Long-term Efficacy and Safety Extension (LTE) Study of Barzolvolimab in Participants with Chronic Spontaneous Urticaria

Who can take part

• Able to read, understand, and provide written informed consent themselves, and if applicable, Health Insurance Portability and Accountability Act (HIPAA) authorization, after the nature of the study has been fully explained, and must be willing to comply with all study requirements and procedures
• Must have completed 52 weeks of treatment and the 16-week follow-up in one of the CDX0159-12 or CDX0159-13 clinical studies
• In the opinion of the Investigator, is eligible to participate in the LTE based on a favorable benefit-risk assessment. For participants receiving barzolvolimab retreatment, participants remain eligible to continue treatment in the LTE by not meeting any of the criteria during CDX0159-12 or CDX0159-13 that would have warranted study drug discontinuation
• Female participants receiving barzolvolimab retreatment at study entry must meet 1 of the following criteria: • If of childbearing potential, agrees to use highly effective contraception from the time of Visit 1 and for 150 days after the receipt of study treatment. Highly effective methods of contraception include the following: − combined (estrogen- and progestogen-containing) hormonal contraception associated with inhibition of ovulation, administered as oral, intravaginal, or transdermal − progestogen-only hormonal contraception associated with inhibition of ovulation administered as oral, injectable, or by implantable means − intrauterine device (IUD) − intrauterine hormone-releasing system (IUS) − a vasectomized male partner (male sterilization ≥ 6 months prior to Visit 1 with a medical assessment of the surgical success) as the sole partner for the participant Total abstinence is acceptable when this is in line with the preferred and usual lifestyle of the participant. Periodic abstinence (eg, calendar, ovulation, symptothermal postovulation methods) and withdrawal are not acceptable methods of contraception. The decision on the contraceptive method should be reviewed every 2 months to evaluate the individual need and compatibility of the method chosen if the participant will receive barzolvolimab or receives barzolvolimab at any time during the study. • Females of non-childbearing potential, who are surgically sterile (ie, had undergone complete hysterectomy, bilateral salpingectomy or bilateral oophorectomy, or bilateral tubal ligation) or in a menopausal state (≥ 1 year without menses), or confirmed by follicle-stimulating hormone (FSH) levels, are eligible
• Male participants receiving barzolvolimab retreatment at study entry and with female partners of childbearing potential must agree to use barrier contraceptive methods or have undergone a vasectomy and agree not to donate sperm during the study and for at least 150 days after receipt of study treatment. Additionally, male participants with female partners of childbearing potential must agree to discuss with their partner the use of highly effective contraception methods during the same period of time. When a male participant has undergone a vasectomy, the participant’s medical history should show that the vasectomized participant has documented medical assessment confirming the surgical success of the vasectomy
• Willing and able to comply with all study requirements and procedures, including the completion of a daily symptom Diary during the final month of the CDX0159-12 or CDX0159-13 and throughout the LTE study

Who cannot take part

• Procedures requiring general or epidural anesthesia within 8 weeks prior to study treatment, minor procedures (eg, dental) within 14 days prior to study treatment, or anticipation of procedures requiring general anesthesia during study participation
• Prior receipt of any investigational product or other anti-KIT therapy (other than barzolvolimab)
• Prohibited non-biologic systemic agents, including investigational agents, within 30 days or 5 half-lives, whichever is longer, prior to enrollment
• Immunomodulating biologic therapy within 3 months prior to enrollment
• Participants in Group 2 (Barzolvolimab Retreatment Group): Women who are pregnant or nursing. All female participants with reproductive potential must have a negative pregnancy test prior to starting barzolvolimab study treatment
• Active chronic or acute infection requiring treatment with systemic antibiotics, antivirals, antifungals, antiparasitics, or antiprotozoals during the enrollment review. The enrollment review may be extended by 2 weeks to allow for recovery of acute infections independent of requirement for anti-infective treatment
• Any other active pruritic skin diseases that would confound CSU assessments (eg, atopic dermatitis, psoriasis, bullous pemphigoid, dermatitis herpetiformis, prurigo nodularis, chronic pruritus of unknown origin) based on the Investigator’s clinical judgment
• History of malignancy within 5 years before enrollment review, except fully treated carcinoma in-situ of the cervix, fully treated and resolved non-metastatic squamous or basal cell carcinoma of the skin
• Severe or uncontrolled chronic diseases (eg, chronic hepatic or renal disease, diabetes mellitus) that might interfere with the evaluation of the clinical effect or safety of study treatment or may confound assessment of safety during the trial
• Participants with moderate-to-severe pulmonary or cardiovascular diseases
• Known active hepatitis B, hepatitis C, or HIV infection
• Any other acute or chronic medical or psychiatric condition or laboratory abnormality that could increase the risk associated with study participation or could interfere with the interpretation of study results and, in the judgment of the investigator, would make the participant inappropriate for entry into the study
• Inadequate compliance with the Diary during CDX0159-12 or CDX0159-13 sufficient to lead to unacceptable safety risk to study participation, according to the Investigator
• Participants who live in detention on court order or on regulatory action will not be enrolled
• Sponsor or contract research organization (CRO) staff directly involved in the conduct of the study, site staff supervised by the Investigator, and their respective family members
• Participants without at least one documented UAS7 score from Weeks 64-68 of the CDX0159-12 or CDX0159-13 trials