Kelun-Biotech and Harbour BioMed's SKB378/WIN378, a fully human, ultra-long-acting TSLP monoclonal antibody (mAb) licensed to Windward Bio in a NewCo structure for up to USD 970 million excluding Greater China and selected Southeast and West Asian markets, hit positive interim Phase II endpoints in POLARIS-1, a seamless global Phase II/III asthma trial.

The Phase II portion enrolled 147 patients against a 120-patient target, and the 98-patient interim showed placebo-corrected FEV1 gains of up to 256 mL at week 24 (p=0.033), FeNO reductions of up to 24 ppb, or 43% (p=0.006), and blood eosinophil drops of up to 200 cells/µL, or 51% (p<0.0001), with effects near maximal by week 2 and sustained through week 24, while no treatment-related serious adverse events, discontinuations, injection-site reactions above 1%, or clinically meaningful anti-drug antibody signals emerged.

SKB378/WIN378's differentiation is mechanistic and pharmacokinetic: it blocks TSLP by binding two distinct epitopes and disrupting TSLP-co-receptor engagement on epithelial cells, while its engineered half-life reaches 75 days versus 19.9 to 25.7 days for marketed TSLP antibodies, supporting a twice-yearly dosing schedule that directly challenges Amgen/AstraZeneca's tezepelumab and Sanofi/Regeneron's dupilumab in uncontrolled, moderate-to-severe asthma.