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Long-Term Safety and Efficacy of Zasocitinib in Adults with Active Psoriatic Arthritis

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What is this trial about?

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

This clinical trial is being done in adults with psoriatic arthritis, a long-term disease that causes painful, swollen joints and can also affect the skin. The study is testing zasocitinib (TAK-279), an oral medicine taken as a tablet, to learn more about its long-term safety, how well it is tolerated, and how it may help people with this condition. Some participants may receive a matching placebo during part of the study.

The study is a long-term extension, which means it follows people over a longer period after earlier treatment. During the trial, the medicine is taken by mouth and participants are watched over time for side effects and other health changes. Regular checkups and laboratory tests are used to follow general health, joint symptoms, and skin symptoms while treatment continues.

The research process

The trial runs in 5 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Trial start

    You enter a phase 3, long-term extension study for adults with active psoriatic arthritis. psoriatic arthritis is a condition that causes joint pain and swelling in people who have psoriasis.

    The study is designed to check the long-term safety, tolerability (how well you can take the treatment), and effectiveness of zasocitinib.

  2. Step 2

    Study treatment

    You take zasocitinib as an oral medicine, which means it is taken by mouth, in the form of a film-coated tablet.

    The source data lists two dose options for zasocitinib and matching placebo tablets, but the exact dose, frequency, and duration are not specified in the provided information.

    A placebo is also listed. a placebo is a tablet that looks like the study medicine but does not contain active medicine.

  3. Step 3

    Monitoring during the trial

    During the study, your side effects are tracked. these include treatment-emergent adverse events (new or worsening health problems that appear after treatment starts), serious adverse events, and adverse events of special interest.

    Your vital signs are checked. vital signs are basic body measurements such as blood pressure, pulse, and temperature.

    Your clinical laboratory parameters are checked. these are results from tests of blood or other samples.

  4. Step 4

    Response checks at set times

    Your arthritis symptoms and treatment response are assessed at week 24, week 48, and week 104.

    At these time points, the study measures acr20, acr50, and acr70. acr means american college of rheumatology, and the numbers show different levels of improvement in arthritis symptoms.

    The study also checks minimal disease activity (mda), which means very low disease activity.

    For patients with psoriasis affecting at least 3% of body surface area at the start, the study checks pasi75 at week 24, week 48, and week 104. pasi means psoriasis area and severity index, and 75 means at least a 75% improvement from the starting score.

  5. Step 5

    Trial end

    The study continues until the planned end of the long-term extension period.

    The estimated study end date is 2029-12-30.

Who can join the trial?

18 criteria

  • The person must be an adult with active psoriatic arthritis.
  • The person must be willing and able to understand the study rules and follow all study procedures, including using any needed digital tools or applications.
  • The person must have given written informed consent, meaning they signed and dated a form saying they agree to join the study, before any study-related tests or procedures start.
  • The person must have completed the full 52-week treatment period in one of the parent studies, no matter which treatment they received, and must not have met the rules for permanent stopping of the study treatment in those studies.
  • The investigator must believe the person may benefit from continuing or starting zasocitinib treatment.
  • The person must still meet the study’s birth control requirements, which means one of the following: they are surgically sterile, they are not able to have children, or if they can become pregnant and are sexually active with a person who can produce sperm and is not sterilized, they agree to use a highly effective method of contraception from the time they sign consent until the study ends and for at least 10 days after the last dose.
  • If the person is taking conventional synthetic disease-modifying antirheumatic drugs (csDMARDs, medicines that help control arthritis), they must be taking no more than 2 of these medicines.
  • If the person is taking methotrexate (MTX), the dose must be no more than 25 mg per week, or no more than 16 mg per week at study sites in Japan.
  • If the person is taking sulfasalazine (SSZ), the dose must be no more than 3000 mg per day.
  • If the person is taking leflunomide (LEF), the dose must be no more than 20 mg per day.
  • If the person is taking hydroxychloroquine (HCQ), the dose must be no more than 400 mg per day.
  • The combination of methotrexate and leflunomide is not allowed.
  • If the person is taking other treatments at the same time, those treatments must be on stable doses, meaning the dose has not changed recently.
  • Allowed stable treatments include oral corticosteroids (steroid medicines taken by mouth) at 10 mg per day or less of prednisone or an equivalent medicine.
  • Allowed stable treatments also include NSAIDs (nonsteroidal anti-inflammatory drugs, common pain and swelling medicines), COX-2 inhibitors (a type of anti-inflammatory medicine), paracetamol/acetaminophen (a pain and fever medicine), and certain low-strength opiates (strong pain medicines), but only tramadol up to 300 mg per day, or acetaminophen combined with codeine or hydrocodone.
  • For people who are 65 years of age or older, the investigator must decide that the possible benefits of joining still outweigh the possible risks.
  • For people who currently smoke or chew tobacco, or who have a long history of smoking or chewing tobacco, the investigator must decide that the possible benefits of joining still outweigh the possible risks.
  • For people who choose to use hormonal contraception (birth control that uses hormones), the investigator must decide that the possible benefits of joining still outweigh the possible risks.

Who cannot join the trial?

30 criteria

  • The person is not helping from the study treatment, meaning their symptoms are not improving or are getting worse.
  • The person met the rules for permanent stopping of the trial treatment in the earlier parent study.
  • The person developed another illness that could make it hard to judge whether the treatment is working, such as rheumatoid arthritis (joint inflammation), axial spondyloarthritis (inflammation of the spine and nearby joints), systemic lupus erythematosus (an immune system disease), Lyme disease, gout, or fibromyalgia (long-lasting widespread pain).
  • The person developed a form of psoriasis that is not plaque psoriasis, such as erythrodermic, pustular, predominantly guttate, predominantly inverse, or drug-induced psoriasis.
  • The person is not willing to limit sun exposure during the study, including natural sunlight and artificial sunlight.
  • The person has new signs or symptoms of active tuberculosis (TB), such as long-lasting fever, long-lasting cough with mucus, night sweats, or weight loss.
  • The person developed hepatitis C with a positive confirmatory test for the virus.
  • The person developed signs of hepatitis B, such as positive HBsAg (hepatitis B surface antigen), indeterminate HBsAg, positive HBcAb (hepatitis B core antibody), or detectable HBV DNA (viral genetic material in the blood).
  • The person tested positive for HIV by blood test.
  • The person had a serious herpes infection, such as widespread herpes, herpes affecting several areas, herpes in the brain, herpes in the eye, or repeated shingles.
  • The person had an opportunistic infection, which is an infection that happens more easily when the body’s defenses are weak, such as Pneumocystis jirovecii pneumonia, histoplasmosis, or coccidioidomycosis.
  • The person had two serious infections during the parent study.
  • The person had one serious infection that the investigator thinks makes study participation unsafe.
  • The person had a cardiovascular event, meaning a serious heart or blood vessel problem, such as acute coronary syndrome, stroke, heart attack, deep vein thrombosis (a blood clot in a deep vein), or pulmonary embolism (a blood clot in the lung).
  • The person had a cardiac hospitalization, such as coronary stenting or coronary bypass surgery.
  • The person developed a new cancer or lymphoproliferative disease (a condition with too many lymph cells), except for certain limited skin or cervical cancers in some cases.
  • The person has a major surgery planned during the study.
  • The person developed a significant or uncontrolled psychiatric illness during the parent study.
  • The person developed a history of clinically significant drug or alcohol abuse, except for stable, allowed medical or legal use of cannabis products.
  • The person received a prohibited treatment for psoriatic arthritis or psoriasis and is expected to keep taking it.
  • The person received prohibited medicines, including strong or moderate CYP3A4 inhibitors or CYP3A4 inducers (drugs that can raise or lower levels of other medicines), any live-attenuated vaccine (a vaccine with weakened live germs), or other marketed or investigational agents, and is expected to keep taking them.
  • The person has blood test results that are outside the allowed range: AST or ALT more than 3 times normal, bilirubin more than 1.5 times normal, hemoglobin below 9.0 g/dL, white blood cells below 3.0 × 109/L, neutrophils below 1.0 × 109/L, lymphocytes below 0.5 × 109/L, platelets below 100 × 109/L, creatinine clearance below 45 mL/min (a measure of kidney function), CPK more than 2.5 times normal, or any other lab problem that the investigator thinks would make participation unsafe.
  • The person cannot have blood drawn by needle, or does not tolerate venipuncture (placing a needle into a vein to collect blood).
  • The person developed a history of a serious drug allergy, such as anaphylaxis (a severe and sudden allergic reaction).
  • The person has a known or suspected allergy to zasocitinib or any ingredient in it.
  • The person has a positive pregnancy test, plans to become pregnant, is pregnant, or is breastfeeding/nursing.
  • The person plans to donate blood during the study.
  • The person is detained for treatment or is in an institution such as prison because of a court or government order.
  • The person is a study site employee, an immediate family member of a study site employee, or depends on a study site employee involved in the study, because this could affect free choice to join.
  • The person developed a new medical condition, or has an unstable condition, such as problems with the heart, kidneys, liver, blood, stomach or intestines, hormone system, lungs, or immune system, or has abnormal vital signs, physical exam findings, blood tests, or ECG (a heart tracing), and the investigator thinks this would make the study unsafe or make the results hard to interpret.
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Investigated drugs

Zasocitinib is an oral medicine taken by mouth as a tablet. It is the study drug being tested in this trial to see how safe it is for long-term use, how well people tolerate it, and how well it helps control the signs and symptoms of active psoriatic arthritis.

What is already known about the treatment

Zasocitinib - Zasocitinib is an oral film-coated tablet taken by mouth, usually once daily as studied in this trial. It is an experimental medicine in clinical research and is not yet a fully established treatment in routine medical practice, although it has been studied for inflammatory joint disease. It is used to help treat active psoriatic arthritis, a condition that causes joint pain, swelling, and stiffness, by blocking a signal inside immune cells that helps drive inflammation; more specifically, it is a type of Janus kinase inhibitor, which means it interferes with enzymes that pass along inflammation signals in the body.

Investigated diseases

Psoriatic Arthritis - Psoriatic arthritis is a long-lasting inflammatory disease that affects the joints and often occurs in people with psoriasis. It can cause joint pain, swelling, stiffness, and reduced movement, and it may also affect the places where tendons and ligaments attach to bone. The disease often develops gradually, with periods of worsening and improvement. Over time, it can lead to ongoing joint inflammation and damage if the inflammation continues.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2025-522586-30-00Protocol codeTAK-279-PsA-3003Estimated enrolment1 182 patientsSponsorTakeda Development Center Americas Inc.

sourced from the EU Clinical Trials Register and site verification

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