A Phase 1 Study to Assess STP938 as a Monotherapy in Adults With High Risk Essential Thrombocythaemia

To join this study, you need to be an adult aged 18 or older with a confirmed diagnosis of essential thrombocythaemia (ET) that is considered high-risk. Your platelet count must be too high, needing treatment to bring it down. You also need to have tried hydroxycarbamide (hydroxyurea) previously, but it either didn't work for you or caused side effects that made it difficult to continue.

There are also some important health requirements concerning your liver, blood clotting, and general health status. For example, you shouldn't have certain other blood disorders or serious ongoing illnesses that are not under control. You also cannot be pregnant or breastfeeding, and if you're a woman of childbearing age or a man, you must agree to use contraception during the study.

Some things would prevent you from taking part, such as if you have recently received other treatments for ET, or if your ET has changed into another type of blood condition. If you've had your spleen removed or have certain conditions affecting how your body absorbs medication, or have specific heart conditions, you would also not be able to join. All these checks are done to ensure the study is as safe as possible for everyone involved.

If you join this study, you will take STP938 capsules by mouth every day. The treatment period is expected to last for about 12 months, although it might be longer if the drug is working well for you and not causing side effects. For the first month, you will visit the clinic once a week for check-ups and tests. After that, you'll have clinic visits every two weeks. In total, you can expect around 26 clinic visits over the 12 months. Throughout the study, you'll also fill out a questionnaire about your symptoms once a month.

During your clinic visits, the study team will carry out various assessments. These include physical examinations, heart checks (ECGs), blood and urine tests, and sometimes more detailed scans like CT or MRI. Bone marrow biopsies will also be part of the assessments. There will be checks to measure how much of the study drug is in your blood and genetic tests will also be performed. Once your treatment period is complete, there will be follow-up visits to ensure your health is stable and you're not experiencing any lasting side effects.