Tofacitinib as monotherapy following methotrexate withdrawal in patients with psoriatic arthritis previously treated with open-label tofacitinib plus methotrexate: a randomised, placebo-controlled substudy of OPAL Balance.

Background: Tofacitinib is an oral Janus kinase inhibitor for the treatment of psoriatic arthritis, rheumatoid arthritis, and ulcerative colitis. This study evaluated the efficacy and safety of tofacitinib 5 mg twice daily monotherapy after methotrexate withdrawal.

Methods: OPAL Balance was an open-label, long-term extension study of tofacitinib in patients with psoriatic arthritis who participated in the OPAL Broaden and OPAL Beyond phase 3 studies. This 12-month, randomised, double-blind, placebo-controlled, methotrexate withdrawal substudy (50 centres, 14 countries) included patients from OPAL Balance who completed tofacitinib treatment for 24 months or more (≥3 months' stable tofacitinib 5 mg twice daily) and were receiving methotrexate (7·5-20 mg/week). Patients were blindly randomised (1:1) using interactive response technology and received open-label tofacitinib 5 mg twice daily with either placebo (tofacitinib 5 mg twice daily plus placebo group) or continued methotrexate (tofacitinib 5 mg twice daily plus methotrexate group). Patients were masked to placebo or methotrexate, with identical capsules used. Coprimary endpoints were changes from substudy baseline in psoriatic arthritis disease activity score (PASDAS) and health assessment questionnaire-disability index (HAQ-DI) at month 6 in all randomised patients with one or more substudy drug dose. Safety was assessed throughout. No specific statistical hypothesis (either superiority or non-inferiority) was tested. The study (OPAL Balance) is registered with ClinicalTrials.gov (NCT01976364) and is complete.

Findings: Between Oct 30, 2017, and May 20, 2019, 180 patients from OPAL Balance who were eligible for the substudy were randomly assigned to treatment (90 patients received tofacitinib 5 mg twice daily plus placebo and 89 patients assigned to tofacitinib plus methotrexate; one patient was not treated because of randomisation error). At month 6, least squares mean (LSM) changes in PASDAS were 0·23 (SE 0·08) for tofacitinib 5 mg twice daily plus placebo and 0·14 (0·08) for tofacitinib 5 mg twice daily plus methotrexate (treatment difference LSM 0·09 [95% CI -0·13 to 0·31]), and changes in HAQ-DI were 0·04 (0·03) and 0·02 (0·03), respectively (treatment difference 0·03 [-0·05 to 0·10]). Rates of adverse events, discontinuations because of adverse events, adverse events of special interest, and laboratory changes were generally similar between treatment groups, although liver enzyme elevations were more common with tofacitinib 5 mg twice daily plus methotrexate than tofacitinib 5 mg twice daily plus placebo. Flares of worsening symptoms was reported in one (1%) of 90 patients in the tofacitinib 5 mg twice daily plus placebo group (recorded as psoriatic arthropathy).

Interpretation: Some patients with psoriatic arthritis who are stable on tofacitinib 5 mg twice daily with background methotrexate might be able to discontinue methotrexate without clinically meaningful changes in disease activity and safety.

Funding: Pfizer Inc.