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.
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.
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).
Single group
STP938
DrugAt 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.
Clinical Efficacy
Complete and partial response rates per European LeukemiaNet criteria
Safety and Tolerability
Toxicity profile based on National Cancer Institute Common Terminology Criteria for Adverse Events
Durability of Response to STP938
Time from achieving response to loss of response
Impact of STP938 on Disease-Related Complications
Prevalence of haemorrhagic complications, thromboembolic events and disease transformation.
Patient Reported Outcomes and Symptom Burden
Myeloproliferative Neoplasm Symptom Assessment Form (18 item). Minimum value is zero (0); the maximum value is 180. A score of zero equates to absence of symptoms, higher scores equate to worse outcome.
Molecular Response
Change in Variant Allele Fraction: For known ET-associated mutations.
Bone Marrow Histology
Changes in Histological Appearances
Spleen Volume
Change in Spleen Volume: Measured by MRI or CT scan.
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