STP938 as a single daily oral treatment for adults with high‑risk essential thrombocythaemia
An Open-Label, Phase 1b 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
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 1 |
|---|---|
| Study type | Interventional |
| Enrollment | 20 (estimated) |
| Ages | 18 Years and up |
| Sex | All |
| Sponsor | Step Pharma, SAS Industry-sponsored |
| Locations | 13 sites (Brest and 12 other locations) |
| Trial ID | NCT06786234 on ClinicalTrials.gov |
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.
Who should consider this trial
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.
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.
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 performed: 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.
Eligibility criteria
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 this trial is running
Brest and 12 other locations
- 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)
- Gustave Roussy — Villejuif, France (Recruiting)
- Royal Hallamshire Hospital — Sheffield, South Yorkshire, United Kingdom (Not_yet_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)
Study contacts
- Study coordinator: Carol M MacLean, PhD
- Email: STP938-301@step-ph.com
- Phone: +33 1 86 26 43 56
How to participate
- Review the eligibility criteria above with your treating physician.
- Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
- Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.