Hemophilia BPhase 3IX-TEND 3004NCT07080905
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
A Phase 3 study testing CSL222 (Adeno-associated viral vector serotype 5 [AAV5]-hFIXco-Padua) in people with Hemophilia B, run by CSL Behring at 17 sites in 8 countries.
Trial 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. Read more about this study
- Who is it for?
- Ages 138 to 206 months, men only
- Conditions the study is for
- Hemophilia B
- What is being tested?
- CSL222 (Adeno-associated viral vector serotype 5 [AAV5]-hFIXco-Padua)
- Type of treatment
- Injection or infusion
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 20 participants
- Where
- 17 sitesin 8 countries
- Study dates
- 28 Jul 2025to 24 Oct 2033
- Phase
- Phase 3
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 138 to 206 months
- Men only
- No healthy volunteers
- Child
Who may be able to join
- Key Inclusion Criteria for the Lead-in Period: 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.
- Additional Key Inclusion Criteria for the Treatment Period:
- 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.
Who cannot join
- Key Exclusion Criteria for the Lead-in Period: 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.
Show all 21Show fewer
- 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).
- Any uncontrolled or untreated infection (human immunodeficiency virus, hepatitis C, etc) or any other significant concurrent, uncontrolled medical condition, as evaluated by the investigator, including, but not limited to renal, hepatic, cardiovascular, hematological, gastrointestinal, endocrine, pulmonary, neurological, cerebral, or psychiatric disease, alcoholism, drug dependency, or any other psychological disorder evaluated by the investigator to interfere with adherence to the Clinical Study Protocol procedures or with the degree of tolerance to CSL222.
- Additional Key Exclusion Criteria for the Treatment Period: Positive FIX inhibitor test at Visit L-Final (based on central laboratory results)
- AAV5 NAb titer > 1:900 as assessed at Visit LX (last visit before Visit L-Final).
- Visit L-Final laboratory values (based on central laboratory results) of:
- Total bilirubin > 2 × the ULN
- ALT > 2 × the ULN.
- AST > 2 × the ULN.
- ALP > 2 × the ULN.
- Serum creatinine > 2 × the ULN.
- Hemoglobin < 8 g/dL.
- Thrombocytopenia, defined as a platelet count below 50 × 10^9/L, at Visit L-Final (based on central laboratory results).
Trial locations and contacts
17 sites in 8 countries. Contact the study team or a site near you to ask about taking part.
17 sites in 8 countries
United States6 sites, 6 recruiting
- Recruiting
University of Michigan Medical Center
Ann Arbor, Michigan, 48109
Trial Contact, 734-232-9335, ummdswp@med.umich.edu
- Recruiting
Arthur M. Blank Hospital - Children's Healthcare of Atlanta
Atlanta, Georgia, 30329
- Recruiting
University of Florida
Gainesville, Florida, 32611
Trial Contact, 352-294-8846, jessicalcline@peds.ufl.edu
- Recruiting
St. Jude Children's Research Hospital
Memphis, Tennessee, 38105
- Recruiting
Center for Inherited Blood Disorders
Orange, California, 92868
- Recruiting
Rady Children's Hospital San Diego
San Diego, California, 92123
Australia2 sites, 2 recruiting
- Recruiting
Queensland Children's Hospital
Brisbane, 4101
- Recruiting
The Children's Hospital at Westmead
Westmead, New South Wales, 2145
France2 sites, 2 recruiting
- Recruiting
Lille University Hospital Center - Coeur Poumon Institute
Lille, 59000
- Recruiting
CHU Hopital de la Timone
Marseille, 13009
Spain2 sites, 2 recruiting
- Recruiting
Hospital Sant Joan de Déu
Barcelona, 08950
- Recruiting
La Paz University Hospital
Madrid, 28046
United Kingdom2 sites, 2 recruiting
- Recruiting
St Thomas Hospital
London, SE1 7EH
- Recruiting
John Radcliffe Hospital - Oxford University Hospitals NHS
Oxford, OX3 9DU
Belgium1 site, 1 recruiting
- Recruiting
UZ Leuven - Centrum voor Moleculaire en Vasculaire Biologie
Leuven, 3000
Israel1 site, 1 recruiting
- Recruiting
Chaim Sheba Medical Center
Ramat Gan, 5262000
About this study
Official title: 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
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.
- Conditions
- Hemophilia B
- Being tested
- CSL222 (Adeno-associated viral vector serotype 5 [AAV5]-hFIXco-Padua)
- Medical subject headings
- Hemophilia B
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
CSL222 (Adeno-associated viral vector serotype 5 [AAV5]-hFIXco-Padua)Genetic
Also called Etranacogene Dezaparvovec
Administered as a single IV infusion.
| Study group | Role | What they receive |
|---|---|---|
| CSL222 | Experimental | Participants will receive CSL222 as a single intravenous (IV) infusion of 2 × 10^13 genome copies per kilogram of body weight (gc/kg). Receives: Genetic: CSL222 (Adeno-associated viral vector serotype 5 [AAV5]-hFIXco-Padua) |
What is being measured
The primary outcome is the main question the study is designed to answer.
Annualized Bleeding Rate (ABR)
Measured: For the Lead-In Period (at least 6 months) and for the 52 weeks after stable FIX expression (months 7 to 18 after treatment with CSL222)
Secondary outcomes (31)
Canadian Hemophilia Outcomes-Kids Life Assessment Tool (CHO-KLAT) total score and change from baseline
The CHO-KLAT is designed to measure aspects of quality of life for boys with hemophilia. CHO-KLAT is a 40-item questionnaire, available in both child self-report (for ages 7 to 18) and parent-proxy versions (for ages 4 to 18). Items are categorized into 7 key domains (Activities, Autonomy, Bleeding, Emotional Health, Hemophilia Knowledge, Social Functioning, and Treatment). The measure is scored on a scale of 0 to 100, with 100 indicating best health-related quality of life.
Measured: At baseline and Month 18 post treatment
Endogenous FIX activity
Measured: At baseline, and at months 6, 12, and 18 after treatment with CSL222
Change from baseline in endogenous FIX activity
Measured: At baseline, and at months 6, 12, and 18 after treatment with CSL222
Annualized consumption of FIX replacement therapy
Mean annualized consumption (IU/year) of FIX replacement therapy (excluding FIX replacement for invasive procedures).
Measured: For the Lead-In Period (at least 6 months), for the 52 weeks following stable FIX expression (months 7 to 18 after treatment with CSL222), and annually in the Posttreatment Follow-up Period (up to 5 years)
Annualized infusion rate of FIX replacement therapy
Mean annualized infusion rate (infusions/year) of FIX replacement therapy (excluding FIX replacement for invasive procedures).
Measured: For the Lead-In Period (at least 6 months), for the 52 weeks following stable FIX expression (months 7 to 18 after treatment with CSL222), and annually in the Posttreatment Follow-up Period (up to 5 years)
Number of participants remaining free of continuous FIX prophylaxis
Measured: During the 52 weeks after stable FIX expression (months 7 to 18 after treatment with CSL222), and during months 7 to: 24, 36, 48, and 60 after treatment with CSL222
Percentage of participants remaining free of continuous FIX prophylaxis
Measured: During the 52 weeks after stable FIX expression (months 7 to 18 after treatment with CSL222), and during months 7 to: 24, 36, 48, and 60 after treatment with CSL222
ABR for spontaneous, joint, and FIX-treated bleeding episodes
Measured: For the Lead-In Period (at least 6 months) and during the 52 weeks after stable FIX expression (months 7 to 18 after treatment with CSL222)
Correlation of FIX activity levels and pre-CSL222 AAV5 NAb titer
Measured: At the end of the Lead-in Period and during 6 to 18 months after treatment with CSL222
Number of new target joints and resolution of preexisting target joints
Measured: During the 52 weeks after stable FIX expression (months 7 to 18 after treatment with CSL222), and then annually during the Posttreatment Follow-up Period (up to 5 years)
Number of participants with zero bleeds and zero FIX-treated bleeds
Measured: During the 52 weeks after stable FIX expression (months 7 to 18 after treatment with CSL222), and during months 7 to: 24, 36, 48, and 60 after treatment with CSL222
Percentage of participants with zero bleeds and zero FIX-treated bleeds
Measured: During the 52 weeks after stable FIX expression (months 7 to 18 after treatment with CSL222), and during months 7 to: 24, 36, 48, and 60 after treatment with CSL222
Change in the EuroQol-5 Dimensions-5 Levels (EQ-5D-5L) Visual Analogue Scale (VAS) Overall Score
The EQ-5D-5L questionnaire visual analogue scale (VAS) measures overall health status on a vertical VAS ranging from 0 to 100. A higher score indicates better quality of life. The change from baseline in the EQ-5D-5L VAS score will be determined.
Measured: At baseline, during the Lead-In Period (at least 6 months), and in the Posttreatment Follow-up Period (up to 5 years)
Change in the EQ-5D-5L Index Scores
The EQ-5D-5L questionnaire descriptive system of health-related quality of life consists of 5 dimensions (mobility, self-care, usual activities, pain/discomfort, anxiety/depression) for which responses will be recorded on 5 levels of severity (no problems, slight problems, moderate problems, severe problems, and extreme problems). The responses will be converted into a single index utility score (typically between -0.6 and 1). A higher score indicates better quality of life. The change from baseline in the EQ-5D-5L index score will be determined.
Measured: At baseline, during the Lead-In Period (at least 6 months), and in the Posttreatment Follow-up Period (up to 5 years)
Change in the Patient-Reported Outcomes Measurement Information System (PROMIS)-25 total score
For participants of age 12-16 years. PROMIS-25 is a collection of short forms measuring quality of life in children. It includes domains of physical function mobility, anxiety, depression, fatigue, peer relationships, and pain interference. Each domain consists of 4 questions and are scored from 1 to 5. PROMIS-25 also includes one question on pain intensity that is available as a numeric rating scale and is scored from 0 (no pain) to 10 (worst imaginable pain).
Measured: At baseline, during the Lead-In Period (at least 6 months), and in the Posttreatment Follow-up Period (up to 5 years)
Change from baseline in PROMIS-29 total score
For participants of age ≥ 17 years. PROMIS-29 is a collection of short forms consisting of 7 PROMIS domains in depression, anxiety, physical function, pain interference, fatigue, sleep disturbance, and ability to participate in social roles and activities. Each domain consists of 4 questions and are scored from 1 to 5. PROMIS-29 also includes 1 question on pain intensity that is available as a numeric rating scale and is scored from 0 (no pain) to 10 (worst imaginable pain).
Measured: At baseline, during the Lead-In Period (at least 6 months), and in the Posttreatment Follow-up Period (up to 5 years)
Number of participants with endogenous FIX activity of ≥ 5%
Measured: Up to 5 years after treatment with CSL222
Percentage of participants with endogenous FIX activity of ≥ 5%
Measured: Up to 5 years after treatment with CSL222
Adverse events - number of participants
Measured: During the Lead-in Period (at least 6 months) and during the Posttreatment Follow-up Period (up to 5 years).
Adverse events - percentage of participants
Measured: During the Lead-in Period (at least 6 months) and during the Posttreatment Follow-up Period (up to 5 years).
Adverse events - number of events
Measured: During the Lead-in Period (at least 6 months) and during the Posttreatment Follow-up Period (up to 5 years).
Change in liver ultrasound
Measured: At baseline, month 12 and every 6 months thereafter up to 5 years after CSL222 treatment
Number of participants with antibodies against AAV5
Measured: From treatment with CSL222 through end of study (up to 5 years after treatment with CSL222)
Number of participants who develop FIX inhibitors
Measured: From treatment with CSL222 through end of study (up to 5 years after treatment with CSL222)
Number of clinically significant clinical laboratory tests (Hematology and Biochemistry) reported as an AE
Measured: At baseline and up to 5 years after treatment with CSL222
Number of participants with clinically significant ALT/AST levels
Measured: At baseline and up to 5 years after treatment with CSL222
Percentage of participants with clinically significant ALT/AST levels
Measured: At baseline and up to 5 years after treatment with CSL222
Number of participants using corticosteroid for change in AST/ALT levels
Measured: Up to 5 years after treatment with CSL222
Duration of corticosteroid use for change in AST/ALT levels
Measured: Up to 5 years after treatment with CSL222
Mean inflammatory markers values
Inflammatory markers include interleukin (IL) -1-beta, IL-2, IL-6, interferon-gamma, and monocyte chemoattractant protein-1 (MCP-1) will be measured and reported as picograms per milliliter (pg/mL).
Measured: Up to 5 years after treatment with CSL222
Change from baseline in Inflammatory markers
Inflammatory markers include IL -1-beta, IL-2, IL-6, interferon-gamma, and MCP-1
Measured: At baseline and up to 5 years after treatment with CSL222
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted23 Jul 2025
- Study start28 Jul 2025
- Primary completion24 Oct 2033 (estimated)
- Study completion24 Oct 2033 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Hemophilia BStudies of the same condition, open and under way.
- More trials run by CSL BehringThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 3
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Enrolment
- 20 participants (estimated)
Sponsor and investigators
- Lead sponsor
- CSL Behring
- Sponsor type
- Industry (pharma, biotech, devices)
- Responsible party
- Sponsor
- Investigators
- Study Director, Study director, CSL Behring
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07080905
- Sponsor's protocol ID
- CSL222_3004
- Other IDs
- 2023-505805-18-00, 2023
- Acronym
- IX-TEND 3004
- Status last verified
- Oct 2026
- First submitted
- 7 Jul 2025
- Last updated
- 20 Oct 2026
- Results posted
- No
- Data monitoring committee
- Yes
- FDA-regulated drug
- Yes
- FDA-regulated device
- Yes
- Individual data sharing
- Yes: CSL will consider on a case-by-case basis requests to share Individual Patient Data (IPD) with external bona-fide, qualified scientific and medical researchers. For information on the process and requirements for submitting a voluntary data sharing request for IPD, please contact CSL at clinicaltrials@cslbehring.com.
Study at a glance
From the registry record, last updated by the sponsor on 20 Oct 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- 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
- ClinicalTrials.gov ID
- NCT07080905
- Acronym / sponsor ID
- IX-TEND 3004 / CSL222_3004
- Conditions
- Hemophilia B
- Phase
- Phase 3
- Study type
- Interventional
- Recruitment status
- Recruiting
- Enrolment
- 20 participants (estimated)
- Lead sponsor
- CSL BehringIndustry (pharma, biotech, devices)
- Study start
- 28 Jul 2025 (actual)
- Primary completion
- 24 Oct 2033 (estimated)
- Study completion
- 24 Oct 2033 (estimated)
- First posted
- 23 Jul 2025 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
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.
Study design
- Primary purpose
- Treatment
- Allocation
- Not applicable
- Intervention model
- Single group
- Masking
- None (open label)
- Number of arms
- 1
| Arm | Type | Receives |
|---|---|---|
| CSL222 | Experimental | Genetic: CSL222 (Adeno-associated viral vector serotype 5 [AAV5]-hFIXco-Padua)Participants will receive CSL222 as a single intravenous (IV) infusion of 2 × 10^13 genome copies per kilogram of body weight (gc/kg). |
Who may qualify
- Ages
- 138 to 206 months
- Sex
- Male only
- Healthy volunteers
- Not accepted
- Age groups
- Child
Key inclusion criteria (8 listed)
- Key Inclusion Criteria for the Lead-in Period: 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.
Key exclusion criteria (21 listed)
- Key Exclusion Criteria for the Lead-in Period: History of FIX inhibitors or positive FIX inhibitor test at Screening (based on central laboratory results).
- Screening laboratory values (based on central laboratory results):
- 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).
- Any uncontrolled or untreated infection (human immunodeficiency virus, hepatitis C, etc) or any other significant concurrent, uncontrolled medical condition, as evaluated by the investigator, including, but not limited to renal, hepatic, cardiovascular, hematological, gastrointestinal, endocrine, pulmonary, neurological, cerebral, or psychiatric disease, alcoholism, drug dependency, or any other psychological disorder evaluated by the investigator to interfere with adherence to the Clinical Study Protocol procedures or with the degree of tolerance to CSL222.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| CSL222 (Adeno-associated viral vector serotype 5 [AAV5]-hFIXco-Padua)Also: Etranacogene DezaparvovecAdministered as a single IV infusion. | Genetic | CSL222 |
Primary outcome
Annualized Bleeding Rate (ABR)
Time frame: For the Lead-In Period (at least 6 months) and for the 52 weeks after stable FIX expression (months 7 to 18 after treatment with CSL222)
31 secondary outcomes
Canadian Hemophilia Outcomes-Kids Life Assessment Tool (CHO-KLAT) total score and change from baseline
Time frame: At baseline and Month 18 post treatment
Endogenous FIX activity
Time frame: At baseline, and at months 6, 12, and 18 after treatment with CSL222
Change from baseline in endogenous FIX activity
Time frame: At baseline, and at months 6, 12, and 18 after treatment with CSL222
Annualized consumption of FIX replacement therapy
Time frame: For the Lead-In Period (at least 6 months), for the 52 weeks following stable FIX expression (months 7 to 18 after treatment with CSL222), and annually in the Posttreatment Follow-up Period (up to 5 years)
Annualized infusion rate of FIX replacement therapy
Time frame: For the Lead-In Period (at least 6 months), for the 52 weeks following stable FIX expression (months 7 to 18 after treatment with CSL222), and annually in the Posttreatment Follow-up Period (up to 5 years)
Number of participants remaining free of continuous FIX prophylaxis
Time frame: During the 52 weeks after stable FIX expression (months 7 to 18 after treatment with CSL222), and during months 7 to: 24, 36, 48, and 60 after treatment with CSL222
Percentage of participants remaining free of continuous FIX prophylaxis
Time frame: During the 52 weeks after stable FIX expression (months 7 to 18 after treatment with CSL222), and during months 7 to: 24, 36, 48, and 60 after treatment with CSL222
ABR for spontaneous, joint, and FIX-treated bleeding episodes
Time frame: For the Lead-In Period (at least 6 months) and during the 52 weeks after stable FIX expression (months 7 to 18 after treatment with CSL222)
Correlation of FIX activity levels and pre-CSL222 AAV5 NAb titer
Time frame: At the end of the Lead-in Period and during 6 to 18 months after treatment with CSL222
Number of new target joints and resolution of preexisting target joints
Time frame: During the 52 weeks after stable FIX expression (months 7 to 18 after treatment with CSL222), and then annually during the Posttreatment Follow-up Period (up to 5 years)
Number of participants with zero bleeds and zero FIX-treated bleeds
Time frame: During the 52 weeks after stable FIX expression (months 7 to 18 after treatment with CSL222), and during months 7 to: 24, 36, 48, and 60 after treatment with CSL222
Percentage of participants with zero bleeds and zero FIX-treated bleeds
Time frame: During the 52 weeks after stable FIX expression (months 7 to 18 after treatment with CSL222), and during months 7 to: 24, 36, 48, and 60 after treatment with CSL222
Change in the EuroQol-5 Dimensions-5 Levels (EQ-5D-5L) Visual Analogue Scale (VAS) Overall Score
Time frame: At baseline, during the Lead-In Period (at least 6 months), and in the Posttreatment Follow-up Period (up to 5 years)
Change in the EQ-5D-5L Index Scores
Time frame: At baseline, during the Lead-In Period (at least 6 months), and in the Posttreatment Follow-up Period (up to 5 years)
Change in the Patient-Reported Outcomes Measurement Information System (PROMIS)-25 total score
Time frame: At baseline, during the Lead-In Period (at least 6 months), and in the Posttreatment Follow-up Period (up to 5 years)
Change from baseline in PROMIS-29 total score
Time frame: At baseline, during the Lead-In Period (at least 6 months), and in the Posttreatment Follow-up Period (up to 5 years)
Number of participants with endogenous FIX activity of ≥ 5%
Time frame: Up to 5 years after treatment with CSL222
Percentage of participants with endogenous FIX activity of ≥ 5%
Time frame: Up to 5 years after treatment with CSL222
Adverse events - number of participants
Time frame: During the Lead-in Period (at least 6 months) and during the Posttreatment Follow-up Period (up to 5 years).
Adverse events - percentage of participants
Time frame: During the Lead-in Period (at least 6 months) and during the Posttreatment Follow-up Period (up to 5 years).
Adverse events - number of events
Time frame: During the Lead-in Period (at least 6 months) and during the Posttreatment Follow-up Period (up to 5 years).
Change in liver ultrasound
Time frame: At baseline, month 12 and every 6 months thereafter up to 5 years after CSL222 treatment
Number of participants with antibodies against AAV5
Time frame: From treatment with CSL222 through end of study (up to 5 years after treatment with CSL222)
Number of participants who develop FIX inhibitors
Time frame: From treatment with CSL222 through end of study (up to 5 years after treatment with CSL222)
Number of clinically significant clinical laboratory tests (Hematology and Biochemistry) reported as an AE
Time frame: At baseline and up to 5 years after treatment with CSL222
Number of participants with clinically significant ALT/AST levels
Time frame: At baseline and up to 5 years after treatment with CSL222
Percentage of participants with clinically significant ALT/AST levels
Time frame: At baseline and up to 5 years after treatment with CSL222
Number of participants using corticosteroid for change in AST/ALT levels
Time frame: Up to 5 years after treatment with CSL222
Duration of corticosteroid use for change in AST/ALT levels
Time frame: Up to 5 years after treatment with CSL222
Mean inflammatory markers values
Time frame: Up to 5 years after treatment with CSL222
Change from baseline in Inflammatory markers
Time frame: At baseline and up to 5 years after treatment with CSL222
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 20 Oct 2026.
- Individual participant dataSharing planned: Yes. CSL will consider on a case-by-case basis requests to share Individual Patient Data (IPD) with external bona-fide, qualified scientific and medical researchers. For information on the process and requirements for submitting a voluntary data sharing request for IPD, please contact CSL at clinicaltrials@cslbehring.com.
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
Study Director study director
CSL Behring
17 sites in 8 countries: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 3 study testing CSL222 (Adeno-associated viral vector serotype 5 [AAV5]-hFIXco-Padua) in people with Hemophilia B, run by CSL Behring at 17 sites in 8 countries.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 8 inclusion and 21 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: looking for participants now, as of the sponsor's last update on 20 Oct 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 17 sites in United States, Australia, France, Spain, United Kingdom and 3 more countries. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Phase 3 studies compare the treatment with the current standard treatment or a placebo in a large group, to confirm how well it works and watch for side effects.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Trial Registration Coordinator (1-610-878-4697, clinicaltrials@cslbehring.com), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
Annualized Bleeding Rate (ABR) (time frame: For the Lead-In Period (at least 6 months) and for the 52 weeks after stable FIX expression (months 7 to 18 after treatment with CSL222)). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 20 Oct 2026.