STP938 as a single daily oral treatment for adults with high‑risk essential thrombocythaemia
Official title: An Open-Label, Phase 2 Study to Evaluate Safety, Tolerability & Preliminary Activity of the CTPS1 Inhibitor STP938 in Adult Subjects With High Risk Essential Thrombocythaemia Who Are Resistant to or Intolerant of Hydroxycarbamide Therapy
Run by Step Pharma, SAS · NCT06786234 · Data updated 2026-11-12
This study will try daily oral STP938 in adults with high‑risk essential thrombocythaemia who are resistant to or intolerant of hydroxycarbamide to see if it safely lowers platelet counts.
Quick facts
| Phase | Phase 2 |
|---|---|
| Study type | Interventional |
| Ages | 18 Years and up |
| Sex | All |
| Enrollment | 50 (estimated) |
| Sponsor | Step Pharma, SAS Industry-sponsored |
| Locations | 14 sites (Poitiers, New Aquitaine and 13 other locations) |
| Status | Recruiting |
| Started | June 18, 2025 |
| Main results expected | June 30, 2028 |
| Study ends | September 30, 2028 |
| Registry record updated | June 16, 2026 |
| Trial ID | NCT06786234 on ClinicalTrials.gov |
Is this trial a fit for you?
✓Likely a good fit
Adults (≥18 years) with confirmed high‑risk essential thrombocythaemia, platelet counts >600×10^9/L, ECOG 0–2, adequate organ function, and documented resistance to or intolerance of hydroxycarbamide are the intended participants.
✕Probably not a fit
Patients who are well controlled on current cytoreductive therapy, who cannot attend frequent visits at the French study sites, or who have severe organ dysfunction or recent exposure to other investigational agents are unlikely to benefit from joining this trial.
A plain-English reading of the study's rules. Only the study team can confirm whether you qualify.
What this trial studies
This open‑label, phase 1b multicenter study gives daily oral STP938 capsules in 28‑day cycles to adults with high‑risk essential thrombocythaemia who are resistant to or intolerant of hydroxycarbamide. Participants may receive the drug for about 12 months with clinic visits weekly for the first month and then every two weeks, and treatment continues if platelet control is maintained and side effects are acceptable. The study will monitor safety and activity with frequent blood tests, ECGs, urine tests, imaging and bone marrow biopsies, and monthly symptom questionnaires. STP938 targets the enzyme CTPS1, a novel mechanism intended to lower platelet counts without the effects seen with existing cytoreductive therapies.
Why it matters
Potential benefit: If successful, STP938 could give people who cannot use hydroxycarbamide an effective oral option to lower platelet counts with manageable side effects.
How similar studies have gone: Inhibition of CTPS1 is a novel approach with limited prior clinical data in essential thrombocythaemia, so similar studies have been few and results are still preliminary.
Who can join: the full rules
Show full inclusion / exclusion criteria
Key Inclusion Criteria: * Adults aged 18 years or older * A confirmed diagnosis of ET according to World Health Organisation (WHO) or British Society for Haematology (BSH) criteria. * Meeting criteria for high risk ET. * Raised platelet count (\>600 x109/L) requiring cytoreductive therapy. * Neutrophil count \>1.0 x109/L. * Either intolerant of or resistant to hydroxycarbamide having met any one of the criteria at any point in their disease whilst receiving hydroxycarbamide. * Adequate hepatic function. * Adequate blood coagulation parameters. * Eastern Cooperative Oncology Group (ECOG) status of 0-2. Key Exclusion Criteria: * Subjects currently or recently receiving cytoreductive therapy for the treatment of essential thrombocythaemia (wash out periods apply). * Subjects who have received any investigational agents for the treatment of essential thrombocythaemia within 4 weeks before enrolment or less than 5 half-lives since completion of prior therapy, whichever is shorter. * Proven or suspected transformation to polycythaemia vera, myelofibrosis, myelodysplasia, acute myeloid leukaemia or another myeloid neoplasm. * Known malabsorption syndrome or other condition that may impair absorption of study medication (e.g. gastrectomy). * Previous splenectomy. * Any uncontrolled intercurrent illness. * Immunocompromised subjects with increased risk of opportunistic infections. * Known active or chronic hepatitis B or active hepatitis C virus (HCV) infection. * Pregnant females, breastfeeding females, and women of child bearing age or males not willing to comply with contraceptive requirements. * Known hypersensitivity to any of the excipients used in the formulation of the study drug. * Corrected QT interval \>470 msec based on averaged triplicate electrocardiogram (ECG) readings at the Screening Visit using the QT interval corrected for heart rate using Fridericia's method (QTcF).
Where it's running
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CHU Brest
Brest, France Recruiting -
Institut Paoli-Calmettes
Marseille, France Recruiting -
CHU Nantes
Nantes, France Recruiting -
CHU Nice
Nice, France Recruiting -
CHU Nîmes
Nîmes, France Recruiting -
Hôpital Saint-Louis
Paris, France Recruiting
Show 8 more locations
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Gustave Roussy
Villejuif, France Recruiting -
Royal Hallamshire Hospital
Sheffield, South Yorkshire, United Kingdom Recruiting -
University Hospital of Wales
Cardiff, United Kingdom Recruiting -
Imperial College London / Hammersmith Hospital
London, United Kingdom Recruiting -
Sarah Cannon Research Institute
London, United Kingdom Recruiting -
Cancer and Haematology Centre, Churchill Hospital
Oxford, United Kingdom Recruiting -
University of Southampton Hospital
Southampton, United Kingdom Recruiting -
Hôpital de la Milétrie, CHU
Poitiers, New Aquitaine, France Not yet recruiting
Study contacts
- Study coordinator: Carol M MacLean, PhD
- Email: STP938-301@step-ph.com
- Phone: +33 1 86 26 43 56
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How to take part
- Review the eligibility criteria above with your treating physician.
- Check the official listing on ClinicalTrials.gov for the latest contact details and recruitment status.
- Contact the study coordinator or principal investigator to ask for pre-screening. Pre-screening is free and never obligates you to enroll.