Hangzhou – October 29, 2026 -- Lynk Pharmaceuticals reported that its oral JAK1 inhibitor zemprocitinib sustained a 91.8% ACR20 response rate at Week 76 in rheumatoid arthritis patients who had failed or could not tolerate biologic therapy, with no new safety signals in the pivotal Phase III trial.
Trial met primary endpoint at Week 24 before long-term extension
The double-blind, placebo-controlled study randomized 430 patients with moderate-to-severe active RA and prior bDMARD inadequate response or intolerance; 429 received at least one dose. Patients received zemprocitinib 12 mg twice daily or placebo for 24 weeks. The trial met its primary ACR20 endpoint and key secondary endpoints versus placebo (p<0.0001). Patients then continued or switched to active treatment, with efficacy and safety tracked through Week 76 and a 4-week safety follow-up.
Continuous dosing delivers 62.4% ACR70 response by Week 76
Among patients on continuous zemprocitinib, ACR20, ACR50 and ACR70 rates were 93.0%, 79.9% and 52.5% at Week 52. At Week 76, ACR20 and ACR50 rates were 91.8% and 80.5%, while ACR70 rose to 62.4%.
Low disease activity by DAS28(CRP) ≤3.2 was reached by 85.5% of patients at Week 52 and 81.4% at Week 76. Under the CDAI (≤10) measure, the figures were 81.5% and 81.0%. On physical function, 84.5% and 86.7% of patients achieved an HAQ-DI improvement of at least 0.22 points from baseline at Weeks 52 and 76, respectively.
Patients who started on placebo and switched to zemprocitinib at Week 24 reached ACR20, ACR50 and ACR70 rates of 92.0%, 77.6% and 55.1% by Week 76. The company said their other efficacy measures were comparable to those of the continuous-dosing group.
Safety profile stays consistent with no new signals
Safety during the first 24 weeks was generally comparable to placebo, as presented at EULAR 2026. Through Week 76, no new safety signals emerged. Lynk pointed to rising mean hemoglobin levels, rare grade 3 or 4 ALT elevations, rare grade 3 AST elevations and no reported grade 4 AST elevations.
Principal investigator Professor Xiaofeng Zeng of Peking Union Medical College Hospital noted favorable efficacy in bDMARD-inadequate responders and in patients with inadequate response to prior JAK inhibitor therapy.
Simcere holds Greater China rights as atopic dermatitis filing proceeds
Lynk and Simcere Pharmaceutical Group agreed in March 2022 to jointly commercialize zemprocitinib for RA and ankylosing spondylitis in Greater China. Zemprocitinib has also completed a pivotal Phase III study in atopic dermatitis, and China's National Medical Products Administration has accepted the New Drug Application for review. A Phase III program in ankylosing spondylitis is underway.
Simcere Chief Medical Officer Dr. Aik Goh cited the data as evidence of zemprocitinib's "best-in-class potential" and said the company looks forward to addressing unmet RA treatment needs in China soon.