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

Harbour BioMed partner Windward Bio reported positive interim Phase 2 results for asthma drug HBM9378/WIN378, including placebo-adjusted FEV1 improvement of up to 256 mL (p=0.033), FeNO reduction of 43% (p=0.006), and eosinophil reduction of 51% (p<0.0001) through Week 24 after a single dose. The antibody demonstrated an approximately 75-day half-life supporting twice-yearly dosing, with no treatment-related serious adverse events, withdrawals, or discontinuations in the interim dataset of 98 patients. Windward has initiated the first Phase 3 POLARIS-1 study using two semiannual doses and plans to begin POLARIS-2 in H1 2027.

Analysis

The commercial differentiation is adherence and site-of-care economics rather than target novelty. If twice-yearly administration translates into a clinically meaningful reduction in annualized exacerbations, WIN378 could pressure the chronic-maintenance franchises of AZN/AMGN (Tezspire), REGN/SNY (Dupixent), GSK (Nucala) and BIIB (Fasenra), particularly in patients who cycle off monthly or every-2/4-week biologics. A low-frequency product also gives payers a countervailing benefit—fewer administration events and potentially lower nonadherence—but will require durable efficacy through the dosing interval and compelling pricing versus established biologics.

The key valuation gap is that biomarker and lung-function improvement are not a sufficient read-through to the pivotal commercial endpoint. Exacerbation-rate reduction, rescue/oral-steroid use, hospitalization outcomes, and efficacy across low-eosinophil phenotypes will determine whether the asset is a broad Tezspire competitor or a narrower severe-asthma entrant; the latter outcome materially limits peak-sales assumptions. Because Windward is private and the ex-China license economics to HKEX:2142 and Kelun-Biotech are not disclosed here, any move in HBM should be treated as option value rather than a modeled earnings inflection.

Near term, medical-congress disclosure of the full dose-response, baseline exacerbation history, and Week-48 durability can extend sentiment over 1-3 months. Over 6-18 months, the main risk is competitive response: incumbents can defend formularies with rebates, while Tezspire's established broad-label positioning sets a high efficacy and safety bar. The contrarian view is that a two-dose annual schedule may be commercially overvalued if specialty-pharmacy refill persistence is already high and payer prior authorization, not injection frequency, is the binding barrier.

Thesis is falsified by weak separation on annualized exacerbations, end-of-interval waning, a meaningful immunogenicity/safety signal with larger exposure, or disclosure that HBM's royalty/milestone participation is too small to alter its funded runway or valuation.

Key Decisions for Investors

• No immediate directional position in HKEX:2142: establish a research alert for the full Phase 2 presentation and licensing economics. Upgrade only if Week-48 durability and severe-exacerbation data support a credible >25% reduction versus placebo and the company quantifies material royalty/milestone exposure.
• Maintain a 6-12 month watchlist short/underweight bias on the most asthma-exposed biologic revenue streams rather than AZN or AMGN outright; AZN/AMGN diversification makes single-asset competitive risk insufficient today. Reassess after pivotal enrollment pace and product-access strategy are disclosed.
• For a liquid competitive basket, consider long REGN / short AZN only if WIN378's later data demonstrate broad phenotype efficacy: REGN has greater upside from continued Dupixent category expansion, while AZN carries more direct Tezspire displacement risk. Size modestly and exit if Tezspire growth reaccelerates or WIN378 fails to show exacerbation efficacy.
• Track COPD read-through separately: do not capitalize respiratory pipeline optionality into HBM before controlled COPD efficacy data, since asthma biomarker activity does not establish a reimbursable COPD indication.