A Phase 2, Randomized, Double-Blind, Placebo-Controlled, Parallel-Group, Multicenter Study to Assess the Efficacy and Safety of THB335 in Adult Participants With Chronic Spontaneous Urticaria (CSU)

NCT07766499 | Not Yet Recruiting Phase 2 DMC FDA Drug

• 2 other identifiers: THB335-2012026-526342-27-00
• Study Type: interventional
• Target: 81
• Locations: 0 countries
• Sites: N/A

Brief Summary

THB335-201 is a Phase 2, randomized, double-blind, placebo-controlled, parallel-group, multicenter study in adults with CSU who remain symptomatic despite standard-of-care treatment. The study includes a Screening Period of up to 4 weeks, a 12-week Treatment Period, and a 4-week Follow-Up Period, for a total participant duration of approximately 20 weeks.

Conditions

Chronic Spontaneous Urticaria (CSU); Chronic Idiopathic Urticaria

Keywords

Chronic spontaneous urticaria; CSU; Chronic hives; THB335; Second-generation H1 antihistamine; Urticaria Activity Score 7; UAS7; Chronic urticaria; Urticaria; Histamine H1 Antagonists

Outcome Measures

Primary Outcomes (1)

• Change From Baseline in Weekly Urticaria Activity Score (UAS7) at Week 12

  UAS7 is the sum of daily Urticaria Activity Scores over 7 days. The daily score combines the Hives Severity Score and Itch Severity Score, each scored from 0 to 3. UAS7 ranges from 0 to 42; higher scores indicate greater disease activity.

  Baseline and Week 12

Secondary Outcomes (9)

• Percentage of Participants With UAS7 ≤ 6

  Through Week 12

• Percentage of Participants With UAS7 = 0

  Week 12

• Change From Baseline in UAS7

  Baseline to Week 8

• Change From Baseline in Weekly Itch Severity Score (ISS7)

  Baseline to Week 12

• Change From Baseline in Weekly Hives Severity Score (HSS7)

  Baseline to Week 12

Study Arms (3)

THB335 Higher Dose

EXPERIMENTAL

Orally-administered THB335 higher dose.

Drug: THB335 Higher Dose

THB335 Lower Dose

EXPERIMENTAL

Orally-administered THB335 lower dose.

Drug: THB335 Lower Dose

Placebo

PLACEBO COMPARATOR

Orally-administered matching placebo.

Drug: Placebo

Interventions

THB335 Lower Dose DRUG

THB335 is an orally administered capsule added to a stable background regimen of a second generation H1 antihistamine.

THB335 Lower Dose

THB335 Higher Dose DRUG

THB335 is an orally administered capsule added to a stable background regimen of a second generation H1 antihistamine.

THB335 Higher Dose

Placebo DRUG

Placebo is an orally administered capsule added to a stable background regimen of a second generation H1 antihistamine.

Placebo

Eligibility Criteria

• Age: 18 Years - 85 Years
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• Males and females 18 through 85 years.
• Diagnosis of chronic spontaneous urticaria (CSU) ≥ 6 months.
• Active CSU despite treatment with a second-generation H1 antihistamine.
• Weekly Urticaria Activity Score (UAS7) ≥ 16 and ISS7 ≥ 8 during the 7 days before randomization, with sufficient electronic diary entries to calculate the baseline scores.
• Body mass index of 18 to 38 kg/m² and minimum body weight of 50 kg for male participants or 45 kg for female participants.
• Willing and able to complete the daily electronic diary, attend scheduled study visits, and comply with study procedures.
• Participants capable of becoming pregnant or producing sperm must agree to follow the protocol-defined contraception requirements.

You may not qualify if:

• Chronic urticaria with an identified cause other than chronic spontaneous urticaria.
• Another active skin condition associated with chronic itching that could interfere with the study assessments.
• Recent treatment with prohibited immunosuppressive therapy, biologic therapy, a Bruton's tyrosine kinase inhibitor, an investigational drug, or another therapy that inhibits the c-KIT receptor.
• Clinically significant hepatic, hematologic, or renal disease or laboratory abnormalities.
• Active, chronic, or recurrent infection, including human immunodeficiency virus or viral hepatitis infection.
• Clinically significant cardiovascular disease or electrocardiogram abnormality, including clinically significant arrhythmia, prolonged QT interval, familial long QT syndrome, or use of medication known to prolong the QT interval that cannot be discontinued.
• History of idiopathic anaphylaxis, a severe allergic reaction that may increase the risk of study participation, or hypersensitivity to the study drug or related compounds.
• History of malignancy within the previous 5 years, except successfully treated nonmetastatic basal cell or squamous cell skin cancer or carcinoma in situ.
• Current or planned use of prohibited medications, including specified inhibitors, inducers, or sensitive substrates of drug-metabolizing enzymes or transporters, or proton pump inhibitors.
• Positive urine drug screen at Screening.
• Pregnancy or breastfeeding.
• Any medical or psychiatric condition that, in the investigator's judgment, could place the participant at increased risk, interfere with the study assessments, or affect the participant's ability to complete the study.
• Additional eligibility criteria are outlined in the full protocol. The study investigator will review all requirements with potential participants to determine whether they are eligible to participate.

Sponsors & Collaborators

• Calixis Inc.: lead

MeSH Terms

Conditions

Chronic Urticaria; Urticaria

Condition Hierarchy (Ancestors)

Skin Diseases, Vascular; Skin Diseases; Skin and Connective Tissue Diseases; Hypersensitivity, Immediate; Hypersensitivity; Immune System Diseases; Chronic Disease; Disease Attributes; Pathologic Processes; Pathological Conditions, Signs and Symptoms

Central Study Contacts

Clinical Trials Monitor

CONTACT

+1 (617) 299 - 6702; info@calixisbio.com

Study Design

• Study Type: interventional
• Phase: phase 2
• Allocation: RANDOMIZED
• Masking: QUADRUPLE
• Who Masked: PARTICIPANT, CARE PROVIDER, INVESTIGATOR, OUTCOMES ASSESSOR
• Masking Details: Sponsor
• Purpose: TREATMENT
• Intervention Model: PARALLEL
• Sponsor Type: INDUSTRY
• Responsible Party: SPONSOR

Study Record Dates

• First Submitted: August 11, 2026
• First Posted: August 14, 2026
• Study Start (Estimated): September 1, 2026
• Primary Completion (Estimated): December 31, 2027
• Study Completion (Estimated): January 31, 2028
• Last Updated: August 14, 2026

Record last verified: 2026-08

Data Sharing

• IPD Sharing: Will not share