Sanofi and Regeneron Pharmaceuticals have recently announced that a Phase 3 study of sarilumab, an investigational, fully-human IL6 receptor antibody, met its co-primary efficacy endpoints of a greater improvement in signs and symptoms of rheumatoid arthritis (RA) at 24 weeks, and physical function at 12 weeks compared to placebo. Sarilumab is the first fully-human monoclonal antibody directed against the IL-6 receptor (IL-6R). Sarilumab binds with high affinity to the IL-6 receptor. It blocks the binding of IL-6 to its receptor and interrupts the resultant cytokine-mediated inflammatory signaling. Sarilumab was developed using Regeneron’s VelocImmune® antibody technology. The study, called SARIL-RA-TARGET, evaluated the efficacy and safety of two subcutaneous sarilumab doses versus placebo, added to non-biologic disease modifying anti-rheumatic drugs (DMARD) therapy in RA patients who were inadequate responders to or intolerant of TNF-alpha inhibitors (TNF-IR).

The SARIL-RA-TARGET trial enrolled 546 TNF-IR patients who were randomized to one of three treatment groups self-administered subcutaneously (SC) every other week (Q2W): sarilumab 200 milligrams (mg), sarilumab 150 mg, or placebo, in addition to DMARD therapy. Both sarilumab groups showed clinically relevant and statistically significant improvements compared to the placebo group in both co-primary endpoints (p < 0.001):

  1. Improvement in signs and symptoms of RA at 24 weeks, as measured by the American College of Rheumatology (ACR20) score of 20 percent improvement, were as follows: 61 percent in the sarilumab 200 mg group; 56 percent in the sarilumab 150 mg group; and 34 percent in the placebo group, all in combination with DMARD therapy.
  2. Improvement in physical function, as measured by change from baseline in the Health Assessment Question-Disability Index (HAQ-DI) at week 12.

The most frequently reported adverse events included infections (30, 22 and 27 percent in the 200 mg, 150 mg and placebo groups respectively) and injection site reactions (8, 7, 1 percent in the 200 mg, 150 mg and placebo groups respectively). Serious infections were uncommon (1, 0.6 and 1 percent in the 200 mg, 150 mg and placebo groups respectively). Reduction in neutrophil count was the most common lab abnormality. No unexpected safety findings were observed. Two additional trials from the Phase 3 program, SARIL-RA-EASY and SARIL-RA-ASCERTAIN, also met their primary endpoints.

SARIL-RA-EASY enrolled 217 patients and was designed to evaluate the technical performance and usability of the sarilumab autoinjector device. There were no product technical failures with the auto-injector, the primary endpoint of the study. SARIL-RA-ASCERTAIN was a 202-patient safety calibrator study, designed to assess the safety of two subcutaneous doses of sarilumab and tocilizumab infusion in combination with DMARDs in patients with RA who were TNF-IR. There were no clinically meaningful differences between the treatment groups in serious adverse events and serious infections.