Jasper Therapeutics, Inc. (NASDAQ:JSPR) stock is experiencing a steep decline on Monday, plummeting by nearly 55%. This significant drop is accompanied by an exceptionally high trading volume of 9.9 million shares, vastly exceeding its average daily volume of 251.9K, according to data from Benzinga Pro.

What Happened?

The company reported updated data from the BEACON Phase 1b/2a study of subcutaneous briquilimab in adult chronic spontaneous urticaria (CSU) participants and provided an update on the program. It reported preliminary data in January.

The primary endpoints are briquilimab’s safety and tolerability, and the secondary endpoints are focused on clinical activity and PK/PD.

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Primary measurements used to assess clinical activity were the sum of the Hives Severity Score and the daily Itch Severity Score (ISS), as measured via the Urticaria Activity Score over 7 days (UAS7) on a 0 to 42-point scale.

Briquilimab administration resulted in disease control in the 240mg and 360mg single-dose cohorts.

Eight of nine (89%) participants enrolled across both cohorts achieved a complete response, and seven of nine (78%) achieved a clinical response by week 2.

Reductions in UAS7 scores were reported with a mean change from baseline at 4 weeks of 28.3 points in the 240mg single-dose cohort and 22.9 points in the 360mg single-dose cohort.

In addition, BEACON participants who rolled over into the open-label extension study dosing at 180mg Q8W demonstrated clinical efficacy with 8 of 11 (73%) participants achieving a complete response at 12 weeks.

Results from the 240mg Q8W and the 240mg followed by 180mg Q8W dose cohorts appear to be confounded by an issue with one drug product lot used in those cohorts, with 10 of the 13 patients dosed with drug from the lot in question.

The company is investigating the drug product lot in question. It expects to have the investigation results in the coming weeks.

Key observations noted in those 10 patients were lower than expected drops in mean tryptase levels and no discernable impact on UAS7 scores. The 2 participants enrolled in the cohorts that have been confirmed as being dosed with drug product from a different lot both achieved complete response.

The company also plans to enroll an additional 10-12 patients across the 240mg Q8W and the 240mg followed by 180mg Q8W cohorts to ensure a robust data set to inform the Phase 2b CSU study.

Data from the additional BEACON patients is expected in the fourth quarter of 2025, and commencement of the Phase 2b study is now expected in mid-2026.

The company has also determined that the drug product lot in question was used to treat participants enrolled in the ETESIAN trial evaluating briquilimab in asthma.

Why It Matters?

To focus resources on advancing briquilimab in CSU, the company is halting the asthma study and pausing development.

In addition, the company is halting development in SCID and will implement several other cost-cutting measures, including a potential restructuring, to extend the runway and reduce expenses.

Briquilimab treatment also resulted in deep and durable disease control in the open-label extension study evaluating briquilimab at 180mg Q8W, with 8 of 11 participants (73%) achieving a complete response at the week 12 assessment.

Substantial reductions in tryptase were observed as early as the week 1 assessment and were correlated with the onset of clinical responses. Tryptase levels below the lower limit of quantification were reported for 8 of 10 (80%) participants across the 240mg and 360mg single-dose cohorts.

Briquilimab was tolerated well in the BEACON study and the open-label extension, with no dose-limiting toxicities observed.

Price Action: JSPR stock is down 54.5% at $3.08 at the last check on Monday.

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