A 16-Week Study to Learn About the Study Medicine Called Ritlecitinib in Adults With Long Lasting Painful Red Skin Lumps, Known by the Medical Term, Hidradenitis Suppurativa, or HS.

A PHASE 2, MULTICENTER, RANDOMIZED, DOUBLE-BLIND, PLACEBO-CONTROLLED, 16-WEEK STUDY EVALUATING THE SAFETY AND EFFICACY OF RITLECITINIB (PF-06651600) IN ADULTS WITH MODERATE TO SEVERE HIDRADENITIS SUPPURATIVA

The purpose of this study is to learn about the safety and effects of the study medicine (called Ritlecitinib) for the possible treatment of hidradenitis suppurativa (HS). HS is a disease causing long lasting painful red skin lumps.

This study is seeking participants who:

• have moderate or severe HS
• have previously received antibiotics for HS that did not help, or could not tolerate antibiotics Participants will be randomly (like a flip of coin) assigned to receive either the study medicine or a placebo (a pill that looks like the study medicine but does not contain any medicine). The study medicine or placebo will be taken by mouth once daily at home. For the first part of the study, participants will receive a loading (starting) dose. For the next part of the study, participants will receive a maintenance (ongoing) dose.

Participants will take part in the study for about 24 weeks (about 6 months). There will be about 10 study clinic visits: a screening visit, Day 1, and then every 1, 2, or 4 weeks until week 16. At each visit, participants will report on their health and have tests such as physical exams, blood and urine tests, vital signs, chest X-rays, ECGs, hearing tests, and questionnaires. Participants will record when they take the study medicine and their HS symptoms every day in an eDiary on a mobile phone.

The experiences of participants receiving the study medicine will be compared to those receiving placebo to help see if the study medicine is safe and effective.

Study Overview

• Status: Active, not recruiting
• Conditions: Hidradenitis Suppurativa
• Intervention / Treatment: Drug: Ritlecitinib; Drug: Placebo

• Study Type: Interventional
• Enrollment (Actual): 128
• Phase: Phase 2

Contacts and Locations

Study Locations

• Canada
  • Québec, Canada, G1W 4R4
    • Centre de Recherche Saint-Louis inc.
  • Alberta
    • Calgary, Alberta, Canada, T2J 7E1
      • Dermatology Research Institute
    • Edmonton, Alberta, Canada, T5J 3S9
      • Laser Rejuvenation Clinics Edmonton D.T. Inc
    • Edmonton, Alberta, Canada, T6W 4V4
      • Skin Physicians Dermatology
    • Red Deer, Alberta, Canada, T4P 1K4
      • CaRe Clinic
  • Ontario
    • Newmarket, Ontario, Canada, L3Y 5G8
      • Ryan Clinical Research Inc.
    • Ottawa, Ontario, Canada, K1V 1C1
      • DAR Clinical Research
    • Toronto, Ontario, Canada, M4E 1R7
      • FACET Dermatology
    • Toronto, Ontario, Canada, M2N 3A6
      • North York Research Inc
• Germany
  • Frankfurt, Germany, 60590
    • Universitätsklinikum Frankfurt
  • Lübeck, Germany, 23538
    • Universitätsklinikum Schleswig Holstein - Campus Lübeck
  • Saxony
    • Dresden, Saxony, Germany, 01307
      • Universitaetsklinikum Carl Gustav Carus, Technischen Universitaet Dresden
• Greece
  • Athens, Greece, 16121
    • Dermatological and Venereological Hospital Andreas Syggros
  • Attica
    • Athens, Attica, Greece, 11525
      • Athens Medical Center - Psychikon branch
  • Thessaloníki
    • Thessaloniki, Thessaloníki, Greece, 564 29
      • Papageorgiou General Hospital of Thessaloniki
  • Thessalía
    • Larissa, Thessalía, Greece, 411 10
      • University General Hospital of Larissa
• Poland
  • Gdansk, Poland, 80-546
    • Penta Hospitals Badania Kliniczne Sp. z o.o.
  • Ostrowiec Świętokrzyski, Poland, 27-400
    • Dermedic Jacek Zdybski
  • Rzeszów, Poland, 35-055
    • Uniwersytecki Szpital kliniczny im. F. Chopina w Rzeszowie
  • Sosnowiec, Poland, 41-200
    • Centrum Zdrowia Dziecka i Rodziny im Jana Pawla II w Sosnowcu
  • Szczecin, Poland, 71-500
    • Twoja Przychodnia Szczecinskie Centrum Medyczne Sp. z o.o.
  • Warsaw, Poland, 02-962
    • Royalderm Agnieszka Nawrocka
  • Warsaw, Poland, 02-507
    • Państwowy Instytut Medyczny MSWiA
  • Warsaw, Poland, 02-953
    • Klinika Ambroziak Dermatologia
  • Warsaw, Poland, 02-482
    • Trialmed CRS - Warszawa
  • Wroclaw, Poland, 50-551
    • Soft Skin Medical Center Dr Elzbieta Wojtowicz-Prus
  • Lower Silesian Voivodeship
    • Wroclaw, Lower Silesian Voivodeship, Poland, 50-566
      • Cityclinic Przychodnia Lekarsko-Psychologiczna Matusiak Spółka Partnerska
• Spain
  • Cadiz, Spain, 11009
    • Hospital Universitario Puerta del Mar
  • Granada, Spain, 18012
    • Hospital Universitario Virgen Nieves
  • Madrid, Spain, 28007
    • Hospital General Universitario Gregorio Marañón
  • Pontevedra, Spain, 36001
    • CHOP-Centro De Especialidades De Mollabao
  • Valencia
    • Manises, Valencia, Spain, 46940
      • Hospital de Manises
• United States
  • Arizona
    • Phoenix, Arizona, United States, 85054
      • Mayo Clinic Hospital
    • Phoenix, Arizona, United States, 85006
      • Medical Dermatology Specialists
    • Phoenix, Arizona, United States, 85054
      • Mayo Clinic Specialty Building
    • Scottsdale, Arizona, United States, 85259
      • Mayo Clinic
  • Arkansas
    • Hot Springs, Arkansas, United States, 71913
      • Burke Pharmaceutical Research
  • California
    • Fountain Valley, California, United States, 92708
      • First OC Dermatology Research Inc
    • Northridge, California, United States, 91325
      • Northridge Clinical Trials
    • Sacramento, California, United States, 95815
      • Integrative Skin Science and Research
    • Santa Ana, California, United States, 92706
      • Wolverine Clinical Trials
  • Florida
    • Boca Raton, Florida, United States, 33486
      • Skin Care Research
    • Largo, Florida, United States, 33770
      • Olympian Clinical Research
    • North Miami Beach, Florida, United States, 33162
      • Ziaderm Research LLC
    • Tamarac, Florida, United States, 33321
      • D&H Tamarac Research Center
    • Tampa, Florida, United States, 33615
      • Alliance Clinical Research of Tampa
    • Tampa, Florida, United States, 33615
      • Olympian Clinical Research
    • Tampa, Florida, United States, 33612
      • USF Health
    • Tampa, Florida, United States, 33607
      • NMC Research LLC
    • Tampa, Florida, United States, 33620
      • USF Florida Hearing Clinic
    • Wellington, Florida, United States, 33449
      • TruDerm & TruSpa
  • Georgia
    • Sandy Springs, Georgia, United States, 30328
      • Advanced Medical Research, PC.
  • Illinois
    • Skokie, Illinois, United States, 60077
      • Endeavor Health
  • Indiana
    • Plainfield, Indiana, United States, 46168
      • The Indiana Clinical Trials Center, PC
    • West Lafayette, Indiana, United States, 47906
      • Options Research Group
  • Kansas
    • Overland Park, Kansas, United States, 66213
      • Essential Medical Research - Overland Park
    • Overland Park, Kansas, United States, 66213
      • Skin and Hair Center
  • Kentucky
    • Louisville, Kentucky, United States, 40241
      • DS Research of Kentucky
  • Michigan
    • Southfield, Michigan, United States, 48034
      • Revival Research Institute, LLC
    • Troy, Michigan, United States, 48084
      • Revival Research Institute, LLC
  • Nebraska
    • Omaha, Nebraska, United States, 68144
      • Skin Specialists, PC dba Schlessinger MD
  • New Hampshire
    • Portsmouth, New Hampshire, United States, 03801
      • StracSkin
  • Ohio
    • Columbus, Ohio, United States, 43213
      • ClinOhio Research Services
  • South Carolina
    • Columbia, South Carolina, United States, 29212
      • Columbia Dermatology & Aesthetics
    • Greenville, South Carolina, United States, 29615
      • Palmetto Clinical Trial Services - Greenville
  • Texas
    • Houston, Texas, United States, 77004
      • Center for Clinical Studies, LTD. LLP
  • Virginia
    • Forest, Virginia, United States, 24551
      • Eurofins CRL

Participation Criteria

Eligibility Criteria

• Ages Eligible for Study: Adult; Older Adult
• Accepts Healthy Volunteers: No

Description

Key Eligibility Criteria:

Inclusion Criteria:

1. Male or female participants ≥18 to ≤75 years of age.
2. Participants with a diagnosis (based on clinical history and physical examination) of moderate to severe HS for at least 6 months prior to Screening Visit and inadequate response to at least 4-week (28 days) treatment with oral antibiotics for the treatment of HS.

Exclusion Criteria:

1. Presence of ≥20 draining fistulae at Screening or BL visit
2. Evidence of other active skin disease or condition at screening
3. Have a known immunodeficiency disorder
4. Having a history of systemic infection requiring hospitalization or parenteral therapy, including history of infection with Mycobacterium TB
5. Specific Viral Infection History (incl. history of herpes zoster, HBV or HCV Infection
6. Current or recent history of clinically significant severe, progressive, or uncontrolled other medical conditions
7. Any medical or psychiatric condition including any active suicidal ideation in the past year or suicidal behavior in the past 5 years

Study Plan

How is the study designed?

Design Details

• Primary Purpose: Treatment
• Allocation: Randomized
• Interventional Model: Parallel Assignment
• Masking: Triple

Number of Arms

2

Arms and Interventions

Participant Group / Arm	Intervention / Treatment
Placebo Comparator: Placebo; Participants will receive matching placebo.	Drug: Placebo; Participant will receive matching placebo
Experimental: Study Intervention; Participants will receive one oral dose once daily (QD), starting with a loading dose of ritlecitinib for 8 weeks, followed by maintenance for 8 weeks.	Drug: Ritlecitinib; Participants will receive one oral dose once daily (QD), starting with a loading dose of ritlecitinib for 8 weeks, followed by maintenance for 8 weeks.; Other Names: Investigational Product

What is the study measuring?

Primary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Difference in proportion of responders based on Hidradenitis Suppurativa Clinical Response achieving at least 50% reduction from baseline (Hidradenitis Suppurativa Clinical Response HiSCR50) in patients with HS treated with ritlecitinib versus placebo.	The difference in proportion of responders based on HiSCR50 response at Week 16 in patients with HS treated with ritlecitinib versus placebo.	Week 16

Secondary Outcome Measures

Outcome Measure	Measure Description	Time Frame
Proportion of participants achieving HiSCR50 response	The difference in proportion of responders based on HiSCR50 response at Weeks 1, 2, 4, 6, 8 and 12 in patients with HS treated with ritlecitinib versus placebo	at Weeks 1, 2, 4, 6, 8 and Week 12.
Proportion of participants achieving HiSCR75 response	The difference in proportion of responders based on HISCR75 response at Weeks 1, 2, 4, 6, 8, 12 and 16 in patients with HS treated with ritlecitinib versus placebo	at Weeks 1, 2, 4, 6, 8, 12 and Week 16.
Proportion of participants achieving HiSCR90 response	The difference in proportion of responders based on HiSCR90 response at Weeks 1, 2, 4, 6, 8, 12 and 16 in patients with HS treated with ritlecitinib versus placebo	at Weeks 1, 2, 4, 6, 8, 12 and Week 16
Response based on a on total abscess and inflammatory nodule count (AN Count) of 0 or 1	The difference in proportion of responders based on a total AN count of 0 or 1 at Week 16 in patients with HS treated with ritlecitinib and placebo	Week 16
Response based on a total AN count of 0, 1, or 2	The difference in proportion of responders based on a total AN count of 0, 1 or 2 at Week 16 in patients with HS treated with ritlecitinib and placebo.	At week 16
Percent change from Baseline(CFB) in total AN count	The difference in mean percent CFB in total AN count at Weeks 1, 2, 4, 6, 8, 12 and 16 in patients with HS treated with ritlecitinib and placebo	Weeks 1, 2, 4, 6, 8, 12 and 16.
Absolute score in Hidradenitis Suppurativa Investigator Global Assessment (HS-IGA)	The difference in mean absolute score in HS-IGA at Weeks 1, 2, 4, 6, 8, 12 and 16 in patients with HS treated with ritlecitinib and placebo	at Weeks 1, 2, 4, 6, 8, 12 and 16
CFB in Hidradenitis Suppurativa Investigator Global Assessment (HS-IGA)	Mean CFB in HS-IGA at Weeks 1, 2, 4, 6, 8, 12 and 16 in patients with HS treated with ritlecitinib and placebo	at Weeks 1, 2, 4, 6, 8, 12 and 16
Proportion of participants achieving a HS-IGA=0 or 1	The difference in proportion of responders based on HS-IGA=0 or 1 at Weeks 1, 2, 4, 6, 8, 12 and 16 in patients with HS treated with ritlecitinib and placebo	Weeks 1, 2, 4, 6, 8, 12 and 16
Participants who experience an HS flare, defined as at least a 25% increase in total AN count with a minimum increase of 2 relative to Baseline	The difference in proportion of HS flare at Weeks 4, 8, 12 and 16 in patients with HS treated with ritlecitinib and placebo	Weeks 4, 8, 12 and 16.
CFB in Hidradenitis Suppurativa Symptom Daily Diary (HSSDD)		Weeks 1, 2, 4, 6, 8, 12 and 16
Skin pain NRS30 (numeric rating scale) response, at worst and on average, respectively among participants with baseline skin pain NRS ≥3		Weeks 1, 2, 4, 6, 8, 12, and 16
Percent CFB in skin pain NRS, at worst and on average, respectively, in participants with baseline skin pain NRS ≥3		Weeks 1, 2, 4, 6, 8, 12, and 16
CFB in skin pain NRS, at worst and on average, respectively		at Weeks 1, 2, 4, 6, 8, 12, and 16
Skin pain NRS50 response, at worst and on average, respectively among participants with baseline skin pain NRS ≥3.		at Weeks 1, 2, 4, 6, 8, 12, and 16
Skin pain NRS70 response, at worst and on average, respectively among participants with baseline skin pain NRS ≥3		at Weeks 1, 2, 4, 6, 8, 12, and 16,
Incidence of treatment emergent adverse events (TEAE), adverse events (AE) and serious adverse events (SAE) leading to discontinuation		up to 24 Weeks
Incidence of clinically significant laboratory abnormalities over time		up to 24 Weeks
Absolute score and CFB in Hidradenitis Suppurativa Quality of Life (HiSQOL)		at Weeks 1, 2, 4, 6, 8, 12 and 16.
Absolute score and % CFB in International Hidradenitis Suppurativa Severity Score System (IHS4)		Weeks 1, 2, 4, 6, 8, 12 and 16.

Collaborators and Investigators

• Sponsor: Pfizer
• Investigators: Study Director: Pfizer CT.gov Call Center, Pfizer

Publications and helpful links

Helpful Links

• To obtain contact information for a study center near you, click here.

Study record dates

Study Major Dates

• Study Start (Actual): November 13, 2025
• Primary Completion (Estimated): December 8, 2026
• Study Completion (Estimated): January 5, 2027

Study Registration Dates

• First Submitted: October 31, 2025
• First Submitted That Met QC Criteria: November 13, 2025
• First Posted (Actual): November 14, 2025

Study Record Updates

• Last Update Posted (Actual): September 1, 2026
• Last Update Submitted That Met QC Criteria: August 28, 2026
• Last Verified: August 1, 2026

More Information

Terms related to this study

• Keywords: Ritlecitinib
• Additional Relevant MeSH Terms: Infections; Skin Diseases; Bacterial Infections; Bacterial Infections and Mycoses; Sweat Gland Diseases; Skin Diseases, Bacterial; Skin Diseases, Infectious; Suppuration; Hidradenitis; Skin and Connective Tissue Diseases; Hidradenitis Suppurativa
• Other Study ID Numbers: B7981119; 2025 (U.S. NIH Grant/Contract: Faculty of Social Sciences Scientific Grant at the University of Gdańsk); 2025-522705-37-00 (Registry Identifier: CTIS (EU))

Plan for Individual participant data (IPD)

• Plan to Share Individual Participant Data (IPD)?: YES
• IPD Plan Description: 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.

Drug and device information, study documents

• Studies a U.S. FDA-regulated drug product: Yes
• Studies a U.S. FDA-regulated device product: No