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Study of SLN124 for Patients with Polycythemia Vera

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What is this trial about?

A plain-language summary of the goals, design and what participants do

This clinical trial is focused on studying a condition called Polycythemia Vera, a rare blood disorder where the body produces too many red blood cells. The study is testing a new treatment called SLN124, which is a special type of medicine designed to target specific genetic material in the body. This medicine is given as an injection under the skin. The trial will also use a placebo for comparison.

The purpose of the study is to understand how safe and tolerable SLN124 is for patients with Polycythemia Vera and to see how it affects the need for phlebotomies, which are procedures to remove blood from the body. The study will be conducted in two phases. In the first phase, patients will receive different doses of SLN124 to assess its safety and how well it is tolerated. In the second phase, the study will compare the effects of SLN124 with a placebo to see if it helps maintain normal levels of hematocrit, which is the proportion of red blood cells in the blood, without needing phlebotomies.

Participants in the study will receive injections of SLN124 or a placebo and will be monitored over several weeks. The study aims to see if SLN124 can help manage Polycythemia Vera by reducing the need for frequent blood removal procedures and maintaining healthy blood levels. The trial will also look at any side effects and how the treatment affects the overall quality of life for the participants.

The research process

The trial runs in 7 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Initial visit and consent

    Upon joining the study, you will attend an initial visit where the study team will explain the trial in detail. You will be asked to provide written informed consent, confirming your understanding and willingness to participate.

    During this visit, your eligibility will be confirmed based on specific criteria, including your medical history and current health status.

  2. Step 2

    Baseline assessments

    Before starting the treatment, baseline assessments will be conducted. These may include blood tests, a physical examination, and other evaluations to establish your health status before the trial begins.

    Women of childbearing potential will undergo a pregnancy test to ensure eligibility.

  3. Step 3

    Treatment phase 1

    In the first phase of the trial, you will receive a single or multiple doses of the study medication, SLN124, administered as a subcutaneous injection. The dosage and frequency will be determined by the study protocol.

    The main goal of this phase is to assess the safety and tolerability of SLN124.

  4. Step 4

    Monitoring and follow-up phase 1

    Throughout the first phase, you will have regular follow-up visits to monitor your health and any side effects. This includes blood tests, vital signs measurements, and physical examinations.

    You will also be asked about any changes in your health or any adverse effects you may experience.

  5. Step 5

    Treatment phase 2

    If you continue to the second phase, you will be randomly assigned to receive either SLN124 or a placebo. This phase is double-blind, meaning neither you nor the study team will know which treatment you are receiving.

    The treatment will continue for a specified period, with the aim of evaluating the effectiveness of SLN124 in maintaining hematocrit levels below 45% without the need for phlebotomies.

  6. Step 6

    Monitoring and follow-up phase 2

    Similar to phase 1, you will have regular follow-up visits during phase 2 to monitor your health and any side effects. This includes blood tests, vital signs measurements, and physical examinations.

    You will be asked to report any changes in your health or any adverse effects you may experience.

  7. Step 7

    End of study visit

    At the end of the study, you will have a final visit where your overall health will be assessed. This may include blood tests and a physical examination.

    The study team will discuss the next steps and any ongoing care or follow-up that may be needed.

Who can join the trial?

15 criteria

  • Male and female patients aged 18 years or older.
  • Patients not receiving cytoreductive therapy (treatment to reduce the number of blood cells) must have stopped any previous cytoreductive therapy for at least 24 weeks before starting the study and must have recovered from any side effects of that therapy.
  • Patients receiving cytoreductive therapy with hydroxyurea, interferon, busulfan, or ruxolitinib must have been on a stable dose for at least 12 weeks before starting the study, with no planned changes in the dose.
  • Patients must have had a skin examination by a doctor within 6 months before the study starts.
  • Must have an Eastern Cooperative Oncology Group (ECOG) score of 0, 1, or 2, which is a measure of how well a patient can perform daily activities.
  • Must be able and willing to follow all study requirements.
  • A confirmed diagnosis of Polycythemia Vera (PV) according to specific medical criteria, including certain blood levels, bone marrow characteristics, genetic mutations, and low levels of a hormone called erythropoietin.
  • Willing and able to provide written consent to participate in the study.
  • Before the study, patients must have had at least 3 bloodletting procedures (phlebotomies) in the last 6 months or 5 or more in the last 12 months, with documented high blood cell levels or symptoms of PV.
  • Records of bloodletting procedures and related blood tests for at least 6 months before the study, if available.
  • Women who can become pregnant must have a negative pregnancy test before starting the study and on the first day of the study.
  • Must agree to use effective birth control methods:
    • Female patients who can become pregnant and are sexually active must use one highly effective method of birth control from the start of the study until 3 months after the last dose of the study drug.
    • Male patients must use a condom if sexually active with a woman who can become pregnant, from the start of the study until 3 months after the last dose of the study drug.
    • Women who can become pregnant must agree not to donate eggs from the start of the study until 3 months after the last dose of the study drug.
    • Male patients must agree not to donate sperm from the start of the study until 3 months after the last dose of the study drug.

Who cannot join the trial?

10 criteria

  • Patients who have any other serious health conditions that could interfere with the study.
  • Patients who are pregnant or breastfeeding.
  • Patients who have had a recent major surgery.
  • Patients who are currently participating in another clinical trial.
  • Patients who have a history of allergic reactions to similar treatments.
  • Patients who have uncontrolled high blood pressure.
  • Patients who have severe liver or kidney problems.
  • Patients who have a history of drug or alcohol abuse.
  • Patients who have an active infection that requires treatment.
  • Patients who have a history of cancer within the last 5 years, except for certain skin cancers.
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Investigated drugs

SLN124 is a medication being studied for its potential to help people with a condition called Polycythemia Vera. This condition causes the body to produce too many red blood cells, which can make the blood thicker and lead to health problems. SLN124 is given as an injection under the skin. The main goal of using SLN124 in this study is to see if it can safely reduce the need for a procedure called phlebotomy, which is often used to remove excess blood from the body. Researchers are also looking at whether SLN124 can help keep the levels of red blood cells in a healthy range without needing phlebotomies.

What is already known about the treatment

SLN124 – SLN124 is administered through subcutaneous injections, meaning it is given as a shot under the skin. It is currently being studied in clinical trials for its potential use in treating Polycythemia Vera, a condition where the body produces too many red blood cells. The main goal of SLN124 is to help reduce the need for blood removal procedures by maintaining normal levels of red blood cells. At the molecular level, SLN124 works by targeting specific genetic pathways to control the production of red blood cells. It is classified as a therapeutic agent under investigation for its effects on blood disorders.

Investigated diseases

Polycythemia Vera – Polycythemia Vera is a blood disorder characterized by an increased number of red blood cells. This condition leads to thicker blood, which can slow down blood flow and cause complications. It often begins with symptoms like headaches, dizziness, and a feeling of fullness in the left upper abdomen due to an enlarged spleen. Over time, it can cause itching, especially after a warm shower, and a reddened complexion. As the disease progresses, there may be an increased risk of blood clots, which can lead to further health issues. The condition is chronic and requires ongoing management to control symptoms and prevent complications.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase ITrial ID2023-503544-13-00Protocol codeSLN124-004Estimated enrolment107 patientsSponsorSilence Therapeutics PLC

sourced from the EU Clinical Trials Register and site verification

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