Background and objective: Atacicept is an inhibitor of the B lymphocyte stimulator (BLyS) and a proliferation-inducing ligand (APRIL), and is being studied in relation to immunological disease. Currently, limited data on atacicept are available in non-Caucasian subjects. Pharmacokinetic data from earlier studies of atacicept were derived using an enzyme-linked immunosorbent assay (ELISA), which was subsequently found to have inadequacies. Hence, a new bioanalytical ELISA for total atacicept was developed and validated. We conducted this randomized, double-blind, placebo-controlled phase I study to compare the safety, tolerability, pharmacokinetics, and pharmacodynamics of atacicept in healthy Japanese and Caucasian subjects while generating pharmacokinetic data using the new ELISA.
Methods: Japanese subjects aged ≥ 18 to ≤ 55 years (n = 24) were randomized (1:1:1:1) to a single subcutaneous dose of atacicept 25, 75, or 150 mg or placebo. Caucasian subjects were then enrolled to match the Japanese subjects' gender, body weight (± 20%), and height (± 15%).
Results: Atacicept was well tolerated and there were no clinically significant differences in treatment-emergent adverse events (TEAEs), vital signs, or laboratory parameters between the Japanese and Caucasian subjects. Most (90%) TEAEs were mild; no severe or serious TEAEs or deaths occurred. Weight-adjusted atacicept exposure was comparable between ethnicities and across doses: the Japanese/Caucasian ratio of the area under the serum concentration-time curve from time zero to the last sampling point (AUC0-t) was 107.21% (90% CI 93.42-123.02%) and the Japanese/Caucasian ratio of maximum serum concentration (Cmax) was 95.74% (90% CI 74.26-123.43%; ANCOVA). Median time to reach Cmax (tmax) was 20-60 h across all subjects. Dose-exposure relationships were comparable for the two ethnicities, with dose-normalized AUC0-t decreasing with increasing dose, indicating nonlinear pharmacokinetics for the doses examined. There were no statistically significant differences between ethnicities in the pharmacokinetics-dose relationship. Some transient dose-related decreases in mean serum immunoglobulin (Ig)A and IgM, but not IgG, were observed after atacicept administration. There were small transient increases in peripheral B cell numbers in the first 4 days after dosing that were larger with atacicept than with placebo, with no apparent dose relationship. No anti-atacicept antibodies were detected.
Conclusion: The safety, pharmacokinetic, and pharmacodynamic profiles of atacicept in healthy Japanese subjects were comparable to those in healthy Caucasian subjects. EudraCT-ID: 2013-002703-34.