Regeneron's COVID-19 antibody cuts medical visits in phase 2/3 trial

Regeneron’s anti-SARS-CoV-2 antibody cocktail has significantly reduced medical visits in ambulatory COVID-19 patients. The phase 2/3 clinical trial linked REGN-COV2 to a 57% decline in medical visits associated with COVID-19 in the 29 days after treatment.

One month ago, Regeneron shared data on the first 275 patients enrolled in the study. That update, which provided early evidence that REGN-COV2 reduces viral load, set Regeneron up to apply for FDA emergency use authorization. Now, Regeneron has shared data on an additional 525 patients to further elucidate the effect of REGN-COV2 on viral load and clinical endpoints.

The primary endpoint looked at average daily change in viral load through to Day 7 of the trial. In patients with a high viral load, REGN-COV2 drove a 0.68 log10 copies/mL greater reduction than the placebo. The effect was particularly pronounced over the first five days of the trial, over which period Regeneron linked REGN-COV2 to a tenfold reduction in viral load. A smaller, but still statistically significant, difference was seen in patients with all levels of viral load at baseline.

Those results validate the preliminary findings Regeneron released one month ago. At that time, the number of patients who had been hospitalized or required emergency room, urgent care or telemedicine visits for COVID-19 was too small to confirm the effect of REGN-COV2 on that clinical endpoint. 

In the expanded data set, Regeneron found 2.8% of patients who received REGN-COV2 had a medical visit related to COVID-19 through to Day 29, compared to 6.5% of people in the placebo cohort. The p-value was 0.024. Regeneron saw a bigger effect in patients with one or more risk factors, such as being over 50 years of age or having a body mass index greater than 30. In that high-risk subgroup, Regeneron linked REGN-COV2 to a 72% reduction in medical visits.

The size of the study population, 799 patients, means the numbers of people who may have been spared a medical visit by REGN-COV2 are relatively small. However, as with data on Eli Lilly’s rival antibody, the direction of the results favors the use of REGN-COV2 as a way to stop the progression of COVID-19.

REGN-COV2 was well tolerated in the trial, with numerically more serious adverse events happening in the placebo cohort. The one negative was the failure to find robust associations between symptom alleviation and viral load, serology status or treatment. The study lacked a formal statistical analysis of symptom alleviation.

The REGN-COV2 data include patients who received the high dose, 8 grams, and low dose, 2.4 grams. Regeneron pooled the two cohorts after finding dose had no significant effect on virologic or clinical efficacy. In light of the finding, Regeneron is considering changing the dose in its ongoing outpatient clinical trial.

Showing that 2.4 grams of REGN-COV2 is as effective as 8 grams could have a significant effect on the availability of the antibody cocktail. Regeneron partnered with Roche in August to more than triple REGN-COV2 manufacturing capacity but, with COVID-19 cases rising around the world, demand may still outstrip supply. Using 2.4 grams of REGN-COV2, a dose that is 70% lower than the high dose, may ease the supply constraints. 

Regeneron has shared the data with the FDA and is continuing to generate data on REGN-COV2. The phase 3 portion of the trial that read out this week is continuing, as are a phase 2/3 study in people hospitalized with COVID-19, an open-label trial of hospitalized patients and a phase 3 trial that is assessing the prophylactic power of REGN-COV2.