Safety, tolerability, pharmacokinetics and immunogenicity of a monoclonal antibody (SCTA01) targeting SARS-CoV-2 in healthy adults: A randomized, double-blind, placebo-controlled, phase I study

SCTA01 is a novel monoclonal antibody with promising prophylactic and therapeutic potential for COVID-19. This study aimed to evaluate the safety, tolerability, pharmacokinetics (PK) and immunogenicity of SCTA01 in healthy adults. This was a randomized, double-blind, placebo-controlled, dose-escalation phase I clinical trial. Healthy adults were randomly assigned into the following four cohorts, Cohort 1 (n=5, 3:2), Cohort 2 (n=8, 6:2), Cohort 3 and Cohort 4 (both n=10, 8:2), to receive SCTA01 (5, 15, 30 and 50 mg/kg, respectively) versus placebo. All participants were followed up for clinical, laboratory, PK and immunogenicity assessments for 84 days. The primary outcomes were the dose-limiting toxicity (DLT) and maximal tolerable dose (MTD), and the secondary outcomes included PK parameters, immunogenicity and adverse events (AE). Of the 33 participants, 18 experienced treatment-related AEs; the frequency was 52.0% (13/25) in participants receiving SCTA01 and 62.5% (5/8) in those receiving placebo. All AEs were mild. There was no serious AE or death. No DLT was reported, and MTD of SCTA01 was not reached. SCTA01 with a dose range 5-50mg/kg had nearly linear dose-proportional increases in C max and AUC parameters. An anti-drug antibody response was detected in four (16.0%) participants receiving SCTA01, with low titers, between the baseline and day 28, but all became negative later. In conclusion, SCTA01 up to 50mg/kg was safe and well-tolerated in healthy participants. Its PK parameters were nearly linear dose-proportional.