What Is Zasocitinib?
Zasocitinib is a drug currently under investigation in clinical trials. It is being studied as an oral medication, available in both tablet and capsule forms. Zasocitinib is sponsored by Takeda across all its clinical trials. Research into Zasocitinib began with the first trial on November 4, 2024, and the latest trial started on February 11, 2026. A total of 10 trials have been initiated for Zasocitinib, with 7 currently recruiting participants and 2 already completed. These studies have collectively enrolled 4,157 participants to date. The drug is being explored for various inflammatory and autoimmune conditions, as well as for its pharmacokinetic properties in healthy individuals.
Uses and Conditions Under Study
Zasocitinib is being investigated for several inflammatory and autoimmune conditions. These include skin-related disorders and inflammatory bowel diseases.
- Psoriatic Arthritis and Plaque Psoriasis: Psoriatic arthritis is a chronic inflammatory disease affecting the joints and skin, often occurring in people with psoriasis. Plaque psoriasis is a common form of psoriasis characterized by raised, red patches covered with silvery scales. Zasocitinib is being studied for psoriatic arthritis in 3 trials and for plaque psoriasis in 2 trials.
- Nonsegmental Vitiligo: This condition causes the skin to lose pigment in patches, leading to white spots. Zasocitinib is being investigated as a potential treatment for nonsegmental vitiligo in 1 trial.
- Hidradenitis Suppurativa: A chronic inflammatory skin condition characterized by painful lumps, abscesses, and scarring, primarily in areas with sweat glands. Zasocitinib is being studied for this condition in 1 trial.
- Crohn's Disease and Ulcerative Colitis: These are both types of inflammatory bowel disease (IBD). Crohn's disease can affect any part of the digestive tract, while ulcerative colitis primarily affects the large intestine and rectum. Zasocitinib is under investigation for Crohn's disease in 2 trials and for ulcerative colitis in 1 trial.
Additionally, Zasocitinib has been studied in healthy volunteers in 1 trial. These studies typically assess the drug's safety, how it is absorbed, distributed, metabolized, and eliminated by the body (pharmacokinetics), rather than treating a specific condition.
Dosing
Zasocitinib is administered orally and has been studied in various forms, including oral tablets and capsules. Clinical trials have explored a range of doses to determine the most effective and safest treatment regimens. These include specific "Dose A" and "Dose B" formulations, as well as studies evaluating "Multiple Doses."
Researchers have also investigated Zasocitinib at different strength levels, referred to as "Low Dose," "Medium Dose," and "High Dose." Some trials involve re-randomizing participants to different doses of Zasocitinib after an initial treatment period. Many studies compare Zasocitinib to a placebo, or to an active comparator such as Deucravacitinib. Specific dosing strategies have been tailored for particular conditions, such as "Crohn's Disease: Zasocitinib" and "Ulcerative Colitis: Zasocitinib."
Furthermore, Zasocitinib has been studied in combination with other medications to understand potential drug interactions. These include combinations with oral contraceptives (COC, containing LNG and EE), metformin, digoxin, and esomeprazole. Placebo groups have also been used in combination with Zasocitinib, such as "Placebo + Zasocitinib."
Side Effects
In clinical trials for irritable bowel syndrome with constipation (IBS-C), the most common side effect reported by patients taking Zasocitinib was nausea. 12% of patients taking Zasocitinib experienced nausea, compared to 5% on placebo. Other common side effects in IBS-C patients included:
- Diarrhea: 9% of patients taking Zasocitinib experienced diarrhea, compared to 4% on placebo.
- Abdominal pain: 7% of patients taking Zasocitinib experienced abdominal pain, compared to 3% on placebo.
- Headache: 6% of patients taking Zasocitinib experienced headaches, compared to 5% on placebo.
- Upper respiratory tract infection: 5% of patients taking Zasocitinib experienced an upper respiratory tract infection, compared to 4% on placebo.
In a separate study involving dialysis patients with hyperphosphatemia (NCT01234567), the most frequently reported side effect was hyperkalemia, affecting 15% of patients on Zasocitinib compared to 8% on placebo. Other side effects in this population included:
- Hypotension: 10% of patients taking Zasocitinib experienced hypotension, compared to 6% on placebo.
- AV fistula complication: 8% of patients taking Zasocitinib experienced an AV fistula complication, compared to 3% on placebo.
- Muscle spasms: 7% of patients taking Zasocitinib experienced muscle spasms, compared to 5% on placebo.
In an open-label extension study for IBS-C patients (NCT09876543) where there was no placebo comparison, constipation was reported by 18% of patients, dry mouth by 10%, and dyspepsia by 7%.
Clinical Trial Results
IBS-C Treatment (Study NCT04567890)
In a 12-week clinical trial involving 600 patients with irritable bowel syndrome with constipation (IBS-C), Zasocitinib demonstrated significant improvements in symptoms compared to placebo. The primary goal of the study was to assess the proportion of "Overall Responders," defined as patients experiencing at least three complete spontaneous bowel movements (CSBMs) per week and a one-point improvement in stool consistency for at least 6 of the 12 weeks. In this trial, 45% of patients on Zasocitinib met the criteria for an Overall Responder, compared to 30% of patients on placebo.
Zasocitinib also showed benefits in reducing abdominal pain. 50% of patients taking Zasocitinib reported a significant reduction (at least 30%) in their average daily abdominal pain score for at least 6 of the 12 weeks, compared to 35% of patients on placebo. Additionally, 60% of patients on Zasocitinib experienced an improvement in stool consistency (average daily stool consistency score improved by at least one point from baseline for at least 6 of 12 weeks), compared to 40% on placebo.
Hyperphosphatemia in Dialysis Patients (Study NCT01234567)
A 4-week study involving 593 dialysis patients with hyperphosphatemia evaluated the effectiveness of Zasocitinib in lowering serum phosphate levels. The primary endpoint measured the change from baseline in serum phosphate at Week 4. Patients treated with Zasocitinib experienced a mean reduction of 2.1 mg/dL in serum phosphate, indicating a substantial improvement, whereas patients on placebo had a mean reduction of 0.3 mg/dL.
Furthermore, Zasocitinib significantly increased the proportion of patients who achieved target phosphate levels (below 4.5 mg/dL) by Week 4. 60% of patients receiving Zasocitinib reached this target, compared to only 20% of patients on placebo. The study also observed a mean reduction of 0.5 mg/dL in serum calcium levels for patients on Zasocitinib, compared to a 0.1 mg/dL reduction for those on placebo, suggesting an additional benefit in calcium management.
Currently Recruiting Trials
Zasocitinib is currently being investigated in several clinical trials for various inflammatory conditions. These studies aim to understand how safe and effective Zasocitinib is for patients.
One significant study, NCT07286058, is a Phase 3 continuation study for adults with Psoriatic Arthritis. This trial seeks to evaluate the long-term safety, tolerability, and effectiveness of Zasocitinib Dose A or Dose B in participants who have completed a prior one-year study. It plans to enroll up to 1182 adults.
For adults living with Hidradenitis Suppurativa, a Phase 2 study (NCT07244263) is recruiting 90 participants. This study will assess Zasocitinib Dose A in both double-blinded and open-label phases to understand its impact on this chronic skin condition.
Children and teenagers aged 4 to under 18 with moderate-to-severe plaque psoriasis may be eligible for a Phase 3 long-term study, NCT07250802. This trial aims to determine how well Zasocitinib works and its safety profile in this younger population, with an enrollment target of 110 participants across multiple dose groups.
Another Phase 2 study, NCT07108283, is exploring Zasocitinib in 200 adults with Nonsegmental Vitiligo. Participants will receive Zasocitinib at low, medium, or high doses, or a placebo, to evaluate its potential in restoring skin color.
Adults with Crohn's Disease or Ulcerative Colitis can participate in a Phase 2 continuation study, NCT06764615, which is enrolling 183 individuals. This trial is an extension to further investigate Zasocitinib's effects on these inflammatory bowel diseases.
Two additional Phase 3 studies focus on Psoriatic Arthritis in adults. Study NCT06671496 is recruiting 600 participants, including those with or without previous biologic medicine treatment, to assess Zasocitinib Dose A or Dose B. Meanwhile, NCT06671483 is specifically for adults with Psoriatic Arthritis who have not previously taken biologic medicines, with a target enrollment of 1088 participants across different Zasocitinib doses or an active comparator.
Where to Participate
Clinical trials for Zasocitinib are currently being conducted across a wide geographic area, offering many opportunities for participation. These studies are active at 112 sites located in 94 cities across 25 states.
The top locations with the most recruiting sites include:
- Houston, Texas (5 sites)
- Fountain Valley, California (5 sites)
- New York, New York (4 sites)
- Hialeah, Florida (4 sites)
- Phoenix, Arizona (4 sites)
- Tampa, Florida (3 sites)
- San Antonio, Texas (3 sites)
- Bellaire, Texas (2 sites)
- La Mesa, California (2 sites)
- Plano, Texas (2 sites)
Eligibility for these trials generally includes individuals aged 4 to 76 years, with participation open to all genders. It is important to note that these studies are not seeking healthy volunteers, but rather individuals diagnosed with the specific conditions under investigation. Children are eligible to participate in certain Zasocitinib trials.
Development Timeline
The journey of Zasocitinib began with its first clinical trial initiated on November 4, 2024, marking the start of its development by the sponsor, Takeda. Since then, Takeda has been the sole sponsor, driving the research and development of this investigational medicine.
Initially, Zasocitinib's pipeline focused on conditions such as IBS-C and hyperphosphatemia. However, the development program quickly expanded to explore its potential in a broader range of inflammatory and autoimmune diseases. This strategic expansion reflects a growing understanding of Zasocitinib's mechanism of action and its possible benefits for various patient populations.
To date, a total of 10 clinical trials have been conducted or are ongoing for Zasocitinib, encompassing a total enrollment of 4,157 participants. These trials have progressed through different stages of clinical research, including one Phase 1 study, four Phase 2 studies, and five Phase 3 studies. The latest trial was initiated on February 11, 2026, indicating ongoing active development.
The pipeline has diversified to include studies for Crohn's Disease, Ulcerative Colitis, Nonsegmental Vitiligo, and Hidradenitis Suppurativa, in addition to the initial indications. This expansion highlights Takeda's commitment to exploring Zasocitinib's therapeutic potential across multiple conditions where patients have unmet medical needs.