Pharmacokinetic, Safety, and Immunogenicity Similarity of High‐ and Low‐Concentration Formulations of Adalimumab Biosimilar <scp>ABP</scp> 501, Adalimumab‐Atto

ABP 501, a monoclonal anti-tumor necrosis factor antibody, was the first adalimumab biosimilar approved in the US and EU as a 50 mg/mL formulation. An ABP 501 100 mg/mL high-concentration formulation is also now approved. This study compares pharmacokinetics (PK), safety, and immunogenicity of the low- (ABP 501-LCF) and high-concentration (ABP 501-HCF) formulations in healthy adults. This was a randomized, single-blind, single-dose, parallel-group study in healthy adults. Participants were randomized to receive 40 mg of ABP 501 as HCF or LCF. Primary PK endpoints were area under the concentration-time curve from time 0 extrapolated to infinity (AUC_inf) and maximum observed concentration (C_max) with a 90% confidence interval (CI) for the ratio of least square (LS) geometric means (GM) with a similarity margin of 0.80-1.25. Secondary endpoints included other PK parameters, safety, and immunogenicity. Baseline demographic and other characteristics were comparable between groups. Following study injection, ratios of LS GM (90% CIs) for AUC_inf and C_max between ABP 501-HCF and ABP 501-LCF were 1.04 (0.9634, 1.1297) and 1.06 (0.9960, 1.138), falling within the similarity margin. Both formulations were well tolerated with comparable adverse events. The occurrence of anti-drug antibodies and neutralizing antibodies was comparable between groups. This study demonstrates PK similarity between ABP 501-HCF and ABP 501-LCF following a single subcutaneous injection in healthy adults. Immunogenicity and safety profiles were also similar. Given the totality of evidence of similarity of ABP 501 with adalimumab reference product (RP), it is anticipated that ABP 501-HCF will perform similarly to the RP. Trial Registration: NCT04270747.