Jasper Investigates Drug Lot Issue in CSU Study

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This week, Jasper Therapeutics released updated findings from its BEACON phase 1b/2a clinical trial investigating briquilimab, a monoclonal antibody targeting the KIT (CD117) receptor, in adults with chronic spontaneous urticaria (CSU). The company says the data further highlight the potential of briquilimab to deliver durable clinical benefit and maintain a favorable safety profile, despite recent manufacturing challenges impacting specific patient cohorts.¹

Background

The BEACON study is a randomized, double-blind, placebo-controlled trial designed to assess multiple ascending doses of subcutaneous briquilimab in patients with moderate to severe CSU who remain symptomatic despite high-dose antihistamines. Primary endpoints include safety and tolerability, with secondary assessments focused on pharmacokinetics, pharmacodynamics, and clinical response using the Urticaria Activity Score over 7 days (UAS7).

An open-label extension (OLE) study complements BEACON, allowing eligible participants to continue treatment with 180mg briquilimab on an every-8-week (Q8W) schedule. Participants from both the BEACON and SPOTLIGHT (chronic inducible urticaria) studies are eligible for enrollment.²

Efficacy Outcomes

In a news release, Jasper stated briquilimab demonstrated rapid and robust clinical activity in the single-dose cohorts:

• 240mg single dose: 5 of 5 participants (100%) achieved complete response (UAS7 = 0).
• 360mg single dose: 3 of 4 participants (75%) achieved complete response.

Across these cohorts, 8 of 9 participants (89%) experienced a complete response, and 7 of 9 (78%) showed clinical improvement by week 2. Mean UAS7 reductions at week 4 were 28.3 points for the 240mg group and 22.9 for the 360mg group.

The OLE study reinforced these findings, with 8 of 11 participants (73%) achieving complete response by week 12 on the 180mg Q8W regimen. These clinical improvements were supported by early and sustained reductions in serum tryptase, observed in 80% of participants in the 240mg and 360mg cohorts, suggesting successful mast cell suppression.

Manufacturing Setback and Response

Jasper reported confounded results in 2 repeat-dose cohorts—240mg Q8W and 240mg followed by 180mg Q8W—which they said is likely due to a compromised drug product lot. Of 13 patients treated in these cohorts, 10 received product from this lot and showed diminished tryptase reduction and no notable improvement in UAS7 scores. Conversely, researchers reported the 2 participants confirmed to have received drug from a separate lot both achieved complete responses.

The company is actively investigating the affected lot and has distributed new drug product to clinical sites. Jasper plans to re-dose the impacted patients and enroll 10–12 additional participants in these cohorts to inform final dose selection for a planned phase 2b study, now expected to begin in mid-2026. Updated data from these efforts are anticipated in Q4 2025.

Safety Profile

Across all dosing levels, the company stated briquilimab continued to show strong tolerability. No dose-limiting toxicities were observed. Events potentially linked to KIT inhibition were infrequent, mild, and resolved without intervention. Transient neutrophil count reductions occurred but were not associated with infections or fever and typically resolved before the next scheduled dose.

Programmatic Changes

In light of the manufacturing issue and to prioritize briquilimab's development in CSU, Jasper has paused its asthma program (ETESIAN trial) and discontinued its SCID program. Additional cost-containment measures, including a potential corporate restructuring, are being implemented to extend the company’s financial runway, according to the release.

Conclusion

The latest data from Jasper's BEACON study and its OLE extension continue to support briquilimab’s potential as a novel therapeutic for CSU. Despite recent manufacturing setbacks, researchers claimed clinical responses in multiple cohorts remain strong, with encouraging early efficacy and safety data. Further investigation and dosing consistency are expected to guide the company’s next clinical phase as development advances.

References

1. Jasper therapeutics reports clinical data update from briquilimab studies in chronic spontaneous urticaria. News Release. Jasper Therapeutics. Published July 7, 2025. Accessed July 8, 2025. https://www.globenewswire.com/news-release/2025/07/07/3110945/0/en/Jasper-Therapeutics-Reports-Clinical-Data-Update-from-Briquilimab-Studies-in-Chronic-Spontaneous-Urticaria.html

2. Jasper therapeutics reports positive data from 180mg cohort in SPOTLIGHT study of briquilimab in chronic inducible urticaria. News Release. Jasper Therapeutics. Published 14, 2025. Accessed July 8, 2025. https://ir.jaspertherapeutics.com/news-releases/news-release-details/jasper-therapeutics-reports-positive-data-180mg-cohort-spotlight