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Evaluating the safety and effectiveness of pozelimab and cemdisiran for treating PNH

A Randomized, Open-Label, C5 Inhibitor-Controlled Study to Evaluate the Efficacy and Safety of Pozelimab and Cemdisiran Combination Therapy in Patients With Paroxysmal Nocturnal Hemoglobinuria Who Are Complement Inhibitor Treatment-Naive or Have Not Recently Received Complement Inhibitor Therapy

PHASE3 · Regeneron Pharmaceuticals · NCT05133531

This study is testing a new combination of two experimental drugs, pozelimab and cemdisiran, to see if they can help adults with paroxysmal nocturnal hemoglobinuria (PNH) better than current treatments.

Quick facts

PhasePHASE3
Study typeInterventional
Enrollment190 (estimated)
Ages18 Years and up
SexAll
SponsorRegeneron Pharmaceuticals (industry)
Drugs / interventionseculizumab, ravulizumab, pozelimab
Locations63 sites (Whittier, California and 62 other locations)
Trial IDNCT05133531 on ClinicalTrials.gov

What this trial studies

This clinical trial investigates the combination therapy of two experimental drugs, pozelimab and cemdisiran, in adult patients diagnosed with paroxysmal nocturnal hemoglobinuria (PNH). The study aims to assess the safety and efficacy of this combination compared to existing treatments, ravulizumab and eculizumab. Participants will be monitored for side effects, blood levels of the study drugs, and the body's immune response to these medications. The trial is designed to provide insights into how well this new treatment option works for patients with active PNH.

Who should consider this trial

Good fit: Ideal candidates for this study are adults diagnosed with PNH who have active disease and meet specific inclusion criteria.

Not a fit: Patients who have recently received treatment with eculizumab or ravulizumab, or those with a history of certain transplants, may not benefit from this study.

Why it matters

Potential benefit: If successful, this combination therapy could offer a new effective treatment option for patients with PNH who have not recently received complement inhibitor treatment.

How similar studies have performed: Other studies have shown success with similar approaches in treating PNH, but this specific combination therapy is novel.

Eligibility criteria

Show full inclusion / exclusion criteria 
Key Inclusion Criteria:

1. Diagnosis of PNH confirmed by high-sensitivity flow cytometry testing with PNH granulocytes or monocytes as described in the protocol
2. Active disease, as defined by the presence of 1 or more PNH-related signs or symptoms as described in the protocol
3. LDH level ≥2 × ULN at the screening visit
4. Willing and able to comply with clinic/remote visits and study-related procedures, including completion of the full series of meningococcal vaccinations required per protocol

Key Exclusion Criteria:

1. Prior treatment with eculizumab within 3 months prior to screening, ravulizumab within 6 months prior to screening, or other complement inhibitors within 5 half-lives of the respective agent prior to screening
2. Receipt of an organ transplant, history of bone marrow transplantation or other hematologic transplant
3. Body weight \<40 kilograms at screening visit
4. Planned use of any complement inhibitor therapy other than study drugs during the treatment period
5. Not meeting meningococcal vaccination requirements and, at a minimum documentation of quadrivalent meningococcal vaccination within 5 years prior to the screening visit and serotype B vaccine within 3 years prior to the screening visit as described in the protocol.
6. Any contraindication for receiving Neisseria meningitidis vaccinations (serotypes ACWY and B).
7. Unable to take antibiotics for meningococcal prophylaxis (if required by local ravulizumab \[Cohort A\] or eculizumab \[Cohort B\] prescribing information, where available, or national guidelines/local practice, or if necessary when administration of the first dose of the vaccination is less than 2 weeks prior to study treatment initiation)
8. Any active, ongoing infection or a recent infection requiring ongoing systemic treatment with antibiotics, antivirals, or antifungals within 2 weeks of screening or during the screening period
9. Documented history of active, uncontrolled, ongoing systemic autoimmune diseases

Note: Other protocol-defined Inclusion/ Exclusion Criteria apply

Where this trial is running

Whittier, California and 62 other locations

+13 more sites — see ClinicalTrials.gov for the full list.

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.

View on ClinicalTrials.gov →

Conditions: Paroxysmal Nocturnal Hemoglobinuria, PNH

Last reviewed 2026-05-15 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.