HBM9378/WIN378, an Ultra-Long-Acting Antibody Targeting TSLP, Achieves Positive Phase 2 Results in Asthma and Initiates Phase 3 Study

• The POLARIS-1 study enrolled 147 patients with uncontrolled, moderate-to-severe asthma, and the interim analysis was conducted on the first 98 patients. The analysis demonstrated a half-life of up to 75 days, with clinical effects consistent with twice-yearly dosing.
• HBM9378/WIN378 produced significant and sustained effects on FEV₁ (up to 174 mL mean increase, placebo-adjusted mean increases up to +256 mL, p=0.033), FeNO and blood eosinophils, key biomarkers that correlate with asthma exacerbations. These effects were rapid and sustained through Week 24 after a single dose of HBM9378/WIN378.
• HBM9378/WIN378 was well tolerated with favorable safety results — there were no treatment-related serious adverse events, withdrawals, or discontinuations; adverse events were balanced between active arms and placebo, with low rates of injection site reactions and anti-drug antibodies.
• The first Phase 3 study of HBM9378/WIN378 has been initiated evaluating two twice-yearly doses. A second Phase 3 trial is planned to begin in the first half of 2027.

CAMBRIDGE, Mass., ROTTERDAM, Netherlands and SHANGHAI, Sept. 8, 2026 /PRNewswire/ -- Harbour BioMed ("HBM" or the "Company"; HKEX: 02142), a global biopharmaceutical company committed to the discovery and development of novel antibody therapeutics in immunology, oncology, and other areas, today announced that its partner, Windward Bio, has reported positive interim results from the Phase 2 portion of the POLARIS-1 clinical trial, which evaluates twice-yearly dosing of HBM9378/WIN378 in asthma.

HBM9378/WIN378 is a novel fully human, ultra-long-acting monoclonal antibody with a unique binding mode to inhibit thymic stromal lymphopoietin (TSLP). It was engineered for improved potency, extended half-life and silenced effector function. It is the only known investigational drug that blocks TSLP signaling by binding to two different sites on TSLP, interfering with the binding of TSLP to both of its co-receptors on the cell surface of epithelial cells.

POLARIS-1 is an operationally seamless, global Phase 2/3 study. The Phase 2 portion of the study is a 48-week, randomized, double-blind study evaluating three dose levels of HBM9378/WIN378 against placebo. It is designed to evaluate the pharmacokinetics, safety, immunogenicity, and pharmacodynamic activity of HBM9378/WIN378 in patients with uncontrolled moderate-to-severe asthma. The study also evaluates the effects of HBM9378/WIN378 on lung function and biomarkers of airway inflammation and informed dose selection for Phase 3 development. The Phase 2 portion of the study enrolled a total of 147 patients, exceeding the initial enrollment target of 120 patients, with the interim analysis conducted on the first 98 patients.

The interim analysis demonstrated the following at Week 24 after a single dose of HBM9378/WIN378:

• Dose-dependent mean increases in FEV₁ of up to 174 mL (placebo-adjusted mean increase up to 256 mL, p=0.033).
• Dose-dependent mean reductions in FeNO of up to 24 ppb (or -43% change, p=0.006).
• Reductions in mean blood eosinophil count (EOS) of up to 200 cells/µL (or -51% change, p<0.0001).
• Near maximal effects seen as early as Week 2 and sustained through Week 24.

Notes: FEV₁ (forced expiratory volume in one second) is a key measure of lung function. FeNO (fractional exhaled nitric oxide) and EOS are key markers of inflammation that correlate with exacerbations.

HBM9378/WIN378 was well tolerated with favorable safety results, and there were no treatment-related serious adverse events, withdrawals, or discontinuations observed as of the cut-off date. Adverse events were balanced between active arms and placebo. Less than 1% of participants experienced injection site reactions, and 2% developed anti-drug antibodies (ADAs), a measure of immunogenicity. ADAs had no impact on the pharmacology of HBM9378/WIN378. The results of the interim analysis and population pharmacokinetic modeling support the potential of twice-yearly dosing of HBM9378/WIN378.

"We are very encouraged by the positive Phase 2 results of HBM9378/WIN378 and its continued progression into Phase 3 development," said Dr. Jingsong Wang, Founder, Chairman and CEO of Harbour BioMed. "HBM9378/WIN378 is an ultra-long-acting fully human monoclonal antibody against TSLP generated from our H2L2 Harbour Mice^® platform. The significant and sustained improvements in lung function and airway inflammation observed with a single dose, together with its potential for twice-yearly dosing, further reinforce the therapeutic potential of this molecule. We are fully confident in the clinical potential of this novel biotherapeutic."

Two twice-yearly doses have been selected for the Phase 3 portion of POLARIS-1, which is designed to evaluate the effect of HBM9378/WIN378 on annualized asthma exacerbation rate and other key efficacy measures in patients with severe asthma. The Phase 3 portion of the study has been initiated by Windward Bio who plans to begin a second Phase 3 study, POLARIS-2, in the first half of 2027. Data from the Phase 2 portion of POLARIS-1 will be presented at an upcoming medical congress.

About POLARIS-1 Study

POLARIS-1 (NCT07120503) is an operationally seamless, global Phase 2/3 study of HBM9378/WIN378 in adults with uncontrolled asthma conducted by Windward Bio. The Phase 2 portion is a randomized, double-blind study evaluating three dose levels of HBM9378/WIN378 administered subcutaneously against placebo, with primary objectives of characterizing pharmacokinetics, safety, immunogenicity and pharmacodynamic activity, as well as informing dose selection for Phase 3. The Phase 3 portion is evaluating two twice-yearly doses of HBM9378/WIN378 against placebo, with a primary endpoint of annualized asthma exacerbation rate in patients with severe asthma.

About HBM9378/WIN378

HBM9378/WIN378 is a novel fully human, ultra-long-acting monoclonal antibody with a unique binding mode to inhibit thymic stromal lymphopoietin (TSLP). This clinically validated target plays a key role in the development and progression of a wide array of immunological diseases, including asthma, chronic obstructive pulmonary disease (COPD), chronic rhinosinusitis with nasal polyps, and eosinophilic esophagitis. HBM9378/WIN378 was engineered for improved potency, extended half-life and silenced effector function. It is the only known investigational drug that blocks TSLP signaling by binding to two different sites on TSLP, interfering with the binding of TSLP to both of its co-receptors on the cell surface of epithelial cells. Phase 2 interim results support the potential of twice-yearly dosing. HBM9378/WIN378 produced significant, sustained and dose-dependent increases in FEV₁, a measure of lung function, together with significant and sustained reductions in FeNO and blood eosinophils — key markers that correlate with asthma exacerbations. HBM9378/WIN378 is being evaluated in the global Phase 2/3 POLARIS-1 study in asthma and the Phase 2 SIRIUS study in COPD, with a second pivotal Phase 3 asthma trial, POLARIS-2, planned to begin in the first half of 2027. HBM9378/WIN378 (also known as SKB378) started as a co-development project jointly conducted by Harbour BioMed and Kelun-Biotech, with both parties equally sharing global rights. Windward Bio licensed the global rights (excluding Greater China and several Southeast and West Asian countries) for this molecule from Harbour BioMed (also known as HBM9378) and Kelun-Biotech (also known as SKB378).

About Harbour BioMed

Harbour BioMed (HKEX: 02142) is a global biopharmaceutical company committed to the discovery and development of novel antibody therapeutics in immunology, oncology and other areas. The Company is building a robust portfolio and differentiated pipeline through internal R&D capability, strategic global collaborations in co-discovery and co-development, and selective acquisitions.

Our proprietary antibody technology platform, Harbour Mice^®, generates fully human monoclonal antibodies in both the conventional two heavy and two light chain (H2L2) format and the heavy chain-only (HCAb) format. Building upon HCAb antibodies, the HCAb-based immune cell engagers (HBICE^®) bispecific antibody technology enables tumor-killing effects that traditional combination therapies cannot achieve. The HCAb-based Antibody Plus technology (HCAb PLUS™) provides comprehensive modality solutions for the development of innovative multi-specific medicines in different disease areas. Additionally, building upon the Harbour Mice^® platform, Harbour BioMed launched its first fully human Generative AI HCAb Model powered by its Hu-mAtrIx™ AI platform, accelerating the development of innovative therapies.

By integrating Harbour Mice^®, HBICE^®, HCAb PLUS™, a single B-cell cloning platform and AI technologies, Harbour BioMed has built a highly efficient and distinctive antibody discovery engine for developing next-generation therapeutic antibodies. For more information, please visit www.harbourbiomed.com.

About Windward Bio

Windward Bio is a clinical-stage biotechnology company with deep discovery, development and commercial expertise, developing ultra-long-acting antibodies for patients with serious respiratory and dermatologic diseases, including asthma, COPD, and atopic dermatitis. The Company is advancing a pipeline of potentially differentiated biologics targeting clinically validated molecular pathways, with the goal of improving clinical outcomes while reducing treatment burden through less frequent dosing. Windward Bio's lead program is WIN378, a novel fully human monoclonal antibody engineered for improved potency, extended half-life and silenced effector function, targeting TSLP. WIN378 is in clinical development for asthma and COPD. The Company's second program is WIN027, an ultra-long-acting, humanized bi-specific antibody targeting TSLP and IL-13 in development for respiratory and dermatologic diseases. Windward Bio was founded in 2024 and is headquartered in Basel, Switzerland, with operations in the United States. For more information, visit www.windwardbio.com.

SOURCE Harbour BioMed