The purpose of this study is to assess the clinical effect, the pharmacodynamics, the safety, and the pharmacokinetics of barzolvolimab (CDX-0159) in patients with Chronic Spontaneous Urticaria

The purpose of this study is to assess the clinical effect, the pharmacodynamics, the safety, and the pharmacokinetics of barzolvolimab in patients with Chronic Spontaneous Urticaria.

There is a screening period of up to 4 weeks, followed by a 16-week placebo-controlled treatment period (Placebo-Controlled Treatment Phase) where patients will receive either barzolvolimab at a dose level of 75mg, 150mg, or 300mg, or placebo, and then a 36-week treatment period where all patients will receive barzolvolimab. Patients who receive barzolvolimab 75mg or placebo in the placebo-controlled treatment phase will be re-randomized to receive either barzolvolimab 150mg or 300mg in the active treatment phase.

Key inclusion criteria:

1. Males and females, >/= 18 years of age.

2. Diagnosis of chronic spontaneous urticaria (CSU) >/= 6 months.

3. Diagnosis of CSU despite the use of a stable regimen of second generation non-sedating H1-antihistamine as defined by:

   1. The presence of hives for >/= 6 weeks at any time prior to Visit 1 despite the use of H1-antihistamines.
   2. Must be on a stable regimen of second generation non-sedating H1-antihistamine for >/= 4 weeks prior to study treatment.
   3. UAS7 of >/= 16 and ISS7 of >/= 8 during the 7 days prior to treatment.

4. Normal blood counts and liver function tests

5. Both males and females of child-bearing potential must agree to use highly effective contraceptives during the study and for 150 days after treatment.

6. Willing and able to complete a daily symptom electronic diary and comply with study visits.

Key exclusion criteria:

1. Women who are pregnant or nursing.
2. Clearly defined cause for chronic urticaria.
3. Active, pruritic skin condition in addition to CSU.
4. Medical condition that would cause additional risk or interfere with study procedures.
5. Known active HIV, hepatitis B or hepatitis C infection.
6. Vaccination of a live vaccine within 2 months prior to study treatment (subjects must agree to avoid vaccination during the study). Inactivated vaccines are allowed such as seasonal influenza injection or COVID-19 vaccine.
7. History of anaphylaxis
8. Prior treatment with barzolvolimab

There are additional criteria that your study doctor will review with you to confirm you are eligible for the study.