Jasper Therapeutics' investigational anti-KIT monoclonal antibody briquilimab has demonstrated striking efficacy in chronic spontaneous urticaria (CSU), with 89% of patients achieving complete response by week 2 in the BEACON Phase 1b/2a trial. However, manufacturing defects have significantly delayed the development timeline and forced strategic program adjustments.
Strong Efficacy Signals in Valid Cohorts
In the single-dose cohorts receiving 240mg and 360mg of briquilimab from valid drug lots, 89% of participants achieved complete response (UAS7=0) by week 2, with 78% maintaining well-controlled disease through week 8. The open-label extension study at the 180mg dose demonstrated 73% complete response rates at 12 weeks, indicating durable therapeutic effects.
The Urticaria Activity Score (UAS7) reductions were substantial, with mean drops of 28.3 points at 4 weeks in the 240mg cohort compared to 22.9 points in the 360mg group. These reductions far exceeded the 13-point threshold considered clinically meaningful for CSU treatment.
Biomarker analysis revealed that 80% of patients achieved tryptase levels below 1.6 μg/mL, a key indicator of mast cell stability. The safety profile appeared favorable, with no grade 3+ treatment-related adverse events reported. Mild neutrophil count reductions were observed but did not correlate with infections or fever.
Manufacturing Crisis Derails Timeline
The promising clinical results were overshadowed by a critical manufacturing defect in drug lot A349954. Of 13 patients in the 240mg Q8W and 240/180mg cohorts, 10 received the faulty batch, resulting in minimal tryptase level drops and no UAS7 improvements. Only two patients who received valid lots achieved complete responses.
This manufacturing issue has created significant delays across Jasper's pipeline. The Phase 2b CSU trial has been pushed from late 2025 to mid-2026, while development programs in asthma (ETESIAN trial) and severe combined immunodeficiency (SCID) have been halted indefinitely.
Strategic Pivot to CSU Focus
In response to the manufacturing challenges, Jasper has implemented a strategic pivot to concentrate resources on CSU development. The company reduced Q3 operating expenses by 25% and is re-enrolling 10-12 patients to strengthen data for the Phase 2b trial.
CSU affects approximately 0.5-1% of the global population, with an estimated 5 million diagnosed cases in major markets. Current standard treatments like Xolair (omalizumab) require subcutaneous injections every 2-4 weeks, while briquilimab's quarterly dosing schedule could offer superior patient convenience.
Market Opportunity and Competitive Positioning
Analysts estimate briquilimab's potential annual revenue in CSU could exceed $500 million if approved. The drug's targeting of KIT, a mast cell-specific receptor, may reduce off-target effects compared to existing therapies. H.C. Wainwright has set a $20 price target for Jasper shares, implying significant upside potential based on a 50% probability of success in CSU.
However, the competitive landscape remains challenging. Xolair maintains market dominance, and potential rivals like AstraZeneca's fostamatinib are advancing through late-stage trials.
Financial Pressures and Execution Risks
Jasper reported $48.8 million in cash as of the latest filing, with projected losses of $5.18 per share in 2025 and $6.21 in 2026. Management plans to raise $5 million by Q4 2025 to extend the cash runway, though analysts estimate the company will need $1.4 billion in cumulative funding through 2040.
The stock has declined 64.6% following the manufacturing news, reaching a record low of $2.27. The current enterprise value of approximately $53 million reflects significant market skepticism about execution capabilities.
Path Forward
Jasper's immediate priorities include definitively resolving the manufacturing defect, securing adequate funding, and delivering robust Phase 2b data by late 2026. The company's ability to navigate these challenges will determine whether briquilimab's promising clinical profile can translate into commercial success in the substantial CSU market.
