Jasper Therapeutics reports data from ETESIAN Phase 1b study

Jasper Therapeutics (JSPR) reported positive preliminary clinical data from Jasper’s ETESIAN Phase 1b study of subcutaneous briquilimab in adult participants with allergic asthma. A single subcutaneous 180mg dose of briquilimab demonstrated substantial reductions in sputum eosinophils at both six and twelve weeks, as well as improvements over baseline in FEV1 in both Early Asthmatic Response, EAR, and Late Asthmatic Response, LAR. Significant reductions in serum tryptase were observed, consistent with reductions observed in other briquilimab studies at the 180mg dose level. Briquilimab was well tolerated in the study, demonstrating a favorable safety profile. Jasper also announced the completion of its internal investigation into the anomalous lack of clinical response observed in the July 2025 BEACON data for cohort 8 and cohort 9, where no US patients achieved Complete Response or Well Controlled UAS7 by week 12. Based on the work completed, the additional data from subsequent dosing of the US patients and input from a panel of CSU KOLs, Jasper has concluded that the unexpected efficacy results observed in the US patients was not the result of any issues with the drug product. Rather, it was likely a result of patient selection issues, as it appears that 9 of the 10 patients in question did not have CSU as their symptoms were not mast cell-driven.