Lynk Pharmaceuticals Co Ltd, a Chinese drug development company focused on immune and inflammatory diseases, on Tuesday announced positive long-term results from its pivotal Phase III clinical trial evaluating zemprocitinib, an investigational, selective, second-generation oral Janus kinase 1 (JAK1) inhibitor, in adult patients with moderate-to-severe active rheumatoid arthritis (RA) who had experienced inadequate response or intolerance to biologic disease-modifying antirheumatic drugs (bDMARDs).

The study met its primary endpoint of ACR20 response and key secondary endpoints at Week 24, demonstrating a statistically significant improvement with zemprocitinib versus placebo. The Week 52 and Week 76 results further demonstrate continued improvements in all disease activity measurements and physical function during long-term treatment by Week 52 and sustained clinical responses through Week 76.

The double-blind, placebo-controlled Phase III study randomised 430 patients with moderate-to-severe active RA who had experienced an inadequate response or intolerance to prior bDMARDs, of whom 429 received at least one dose of study treatment. During the initial 24-week double-blind treatment period, patients received zemprocitinib 12 mg twice daily or placebo. Following this period, patients continued or transitioned to active treatment, with efficacy and safety assessed through Week 76.

Lynk says that during the initial 24-week double-blind, placebo-controlled period, the safety profile of zemprocitinib was generally comparable to that of placebo as reported at EULAR 2026. The safety profile remained consistent to Week 76 with no new safety signals identified during long-term treatment. An additional observation was the cleaner lab parameters suggesting a cleaner profile of zemprocitinib, particularly with the increase in mean haemoglobin levels, rare incidence of grade 3 or 4 in ALT elevations and grade 3 in AST elevations, and the lack of reports on grade 4 AST elevations. These findings provide additional information on the safety and tolerability of zemprocitinib during long-term treatment in patients with RA.