Sponsor Decision - terminated due to changes in company priorities and not related to safety concerns.

Study JSP-CP-012 is designed as a proof of concept, parallel-group, single dose, double blind, placebo-controlled study using an allergen challenge model. A single dose proof of concept approach at a dose level shown to be biologically active should inform the impact of briquilimab on allergic asthma as compared to placebo while minimizing exposure to participants, in a new indication.

Inclusion Criteria:

• Men and women 18 to 65 years of age; stable, allergic asthma; history of episodic wheeze and shortness of breath; forced expiratory volume in 1 second (FEV1) at baseline at least 70% of the predicted value; able to comprehend and follow all required study procedures; willing and able to sign an informed consent form; positive methacholine challenge at baseline (concentration of methacholine causing 20% decrease in FEV1 [PC20] PC20 ≤ 16 mg/mL or PD20 equivalent to ≤400µg); and positive skin-prick test and positive allergen-induced early and late airway bronchoconstriction to common aeroallergens.

Exclusion Criteria:

• Worsening of asthma or respiratory infection in the preceding 6 weeks; lung disease other than allergic asthma; prior treatment with a c-Kit inhibiting therapy; anaphylaxis to any parenterally administered biologics; use of asthma medications (note: intermittent doses of short-acting β2-agonist are allowed once weekly for relief of symptoms but prophylactic use for exercise is allowed as-needed); pregnant or lactating women; and women actively seeking pregnancy or who are not using adequate contraception.