A Phase 2 interventional study of Ritlecitinib 50 mg and Ritlecitinib 100 mg in Chronic Spontaneous Urticaria, sponsored by Pfizer. Recruiting at 77 sites in 10 countries. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-10-26.
Sponsored by Pfizer · Phase 2, Interventional, and Treatment
The purpose of the study is to learn about the safety and effects of the study medicine (called ritlecitinib) for the treatment of chronic spontaneous urticaria (CSU) that is not effectively treated by antihistamines which are used to stop the body's "allergy alarm system" from overreacting. Chronic spontaneous urticaria is a disease that causes itchy hives and swellings in the deep layers of skin and fatty tissue just underneath the skin that come and go without a clear reason.
This study will look at both the 50 milligrams (mg) once daily (QD) oral dose and 100 milligrams (mg) once daily (QD) oral dose and compare them to placebo (pill with no active medicine).
This study is seeking participants who:
About 150 participants will take part in this study. Participants will be chosen by chance, like drawing names out of a hat, to receive either the 50 mg dose or 100 mg dose or placebo, taken by mouth once daily for 12 weeks( Period A). Thereafter the participants on 50 mg and 100 mg will continue on their doses while the participants receiving placebo will be switched to 100mg for an additional 12 weeks (Period B). The 2 doses of ritlecitinib in this study will be compared to each other and to the placebo. This will help to see if the 50 mg and/or 100 mg dose of ritlecitinib is safe and effective.
Participants will be in this study for about 8 months. During the study, participants will need to visit the study site up to 9 times. Participants will undergo various tests and procedures such as:
194 studies on the registry are indexed under Chronic Urticaria; 46 are open to participants now.
This study's planned enrollment of 200 is above the median of 80 across 145 interventional studies indexed under Chronic Urticaria.
Browse Chronic Urticaria studies →Pfizer is the lead sponsor of 3,334 studies on the registry; 149 are open to participants now.
Of its 601 completed or terminated interventional studies of FDA-regulated products, 391 (65%) have results posted.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Age:
18 years of age or older (or the minimum legal adult age as defined per local regulations, whichever is greater) at screening.
Disease Characteristics:
Participants must meet the following Chronic Spontaneous Urticaria (CSU) criteria:
a. Chronic spontaneous urticaria diagnosis for ≥3 months at the time of screening (with the onset date assessed by the Investigator based on all available records) b. Diagnosis of CSU inadequately controlled by second generation antihistamine (sgAH) at the time of randomization, defined as: (i) The presence of itch and hives for ≥6 consecutive weeks prior to screening despite the use of sgAH during this time period.
(ii) Participants must have been on a sgAH at locally approved dose or higher for treatment of CSU for at least 7 consecutive days before screening assessment of UAS7 and ISS7 is initiated.
(iii) Urticaria Activity Score 7 (UAS7) ≥16 (range 0-42) and an Itch Severity Score 7 (ISS7) ≥8 (range: 0-21) during the 7 days prior to randomization Day 1 c. Participants must complete at least 5 Urticaria Activity Score (UAS) eDiary entries during the 7 days immediately preceding randomization (Day 1) to confirm eligibility. If this requirement is not met due to documented, limited circumstances such as technical issues or short-term illness, the screening period may be extended only for the number of days necessary to allow completion of 5 UAS entries within any 7-day window. This extension period must not exceed 7 days.
d. Anti-Immunoglobulin E-naïve (IgE-naïve) and Anti-Immunoglobulin E-experienced (Anti-IgE-experienced) participants. Anti-IgE-experienced participants are defined as meeting any of the following criteria confirmed by the Site Investigator: (i) Did not adequately respond to the approved dosage of an anti-IgE therapy (eg, omalizumab 300 mg Q4W or an alternate approved anti-IgE therapy) for at least 3 months, as assessed by the Investigator (ii) Could not tolerate an anti-IgE therapy (iii) Stopped an anti-IgE therapy for any reason, eg, loss of access e. Anti-IgE-experienced participants must have stopped anti-IgE therapy for at least 16 weeks, or 5 half-lives, whichever is longer, prior to randomization Day 1
Exclusion Criteria:
Medical Conditions:
Medical conditions pertaining to CSU and other diseases/conditions affecting the skin
General Infection History:
Specific Viral Infection History
Other Medical Conditions
Any medical or psychiatric condition including any active suicidal ideation in the past year or suicidal behavior in the past 5 years or laboratory abnormality that may increase the risk of study participation or, in the investigator's judgment, make the participant inappropriate for the study. Any psychiatric condition including recent or active suicidal ideation or behavior that protocol-defined criteria.
Prior/Concomitant Therapy:
Current or prior use of any prohibited medication(s), vaccine(s), or treatment(s) within the protocol defined timelines.
Prior/Concurrent Clinical Study Experience:
Previous administration of an investigational product (drug or vaccine) within 8 weeks or 5 half-lives preceding the first dose of study intervention used in this study (whichever is longer). Participation in studies of other investigational products (drug or vaccine) at any time during participation in this study.
Diagnostic Assessments:
Screening standard 12-lead (ECG) that demonstrates clinically relevant abnormalities that may affect participant safety or interpretation of study results.
Other Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
The other ingredients in a medicine besides the active drug, such as fillers, colours or preservatives.
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Hepatitis B is a virus that infects the liver. These are separate tests: HBsAg positive usually means a current infection (a recent vaccination can briefly cause it too); total anti-HBc (HBcAb) positive means an infection now or in the past; HBV DNA measures how much virus is in the blood.
Some studies accept a past infection if HBV DNA is undetectable, sometimes with antiviral medicine during the study. Check what this study allows.
Hepatitis C is a virus that infects the liver. An HCV antibody test can stay positive after an infection has cleared (and is occasionally positive without one); an HCV RNA test shows whether the virus is there now.
After treatment, hepatitis C counts as cured when HCV RNA is still undetectable 12 weeks or more after the treatment ended. Studies often accept people cured this way.
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
A recording of the heart’s electrical activity, taken with stickers on the chest, arms and legs. It takes a few minutes and does not hurt.
Hypersensitivity
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Excipients
The other ingredients in a medicine besides the active drug, such as fillers, colours or preservatives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Clinically significant
Judged by the study doctor to matter for your health or for the study. It is a doctor’s decision, so ask the study team if you are unsure whether something counts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hepatitis B tests
Hepatitis B is a virus that infects the liver. These are separate tests: HBsAg positive usually means a current infection (a recent vaccination can briefly cause it too); total anti-HBc (HBcAb) positive means an infection now or in the past; HBV DNA measures how much virus is in the blood.
Some studies accept a past infection if HBV DNA is undetectable, sometimes with antiviral medicine during the study. Check what this study allows.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hepatitis C tests
Hepatitis C is a virus that infects the liver. An HCV antibody test can stay positive after an infection has cleared (and is occasionally positive without one); an HCV RNA test shows whether the virus is there now.
After treatment, hepatitis C counts as cured when HCV RNA is still undetectable 12 weeks or more after the treatment ended. Studies often accept people cured this way.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
HIV
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Investigational drug or device
A drug or device being studied in a clinical trial.
It may be new, or already approved and being studied for another use, dose or form. Criteria often leave out people who took part in another study of one within a recent period, commonly 30 days or five half-lives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Cancer (malignancy)
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ECG (electrocardiogram)
A recording of the heart’s electrical activity, taken with stickers on the chest, arms and legs. It takes a few minutes and does not hurt.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Randomized to Ritlecitinib 50 mg for 24 weeks Periods A and B). In addition to the active Ritlecitinib 50 mg capsule, a placebo matching the Ritlecitinib 100 mg capsule will be given to maintain blind
Drug: Ritlecitinib 50 mg · Drug: Placebo - 100 mg
Randomized to Ritlecitinib 100 mg for 24 weeks (Periods A and B). In addition to the active Ritlecitinib 100 mg capsule, a placebo matching the Ritlecitinib 50 mg capsule will be given to maintain blind
Drug: Ritlecitinib 100 mg · Drug: Placebo - 50 mg
Randomized to placebos matching the Ritlecitinib 50 mg and Ritlecitinib 100 mg capsules will be given to maintain blind from Day 1 to Week 12 (Period A). From Week 12 to Week 24 (Period B), will be switched to Ritlecitinib 100 mg. In addition to the active Ritlecitinib 100 mg capsule, a placebo matching the Ritlecitinib 50 mg capsule will be given to maintain blind.
Drug: Ritlecitinib 100 mg · Drug: Placebo - 50 mg · Drug: Placebo - 100 mg
50 mg Capsule
Also known as: PF-06651600, Litfulo
100 mg Capsule
Also known as: PF-06651600, Litfulo
Matching Capsule
Matching Capsule
Change from baseline in Urticaria Activity Score 7 (UAS7) at Week 12
Time frame: Week 12
Incidence of Treatment Emergent Adverse Events, Serious Adverse Events, and Adverse Events leading to discontinuation
Time frame: Week 12
Change from baseline in UAS7 at all timepoints except Week 12
Time frame: Week 1 through Week 11
Change from baseline in Itch Severity Score 7 (ISS7) at Week 12
Time frame: Week 12
Change from baseline in Hives Severity Score 7 (HSS7) at Week 12
Time frame: Week 12
Achieving complete response defined as UAS7=0 at Week 12
Time frame: Week 12
Achieving UAS7 ≤6 at Week 12
Time frame: Week 12
Achieving complete response defined as ISS7=0 at Week 12
Time frame: Week 12
Achieving complete response defined as HSS7=0 at Week 12
Time frame: Week 12
Time to achieving UAS7 ≤6
Time frame: Week 12
Time to achieving improvement from baseline ≥10 in UAS7
Time frame: Week 12
Incidence of TEAEs, SAEs, and AEs leading to discontinuation
Time frame: After Week 12 through Week 24
Plan to share: Yes — Pfizer will provide access to individual de-identified participant data and related study documents (e.g. protocol, Statistical Analysis Plan (SAP), Clinical Study Report (CSR)) upon request from qualified researchers, and subject to certain criteria, conditions, and exceptions. Further details on Pfizer's data sharing criteria and process for requesting access can be found at: https://www.pfizer.com/science/clinical_trials/trial_data_and_results/data_requests.
Data sharing details ↗ · www.pfizer.com
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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Studies of the drug tested here: PF-06651600