Kelun-Biotech’s WIN378 Advances to Phase 3 in Asthma

Chengdu, China, September 8, 2026

WIN378 Delivers Sustained Lung Function Benefits

The Phase 2 portion of POLARIS-1 enrolled 147 patients with uncontrolled, moderate-to-severe asthma, exceeding the initial enrollment target of 120 participants. The interim analysis was conducted on the first 98 patients and evaluated three dose levels of SKB378/WIN378 against placebo. The study was designed to characterize pharmacokinetics, safety, immunogenicity and pharmacodynamic activity, while also assessing lung function and inflammatory biomarkers to support dose selection for Phase 3. At Week 24 after a single dose, SKB378/WIN378 produced dose-dependent increases in forced expiratory volume in one second (FEV1), an established measure of lung function. Mean increases reached 174 mL, while placebo-adjusted mean increases reached 256 mL, with a reported p-value of 0.033. The treatment effect appeared rapidly, with near-maximal effects observed as early as Week 2 and maintained through Week 24. These findings support the potential for prolonged biological activity following infrequent administration. The sustained FEV1 response is particularly relevant to the development strategy for WIN378 because the program is designed around ultra-long-acting treatment. The reported pharmacokinetic profile showed a half-life of up to 75 days, providing the pharmacological rationale for evaluating twice-yearly dosing in pivotal studies.

TSLP Targeting Reduces Key Inflammatory Biomarkers

The interim analysis also showed significant changes in biomarkers associated with airway inflammation and asthma exacerbations. Mean fractional exhaled nitric oxide (FeNO) decreased by up to 24 parts per billion, representing a 43% reduction, with a reported p-value of 0.006. Mean blood eosinophil counts declined by as much as 200 cells/µL, corresponding to a 51% reduction, with p<0.0001. SKB378/WIN378 is a fully human, ultra-long-acting monoclonal antibody engineered to inhibit TSLP through a differentiated binding mechanism. According to Kelun-Biotech, the antibody binds to two distinct sites on TSLP, interfering with the interaction between TSLP and both of its co-receptors on epithelial cells. The molecule was engineered for improved potency, extended half-life and silenced effector function. TSLP is an upstream cytokine involved in the development and progression of several inflammatory diseases, including asthma and COPD. By blocking TSLP signaling, WIN378 is intended to suppress inflammatory pathways that contribute to respiratory disease. The combination of FEV1 improvement and reductions in FeNO and eosinophils provides evidence of pharmacodynamic activity, although the ongoing Phase 3 program will be needed to establish whether these effects translate into meaningful reductions in asthma exacerbations.

Kelun-Biotech Moves WIN378 Into Phase 3

The investigational therapy demonstrated a favorable interim safety and tolerability profile. As of the data cutoff, there were no treatment-related serious adverse events, withdrawals or discontinuations. Overall adverse events were balanced between active-treatment groups and placebo. Less than 1% of participants experienced injection-site reactions, while 2% developed anti-drug antibodies, with no reported impact on the pharmacology of SKB378/WIN378. The Phase 2 findings and pharmacokinetic modeling supported selection of two twice-yearly doses for the Phase 3 portion of POLARIS-1. The pivotal study is designed to evaluate the effect of WIN378 on annualized asthma exacerbation rate and other key efficacy measures in patients with severe asthma. A second Phase 3 study, POLARIS-2, is planned to begin in the first half of 2027. The program also extends into COPD, where WIN378 is being evaluated in the Phase 2 SIRIUS study. The asset originated as a co-development program between Kelun-Biotech and Harbour BioMed, with Windward Bio holding global rights outside Greater China and several Southeast and West Asian countries. The Phase 2 results therefore mark an important clinical development milestone for Kelun-Biotech’s WIN378, combining sustained lung-function improvement, reductions in inflammatory biomarkers, favorable interim safety findings and pharmacokinetic support for twice-yearly dosing as the program advances into pivotal Phase 3 testing.

Source: Kelun-Biotech press release