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Pharmacokinetic Study of Ritlecitinib Tosilate in Healthy Adults: Oral Solution, Short‑and Long‑Duration Capsules Fed vs Fasted – for ulcerative colitis

InvestigationalNo placebo
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What is this trial about?

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

The study involves a medicine called Ritlecitinib tosilate, which is being developed for several conditions such as ulcerative colitis, Crohn’s Disease, alopecia areata, rheumatoid arthritis and vitiligo. The drug is available as an oral solution and as two types of capsules that release the medicine over time. The goal is to learn how much of the medicine reaches the bloodstream and how quickly it does so, which helps understand how the drug works in the body.

In this trial, healthy adults receive a single dose of each formulation. Some doses are taken on an empty stomach (fasted) and others with a meal (fed). Blood samples are collected at several time points after each dose to measure the medicine’s level. This measurement of how the body absorbs and processes the drug is called pharmacokinetics, and the proportion that enters the bloodstream is referred to as bioavailability. Throughout the study, participants are checked for any side effects, and routine tests such as blood work, vital signs and a simple heart test (ECG) are performed to ensure safety.

The research process

The trial runs in 13 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Enrollment and baseline assessments

    After giving informed consent, basic health information is recorded, including vital signs, a 12‑lead ecg, and routine laboratory tests.

    These assessments establish that you are a healthy adult and determine that you can safely take the study medication.

  2. Step 2

    First dose – oral solution under fasted condition

    You will fast for at least 10 hours before the visit; only water is allowed.

    A single dose of ritlecitinib tosilate oral solution (100 mg) is taken by mouth.

    Blood samples are drawn at several time points after the dose (for example, at 0, 1, 2, 4, 8, 12 and 24 hours) to measure how the drug enters the bloodstream.

    Vital signs, a repeat ecg, and a short safety questionnaire are completed to check for any adverse events.

  3. Step 3

    Washout period after oral solution dose

    You will wait several days (the exact length is determined by the study team) before receiving the next dose, allowing the previous dose to be cleared from your body.

  4. Step 4

    Second dose – oral solution under fed condition

    You will eat a standardized meal provided by the study staff.

    Within 30 minutes after finishing the meal, you take a single dose of ritlecitinib tosilate oral solution (100 mg).

    Blood samples are collected at the same time points as the fasted visit to compare drug absorption with food.

    Vital signs, ecg and safety checks are repeated.

  5. Step 5

    Washout period after oral solution fed dose

    You wait again for the drug to be cleared before moving to the capsule formulations.

  6. Step 6

    Third dose – short‑duration capsule under fasted condition

    You fast for at least 10 hours.

    A single dose of ritlecitinib tosilate short duration capsule (100 mg) is swallowed with water.

    Blood is drawn at the same scheduled intervals to assess drug levels.

    Vital signs, ecg and safety monitoring are performed.

  7. Step 7

    Washout period after short‑duration capsule fasted dose

    A few days are allowed for the drug to leave your system.

  8. Step 8

    Fourth dose – short‑duration capsule under fed condition

    You eat the standardized meal.

    Within 30 minutes after the meal, you take a single dose of ritlecitinib tosilate short duration capsule (100 mg).

    Blood sampling, vital signs, ecg and safety checks follow the same schedule as previous visits.

  9. Step 9

    Washout period after short‑duration capsule fed dose

    Another clearance period is observed before the final formulation.

  10. Step 10

    Fifth dose – long‑duration capsule under fasted condition

    You fast for at least 10 hours.

    A single dose of ritlecitinib tosilate long duration capsule (100 mg) is taken with water.

    Blood samples are collected over the same time frame to evaluate how the drug is released over time.

    Vital signs, ecg and safety assessments are repeated.

  11. Step 11

    Washout period after long‑duration capsule fasted dose

    You wait for the medication to be cleared before the final dosing.

  12. Step 12

    Sixth dose – long‑duration capsule under fed condition

    You consume the standardized meal.

    Within 30 minutes after the meal, you take a single dose of ritlecitinib tosilate long duration capsule (100 mg).

    Blood sampling, vital signs, ecg and safety monitoring are performed as in earlier visits.

  13. Step 13

    Final follow‑up

    After the last dose, a final safety assessment is performed, including laboratory tests, vital signs and a 12‑lead ecg.

    Any adverse events that occurred during the study are recorded and reviewed.

Who can join the trial?

5 criteria

  • Be at least 18 years old (or the minimum age required by local laws) when screened.
  • Be a healthy man or woman, as confirmed by a medical check that includes a review of your health history, a full physical exam (checking things like blood pressure and heart rate), lab tests, and a 12‑lead ECG (a test that records the heart’s electrical activity).
  • Have a body mass index (BMI) between 16 and 32 kg/m² and weigh more than 45 kg (about 99 lb). BMI is a number that relates your weight to your height.
  • Be willing and able to attend all scheduled visits, follow the treatment plan, complete laboratory tests, and follow any lifestyle instructions required by the study.
  • Be able to sign a written informed consent form, showing that you understand the study and agree to take part.

Who cannot join the trial?

8 criteria

  • Having a current or past serious disease of the blood (hematological), kidneys (renal), hormone‑producing glands (endocrine), lungs (pulmonary), digestive system (gastrointestinal), heart or blood vessels (cardiovascular), liver (hepatic), mental health (psychiatric), nervous system (neurological), or serious allergies.
  • Having any condition that could change how the medicine is absorbed, such as having had part or all of the stomach removed (gastrectomy) or having had the gallbladder removed (cholecystectomy).
  • Having a weak immune system (immunodeficiency), including a positive blood test for HIV (HIV serology) or a close family member with an inherited immune disorder.
  • Having or having had infection with hepatitis B or hepatitis C viruses, which are viruses that affect the liver.
  • Having any other active or past serious infections (short‑term or long‑term).
  • Having had a feverish illness in the five days before taking the first dose of the study medication (febrile illness).
  • Having a history of diseases where lymph cells grow too much (lymphoproliferative disorders), such as Epstein‑Barr virus‑related disorders, lymphoma, leukemia, or any signs of current disease of the lymph system.
  • Having a current or past cancer (malignancy), except for skin cancers (basal cell or squamous cell) that were completely removed and did not spread (non‑metastatic), or early‑stage cervical cancer that has not invaded deeper tissue (cervical carcinoma in situ).
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Investigated drugs

Ritlecitinib tosilate oral solution
This is a liquid form of the investigational drug ritlecitinib. In the study, participants took the solution by mouth. The researchers used it as a reference point to see how the drug is absorbed and processed in the body when given as a liquid, compared with the capsule forms. Ritlecitinib tosilate short duration capsule
This is a solid capsule that contains ritlecitinib and is designed to release the drug quickly after it is swallowed. The trial gave participants this capsule to understand how fast the drug becomes available in the bloodstream and to compare its performance with the liquid solution. Ritlecitinib tosilate long duration capsule
This capsule also contains ritlecitinib but is formulated to release the drug more slowly over time. The study used it to see how a slower‑release version affects the amount of drug in the body and to compare its overall exposure to that of the short‑duration capsule and the oral solution.

What is already known about the treatment

  • Ritlecitinib tosilate oral solution

    This medication is taken by mouth as a liquid that is swallowed, delivering a 100 mg dose of the drug. Ritlecitinib is already approved for treating alopecia areata and is being studied for ulcerative colitis, Crohn’s disease, rheumatoid arthritis, and vitiligo. It works by blocking specific proteins called Janus kinases, which helps calm an over‑active immune system and reduces inflammation. It belongs to the class of oral Janus kinase (JAK) inhibitors.

  • Ritlecitinib tosilate Short Duration Capsule

    The short‑duration capsule is swallowed whole and provides a single 100 mg oral dose of ritlecitinib. The drug is approved for alopecia areata and is under investigation for several other immune‑related diseases such as ulcerative colitis and rheumatoid arthritis. Its action comes from inhibiting Janus kinase enzymes, which lowers the signals that cause inflammation. This product is classified as an oral JAK inhibitor.

  • Ritlecitinib tosilate Long Duration Capsule

    The long‑duration capsule is also taken by mouth, delivering a 100 mg dose that is released slowly over time. Ritlecitinib has market approval for alopecia areata and is being tested for conditions like Crohn’s disease, vitiligo, and other inflammatory disorders. It reduces disease activity by blocking JAK enzymes, which dampens the immune response. It is part of the oral Janus kinase inhibitor drug class.

Investigated diseases

  • Ulcerative colitis

    A long‑lasting inflammation of the lining of the colon that usually begins in the rectum and can extend upward. It creates ulcers and causes frequent, urgent bowel movements. The condition often waxes and wanes, with periods of worsening symptoms followed by quieter phases. Over time the affected area can become larger, leading to more frequent symptoms.

  • Crohn’s disease

    An inflammatory bowel disease that can affect any part of the digestive tract, from mouth to anus. Inflammation occurs in patches, causing thickening of the intestinal wall and sometimes narrowing (strictures). These changes can lead to abdominal pain, diarrhea, and weight loss. The disease may progress gradually, with new sections becoming involved over the years.

  • Alopecia areata

    An autoimmune disorder that results in sudden, patchy hair loss on the scalp or other body areas. Hair follicles stop growing hair, creating smooth, round bald spots. In many cases hair can regrow on its own, but new patches may appear. The pattern of loss can spread to larger areas over time.

  • Rheumatoid arthritis

    A chronic autoimmune condition that primarily attacks the lining of small joints, especially in the hands and feet. It causes swelling, stiffness, and pain that are often worse in the morning. Repeated inflammation can gradually erode joint surfaces. The disease typically progresses slowly, affecting more joints as time goes on.

  • Vitiligo

    A skin condition in which pigment‑producing cells are lost, leading to smooth, white patches on the skin. These patches may appear on any part of the body and often start small. Over months or years, the depigmented areas can enlarge or new spots can develop. The condition usually follows a slow, unpredictable course.

Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase ITrial ID2023-505603-23-00Protocol codeB7981086Estimated enrolment12 patientsSponsorPfizer Inc.

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