Essential ThrombocythaemiaPhase 2NCT06786234
A Phase 2 Study to Assess STP938 (Dencatistat) as a Monotherapy in Adults With High Risk Essential Thrombocythaemia - The VECTRA Trial
A Phase 2 study testing STP938 in people with Essential Thrombocythaemia, run by Step Pharma, SAS at 14 sites in 2 countries.
Trial summary
The goal of this clinical trial is to learn if the drug STP938 works to treat adults with high risk essential thrombocythaemia (ET) who are resistant to, or intolerant of, hydroxycarbamide (also known as hydroxyurea) therapy. The trial will also learn about the safety of STP938. Read more about this study
- Who is it for?
- Ages 18 years and older
- Conditions the study is for
- Essential Thrombocythaemia
- What is being tested?
- STP938
- Type of treatment
- Pill or oral medicine
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 50 participants
- Where
- 14 sitesin 2 countries
- Study dates
- 18 Jun 2025to 30 Sep 2028
- Phase
- Phase 2
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 18 years and older
- All sexes
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- 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.
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- Adequate hepatic function.
- Adequate blood coagulation parameters.
- Eastern Cooperative Oncology Group (ECOG) status of 0-2.
Who cannot join
- 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.
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- 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).
Trial locations and contacts
14 sites in 2 countries. Contact the study team or a site near you to ask about taking part.
14 sites in 2 countries
France8 sites, 8 recruiting
- Recruiting
CHU Brest
Brest
- Recruiting
Institut Paoli-Calmettes
Marseille
- Recruiting
CHU Nantes
Nantes
- Recruiting
CHU Nice
Nice
- Recruiting
CHU Nîmes
Nîmes
- Recruiting
Hôpital Saint-Louis
Paris
- Not yet recruiting
Hôpital de la Milétrie, CHU
Poitiers, New Aquitaine, 86021
- Recruiting
Gustave Roussy
Villejuif
United Kingdom6 sites, 6 recruiting
- Recruiting
University Hospital of Wales
Cardiff
- Recruiting
Imperial College London / Hammersmith Hospital
London
- Recruiting
Sarah Cannon Research Institute
London
- Recruiting
Cancer and Haematology Centre, Churchill Hospital
Oxford, OX3 7LE
- Recruiting
Royal Hallamshire Hospital
Sheffield, South Yorkshire, S10 2JF
Sebastian Francis, MBChB, +44114271 1670, sebastian.francis1@nhs.net
- Recruiting
University of Southampton Hospital
Southampton
About this study
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
The goal of this clinical trial is to learn if the drug STP938 works to treat adults with high risk essential thrombocythaemia (ET) who are resistant to, or intolerant of, hydroxycarbamide (also known as hydroxyurea) therapy. The trial will also learn about the safety of STP938. The main questions the trial aims to answer are:
- Does STP938 control platelet counts
- Does STP938 control platelet counts without inducing unwanted side effects
Participants will:
- Take STP938 every day for up to 12 months.
- Visit the clinic once every week for the first month, then every 2 weeks for checkups and tests.
- Complete a questionnaire about symptoms once a month.
Read the detailed description
The aim of the study is to assess a new drug called STP938 for the treatment of essential thrombocythaemia (ET). The study with assess how effective STP938 in treating ET, and also assess any side effects of taking the drug. The study will enrol individuals with high risk ET who require treatment to lower their platelet count. Individuals enrolling on the study will have already tried treatment with hydroxycarbamide (also known as hydroxyurea) but are in need of a different treatment as hydroxycarbamide either did not control the platelet count or produced unwanted side effects.
STP938 is a new class of drug that inhibits the enzyme cytidine triphosphate synthase 1 (CTPS1). Inhibition of CTPS1 is a novel way of lowering the platelet count. This study is a phase 1b, open-label, multicentre trial. Participants will receive STP938 capsules every day, in cycles of 28 days, for approximately 12 months. Participants may continue to receive study drug for a longer period, so long as it is controlling the platelet count and not causing side effects. During the study, participants will visit the study site about 26 times (2 times per cycle) over an estimated 12 months. Once the treatment is complete, safety follow-up visit(s) will occur to make sure the participant is not experiencing any adverse effects. The following study procedures will be performed: (a) physical examinations (b) ECGs (c) blood tests, (d) urine tests (e) CT/MRI scans (f) bone marrow biopsies (g) drug administration (h) study drug blood level tests and (i) gene testing.
- Conditions
- Essential Thrombocythaemia
- Being tested
- STP938
- Keywords
- Essential Thrombocythemia, High risk, Resistant to or Intolerant of Hydroxycarbamide Therapy, Resistant to or Intolerant of Hydroxyurea Therapy, Oral therapy
- Medical subject headings
- Thrombocythemia, Essential
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
STP938Drug
At enrolment all patients will be assigned to a single dose level of STP938 for 4 weeks. After 4 weeks the dose level may be adjusted as needed by the Investigator.
| Study group | Role | What they receive |
|---|---|---|
| Phase 2 | Experimental | Adjustable dose levels with STP938 administered as oral therapy Receives: Drug: STP938 |
What is being measured
The primary outcome is the main question the study is designed to answer.
Clinical Efficacy
Complete and partial response rates per European LeukemiaNet criteria
Measured: Through study completion, an average of 12 months
Safety and Tolerability
Toxicity profile based on National Cancer Institute Common Terminology Criteria for Adverse Events
Measured: Through study completion, an average of 12 months
Secondary outcomes (2)
Durability of Response to STP938
Time from achieving response to loss of response
Measured: Through study completion, an average of 12 months
Impact of STP938 on Disease-Related Complications
Prevalence of haemorrhagic complications, thromboembolic events and disease transformation.
Measured: Through study completion, an average of 12 months
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted22 Jan 2025
- Study start18 Jun 2025
- Primary completion30 Jun 2028 (estimated)
- Study completion30 Sep 2028 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Essential ThrombocythaemiaStudies of the same condition, open and under way.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 2
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Enrolment
- 50 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Step Pharma, SAS
- Sponsor type
- Industry (pharma, biotech, devices)
- Responsible party
- Sponsor
- Investigators
- Maureen Higgins, Study director, Step Pharma
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT06786234
- Sponsor's protocol ID
- STP938-301
- Other IDs
- The VECTRA Trial
- Status last verified
- Jun 2026
- First submitted
- 8 Jan 2025
- Last updated
- 16 Jun 2026
- Results posted
- No
- Data monitoring committee
- No
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- No
Study at a glance
From the registry record, last updated by the sponsor on 16 Jun 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- 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
- ClinicalTrials.gov ID
- NCT06786234
- Acronym / sponsor ID
- STP938-301
- Conditions
- Essential Thrombocythaemia
- Keywords
- Essential Thrombocythemia, High risk, Resistant to or Intolerant of Hydroxycarbamide Therapy, Resistant to or Intolerant of Hydroxyurea Therapy, Oral therapy
- Phase
- Phase 2
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 50 participants (estimated)
- Lead sponsor
- Step Pharma, SASIndustry (pharma, biotech, devices)
- Study start
- 18 Jun 2025 (actual)
- Primary completion
- 30 Jun 2028 (estimated)
- Study completion
- 30 Sep 2028 (estimated)
- First posted
- 22 Jan 2025 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
The goal of this clinical trial is to learn if the drug STP938 works to treat adults with high risk essential thrombocythaemia (ET) who are resistant to, or intolerant of, hydroxycarbamide (also known as hydroxyurea) therapy. The trial will also learn about the safety of STP938. The main questions the trial aims to answer are:
- Does STP938 control platelet counts
- Does STP938 control platelet counts without inducing unwanted side effects
Participants will:
- Take STP938 every day for up to 12 months.
- Visit the clinic once every week for the first month, then every 2 weeks for checkups and tests.
- Complete a questionnaire about symptoms once a month.
Detailed description
The aim of the study is to assess a new drug called STP938 for the treatment of essential thrombocythaemia (ET). The study with assess how effective STP938 in treating ET, and also assess any side effects of taking the drug. The study will enrol individuals with high risk ET who require treatment to lower their platelet count. Individuals enrolling on the study will have already tried treatment with hydroxycarbamide (also known as hydroxyurea) but are in need of a different treatment as hydroxycarbamide either did not control the platelet count or produced unwanted side effects.
STP938 is a new class of drug that inhibits the enzyme cytidine triphosphate synthase 1 (CTPS1). Inhibition of CTPS1 is a novel way of lowering the platelet count. This study is a phase 1b, open-label, multicentre trial. Participants will receive STP938 capsules every day, in cycles of 28 days, for approximately 12 months. Participants may continue to receive study drug for a longer period, so long as it is controlling the platelet count and not causing side effects. During the study, participants will visit the study site about 26 times (2 times per cycle) over an estimated 12 months. Once the treatment is complete, safety follow-up visit(s) will occur to make sure the participant is not experiencing any adverse effects. The following study procedures will be performed: (a) physical examinations (b) ECGs (c) blood tests, (d) urine tests (e) CT/MRI scans (f) bone marrow biopsies (g) drug administration (h) study drug blood level tests and (i) gene testing.
Study design
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Number of arms
- 1
| Arm | Type | Receives |
|---|---|---|
| Phase 2 | Experimental | Drug: STP938Adjustable dose levels with STP938 administered as oral therapy |
Who may qualify
- Ages
- 18 years and older
- Sex
- All
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (9 listed)
- 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.
Key exclusion criteria (11 listed)
- 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.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| STP938At enrolment all patients will be assigned to a single dose level of STP938 for 4 weeks. After 4 weeks the dose level may be adjusted as needed by the Investigator. | Drug | Phase 2 |
Primary outcome
Clinical Efficacy
Time frame: Through study completion, an average of 12 months
Complete and partial response rates per European LeukemiaNet criteria
Safety and Tolerability
Time frame: Through study completion, an average of 12 months
Toxicity profile based on National Cancer Institute Common Terminology Criteria for Adverse Events
2 secondary outcomes
Durability of Response to STP938
Time frame: Through study completion, an average of 12 months
Impact of STP938 on Disease-Related Complications
Time frame: Through study completion, an average of 12 months
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 16 Jun 2026.
- Individual participant dataSharing planned: No
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Maureen Higgins study director
Step Pharma
14 sites in 2 countries: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 2 study testing STP938 in people with Essential Thrombocythaemia, run by Step Pharma, SAS at 14 sites in 2 countries.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 9 inclusion and 11 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 16 Jun 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 14 sites in France, United Kingdom. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Phase 2 studies give the treatment to a larger group to see whether it has the intended effect and to keep checking safety.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Carol M MacLean, PhD (+33 1 86 26 43 56, STP938-301@step-ph.com), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Clinical Efficacy (time frame: Through study completion, an average of 12 months). The study lists 2 primary outcomes in all. It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 16 Jun 2026.