The study focuses on Polycythemia Vera, a rare blood condition where the body makes too many red blood cells, causing the blood to become thicker than normal. The investigational medication being tested is called Sapablursen, which is given as a subcutaneous injection (a small needle placed under the skin). A matching placebo that looks the same but does not contain the active drug is also used. The purpose of the study is to compare how well Sapablursen works against the placebo in controlling the disease over a period of about eight months.
Participants are randomly assigned to receive either Sapablursen or the placebo, and neither the participants nor the study staff know which treatment is given (double‑blind). Throughout the study, regular blood tests are performed to measure the hematocrit level (the proportion of red blood cells in the blood). If the hematocrit rises above a certain level, a phlebotomy—a simple procedure where a small amount of blood is drawn to lower the count—may be needed. Researchers also ask participants to complete short questionnaires about fatigue and other symptoms to see how the treatment affects daily feeling. The trial lasts roughly 32 weeks, with visits scheduled at regular intervals to monitor safety, any side effects, and overall health.
1initial study visit and randomization
you attend the first clinic appointment after joining the study. during this visit baseline blood tests are taken and your medical information is recorded. you are randomly assigned to receive either Sapablursen or a matching placebo. the assigned product is prepared as a subcutaneous injection (injection under the skin) in a solution for injection.
the injection contains a concentration of 0 mg/ml as described in the product information. the exact schedule for receiving the injection is defined by the study protocol and will be followed at each subsequent clinic visit.
2regular study medication administration
you receive the assigned injection at each scheduled clinic visit. the injection is given under the skin (subcutaneous). the dose remains the same throughout the period you are on study treatment.
the treatment period lasts for at least 32 weeks for all participants. participants who continue in the extended phase may receive the medication for up to 52 weeks.
3routine blood testing for hematocrit monitoring
at every clinic visit you provide a blood sample that is used to measure hematocrit (Hct), the proportion of red blood cells in the blood. these measurements are taken from week 0 through week 32, and for some participants also through week 52.
the study aims to keep Hct values below 45 % without the need for phlebotomy. a single Hct value of 45 % or higher is allowed, but higher values may trigger additional actions.
4assessment of phlebotomy need
based on the Hct results, the study team determines whether you meet criteria for phlebotomy (removal of blood to lower Hct). criteria include Hct ≥45 % that is at least 3 % above the baseline on two consecutive tests, or Hct ≥48 %. if criteria are met, phlebotomy may be performed according to the study rules.
5patient‑reported outcomes questionnaire
at week 32 you complete questionnaires that assess fatigue and other symptoms. the tools used are the PROMIS Fatigue Short Form 8a and the Myelofibrosis Symptom Assessment Form version 4.0. your responses are recorded to evaluate how the study medication affects quality of life.
6safety monitoring and reporting
throughout the study you are asked to report any new symptoms, side effects, or health changes. regular laboratory tests are performed to identify any treatment‑emergent adverse events. if serious problems occur, the study medication may be reduced, paused, or stopped according to safety guidelines.
7final study assessments and treatment discontinuation
at the end of the primary 32‑week period (or at week 52 for the extended follow‑up) you attend a final clinic visit. final blood tests, safety evaluations, and outcome assessments are completed. the study medication is discontinued, and you receive information about any further medical care that may be needed.
Who Can Join the Study?
You must sign a written informed consent form, meaning you understand the study and can follow its rules.
You need to have a confirmed diagnosis of Polycythemia Vera that meets the 2022 World Health Organization (WHO) and International Consensus Classification (ICC) guidelines (these are official ways doctors identify the disease).
You must be phlebotomy‑dependent, which means you regularly need blood removal to keep your condition under control.
Your hematocrit level (the percentage of red blood cells in your blood) must be less than 45% when the study starts.
You must have adequate organ function and normal electrolytes (the chemicals in your body that help muscles and nerves work properly).
If you are taking cytoreduction therapy (CRT) (medication that lowers blood cell production), your dose must be stable and unchanged at the beginning of the study.
Both men and women are eligible to participate.
Who Cannot Join the Study?
You have already been treated for Polycythemia Vera with medicines that block a protein called TMPRSS6 (such as sapablursen or drugs that act like the natural hormone hepcidin); this means you cannot join the study.
You had a serious blood clot (called thrombosis) such as a heart attack, stroke, deep vein clot, or clot in the spleen’s vein within the month before the study starts.
You need regular blood removal (called phlebotomy) because your blood’s hematocrit level is below 45%, which makes you ineligible.
You meet the medical definition of post‑PV myelofibrosis, a condition where scar tissue forms in the bone marrow after Polycythemia Vera.
You have any serious, unstable medical problem or an uncontrolled mental health (psychiatric) condition that the doctor thinks would prevent you from following the study rules.
If you are a woman who is currently pregnant, planning to become pregnant during the study, or breastfeeding, you cannot take part.
Sapablursen is an experimental drug being tested in this study for people with polycythemia vera, a condition where the blood makes too many red cells. It is given as a liquid that is injected just under the skin (subcutaneous injection). The purpose of the drug in the trial is to see if it can reduce the number of red blood cells and improve symptoms compared with no active treatment.
Polycythemia vera – Polycythemia vera is a blood disorder in which the bone marrow produces too many red blood cells. The excess cells make the blood thicker, which can cause the spleen to enlarge and may increase overall blood volume. Over time, the condition can also raise the numbers of white blood cells and platelets. As the disease advances, the bone marrow may become scarred, leading to changes in the production of other blood cells.
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