A Phase 3 interventional study of Pozelimab and Cemdisiran in Paroxysmal Nocturnal Hemoglobinuria, sponsored by Regeneron Pharmaceuticals. Recruiting at 50 sites in 21 countries. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-11-05.
Sponsored by Regeneron Pharmaceuticals · Phase 3, Interventional, and Treatment
This study is researching an experimental treatment combination with two experimental drugs called pozelimab and cemdisiran. The study is focused on people with paroxysmal nocturnal hemoglobinuria (PNH). The aim of this study is to see how safe and effective the pozelimab + cemdisiran combination is for people with PNH in the long term. The pozelimab + cemdisiran combination may be referred to as "study drugs" in this section.
This study is looking at several other research questions, including:
191 studies on the registry are indexed under Hemoglobinuria, Paroxysmal; 49 are open to participants now.
This study's planned enrollment of 202 is above the median of 33 across 150 interventional studies indexed under Hemoglobinuria, Paroxysmal.
Browse Hemoglobinuria, Paroxysmal studies →Regeneron Pharmaceuticals is the lead sponsor of 411 studies on the registry; 90 are open to participants now.
Of its 125 completed or terminated interventional studies of FDA-regulated products, 79 (63%) have results posted.
Counted across the registry records on this site, refreshed daily.
Key Inclusion Criteria:
Patients Entering from the Parent Study
Patients Entering with C5 polymorphism
Key Exclusion Criteria:
Patients Entering from the Parent Study
Patients Entering with C5 polymorphism
Note: Other protocol-defined Inclusion/ Exclusion Criteria apply
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Relapsed: the illness came back after treatment had worked. Refractory: it did not respond to treatment, or stopped responding while still on it.
The top of the normal range for a blood test, as set by the laboratory that runs it. Each lab prints its own range next to your result.
“≤ 2.5 × ULN” means the result can be up to two and a half times that top value.
Hepatitis B is a virus that infects the liver. These are separate tests: HBsAg positive usually means a current infection (a recent vaccination can briefly cause it too); total anti-HBc (HBcAb) positive means an infection now or in the past; HBV DNA measures how much virus is in the blood.
Some studies accept a past infection if HBV DNA is undetectable, sometimes with antiviral medicine during the study. Check what this study allows.
Hepatitis C is a virus that infects the liver. An HCV antibody test can stay positive after an infection has cleared (and is occasionally positive without one); an HCV RNA test shows whether the virus is there now.
After treatment, hepatitis C counts as cured when HCV RNA is still undetectable 12 weeks or more after the treatment ended. Studies often accept people cured this way.
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
A condition in which the immune system attacks the body’s own tissues, such as rheumatoid arthritis, lupus, psoriasis, type 1 diabetes or inflammatory bowel disease.
Immunotherapy studies often leave out active autoimmune disease, and some name exceptions, such as thyroid disease on replacement hormone. Check the exceptions this study lists.
Two enzymes measured in a routine blood test of the liver. Higher levels can mean the liver is under strain or damaged. SGPT and SGOT are older names for ALT and AST.
Criteria usually give a limit as a multiple of the upper limit of normal (ULN), often higher when cancer has spread to the liver.
Relapsed and refractory
Relapsed: the illness came back after treatment had worked. Refractory: it did not respond to treatment, or stopped responding while still on it.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ULN (upper limit of normal)
The top of the normal range for a blood test, as set by the laboratory that runs it. Each lab prints its own range next to your result.
“≤ 2.5 × ULN” means the result can be up to two and a half times that top value.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hepatitis B tests
Hepatitis B is a virus that infects the liver. These are separate tests: HBsAg positive usually means a current infection (a recent vaccination can briefly cause it too); total anti-HBc (HBcAb) positive means an infection now or in the past; HBV DNA measures how much virus is in the blood.
Some studies accept a past infection if HBV DNA is undetectable, sometimes with antiviral medicine during the study. Check what this study allows.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hepatitis C tests
Hepatitis C is a virus that infects the liver. An HCV antibody test can stay positive after an infection has cleared (and is occasionally positive without one); an HCV RNA test shows whether the virus is there now.
After treatment, hepatitis C counts as cured when HCV RNA is still undetectable 12 weeks or more after the treatment ended. Studies often accept people cured this way.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
HIV
The human immunodeficiency virus, which weakens the immune system.
Many studies now accept people whose HIV is controlled on treatment, judged by the viral load and the CD4 count. Check the limits this study sets.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Autoimmune disease
A condition in which the immune system attacks the body’s own tissues, such as rheumatoid arthritis, lupus, psoriasis, type 1 diabetes or inflammatory bowel disease.
Immunotherapy studies often leave out active autoimmune disease, and some name exceptions, such as thyroid disease on replacement hormone. Check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
ALT and AST (liver enzymes)
Two enzymes measured in a routine blood test of the liver. Higher levels can mean the liver is under strain or damaged. SGPT and SGOT are older names for ALT and AST.
Criteria usually give a limit as a multiple of the upper limit of normal (ULN), often higher when cancer has spread to the liver.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Patients with PNH who completed treatment/ protocol requirements (as applicable) in the parent study (R3918-PNH-2021 \[NCT05133531\])
Drug: Pozelimab · Drug: Cemdisiran
Patients who have not been treated in either parent study but who have a documented complement component 5 (C5) variation rendering them refractory to eculizumab/ravulizumab. Note: Loading dose of pozelimab administered IV on Day 1.
Drug: Pozelimab · Drug: Cemdisiran
Administered per the protocol
Also known as: REGN3918
Administered per the protocol
Also known as: ALN-CC5
Incidence of treatment-emergent serious adverse events (SAEs)
An SAE is any untoward medical occurrence that at any dose: * Results in death * Is life-threatening * Requires in-patient hospitalization or prolongation of existing hospitalization. * Results in persistent or significant disability/incapacity * Is a congenital anomaly/birth defect. * Is an important medical event
Time frame: Up to week 108
Severity of treatment-emergent SAEs
Time frame: Up to week 108
Incidence of treatment emergent adverse events of special interest (AESIs)
An AESI (serious or non-serious) is one of scientific and medical concern specific to the sponsor's product or program, for which ongoing monitoring and rapid communication by the Investigator to the sponsor can be appropriate. Such an event might warrant further investigation in order to characterize and understand it
Time frame: Up to week 108
Severity of treatment emergent AESIs
Time frame: Up to week 108
Incidence of adverse events (AEs) leading to permanent treatment discontinuation
Any untoward medical occurrence in a patient administered a study drug which may or may not have a causal relationship with the study drug.
Time frame: Up to week 108
Severity of adverse events (AEs) leading to permanent treatment discontinuation
Any untoward medical occurrence in a patient administered a study drug which may or may not have a causal relationship with the study drug.
Time frame: Up to week 108
Percent change from baseline in lactate dehydrogenase (LDH)
Time frame: Baseline to week 36
Adequate control of hemolysis (LDH ≤1.5 × ULN)
Time frame: Post-baseline through week 108
Transfusion avoidance
Not requiring red blood cell (RBC) transfusion as per protocol algorithm based on hemoglobin values
Time frame: Post-baseline through week 36
Transfusion avoidance
Not requiring red blood cell (RBC) transfusion as per protocol algorithm based on hemoglobin values
Time frame: Post-baseline through week 48
Transfusion avoidance
Not requiring red blood cell (RBC) transfusion as per protocol algorithm based on hemoglobin values
Time frame: Post-baseline through week 76
Transfusion avoidance
Not requiring red blood cell (RBC) transfusion as per protocol algorithm based on hemoglobin values
Time frame: Post-baseline through week 108
Breakthrough hemolysis (defined as LDH ≥2 × ULN [subsequent to initial achievement of LDH ≤1.5 × ULN] concomitant with signs or symptoms associated with hemolysis)
Time frame: Post-baseline through week 36
Breakthrough hemolysis (defined as LDH ≥2 × ULN [subsequent to initial achievement of LDH ≤1.5 × ULN] concomitant with signs or symptoms associated with hemolysis)
Time frame: Post-baseline through week 48
Breakthrough hemolysis (defined as LDH ≥2 × ULN [subsequent to initial achievement of LDH ≤1.5 × ULN] concomitant with signs or symptoms associated with hemolysis)
Time frame: Post-baseline through week 76
Breakthrough hemolysis (defined as LDH ≥2 × ULN [subsequent to initial achievement of LDH ≤1.5 × ULN] concomitant with signs or symptoms associated with hemolysis)
Time frame: Post-baseline through week 108
Hemoglobin stabilization
Patients who do not receive an RBC transfusion and have no decrease in hemoglobin level of ≥2 g/dL
Time frame: Post-baseline through week 36
Hemoglobin stabilization
Patients who do not receive an RBC transfusion and have no decrease in hemoglobin level of ≥2 g/dL
Time frame: Post-baseline through week 48
Hemoglobin stabilization
Patients who do not receive an RBC transfusion and have no decrease in hemoglobin level of ≥2 g/dL
Time frame: Post-baseline through week 76
Hemoglobin stabilization
Patients who do not receive an RBC transfusion and have no decrease in hemoglobin level of ≥2 g/dL
Time frame: Post-baseline through week 108
Percent change in LDH
Time frame: From baseline to week 48
Percent change in LDH
Time frame: From baseline to week 76
Percent change in LDH
Time frame: From baseline to week 108
Change in fatigue
Measured by the FACIT-Fatigue scale The FACIT-F is a 13-item, self-reported PRO measure assessing an individual's level of fatigue during their usual daily activities over the past week. This questionnaire is part of the FACIT measurement system, a compilation of questions measuring health-related QoL in patients with cancer and other chronic illnesses. The FACIT-fatigue assesses the level of fatigue using a 5-point Likert scale ranging from 0 (not at all) to 4 (very much). Scores range from 0 to 52, with higher scores indicating greater fatigue.
Time frame: From baseline to week 36
Change in fatigue
Measured by the FACIT-Fatigue scale The FACIT-F is a 13-item, self-reported PRO measure assessing an individual's level of fatigue during their usual daily activities over the past week. This questionnaire is part of the FACIT measurement system, a compilation of questions measuring health-related QoL in patients with cancer and other chronic illnesses. The FACIT-fatigue assesses the level of fatigue using a 4-point Likert scale ranging from 0 (not at all) to 4 (very much). Scores range from 0 to 52, with higher scores indicating greater fatigue.
Time frame: From baseline to week 48
Change in fatigue
Measured by the FACIT-Fatigue scale The FACIT-F is a 13-item, self-reported PRO measure assessing an individual's level of fatigue during their usual daily activities over the past week. This questionnaire is part of the FACIT measurement system, a compilation of questions measuring health-related QoL in patients with cancer and other chronic illnesses. The FACIT-fatigue assesses the level of fatigue using a 4-point Likert scale ranging from 0 (not at all) to 4 (very much). Scores range from 0 to 52, with higher scores indicating greater fatigue.
Time frame: From baseline to week 76
Change in fatigue
Measured by the FACIT-Fatigue scale The FACIT-F is a 13-item, self-reported PRO measure assessing an individual's level of fatigue during their usual daily activities over the past week. This questionnaire is part of the FACIT measurement system, a compilation of questions measuring health-related QoL in patients with cancer and other chronic illnesses. The FACIT-fatigue assesses the level of fatigue using a 4-point Likert scale ranging from 0 (not at all) to 4 (very much). Scores range from 0 to 52, with higher scores indicating greater fatigue.
Time frame: From baseline to weeks 108
Change in physical function (PF) scores on the EORTC QLQ-C30
EORTC QLQ-C30 (European Organization for Research and Treatment of Cancer Quality of Life Core Questionnaire) EORTC-QLQ-C30 is a 30-item subject self-report questionnaire composed of both multi-item and single scales, including a global health status/quality of life (GHS/QoL) scale. Participants rate items on a four-point scale, with 1 as "not at all" and 4 as "very much." A change of 5 - 10 points is considered a small change. A change of 10 - 20 points is considered a moderate change.
Time frame: From baseline to week 36
Change in PF scores on the EORTC QLQ-C30
EORTC QLQ-C30 (European Organization for Research and Treatment of Cancer Quality of Life Core Questionnaire) EORTC-QLQ-C30 is a 30-item subject self-report questionnaire composed of both multi-item and single scales, including a global health status/quality of life (GHS/QoL) scale. Participants rate items on a four-point scale, with 1 as "not at all" and 4 as "very much." A change of 5 - 10 points is considered a small change. A change of 10 - 20 points is considered a moderate change.
Time frame: From baseline to week 48
Change in PF scores on the EORTC QLQ-C30
EORTC QLQ-C30 (European Organization for Research and Treatment of Cancer Quality of Life Core Questionnaire) EORTC-QLQ-C30 is a 30-item subject self-report questionnaire composed of both multi-item and single scales, including a global health status/quality of life (GHS/QoL) scale. Participants rate items on a four-point scale, with 1 as "not at all" and 4 as "very much." A change of 5 - 10 points is considered a small change. A change of 10 - 20 points is considered a moderate change.
Time frame: From baseline to week 76
Change in PF scores on the EORTC QLQ-C30
EORTC QLQ-C30 (European Organization for Research and Treatment of Cancer Quality of Life Core Questionnaire) EORTC-QLQ-C30 is a 30-item subject self-report questionnaire composed of both multi-item and single scales, including a global health status/quality of life (GHS/QoL) scale. Participants rate items on a four-point scale, with 1 as "not at all" and 4 as "very much." A change of 5 - 10 points is considered a small change. A change of 10 - 20 points is considered a moderate change.
Time frame: From baseline to week 108
Change in GHS/quality of life (QOL) scale on the EORTC QLQ-C30
GHS/QoL (Global Health Status/ Quality of Life) Global Health Status/Quality of Life (GHS/Qol) Score (Items 29 and 30) Using the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire-Core 30 (EORTC QLQ-C30). Participants rate items on a four-point scale, with 1 as "not at all" and 4 as "very much." A change of 5 - 10 points is considered a small change. A change of 10 - 20 points is considered a moderate change.
Time frame: From baseline to week 36
Change in GHS/quality of life (QOL) scale on the EORTC QLQ-C30
GHS/QoL (Global Health Status/ Quality of Life) Global Health Status/Quality of Life (GHS/Qol) Score (Items 29 and 30) Using the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire-Core 30 (EORTC QLQ-C30). Participants rate items on a four-point scale, with 1 as "not at all" and 4 as "very much." A change of 5 - 10 points is considered a small change. A change of 10 - 20 points is considered a moderate change.
Time frame: From baseline to week 48
Change in GHS/quality of life (QOL) scale on the EORTC QLQ-C30
GHS/QoL (Global Health Status/ Quality of Life) Global Health Status/Quality of Life (GHS/Qol) Score (Items 29 and 30) Using the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire-Core 30 (EORTC QLQ-C30). Participants rate items on a four-point scale, with 1 as "not at all" and 4 as "very much." A change of 5 - 10 points is considered a small change. A change of 10 - 20 points is considered a moderate change.
Time frame: From baseline to week 76
Change in GHS/quality of life (QOL) scale on the EORTC QLQ-C30
GHS/QoL (Global Health Status/ Quality of Life) Global Health Status/Quality of Life (GHS/Qol) Score (Items 29 and 30) Using the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire-Core 30 (EORTC QLQ-C30). Participants rate items on a four-point scale, with 1 as "not at all" and 4 as "very much." A change of 5 - 10 points is considered a small change. A change of 10 - 20 points is considered a moderate change.
Time frame: From baseline to week 108
Normalization of LDH
Time frame: From post-baseline through week 108
Rate of red blood cell (RBC) transfusion
Per protocol algorithm
Time frame: Post-baseline through week 36
Rate of RBC transfusion
Per protocol algorithm
Time frame: Post-baseline through week 48
Rate of RBC transfusion
Per protocol algorithm
Time frame: Post-baseline through week 76
Rate of RBC transfusion
Per protocol algorithm
Time frame: Post-baseline through week 108
Number of units of RBC transfusion
Per protocol algorithm
Time frame: Post-baseline through week 36
Number of units of RBC transfusion
Per protocol algorithm
Time frame: Post-baseline through week 48
Number of units of RBC transfusion
Per protocol algorithm
Time frame: Post-baseline through week 76
Number of units of RBC transfusion
Per protocol algorithm
Time frame: Post-baseline through week 108
Percentage of days with LDH ≤1.5x upper limit of normal (ULN)
Time frame: Post-baseline through week 36
Percentage of days with LDH ≤1.5x ULN
Time frame: Post-baseline through week 48
Percentage of days with LDH ≤1.5x ULN
Time frame: Post-baseline through week 76
Percentage of days with LDH ≤1.5x ULN
Time frame: Post-baseline through week 108
Change in hemoglobin levels
Time frame: From baseline to week 36
Change in hemoglobin levels
Time frame: From baseline to week 48
Change in hemoglobin levels
Time frame: From baseline to week 76
Change in hemoglobin levels
Time frame: From baseline to week 108
Change in total complement hemolytic activity assay (CH50)
Time frame: Through week 108
Percent change in CH50
Time frame: Through week 108
Concentrations of total pozelimab in serum
Time frame: Through week 108
Concentrations of cemdisiran in plasma
Time frame: Through week 24
Incidence of treatment-emergent anti-drug antibodies to pozelimab
Time frame: Through week 108
Incidence of treatment-emergent anti-drug antibodies to cemdisiran
Time frame: Through week 108
Concentration of total complement component 5 (C5) in plasma
Time frame: Through week 108
Percent change of concentration of total C5 in plasma
Time frame: Through week 108
Not enrolling at this site — choose another above.
Not enrolling at this site — choose another above.
Plan to share: Yes — All Individual Patient Data (IPD) that underlie publicly available results will be considered for sharing
Supporting information: Study protocol, Statistical analysis plan, Informed consent form, Clinical study report, Analytic code
Time frame: When Regeneron has: received marketing authorization from major health authorities (e.g., FDA, European Medicines Agency (EMA), Pharmaceuticals and Medical Devices Agency (PMDA), etc.) for the product and indication or has globally discontinued development of the product for all indications on or after April 2020 and has no plans for future development made the study results publicly available (e.g., scientific publication, scientific conference, clinical trial registry), the legal authority to share the data, and ensured the ability to protect participant privacy.
Access criteria: Qualified researchers can submit a proposal for access to individual patient or aggregate level data from a Regeneron-sponsored clinical trial through Vivli. Regeneron's Independent Research Request Evaluation Criteria can be found at: https://www.regeneron.com/sites/default/files/Regeneron-External-Data-Sharing-Policy-and-Independent-Research-Request-Evaluation-Criteria.pdf
Data sharing details ↗ · vivli.org
No publications or documents are linked to this record.
Started Mar 2023 (actual). Primary completion is estimated for Oct 2028, 67 months after the start.
Of 35 industry-sponsored phase 3 interventional studies under Hemoglobinuria, Paroxysmal, half reached primary completion within 23 months of starting (the median), counting those still running; a quarter within 15 and three quarters within 41. This study's planned 67 months is above that.
Counting every sponsor, half of 35 studies reached it within 23 months; a quarter within 15 and three quarters within 41.
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
Eligibility is decided by the study team. Share this record with your doctor or contact the team directly.
Contact study teamGet an email when the registry record changes — status, dates, results — or when someone posts here.
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Studies of the drugs tested here: Pozelimab · Cemdisiran