We report pharmacokinetics, pharmacodynamics, and safety of a novel anti‐CD28 domain antibody antagonist (lulizumab pegol) in healthy subjects following single‐ or multiple‐dose administration. A minimal anticipated biological effect level approach was used to select a 0.01 mg starting dose for a single‐ascending‐dose (SAD), double‐blind, first‐in‐human study. Part 1 included 9 intravenous (IV; 0.01‐100 mg) and 3 subcutaneous (SC; 9‐50 mg) doses or placebo. In part 2, a keyhole limpet hemocyanin (KLH) immunization was performed in 16 subjects/panel, who received 1 of 3 IV doses (9‐100 mg) or placebo. In a double‐blind, multiple‐ascending‐dose (MAD) study, subjects received SC lulizumab 6.25 mg every 2 weeks, 12.5 mg weekly, 37.5 mg weekly, or placebo. Among 180 treated subjects, 169 completed the studies. Peak concentrations and areas under the curve from time 0 to infinity increased dose proportionally. Estimated SC bioavailability was 68.2%. Receptor occupancy of approximately ≥80% was maintained for ≥2 weeks at ≥9‐mg doses (SAD) and throughout the dosing interval (MAD). IV doses ≥9 mg inhibited antibody production against KLH for 2 weeks. No significant cytokine or immune cell changes were observed. No immunogenicity responses persisted, and there was no correlation to adverse events. Headache occurred in 21 SAD and 4 MAD subjects receiving lulizumab; in the MAD study 5 lulizumab subjects experienced infections. Lulizumab IV or SC was safe at all doses studied, without evidence of cytokine release.
