A randomised, double-blind, placebo-controlled, first-in-human phase I study to characterise the safety, pharmacokinetics and immunogenicity of 9MW1411 in healthy Chinese subjects

9MW1411 is a humanised monoclonal antibody against Staphylococcus aureus alpha-toxin. The safety, pharmacokinetics (PK) and immunogenicity of 9MW1411 should be characterised in humans before further clinical development. A single-centre, randomised, double-blind, placebo-controlled phase I clinical study was conducted in humans for the first time. A total of 42 healthy Chinese subjects were randomised to receive a single ascending dose of 9MW1411 (200, 600, 1500, 3000 or 5000 mg) or placebo. Safety, PK parameters and anti-drug antibody (ADA) were analysed. Monte Carlo simulations (MCS) were performed to predict the probability of target attainment (PTA) after single dose IV administration of 1500, 3000 and 5000 mg of 9MW1411. Thirty-four subjects received 9MW1411, completed the study and were included in data analysis. Five cases of drug-related AEs occurred in four subjects. All the adverse events (AEs) were mild or moderate. The Cmax, AUC0-t and AUC0-∞ of 9MW1411 increased with dose after IV administration of 200 to 5000 mg 9MW1411. The mean Cmax increased from 85.40 ± 5.43 to 2082.11 ± 343.10 µg/mL and AUC0-∞ from 29,511.68 ± 5550.91 to 729,985.49 ± 124,932.18 h·µg/mL. The elimination half-life (T1/2) was 19–23 days. 9MW1411 ADA was positive in three subjects. MCS indicated that a single dose of 3000 or 5000 mg 9MW1411 could achieve PTA > 90% for S. aureus. 9MW1411 has shown a good safety profile in healthy Chinese subjects after a single dose up to 5000 mg. A single dose of 3000 mg 9MW1411 is appropriate for use in subsequent studies.