P655 Immunogenicity after transition from adalimumab to ABP 501 in patients with plaque psoriasis

Abstract

Background: ABP 501 (AMGEVITA®; adalimumab) is the first approved biosimilar to adalimumab (Humira®). Here we report immunogenicity results from a Phase 3 study in patients with moderate‐to‐severe plaque psoriasis without concomitant immunosuppressive therapy that undergo a single transition from adalimumab reference product (RP) to ABP 501. In this report we have examined the incidence of anti‐drug antibodies (ADAs) and the relative magnitude of the ADA response among patients that transitioned from adalimumab RP to ABP 501. Methods: Patients were randomised 1: 1 (ABP 501: n = 175; adalimumab RP: n = 175) to receive ABP 501 or adalimumab every 2 weeks for 16 weeks. Eligible subjects who continued treatment beyond Week 16 were re‐randomised in a blinded fashion such that all subjects initially randomised to ABP 501 continued treatment with ABP 501, and subjects initially randomised to adalimumab RP either continued treatment with adalimumab RP or underwent a single transition to ABP 501 in a 1: 1 ratio. The last dose was at Week 48; end of study at Week 52. After re‐randomisation, ADAs were assessed on weeks 20, 32, and 52. A validated electrochemiluminescent assay was used for detection of binding ADAs. Samples positive for binding ADAs were then tested in a TNFα‐target binding assay for neutralising activity. Neutralising antibody titre was reported as the highest dilution that tested positive in the assay. Results: The proportion of subjects positive for binding and neutralising antibodies was comparable from baseline through Week 52, regardless of the transition (adalimumab RP/adalimumab RP 74.7% (59 of 79) binding and 20.3% (16 of 79) neutralising; adalimumab RP/ABP 501 74.0% (57 of 77) binding and 24.7% (19 of 77) neutralising). The overall incidence of binding antibodies that formed after the re‐randomisation at Week 16 was comparable from Week 16 through end of study [adalimumab RP/adalimumab RP 72.2% (57 of 79) vs. adalimumab RP/ABP 501 72.7% (56 of 77)]. To determine the true effect of transition from adalimumab RP to ABP 501, the rate of ADA development was assessed in subjects who were binding ADA negative through Week 16. In this subset, the incidence of binding ADA was similar between the transition group [28.6% (8 of 28)] and those who remained on adalimumab RP [35.5% (11 of 31)]. None of these subjects that tested ADA negative through Week 16 developed neutralising antibodies after transition through Week 52. Conclusions: Transition from adalimumab RP to ABP 501 was not associated with higher immunogenicity.