Efficacy of subcutaneous vs intravenous infliximab in rheumatoid arthritis: a post-hoc analysis of a randomized phase III trial.

Objectives: The primary endpoint of the pivotal phase III study of infliximab (IFX) s.c. demonstrated non-inferiority of s.c. to i.v. IFX, based on 28-joint DAS-CRP (DAS28-CRP) improvement at week (W) 22 (NCT03147248). This post-hoc analysis investigated whether numerical differences in efficacy outcomes at W30/54 were statistically significant, using conservative imputation methods.

Methods: Patients with active RA and inadequate response to MTX received IFX i.v. 3 mg/kg at W0 and W2 (induction) and were randomized (1:1) to IFX s.c. 120 mg every 2 weeks or i.v. 3 mg/kg every 8 weeks thereafter (maintenance). Patients randomized to IFX i.v. switched to IFX s.c. from W30-54. This post-hoc analysis compared efficacy outcomes for s.c. and i.v. groups pre-switch (W30) and post-switch (W54) using last observation carried forward (LOCF) and non-responder imputation (NRI) methods.

Results: Of 343 randomized patients, 165 (IFX s.c.) and 174 (IFX i.v.) were analysed. At W30, significantly improved outcomes were identified with s.c. vs i.v. IFX for DAS28-CRP/DAS28-ESR/Clinical Disease Activity Index (CDAI)/Simplified Disease Activity Index (SDAI) scores (LOCF); ACR/good EULAR responses, DAS28-CRP/Boolean remission, and DAS28-CRP/DAS28-ESR/CDAI/SDAI low disease activity and remission (LOCF and/or NRI); and minimal clinically important difference in HAQ score (LOCF and NRI). After switching to IFX s.c. from IFX i.v., fewer significant between-group differences were identified at W54.

Conclusion: IFX s.c. showed improved efficacy at W30 compared with IFX i.v., and the reduced between-group difference in efficacy outcomes at W54 after switching supports the results suggesting benefits of IFX s.c. compared with IFX i.v. at W30.

Trial Registration: ClincialTrials.gov, http://clinicaltrials.gov, NCT03147248, https://clinicaltrials.gov/ct2/show/NCT03147248.