Background/Purpose: Based on the evaluation of physicochemical, biological, preclinical, and clinical data, a biosimilar may be approved for use in the same indications for which the reference medicine is approved. A prerequisite for this extrapolation is clinical confirmation of biosimilarity in a  population sensitive enough to detect potential differences in efficacy, safety, or immunogenicity between the proposed biosimilar and the reference medicine. GP2017, a proposed biosimilar to adalimumab, was investigated in patients with moderate-to-severe chronic plaque psoriasis.

Methods: Eligible patients were randomized to receive an initial dose of 80 mg subcutaneous GP2017 or reference adalimumab, followed by 40 mg every other week, starting one week after the initial dose. To evaluate long-term effects and the impact of multiple switches between GP2017 and reference adalimumab, patients with ≥PASI 50 at Week 16 were re-randomized at Week 17 in a 2:1 ratio to either remain on their initial study treatment or undergo a sequence of three treatment switches between GP2017 and reference adalimumab until Week 35. Thereafter, patients were returned to their originally randomized treatment up to Week 51.

Results: Initially, 465 patients, including 98 (21.1%) with psoriatic arthritis, were randomized to GP2017 (n=231) or reference adalimumab (n=234). At Week 17, 379 patients were re-randomized to continue treatment with GP2017 (n=126) or reference adalimumab (n=127) or to switch between GP2017 and reference adalimumab, or vice versa (n=63 in each group). There were no clinically relevant differences in efficacy and safety between the continued and switched groups across the entire study duration (Table). At preferred term level, no severe/serious adverse events (AEs) were reported by more than one patient in a treatment group. Infections/infestations were the most common treatment-emergent AEs, with nasopharyngitis most frequently reported by 11.1% (reference adalimumab to GP2017), 12.6% (continued adalimumab), 12.7% (GP2017 to reference adalimumab) and 9.5% (continued GP2017) of patients. The incidence of injection site reactions was low and similar among the individual groups. Overall, from Week 1 to 51, differences in the frequency of antidrug antibody (ADA) detection were <11% among the individual groups; most ADA (75–100%) were neutralizing.

Conclusion: There were no clinically meaningful differences in long-term efficacy among patients who received continued GP2017 and reference adalimumab, or who switched between GP2017 and reference adalimumab multiple times. Switching treatments was well tolerated; overall safety profiles and immunogenicity rates were similar between the individual treatment groups. The data add to the totality of evidence suggesting GP2017 could be used as a biosimilar for the treatment of the same indications for which reference adalimumab is approved.