CT-P17 Adalimumab Biosimilar in Patients with Moderate-to-Severe Chronic Plaque Psoriasis: An Open-Label Extension of a Phase 3 Interchangeability Study

Introduction: A 27-week analysis of this phase 3 study demonstrated the interchangeability of the adalimumab biosimilar CT-P17 and reference adalimumab. The current 52-week analysis reports secondary data from the open-label extension period (OLE) of the study. Methods: In this randomized, double-blind, active-controlled phase 3 study, adults with moderate-to-severe chronic plaque psoriasis received (via prefilled syringe) 80 mg subcutaneous reference adalimumab on day 1, then 40 mg 1 week later, and every other week (EOW) until week 11. At week 13, patients were randomized (1:1) to continue reference adalimumab (“continuous” group) or undergo repeated switching between CT-P17 and reference adalimumab (“switching” group) until week 25. Thereafter, patients entered an OLE and received 40 mg CT-P17 EOW from week 27 to 49, with an end-of-study visit at week 52. Here we present findings from the OLE. Pharmacokinetics (PK), efficacy (including mean percent improvement from baseline in Psoriasis Area Severity Index [PASI] score), safety, and immunogenicity were evaluated. Post hoc subgroup analyses were also conducted. Results: Of 327 patients who initiated the OLE, 152 and 160 patients from the switching group and continuous group, respectively, completed the study. Mean serum concentrations were similar between groups throughout the OLE. Efficacy improvements observed up to week 27 were maintained during the OLE and were comparable between groups. At week 52, overall mean (standard deviation [SD]) improvement from baseline in PASI score was 90.34% (16.59). Safety profiles were similar between groups, and immunogenicity did not increase during the OLE. The mean (SD) percent improvement from baseline in PASI score was slightly lower in patients who were antidrug antibody (ADA)-positive versus those who were ADA-negative (89.57 [17.27] versus 97.29 [4.08]) at week 52. Conclusions: PK, efficacy, safety, and immunogenicity findings remained consistent throughout the OLE, regardless of prior treatment, and were generally comparable across timepoints. Trial registration: ClinicalTrials.gov: NCT05495568.