Chronic Spontaneous Urticaria (CSU)Phase 2NCT07766499
A Study to Assess the Efficacy and Safety of THB335 in Adults With Chronic Spontaneous Urticaria (CSU)
A Phase 2 study testing THB335 Lower Dose and THB335 Higher Dose in people with Chronic Spontaneous Urticaria (CSU) and Chronic Idiopathic Urticaria, run by Calixis Inc. at 15 sites in United States.
Trial 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. Read more about this study
- Who is it for?
- Ages 18 to 85 years
- Conditions the study is for
- Chronic Spontaneous Urticaria (CSU), Chronic Idiopathic Urticaria
- What is being tested?
- THB335 Lower Dose and THB335 Higher Dose
- Type of treatment
- Pill or oral medicine
- Could I receive a placebo?
- Yes, some participants may receive a placebo
- How many people
- 81 participants
- Where
- 15 sitesUnited States
- Study dates
- 15 Sep 2026to 31 Jan 2028
- Phase
- Phase 2
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 to 85 years
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- 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.
Who cannot join
- 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.
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- 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.
Trial locations and contacts
15 sites in 1 country. Contact the study team or a site near you to ask about taking part.
15 sites in 1 country
United States15 sites, 15 recruiting
- Recruiting
Calixis Study Site
Altamonte Springs, Florida, 32701
Clinical Trials Monitor
- Recruiting
Calixis Study Site
Asheville, North Carolina, 28803
Clinical Trials Monitor
- Recruiting
Calixis Study Site
Atlanta, Georgia, 30329
Clinical Trials Monitor
- Recruiting
Calixis Study Site
Austin, Texas, 78726
Clinical Trials Monitor
- Recruiting
Calixis Study Site
Baton Rouge, Louisiana, 70809
Clinical Trials Monitor
- Recruiting
Calixis Study Site
Boise, Idaho, 83706
Clinical Trials Monitor
- Recruiting
Calixis Study Site
Houston, Texas, 77082
Clinical Trials Monitor
- Recruiting
Calixis Study Site
Pasadena, California, 91106
Clinical Trials Monitor
- Recruiting
Calixis Study Site
Prosper, Texas, 75078
Clinical Trials Monitor
- Recruiting
Calixis Study Site
Smyrna, Tennessee, 37167
Clinical Trials Monitor
- Recruiting
Calixis Study Site
Tampa, Florida, 33607
Clinical Trials Monitor
- Recruiting
Calixis Study Site
Ventura, California, 93003
Clinical Trials Monitor
- Recruiting
Calixis Study Site
Walnut Creek, California, 94596
Clinical Trials Monitor
- Recruiting
Calixis Study Site
White Marsh, Maryland, 21162
Clinical Trials Monitor
- Recruiting
Calixis Study Site
Wildwood, Missouri, 63040
Clinical Trials Monitor
About this study
Official title: 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) Who Remain Symptomatic Despite Standard-of-Care Treatment
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.
Read the detailed description
This study will evaluate the efficacy and safety of THB335 in adults with chronic spontaneous urticaria (CSU) who continue to have hives and itching despite treatment with a second-generation H1 antihistamine. Approximately 81 participants will be randomly assigned to receive 1 of 2 doses of THB335 or matching placebo orally once daily for 12 weeks, in addition to their stable antihistamine treatment. Neither participants nor study personnel will know the assigned treatment. Participants will then be followed for 4 weeks. The main assessment is the change in weekly Urticaria Activity Score (UAS7) from baseline to Week 12.
This study will have approximately 40 locations.
- Being tested
- THB335 Lower Dose, THB335 Higher Dose, Placebo
- Keywords
- Chronic spontaneous urticaria, CSU, Chronic hives, THB335, Second-generation H1 antihistamine, Urticaria Activity Score 7, UAS7, Chronic urticaria, Urticaria, Histamine H1 Antagonists
- Medical subject headings
- Chronic Urticaria, Urticaria
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
THB335 Lower DoseDrug
THB335 is an orally administered capsule added to a stable background regimen of a second generation H1 antihistamine.
THB335 Higher DoseDrug
THB335 is an orally administered capsule added to a stable background regimen of a second generation H1 antihistamine.
PlaceboDrug
Placebo is an orally administered capsule added to a stable background regimen of a second generation H1 antihistamine.
| Study group | Role | What they receive |
|---|---|---|
| THB335 Higher Dose | Experimental | Orally-administered THB335 higher dose. Receives: Drug: THB335 Higher Dose |
| THB335 Lower Dose | Experimental | Orally-administered THB335 lower dose. Receives: Drug: THB335 Lower Dose |
| Placebo | Placebo comparator | Orally-administered matching placebo. Receives: Drug: Placebo |
What is being measured
The primary outcome is the main question the study is designed to answer.
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.
Measured: Baseline and Week 12
Secondary outcomes (9)
Percentage of Participants With UAS7 ≤ 6
UAS7 ranges from 0 to 42. UAS7 ≤ 6 represents well-controlled urticaria.
Measured: Through Week 12
Percentage of Participants With UAS7 = 0
UAS7 = 0 indicates no reported hives or itching during the 7-day scoring period.
Measured: Week 12
Change From Baseline in UAS7
UAS7 ranges from 0 to 42.
Measured: Baseline to Week 8
Change From Baseline in Weekly Itch Severity Score (ISS7)
ISS7 is the sum of daily itch-severity scores over 7 days. Daily itch severity is scored from 0 (no itch) to 3 (severe itch); ISS7 ranges from 0 to 21.
Measured: Baseline to Week 12
Change From Baseline in Weekly Hives Severity Score (HSS7)
HSS7 is the sum of daily hives-severity scores over 7 days. Daily hives severity is scored from 0 (no hives) to 3 (many hives); HSS7 ranges from 0 to 21.
Measured: Baseline to Week 12
Change From Baseline in Urticaria Control Test (UCT) Score
The UCT contains 4 questions scored from 0 to 4. Total scores range from 0 to 16.
Measured: Baseline and Week 12
Incidence and Severity of Treatment-Emergent Adverse Events (TEAEs) and Serious Adverse Events (SAEs)
Number and percentage of participants with TEAEs, treatment-related TEAEs, SAEs, AEs leading to discontinuation, and AEs by severity.
Measured: Through Week 16
Number of Participants With Clinically Significant Changes in Vital Signs
Clinically significant changes or abnormalities in blood pressure, heart rate, respiratory rate, pulse oximetry, and body temperature will be assessed.
Measured: Through Week 16
Number of Participants With Clinically Significant Changes in Clinical Laboratory Test Results
Clinically significant changes or abnormalities in hematology, chemistry, coagulation, and urinalysis results will be assessed.
Measured: Through Week 16
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted14 Aug 2026
- Study start15 Sep 2026
- Primary completion31 Dec 2027 (estimated)
- Study completion31 Jan 2028 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Chronic Spontaneous Urticaria (CSU)Studies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 2
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Quadruple blind
- Who is masked
- Participant, Care provider, Investigator, Outcomes assessor
- Enrolment
- 81 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Calixis Inc.
- Sponsor type
- Industry (pharma, biotech, devices)
- Responsible party
- Sponsor
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07766499
- Sponsor's protocol ID
- THB335-201
- Other IDs
- 2026-526342-27-00
- Status last verified
- Oct 2026
- First submitted
- 11 Aug 2026
- Last updated
- 2 Nov 2026
- Results posted
- No
- Data monitoring committee
- Yes
- FDA-regulated drug
- Yes
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 2 Nov 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- 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) Who Remain Symptomatic Despite Standard-of-Care Treatment
- ClinicalTrials.gov ID
- NCT07766499
- Acronym / sponsor ID
- THB335-201
- Keywords
- Chronic spontaneous urticaria, CSU, Chronic hives, THB335, Second-generation H1 antihistamine, Urticaria Activity Score 7, UAS7, Chronic urticaria
- Phase
- Phase 2
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 81 participants (estimated)
- Lead sponsor
- Calixis Inc.Industry (pharma, biotech, devices)
- Study start
- 15 Sep 2026 (actual)
- Primary completion
- 31 Dec 2027 (estimated)
- Study completion
- 31 Jan 2028 (estimated)
- First posted
- 14 Aug 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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.
Detailed description
This study will evaluate the efficacy and safety of THB335 in adults with chronic spontaneous urticaria (CSU) who continue to have hives and itching despite treatment with a second-generation H1 antihistamine. Approximately 81 participants will be randomly assigned to receive 1 of 2 doses of THB335 or matching placebo orally once daily for 12 weeks, in addition to their stable antihistamine treatment. Neither participants nor study personnel will know the assigned treatment. Participants will then be followed for 4 weeks. The main assessment is the change in weekly Urticaria Activity Score (UAS7) from baseline to Week 12.
This study will have approximately 40 locations.
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- Quadruple blind (participant, care provider, investigator, outcomes assessor)
- Number of arms
- 3
| Arm | Type | Receives |
|---|---|---|
| THB335 Higher Dose | Experimental | Drug: THB335 Higher DoseOrally-administered THB335 higher dose. |
| THB335 Lower Dose | Experimental | Drug: THB335 Lower DoseOrally-administered THB335 lower dose. |
| Placebo | Placebo comparator | Drug: PlaceboOrally-administered matching placebo. |
Who may qualify
- Ages
- 18 to 85 years
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (7 listed)
- 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.
Key exclusion criteria (13 listed)
- 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.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| THB335 Lower DoseTHB335 is an orally administered capsule added to a stable background regimen of a second generation H1 antihistamine. | Drug | THB335 Lower Dose |
| THB335 Higher DoseTHB335 is an orally administered capsule added to a stable background regimen of a second generation H1 antihistamine. | Drug | THB335 Higher Dose |
| PlaceboPlacebo is an orally administered capsule added to a stable background regimen of a second generation H1 antihistamine. | Drug | Placebo |
Primary outcome
Change From Baseline in Weekly Urticaria Activity Score (UAS7) at Week 12
Time frame: Baseline and 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.
9 secondary outcomes
Percentage of Participants With UAS7 ≤ 6
Time frame: Through Week 12
Percentage of Participants With UAS7 = 0
Time frame: Week 12
Change From Baseline in UAS7
Time frame: Baseline to Week 8
Change From Baseline in Weekly Itch Severity Score (ISS7)
Time frame: Baseline to Week 12
Change From Baseline in Weekly Hives Severity Score (HSS7)
Time frame: Baseline to Week 12
Change From Baseline in Urticaria Control Test (UCT) Score
Time frame: Baseline and Week 12
Incidence and Severity of Treatment-Emergent Adverse Events (TEAEs) and Serious Adverse Events (SAEs)
Time frame: Through Week 16
Number of Participants With Clinically Significant Changes in Vital Signs
Time frame: Through Week 16
Number of Participants With Clinically Significant Changes in Clinical Laboratory Test Results
Time frame: Through Week 16
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 2 Nov 2026.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
15 sites in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 2 study testing THB335 Lower Dose and THB335 Higher Dose in people with Chronic Spontaneous Urticaria (CSU) and Chronic Idiopathic Urticaria, run by Calixis Inc. at 15 sites in United States.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 7 inclusion and 13 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 2 Nov 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 15 sites in United States. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. Some participants in this study may receive a placebo. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Clinical Trials Monitor (+1 (617) 299 - 6702, info@calixisbio.com), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Change From Baseline in Weekly Urticaria Activity Score (UAS7) at Week 12 (time frame: Baseline and Week 12). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 2 Nov 2026.