Long-term efficacy, safety, and immunogenicity of the adalimumab biosimilar, PF-06410293, in patients with rheumatoid arthritis after switching from reference adalimumab (Humira®) or continuing biosimilar therapy: week 52–92 data from a randomized, double-blind, phase 3 trial

BACKGROUND/OBJECTIVE: REFLECTIONS B538–02 is a randomized, double-blind comparative study of the adalimumab (ADL) biosimilar PF-06410293, (ADL-PF), and reference ADL sourced from the European Union (ADL-EU) in patients with active RA. Therapeutic equivalence was demonstrated based on ACR20 responses at week 12 (primary endpoint). We report long-term safety, immunogenicity, and efficacy of ADL-PF in patients who continued ADL-PF treatment throughout 78 weeks or who switched from ADL-EU to ADL-PF at week 26 or week 52. METHODS: Eligible patients (2010 ACR/EULAR RA diagnosis criteria for ≥ 4 months; inadequate response to MTX, ≤ 2 doses non-ADL biologic), stratified by geographic regions were initially randomized (1:1) in treatment period 1 (TP1) to ADL-PF or ADL-EU (40 mg subcutaneously, biweekly), both with MTX (10–25 mg/week). At week 26 (start of TP2), patients receiving ADL-EU were re-randomized to remain on ADL-EU or transition to ADL-PF for 26 weeks. At week 52 (start of TP3), all patients received open-label treatment with ADL-PF for 26 weeks and were followed after last treatment dose to week 92. To evaluate maintenance of response after switching or remaining on ADL-PF, ACR20, DAS28-4(CRP), and other measures of clinical response/remission were assessed through week 78 as secondary endpoints. Three groups were evaluated: biosimilar, week 26 switch, and week 52 switch. RESULTS: Overall, 507 patients participated in TP3. ACR20 response rates at week 52 were 88.4%, 88.2%, and 87.6% for the biosimilar, week 26, and week 52 switch groups, respectively. ACR20 response rates and DAS28-4(CRP) scores were sustained and comparable across groups in TP3. Incidence of treatment-emergent adverse events (AEs) during TP3 and follow-up was 42.6% (biosimilar), 37.0% (week 26 switch), and 50.8% (week 52 switch); 3 (0.6%) patients (all week 52 switch) reported treatment-related serious AEs. ADL-PF was generally well tolerated, with a comparable safety profile across groups. Overall, incidences of patients with anti-drug antibodies in TP3 and follow-up were comparable among groups (46.1%, 46.5%, and 54.2%, respectively). CONCLUSIONS: There were no clinically meaningful differences in safety, immunogenicity, and efficacy for patients who were maintained on ADL-PF for 78 weeks and those who had switched from ADL-EU at week 26 or week 52. TRIAL REGISTRATION: ClinicalTrials.gov, NCT02480153. First posted on June 24, 2015; EU Clinical Trials Register; EudraCT number: 2014-000352-29. Start date, October 27, 2014 SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s13075-021-02626-4.