Sanofi and Regeneron's would-be blockbuster tops Humira in arthritis

Sanofi ($SNY) and Regeneron ($REGN), awaiting FDA approval for a potential blockbuster rheumatoid arthritis treatment, burnished the drug's profile with Phase III data showing it beat AbbVie's ($ABBV) top-selling Humira head to head.

The treatment, sarilumab, is an antibody targeting the inflammation-related protein interleukin-6 to treat autoimmune disease. In a late-stage trial enrolling 369 patients, the therapy beat out Humira in clearing up rheumatoid arthritis symptoms after 24 weeks by a statistically significant margin, at the same time meeting secondary goals of improving disease scores and physical function, Sanofi and Regeneron said.

On the safety side, the two treatments came through with similar rates of the most common side effects, according to the companies, but sarilumab led to more instances of neutropenia, which affected 14% of patients versus just 1% of those taking Humira.

The partners have already submitted sarilumab for FDA approval, and the agency has promised to hand down a decision by Oct. 30. Regulators won't consider the antibody's head-to-head victory over Humira in their review, but the positive data will likely help Sanofi and Regeneron make their case to payers and physicians if and when sarilumab is approved.

The treatment has long been pegged as a blockbuster in waiting, with 2020 sales predicted to hit $1.8 billion, according to analyst estimates compiled by EvaluatePharma.

Sarilumab is positioned to become the second approved product to come out of from Sanofi's wide-ranging partnership with Regeneron, following last year's launch of Praluent, an antibody designed to clear out bad cholesterol by blocking a protein called PCSK9. Analysts expect that treatment to eventually bring in as much as $3 billion as it competes with a similar injection from Amgen ($AMGN), also approved in 2015.

Sarilumab has already demonstrated its efficacy in 7 Phase III trials in more than 2,500 subjects, beating out placebo in a variety of RA disease states and making a difference for patients who can't tolerate Humira and its rival Enbrel, made by Amgen.

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