IV, SC doses of biologic combo effective in asymptomatic, low-risk COVID-19 patients

All intravenous (IV) and subcutaneous (SC) doses of the monoclonal antibody combination of casirivimab plus imdevimab effectively reduces viral load in COVID-19 patients with asymptomatic or low-risk symptomatic infection, according to the results of a phase II study.

The study randomized 815 patients to receive a single IV dose (n=523) of casirivimab plus imdevimab at 300, 600, 1,200, or 2,400 mg or placebo; or a single SC dose (n=292) of casirivimab plus imdevimab at 600 or 1,200 mg or placebo.

For the primary endpoint, researchers assessed the time-weighted average daily change from baseline (TWACB) in viral load from day 1 (baseline) through day 7 in patients seronegative for SARS-CoV-2 at baseline.

A total of 507 patients were seronegative at baseline and included in the primary efficacy analysis. Of these, 282 patients were randomized to IV treatment (mean age 34.6 years, 44.6 percent men), 148 to SC treatment (mean age 34.1 years, 45.3 percent men), and 77 to placebo. 

All patients who received the investigational drug, regardless of the route of administration and dose, showed significant virologic reduction through day 7. Least-squares mean differences in TWACB viral load with casirivimab plus imdevimab vs placebo ranged from –0.56 log10 copies/mL (95 percent confidence interval [CI], –0.89 to –0.24) for the 1,200-mg IV dose to –0.71 log10 copies/mL (95 percent CI, –1.05 to –0.38) for the 2,400-mg IV dose.

There were no reports of adverse safety signals or dose-related safety findings, grade ≥2 infusion-related or hypersensitivity reactions, grade ≥3 injection-site reactions, or fatalities. Two patients had serious adverse events not related to COVID-19 or the study drug.