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Phase 3, Open-label, Single-dose Study of CSL222 in Adolescent Male Subjects (≥ 12 to < 18 Years of Age) With Severe or Moderately Severe Hemophilia B | Clinical Trials | Clareo Health

RECRUITINGPHASE3

Phase 3, Open-label, Single-dose Study of CSL222 in Adolescent Male Subjects (≥ 12 to < 18 Years of Age) With Severe or Moderately Severe Hemophilia B

Phase 3, Open-label, Single-dose, Multicenter Study Investigating Efficacy, Safety, and Tolerability of CSL222 (Etranacogene Dezaparvovec) Administered to Adolescent Male Subjects (≥ 12 to < 18 Years of Age) With Severe or Moderately Severe Hemophilia B

NCT07080905•CSL Behring

View on ClinicalTrials.gov

Summary

This is a phase 3, prospective, open-label, single-arm, single-dose, multicenter study investigating the efficacy, safety, and tolerability of CSL222 (AAV5-hFIXco-Padua) in adolescent male participants with severe or moderately severe hemophilia B.

Eligibility

Age

11 - 17 years

Sex

MALE

Healthy Volunteers

Inclusion Criteria

•Assigned male sex at birth
•Aged \>=138 months (11 years and 6 months) to less than (\<) 206 months (17 years and 2 months) at the time of informed consent / assent.
•Congenital hemophilia B with known severe or moderately severe FIX deficiency (less than or equal to \[\<=\] 2% of normal circulating FIX) for which the participant has been on continuous FIX prophylaxis.
•On stable continuous FIX prophylaxis for at least 2 months before Screening.
•Minimum of 75 previous exposure days of treatment with FIX protein before Screening.
•Completed the Lead-in Period: minimum of 6 months (26 weeks) of lead-in data collected and eligibility has been confirmed.
•Aged \>= 12 to \< 18 years at the time of CSL222 treatment.

Exclusion Criteria

•History of FIX inhibitors or positive FIX inhibitor test at Screening (based on central laboratory results).
•Screening laboratory values (based on central laboratory results):
•* Total bilirubin \> 2 × the upper limit of normal (ULN).
•* Alanine aminotransferase (ALT) \> 2 × the ULN.
•* Aspartate aminotransferase (AST) \> 2 × the ULN.
•* Alkaline phosphatase (ALP) \> 2 × the ULN.
•* Serum creatinine \> 2 × the ULN.
•* Hemoglobin \< 8 g/dL.
•Any condition other than hemophilia B resulting in an increased bleeding tendency.
•Thrombocytopenia, defined as a platelet count below 50 × 10\^9/L, at screening (based on central laboratory results).
+11 more criteria

Locations (7)

University of Florida

Gainesville, Florida, United States

Arthur M. Blank Hospital - Children's Healthcare of Atlanta

Atlanta, Georgia, United States

University of Michigan Medical Center

Ann Arbor, Michigan, United States

St. Jude Children's Research Hospital

Memphis, Tennessee, United States

Chaim Sheba Medical Center

Ramat Gan, Israel

St Thomas Hospital

London, United Kingdom

John Radcliffe Hospital - Oxford University Hospitals NHS

Oxford, United Kingdom

Key Dates

Start Date

July 28, 2025

Primary Completion Date

October 24, 2033

Completion Date

October 24, 2033

Last Updated

February 5, 2026

Enrollment

ESTIMATED participants

Conditions

Hemophilia B

Interventions

CSL222 (Adeno-associated viral vector serotype 5 [AAV5]-hFIXco-Padua)

GENETIC

Contacts

Trial Registration Coordinator

CONTACT

1-610-878-4697 clinicaltrials@cslbehring.com

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Data Source & Attribution

This clinical trial information is sourced from ClinicalTrials.gov, a service of the U.S. National Institutes of Health.

ClinicalTrials.gov last update: February 5, 2026Data synced to Clareo: March 29, 2026

Modifications: This data has been reformatted for display purposes. Eligibility criteria have been parsed into inclusion/exclusion sections. Location data has been geocoded to enable distance-based search. For the authoritative and most current information, please visit ClinicalTrials.gov.

Neither the United States Government nor Clareo Health make any warranties regarding the data. Check ClinicalTrials.gov frequently for updates.

View ClinicalTrials.gov Terms and Conditions

Phase 3, Open-label, Single-dose Study of CSL222 in Adolescent Male Subjects (≥ 12 to < 18 Years of Age) With Severe or Moderately Severe Hemophilia B

Inclusion Criteria

Exclusion Criteria

A Study to Investigate the Safety and Effectiveness of a Coagulation Factor IX Gene Insertion Therapy (REGV131-LNP1265) in Pediatric, Adolescent and Adult Participants With Hemophilia B

An Observational Cohort Study to Characterize the Effectiveness and Safety of HEMGENIX® in Patients With Hemophilia B

National Longitudinal Cohort of Hematological Diseases

An Open-Label, Comparative Study of the Efficacy, Safety and Pharmacodynamics of Single Dose of ANB-002 in Patients With Hemophilia B

Efficacy and Safety of KN057 Prophylaxis in Patients With Haemophilia A or B With Inhibitors

Liver Biopsy Following Gene Therapy For Hemophilia

Phase 3, Open-label, Single-dose Study of CSL222 in Adolescent Male Subjects (≥ 12 to &lt; 18 Years of Age) With Severe or Moderately Severe Hemophilia B

Inclusion Criteria

Exclusion Criteria

A Study to Investigate the Safety and Effectiveness of a Coagulation Factor IX Gene Insertion Therapy (REGV131-LNP1265) in Pediatric, Adolescent and Adult Participants With Hemophilia B

An Observational Cohort Study to Characterize the Effectiveness and Safety of HEMGENIX® in Patients With Hemophilia B

National Longitudinal Cohort of Hematological Diseases

An Open-Label, Comparative Study of the Efficacy, Safety and Pharmacodynamics of Single Dose of ANB-002 in Patients With Hemophilia B

Efficacy and Safety of KN057 Prophylaxis in Patients With Haemophilia A or B With Inhibitors

Liver Biopsy Following Gene Therapy For Hemophilia

Phase 3, Open-label, Single-dose Study of CSL222 in Adolescent Male Subjects (≥ 12 to < 18 Years of Age) With Severe or Moderately Severe Hemophilia B