Safety and efficacy of baricitinib at 24 weeks in patients with rheumatoid arthritis who have had an inadequate response to methotrexate

Objectives To investigate baricitinib (LY3009104, formerly INCB028050), a novel, oral inhibitor of JAK1/JAK2 in patients with moderate to severe rheumatoid arthritis (RA) despite treatment with methotrexate. Methods In this phase IIb study, 301 patients were randomised 2:1:1:1:1 to receive once daily doses of placebo or 1, 2, 4 or 8 mg baricitinib for 12 weeks. Patients assigned to 2, 4 and 8 mg baricitinib continued blinded treatment for an additional 12 weeks. Patients assigned to placebo or 1 mg baricitinib were reassigned to 2 mg twice daily or 4 mg once daily baricitinib between weeks 12–24. The primary endpoint was the proportion of patients in the combined 4 and 8 mg groups achieving an American College of Rheumatology 20% (ACR20) response versus placebo at week 12. Results Significantly more patients in the combined baricitinib 4 and 8 mg groups compared with placebo achieved an ACR20 response at week 12 (76% vs 41%, p