Lilly and Incyte have filed for US approval of the experimental JAK inhibitor baricitinib as a treatment for moderately-to-severely active rheumatoid arthritis.

The drug is the only once-daily oral selective JAK1 and JAK2 inhibitor currently in late-stage clinical studies for inflammatory and autoimmune diseases and so, if approved, would offer patients a new treatment option.

Data from the Phase III RA-BEAM trial showed that baricitinib scored significantly better than placebo on the ACR20 response, a standard clinical measure that represents at least a 20% improvement in RA disease activity, as well as demonstrating superiority to AbbVie’s multi-billion-dollar blockbuster Humira (adalimumab), the world’s biggest selling drug.

After 24 weeks, the drug was also superior to placebo in preventing progressive radiographic structural joint damage, and its treatment benefits were maintained through 52 weeks of therapy.

In the RA-BEGIN trial, the drug also outperformed methotrexate on the ACR20 measure while, elsewhere, data showed efficacy in RA patients with inadequate responses to traditional disease-modifiying anti-rheumatic drugs (in the RA-BUILD trial) and biological therapies (in RA-BEACON).

As per the terms of their 2009 agreement, submission of the new drug application has triggered a $35-million milestone payment from Lilly to Incyte, while US approval would also bring the latter a further $100 million, as well sales-based milestones and royalties. 

Lilly will lead launch and global commercialisation efforts for baricitinib in RA if it gain the regulatory nod, and also owns global rights to develop and commercialise the drug as an oral treatment for all inflammatory conditions. Phase II trials are ongoing in psoriasis, diabetic nephropathy, atopic dermatitis and systemic lupus erythematosus.