Jasper Therapeutics Reports Positive Phase 1b Data for Briquilimab in Asthma, Completes BEACON Study Investigation
Key Insights
Jasper Therapeutics announced positive preliminary data from the ETESIAN Phase 1b study showing that a single 180mg dose of briquilimab significantly reduced airway hyperresponsiveness and sputum eosinophils in allergic asthma patients at both 6 and 12 weeks.
The study demonstrated improvements in lung function measures, with briquilimab showing 10.4% improvement in Late Asthmatic Response at 6 weeks and 8.7% at 12 weeks compared to baseline.
The company completed its internal investigation into anomalous BEACON study results, concluding that patient selection issues rather than drug product problems caused the unexpected lack of efficacy in US patients.
Jasper Therapeutics reported positive preliminary clinical data from its ETESIAN Phase 1b study of briquilimab in allergic asthma, marking the first clinical evaluation of a mast cell-targeting therapy in asthma patients. The single-dose study demonstrated significant reductions in airway hyperresponsiveness and inflammatory markers, supporting further development of the KIT (search)-targeting antibody for respiratory indications.
ETESIAN Study Shows Promise for Mast Cell Depletion in Asthma
The Phase 1b/2a ETESIAN study enrolled 17 patients across six Canadian sites in a double-blind, placebo-controlled design. Preliminary results from 14 participants who completed at least six weeks of follow-up showed that a single 180mg subcutaneous dose of briquilimab produced measurable improvements in key asthma parameters.
Patients receiving briquilimab demonstrated substantial improvements in Late Asthmatic Response (LAR) measurements compared to baseline. The treatment group showed a 10.4% improvement in LAR maximum percentage fall in FEV1 at six weeks and 8.7% at 12 weeks. Area under the curve measurements for LAR showed even more pronounced benefits, with 25.4% improvement at six weeks and 23.3% at 12 weeks.
"The initial results demonstrate the potential to reduce both airway hyperresponsiveness and the accumulation of eosinophils in the airways, both of which are key factors in managing chronic asthma and reducing exacerbations," said Dr. Elliot Israel, Director of Clinical Research in the Pulmonary and Critical Care Division at Brigham and Women's Hospital in Boston.
Significant Reduction in Inflammatory Markers
The study revealed marked decreases in sputum eosinophil levels, a key inflammatory marker in asthma. Patients in the briquilimab group showed reduced mean sputum eosinophil levels from 1.88% at baseline to 0.44% at day 41 and 0.38% at day 83. Following allergen challenge, 24-hour post-challenge eosinophil levels dropped from 10.3% at baseline to 2.32% at six weeks and 3.98% at 12 weeks.
Airway hyperresponsiveness assessments using methacholine PD20 testing showed increased resistance to methacholine in briquilimab-treated patients. At the 12-week challenge, the shift in methacholine PD20 response was 1.58 for briquilimab compared to 0.60 for placebo, indicating improved airway stability.
Briquilimab was well-tolerated with no dose-limiting toxicities observed. Safety events potentially related to KIT (search) blockade were infrequent and generally low-grade, with none resulting in discontinuations or dose delays.
BEACON Study Investigation Concludes
Jasper also announced completion of its internal investigation into anomalous results from the BEACON study's cohorts 8 and 9, where no US patients achieved complete response or well-controlled urticaria activity scores by week 12. The comprehensive investigation included switching patients to new drug lots, reviewing manufacturing records, testing drug samples, and assembling a key opinion leader panel.
"Based on the work completed, the additional data from subsequent dosing of the US patients and input from the KOL panel, Jasper has concluded that the unexpected lack of efficacy observed in the US patients was not the result of any issues with drug product, but rather appears to be the result of patient selection issues," the company stated. The investigation found that nine of the 10 patients likely did not have mast cell-driven chronic spontaneous urticaria.
"I commend the Jasper team for the professional manner in which they managed the anomalous results received in July, by promptly notifying clinical sites and conducting a thorough investigation into the root cause," said Dr. Martin Metz, Professor of Dermatology and Allergy at Charité – Universitätsmedizin Berlin and KOL panel member.
Mechanism and Future Development
Briquilimab is a targeted aglycosylated monoclonal antibody that blocks stem cell factor from binding to the KIT (search) receptor, disrupting critical survival signals and leading to mast cell depletion through apoptosis. This mechanism removes the underlying source of inflammatory response in mast cell-driven diseases.
"Mast cells are believed to be a key driver of the inflammatory cascade underlying chronic asthma, and both the reductions in airway hyperresponsiveness and the significant reduction in sputum eosinophils demonstrated at 6 weeks after a single 180mg dose of briquilimab strongly support the potential of mast cell depletion to drive a therapeutic benefit for asthma patients," said Dr. Daniel Adelman, Acting Chief Medical Officer of Jasper.
The company plans to use learnings from the BEACON investigation to improve patient selection for future studies. Additional BEACON data is expected in Q1 2026 to inform dose selection for a Phase 2b chronic spontaneous urticaria study planned for mid-2026.