Skip to content
Clinical Trials – home
Not recruiting

A Study to Evaluate the Safety and Effectiveness of Ritlecitinib Tosilate in Adults with Moderate to Severe Hidradenitis Suppurativa

Fast replyInvestigational
Clinical Trials Concierge

Prefer not to search? Our Concierge searches the trials for you.

What is this trial about?

A plain-language summary of the goals, design and what participants do

This study focuses on individuals living with Hidradenitis Suppurativa, a chronic skin condition characterized by painful, red lumps under the skin that can form abscesses or tunnels. The purpose of the study is to evaluate the safety and effectiveness of a medication called ritlecitinib, also known as PF-06651600, compared to a placebo.

During the study, participants will be assigned to receive either the active medication or a placebo in a randomized way, meaning the group assignment is decided by chance. The process is double-blind, which means neither the participants nor the researchers know which substance is being administered. The study will last for a total of 16 weeks, during which time the effects of the treatment on the skin and symptoms will be monitored.

The research process

The trial runs in 2 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Participation in the study

    The study involves taking either ritlecitinib tosilate, which is an oral capsule, or a placebo, which is a substance that does not contain active medicine.

    The treatment lasts for a total of 16 weeks.

  2. Step 2

    Monitoring and assessment

    During the 16-week period, regular assessments are conducted at weeks 1, 2, 4, 6, 8, 12, and 16.

    These assessments evaluate the effectiveness of the medicine by measuring changes in skin lumps (abscesses and nodules), skin pain, and skin severity.

    A daily diary is used to track symptoms throughout the study.

    The impact of the medicine on quality of life is also monitored at each scheduled visit.

Who can join the trial?

4 criteria

  • You must be between 18 and 75 years old.
  • You must have a confirmed medical diagnosis of Hidradenitis Suppurativa (a chronic skin condition that causes painful lumps under the skin) for at least 6 months.
  • Your condition must be moderate to severe, which means you have Hurley Stage II or III (levels used to describe how much the skin is affected by the disease) and at least 5 inflammatory lesions (painful, red, swollen bumps like abscesses or nodules) located in at least 2 different body areas.
  • You must have either not seen enough improvement after taking systemic therapy (medicine that travels through the entire body, such as a pill) for at least 4 weeks, or you must have a medical reason why you cannot take this type of medicine.

Who cannot join the trial?

5 criteria

  • Having 20 or more draining fistulas, which are abnormal tunnels or passages that form under the skin and leak fluid.
  • Having other skin conditions that might make it difficult to tell if the treatment is working for your specific condition.
  • Having previously used a JAK inhibitor or a BTK inhibitor, which are types of medicines used to change how the immune system works.
  • Having any serious medical or mental health illnesses.
  • A limited number of people in the study may have previously used anti-TNF-α, IL-17 inhibitors, or IL-23 inhibitors, which are specific types of medications used to calm an overactive immune system.
Clinical Trials Concierge

Prefer not to search? Our Concierge searches the trials for you.

Tell us about your condition – we search every trial in Europe and connect you with the right site.

We usually reply within a few days

Verified sites

All sites with verified contact details – recruitment status may not be available; ask directly

Trial locations

Where you can join this trial

Countries are shaded by recruitment status. Click a recruiting country to ask about joining there.

Not recruiting
Not finding your country?

Not sure what to do next?

Joining a clinical trial can seem overwhelming. We guide you step by step, so you know exactly what to expect and how we support you through the process.

See the full process and FAQ

Investigated drugs

Ritlecitinib is an oral medication taken in capsule form that is being tested to see if it can help reduce the symptoms and improve the skin condition in adults living with moderate to severe hidradenitis suppurativa.

What is already known about the treatment

  • Placebo for pf-06651600-15

    This is an inactive substance administered in the same way as the study medication to serve as a comparison tool. It contains no active medicinal ingredients and is used in clinical trials to help researchers determine if the actual drug is effective. It has no therapeutic purpose or mechanism of action on the body.

  • Ritlecitinib Tosilate

    This medication is taken orally in the form of a capsule to treat moderate to severe hidradenitis suppurativa, a painful skin condition. Currently being studied in clinical trials, it works by blocking a specific protein called Janus kinase 3, which helps reduce the overactive immune response that causes skin inflammation. It is classified as a selective kinase inhibitor designed to calm the body's inflammatory processes at a molecular level.

Investigated diseases

Hidradenitis suppurativa - This is a chronic skin condition that causes painful lumps to form underneath the skin. These lumps typically appear in areas where skin rubs together, such as the armpits or groin. As the condition progresses, these lumps can break open and drain fluid or pus. Over time, the inflammation may lead to the formation of tunnels or tracts under the skin. These connections can link multiple lumps together and cause scarring. The disease often occurs in recurring episodes.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IITrial ID2025-522705-37-00Protocol codeB7981119Estimated enrolment120 patientsSponsorPfizer Inc.

sourced from the EU Clinical Trials Register and site verification

Want to learn more about this trial or check if you can participate?

Clinical Trials Concierge

Prefer not to search? Our Concierge searches the trials for you.

Tell us about your condition – we search every trial in Europe and connect you with the right site.