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Not yet recruitingRare disease

Study of Pozelimab and Cemdisiran in Adults with Paroxysmal Nocturnal Hemoglobinuria Not Responding Well to Current C5 Inhibitor Treatment

Verified siteInvestigationalNo placebo
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What is this trial about?

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

This study focuses on patients with Paroxysmal Nocturnal Hemoglobinuria (PNH), a rare blood disorder where the immune system attacks and destroys red blood cells. The study will test a combination of two medications: Pozelimab and Cemdisiran. This treatment is specifically intended for patients whose current PNH treatment is not working effectively to control the breakdown of red blood cells.

The study will evaluate how well the combination of Pozelimab (also known as REGN3918) and Cemdisiran (also known as ALN-CC5) works in treating PNH. Both medications will be given as injections - Pozelimab can be administered into a vein or under the skin, while Cemdisiran is given as an injection under the skin. The treatment period will last for approximately 80 weeks.

During the study, researchers will monitor how effectively this combination therapy controls the destruction of red blood cells in patients. They will also track other important factors such as changes in blood tests, energy levels, and any side effects that may occur. The study aims to help determine if this new combination treatment could be beneficial for PNH patients who are not responding well to their current therapy.

The research process

The trial runs in 5 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Initial treatment phase

    You will receive two medications: pozelimab and cemdisiran, both given as injections

    The medications will be administered either into a vein (intravenously) or under the skin (subcutaneously)

    Treatment continues for an initial period of 28 weeks

  2. Step 2

    Blood tests and monitoring at 28 weeks

    Your blood will be tested to measure lactate dehydrogenase (LDH) levels - a marker that shows how well the treatment is working

    The medical team will evaluate changes in your LDH levels compared to when you started treatment

  3. Step 3

    Extended treatment phase

    Treatment continues for additional 24 weeks, reaching a total of 52 weeks

    Regular monitoring of your blood test results will continue

    Your energy levels will be assessed using a special questionnaire called FACIT-Fatigue Scale

  4. Step 4

    Ongoing evaluations throughout 52 weeks

    Regular checks of your hemoglobin levels

    Monitoring for any side effects or reactions to the medications

    Assessment of your need for blood transfusions

    Blood tests to check how your body responds to the medications

    Required to maintain up-to-date meningococcal vaccinations throughout the study period

  5. Step 5

    Final assessment at 52 weeks

    Complete evaluation of your response to treatment

    Final blood tests to measure medication levels in your body

    Assessment of overall treatment effectiveness and safety

Who can join the trial?

11 criteria

  • Must have Paroxysmal Nocturnal Hemoglobinuria (PNH) confirmed by special blood flow testing (high-sensitivity flow cytometry)
  • Must be currently taking one of these medications for at least 6 months at the standard prescribed dose:
    • eculizumab
    • ravulizumab
    • crovalimab
    • Must have consistently high levels of LDH (a blood enzyme that indicates cell breakdown) that are more than 1.5 times the normal upper limit over the past 6 months
    • Must complete at least 2 separate blood tests measuring LDH levels during the screening period
    • Must be willing and able to:
      • Attend clinic appointments and remote visits
      • Complete all required study procedures
      • Receive and stay up-to-date with required meningococcal vaccinations throughout the study
      • Must be an adult (18 years or older)
      • Can be either male or female

Who cannot join the trial?

13 criteria

  • Age below 18 years or above 75 years
  • Not diagnosed with Paroxysmal Nocturnal Hemoglobinuria (PNH) - a rare blood disorder where the immune system attacks red blood cells
  • Not currently receiving C5 inhibitor treatment (a type of medication that helps control PNH symptoms)
  • Pregnant or breastfeeding women
  • Participation in other clinical trials within the last 30 days
  • History of severe allergic reactions to similar medications
  • Severe kidney or liver disease
  • Active infections or serious medical conditions that could interfere with the study
  • Unable to provide informed consent
  • History of blood clots in the past 3 months
  • Major surgery planned during the study period
  • History of organ transplantation
  • Active cancer or cancer treatment
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Investigated drugs

Pozelimab is a medication designed to treat a rare blood disorder called paroxysmal nocturnal hemoglobinuria (PNH). It works by targeting and blocking specific proteins in the immune system that cause the destruction of red blood cells. Cemdisiran is also a medication used in treating paroxysmal nocturnal hemoglobinuria. It works differently from pozelimab by interfering with the production of certain proteins that contribute to red blood cell destruction. The combination of pozelimab and cemdisiran is being studied as a potential treatment for patients whose condition is not well controlled with current treatments that target the C5 protein in the blood. This combination therapy aims to provide better control of the breakdown of red blood cells that occurs in patients with this blood disorder.

What is already known about the treatment

  • Pozelimab

    A monoclonal antibody medication administered through intravenous infusion, specifically designed to target and inhibit C5 complement protein in patients with Paroxysmal Nocturnal Hemoglobinuria (PNH). This investigational drug works by preventing the destruction of red blood cells in patients who have not responded adequately to existing complement inhibitor therapies. Currently undergoing clinical trials, it represents a potential new treatment option for patients with difficult-to-manage PNH.

  • Cemdisiran

    An investigational RNA interference (RNAi) therapeutic agent administered subcutaneously, designed to reduce the production of complement component C5 in the liver. This medication works at the genetic level by preventing the formation of C5 protein, which is responsible for red blood cell destruction in PNH patients. When used in combination with Pozelimab, it aims to provide better control of intravascular hemolysis in patients who have inadequate response to current C5 inhibitor treatments.

Investigated diseases

Paroxysmal Nocturnal Hemoglobinuria (PNH) - A rare blood disorder where the body's immune system attacks and destroys red blood cells prematurely. In this condition, red blood cells break down faster than the body can replace them, a process called hemolysis. The condition is caused by a genetic mutation that occurs in blood-forming stem cells. PNH can develop at any age but is most often diagnosed in young adults. The name comes from the fact that symptoms were historically noted to be worse at night, though we now know the destruction of red blood cells occurs throughout the day. Patients may experience episodes where symptoms become more severe, followed by periods of relative stability.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2024-519709-37-00Protocol codeR3918-PNH-2483Estimated enrolment35 patientsSponsorRegeneron Pharmaceuticals Inc.

sourced from the EU Clinical Trials Register and site verification

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