Sanofi and Regeneron's investigational rheumatoid arthritis drug sarilumab has succeeded in a late-stage trial.

The year-long Phase III study enrolled 1,200 patients with active, moderate-to-severe RA who were inadequate responders to methotrexate. Patients were randomised to one of three subcutaneous treatment groups, all in combination with MTX and dosed every other week - sarilumab 200mg, 150mg or placebo.

Both sarilumab groups met all three co-primary endpoints. First up, 66% of patients on 200mg reached an ACR20 response rate (ie a 20% improvement in the condition), while the ACR20 response rate for the 150mg dose was 58% and 33% for placebo plus MTX. In terms of the other two endpoints, sarilumab improved physical function at week 16 and inhibiting progression of joint damage at week 52.

Sarilumab is a subcutaneously administered, fully-human antibody targeting the interleukin-6 receptor and Neil Graham, head of immunology and inflammation at Regeneron, noted that “IL-6 blockade is emerging as an important therapeutic approach for rheumatoid arthritis". Tanya Momtahen, who leads the sarilumab project at Sanofi, added that the firm was particularly encouraged by the impact sarilumab demonstrated on inhibition of progression of structural damage.

The treatment is in the same class as Roche's RA blockbuster Actemra/RoActemra (tocilizumab) and earlier this year, Sanofi started enrolling patients for two late-stage trials comparing sarilumab with the Swiss major's treatment and Pfizer/Amgen's Enbrel (etanercept).