Jasper Therapeutics’ stock has dropped by more than 50% after the company announced it was looking into the impact of a faulty batch of its investigational antibody therapy that was dosed in a Phase Ib/IIa trial.

The BEACON study (NCT06162728) was investigating subcutaneous briquilimab in patients with chronic spontaneous urticaria (CSU)

The faulty batch of briquilimab, a novel antibody therapy targeting KIT (CD117), impacted around ten of 13 patients from two arms. The patients affected were in the arm receiving 240mg every eight weeks, along with the arm being administered 240mg followed by 180mg every eight weeks. There were lower-than-expected drops in mean tryptase levels and no discernible impact on UAS7 scores among the impacted patients.

Two of the other three patients enrolled in these two cohorts who were dosed with drug products from a different lot both achieved a complete response.

Jasper Therapeutics' president and CEO Ronald Martell expressed disappointment over the unexpected results seen in the two multi-dose groups of the BEACON study. He noted that Jasper is currently investigating the underlying cause and is taking action to retrieve the affected drug batch.

Jasper’s shares plunged by 55%, from 3 July ($6.77) to 7 July ($3.04). The company now holds a market cap of $101.7m.

In patients dosed with a non-impacted batch of briquilimab, there was deep and rapid disease control, with eight out of nine patients achieving a complete response. Seven of those achieved a clinical response by week two.

In those who enrolled on the open-label extension study, robust clinical efficacy was seen in eight of the 11 patients who maintained a complete response at 12 weeks.

New drug products are being sent to clinical trial sites to dose the ten patients impacted by the compromised batch, and Jasper plans on enrolling another ten or 12 patients in the study to ensure a robust data set to inform the planned Phase IIb study.

Impacted batch also hits asthma trial

The defective batch was also used to dose several patients in the ETESIAN trial (NCT06592768) evaluating briquilimab in allergic asthma.

Due to both this and the company refocusing resources on the development of briquilimab in CSU, the asthma study is being halted. Development of the therapy in severe combined immunodeficiency (SCID) is also being halted.

The drug is also being investigated in the SPOTLIGHT study (NCT06353971) in patients with chronic inducible urticaria (CIndU), but it is not clear whether this study is affected.

Jasper is also considering other cost-cutting measures, including a potential restructuring, to extend the runway and reduce expenses.