Efficacy and safety of Sandoz biosimilar rituximab for active rheumatoid arthritis: 52-week results from the randomized controlled ASSIST-RA trial

Objectives. This report provides data for the extent of B cell depletion and recovery, efficacy, safety and immunogenicity of Sandoz rituximab (SDZ-RTX; GP2013; Rixathon (R)) compared with reference rituximab (Ref-RTX) up to week 52 of the ASSIST-RA study. Methods. Patients were randomized to SDZ-RTX or Ref-RTX in combination with methotrexate according to the RTX label. The primary endpoint was analysed at week 24. Responders (28-joint DAS [DAS28] decrease from baseline >1.2) at week 24 with residual disease activity (DAS28 >= 2.6) were eligible for a second treatment course between week 24 and 52. Endpoints after week 24 included change from baseline in peripheral B cells, DAS28, ACR 20% response rate (ACR20), Clinical and Simplified Disease Activity Indexes (CDAI, SDAI) and HAQ disability index (HAQ-DI). Safety and immunogenicity were assessed by the incidence of adverse events and antidrug antibodies. Results. Primary and secondary endpoints up to week 24 were met. Overall, 260/312 randomized patients completed treatment up to week 52. SDZ-RTX resulted in B cell concentrations over time similar to Ref-RTX. The efficacy of SDZ-RTX was similar to Ref-RTX up to week 52, as measured by DAS28, ACR20/50/70, CDAI, SDAI and HAQ-Dl. Safety of SDZ-RTX was similar to Ref-RTX regarding frequency, type and severity of adverse events, which were consistent with the known Ref-RTX safety profile. The incidence of antidrug antibodies was low and transient similarly across treatment groups. Conclusion. SDZ-RTX demonstrated similar B cell concentrations over time, efficacy, safety and immunogenicity to Ref-RTX over 52 weeks of the ASSIST-RA study.