SAN FRANCISCO, CA—The efficacy and safety profiles of SB4, an etanercept biosimilar, were comparable to those of etanercept in patients with moderate to severe rheumatoid arthritis (RA) to Week 52, according to study findings presented at the 2015 ACR/ARHP Annual Meeting.

In the randomized, double-blind, multi-center study, researchers aimed to compare long-term efficacy, safety, and immunogenicity between SB4 and the reference etanercept product. The primary end point was ACR20 at Week 24; study authors also reported on radiographic progression.

In this presentation, Paul Emery, MD, from the Leeds Institute of Rheumatic and Musculoskeletal Medicine, University of Leeds, United Kingdom reported on the Phase 3 study’s 52-week results.

The trial randomly assigned patients with moderate to severe RA (n=596) to 50g/week of SB4 or etanercept with background methotrexate therapy; 505 patients completed 52 weeks of treatment. At Week 52, the ACR20 response rate was 80.8% in the SB4 group vs. 81.5% in the etanercept group under the per-protocol set (PPS). According to the full analysis set, the ACR20 response rate was 70.2% vs. 65.7%, respectively (95% CI: -2.90%, 11.87%). Both study groups showed similar ACR50 (47.8% vs. 42.1%) and ACR70 (30.4% vs. 24.6%) response rates and mean change from baseline in mTSS.

SB4 and etanercept demonstrated generally comparable safety profiles, Dr. Emery noted. Serious infections were reported in 1 patient in the SB4 group (cholecystitis, liver abscess and peritonitis) and 5 patients in the etanercept group (cellulitis, appendicitis, cholecystitis, erysipelas, liver abscess, peritonitis, and pneumonia). No cases of active tuberculosis were observed.

The SB4 group reported fewer injection site reactions compared with the etanercept group (3.7% vs. 17.5%), and significantly fewer anti-drug antibody formation vs. the etanercept group (3 vs. 39 patients; P<0.001) was observed. However, this lower immunogenicity profile when compared with etanercept “does not preclude SB4 as a biosimilar,” he noted. In addition, there was “no correlation between anti-drug antibody development and injection site reactions.”

Study findings demonstrated “comparable and negligible” radiographic progression up to Week 52, he concluded.