Safety and Efficacy of Baricitinib Through 128 Weeks in an Open-label, Longterm Extension Study in Patients with Rheumatoid Arthritis

Objective: To assess the safety and efficacy of baricitinib in patients with rheumatoid arthritis (RA) up to 128 weeks in a phase IIb study (NCT01185353).

Methods: After a 24-week blinded period, eligible patients entered an initial 52-week open-label extension (OLE); patients receiving 8 mg once daily (QD) continued with that dose and all others received 4 mg QD. Doses could be escalated to 8 mg QD at 28 or 32 weeks at investigator discretion when ≥ 6 tender and ≥ 6 swollen joints were present. Patients completing the first OLE were eligible to enter a second 52-week OLE and receive 4 mg QD regardless of previous dose.

Results: In the 4-mg (n = 108) and 8-mg (n = 93) groups, treatment-emergent adverse events (AE) occurred in 63% and 67%, serious AE in 16% and 13%, infections in 35% and 40%, and serious infections in 5% and 3% of patients, respectively. Exposure-adjusted incidence rates for AE for all baricitinib groups in the second OLE were similar to or lower than rates observed in the first OLE. No opportunistic infections, tuberculosis cases, or lymphomas were observed through 128 weeks; 1 death occurred during the first OLE. Among all patients in both OLE, the proportions who achieved disease improvement at Week 24 were similar or increased at weeks 76 and 128.

Conclusion: In a phase IIb study in RA, the safety and tolerability profile of baricitinib, up to 128 weeks, remained consistent with earlier observations, without unexpected late signals. Clinical improvements seen in the 24-week blinded period were maintained during the OLE.