Long-time collaborators Sanofi and Regeneron Pharmaceuticals have presented positive mid-stage data on sarilumab for rheumatoid arthritis but another trial showed that the antibody is less effective for ankylosing spondylitis.

The 306-patient Phase IIb MOBILITY trial looked at sarilumab, a subcutaneously administered, fully-human antibody targeting the interleukin-6 receptor, in combination with a standard RA treatment, methotrexate (MTX). It demonstrated that patients achieved a significant and clinically meaningful improvement in signs and symptoms of moderate-to-severe RA compared to patients treated with MTX alone. The primary endpoint of the study was the proportion of patients achieving at least a 20% improvement in RA symptoms (ACR20) after 12 weeks.

An ACR20 response after 12 weeks was seen in 49.0% of patients receiving the lowest sarilumab dose regimen and 72.0% of patients receiving the highest dose regimen compared to 46.2% of patients receiving placebo and MTX.  The most common adverse events reported more frequently in active treatment arms included infections (non-serious), neutropenia, and liver function test abnormalities, though Sanofi noted that these side effects were consistent with those previously reported with IL-6 inhibition.

Elias Zerhouni, head of R&D at Sanofi, noted that "following these encouraging Phase IIb results in RA the companies are currently discussing the dose(s) of sarilumab to advance into the Phase III portion of the MOBILITY  trial". If all goes well, sarilumab would go up against Roche's IL-6 inhibitor RoActemra/Actemra (tocilizumab).

Less successful was the Phase IIb ALIGN trial in ankylosing spondylitis. Sarilumab did not demonstrate significant and clinically meaningful improvements in signs and symptoms of active AS compared to placebo in patients who had inadequate response to nonsteroidal anti-inflammatory drugs (NSAIDs).

Sanofi and Regeneron have been working together on a number of projects since 2007 and their most advanced project is the colon cancer treatment Zaltrap (aflibercept). Marketing applications will be made to the US Food and Drug Administration and the European Medicines Agency in the second half of the year.