Phase 2 Safety and Antiviral Activity of SAB-185, a Novel Polyclonal Antibody Therapy for Nonhospitalized Adults With COVID-19

Abstract Background SAB-185, a novel fully human IgG polyclonal immunoglobulin product, underwent phase 2 evaluation for nonhospitalized adults with mild-moderate coronavirus disease 2019 (COVID-19). Methods Participants received intravenous SAB-185 3840 units/kg (low-dose) or placebo, or 10 240 units/kg (high-dose) or placebo. Primary outcome measures were nasopharyngeal severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) RNA < lower limit of quantification (LLOQ) at study days 3, 7, and 14, time to symptomatic improvement, and safety through day 28. Results Two-hundred thirteen participants received low-dose SAB-185/placebo (n = 107/106) and 215 high-dose SAB-185/placebo (n = 110/105). The proportions with SARS-CoV-2 RNA < LLOQ were higher for SAB-185 versus placebo at days 3 and 7 and similar at day 14, and significantly higher at day 7 for high-dose SAB-185 versus placebo only, relative risk 1.23 (95% confidence interval, 1.01–1.49). At day 3, SARS-CoV-2 RNA levels were lower with low-dose and high-dose SAB-185 versus placebo: differences in medians of −0.78 log 10} copies/mL ( P = .08) and −0.71 log 10} copies/mL ( P = .10), respectively. No difference was observed in time to symptom improvement: median 11/10 days ( P = .24) for low-dose SAB-185/placebo and 8/10 days ( P = .50) for high-dose SAB-185/placebo. Grade ≥3 adverse events occurred in 5%/13% of low-dose SAB-185/placebo and 9%/12% of high-dose SAB-185/placebo. Conclusions SAB-185 was safe and generally well tolerated and demonstrated modest antiviral activity in predominantly low-risk nonhospitalized adults with COVID-19. Clinical Trials Registration.  NCT04518410.