About 45% of patients were seropositive, 41% were seronegative, and 14% were categorized as “other” due to unclear or unknown serology status.

The researchers found that serological status at baseline predicted how rapidly patients’ COVID-19 clinical symptoms were alleviated. In the untreated (placebo) group, seropositive patients had a median time to alleviation of symptoms of 7 days compared with seronegative patients, who had a median time to alleviation of symptoms of 13 days, according to the trial.

Regeneron also advised that REGN-COV2 rapidly reduced viral load through Day 7 in seronegative patients, which was a key virologic endpoint, and that patients with increasingly higher baseline viral levels had correspondingly greater reductions in viral load at Day 7 with treatment.

Meanwhile, patients who were seronegative and/or had higher baseline viral levels also had greater benefits in terms of symptom alleviation. Those receiving placebo saw symptoms become mild or resolve in an average of 13 days compared with 8 days with a high dose of the monoclonal antibody and 6 days with a low dose.

The company press release noted that few patients had to have medically attended visits—hospitalization, emergency department, urgent care, or telemedicine visits—for COVID-19. Most occurred in patients who were seronegative at baseline, the researchers wrote. In the seronegative group, 15.2% of placebo-treated patients, 7.7% of patients treated with the high dose, and 4.9% of patients treated with the low dose required additional medical visits.

Both the high and low doses were well tolerated, the researchers added.

The FDA strongly emphasizes that “prophylaxis with REGEN-COV is not a substitute for vaccination against COVID-19.”

The FDA notes that monoclonal antibodies are laboratory-made proteins that mimic the immune system’s ability to fight off harmful pathogens, such as viruses like SARS-CoV-2. The authorized dose for REGEN-COV for both treatment and as postexposure prophylaxis is 600 mg of casirivimab and 600 mg of imdevimab administered together.

While regulators strongly recommend IV infusion, SC injection is authorized as an alternative route of administration when IV infusion is not feasible and would lead to delay in treatment.

The content contained in this article is for informational purposes only. The content is not intended to be a substitute for professional advice. Reliance on any information provided in this article is solely at your own risk.