A Phase 3 interventional study of CSL222 (AAV5-hFIXco-Padua) in Hemophilia B, sponsored by CSL Behring. Recruiting at 32 sites in 15 countries. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-08-27.
Sponsored by CSL Behring (part of CSL Limited) · Phase 3, Interventional, and Treatment
Among 18 studies in Hemophilia B by CSL Limited — 4 open to participants now, 5 under way, 2 of them phase 3. Hemophilia B · CSL Limited.
Among the 18 studies in Hemophilia B by CSL Limited, this one is the 6th largest by planned enrollment of the 14 interventional ones that give a count, is one of 2 that started in 2024, is one of 8 in phase 3, and was the 15th registered.
292 studies on the registry are indexed under Hemophilia B; 51 are open to participants now.
Browse Hemophilia B studies →4 of the 18 studies in Hemophilia B by CSL Limited are open now, in 12 countries. Recruiting first, the newest first:
CSL Behring · Sites in United States, Australia, Austria and 5 more countries
Ages 138 mo–206 mo · Men only
CSL Behring · Sites in United States, Austria, Denmark and 4 more countries
Ages 18+
CSL Behring · Sites in United States, Belgium, Denmark and 5 more countries
Ages 18+ · Men only
By country, each count listing its studies:
Of the 30 Hemophilia B studies recruiting now, 17 (57%) set no upper age limit and 11 (37%) stop at 75 or younger; 16 take children under 18; 3 take healthy volunteers.
This study: 18 Years and older · all sexes · no healthy volunteers.
The full table on the hub →This tab as a report to print or save as PDF → With an account.
18 studies; the count open now beside each. This study's row is marked.
A study in two phases is counted once above. Listed by phase, each with its combined phases: Phase 1 3 · Phase 2 5 · Phase 3 10
First in 2005; this study’s year is marked. 2 started in 2024.
This study's planned enrollment of 35 is above the median of 26 across 171 interventional studies indexed under Hemophilia B.
Median enrollment 26 across the 14 interventional studies, 139 across the 4 observational. Of the 13 that completed or were terminated, 8 (62%) have results posted.
This tab as a report to print or save as PDF → With an account.
This study is registered under CSL Behring, one of the names counted as CSL Limited. Under that name alone:
CSL Behring is the lead sponsor of 145 studies on the registry; 17 are open to participants now.
Of its 24 completed or terminated interventional studies of FDA-regulated products, 17 (71%) have results posted.
None of the studies under way reaches primary completion within a year.
Among the 18 studies in Hemophilia B by CSL Limited, from their registry updates:
Nothing recorded among them since 2026-09-25.
This tab as a report to print or save as PDF → With an account.
The purpose of this study is to assess the risk of bleeding due to failure of expected pharmacological action of CSL222 in adults with severe or moderately severe hemophilia B with detectable pretreatment AAV5 Nabs.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Screening or Visit L-Final laboratory values (based on central laboratory results) of any of the following laboratory abnormalities:
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.
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
A yellow substance made when red blood cells are broken down, which the liver clears. A high level can mean a problem with the liver or the bile ducts.
Criteria often allow more for people with Gilbert’s syndrome, a harmless inherited condition that raises bilirubin.
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.
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.
The protein in red blood cells that carries oxygen. A low level is anaemia, which can cause tiredness and breathlessness. Measured in g/dL or g/L (9 g/dL is 90 g/L).
Blood cells that help blood clot. Too few raises the risk of bleeding and bruising. A usual adult range is about 150–400 × 10⁹/L (150,000–400,000 per µL); each lab has its own reference range.
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.
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.
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
The other ingredients in a medicine besides the active drug, such as fillers, colours or preservatives.
Contraception
Ways of preventing pregnancy. “Highly effective” methods fail less than 1% of the time a year when used correctly — for example an IUD or an implant.
Criteria usually say which methods count and how long to keep using them after the last dose, sometimes for male participants too. Some studies accept a partner’s vasectomy if it was confirmed successful and that person is the participant’s only sexual partner.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Bilirubin
A yellow substance made when red blood cells are broken down, which the liver clears. A high level can mean a problem with the liver or the bile ducts.
Criteria often allow more for people with Gilbert’s syndrome, a harmless inherited condition that raises bilirubin.
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.
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.
Hemoglobin (Hb)
The protein in red blood cells that carries oxygen. A low level is anaemia, which can cause tiredness and breathlessness. Measured in g/dL or g/L (9 g/dL is 90 g/L).
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Platelets
Blood cells that help blood clot. Too few raises the risk of bleeding and bruising. A usual adult range is about 150–400 × 10⁹/L (150,000–400,000 per µL); each lab has its own reference range.
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.
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.
Corticosteroids (steroids)
Anti-inflammatory medicines such as prednisone, prednisolone and dexamethasone — not the anabolic steroids used for muscle.
Studies differ in what they allow: check which steroid medicines, routes (tablets, injections, creams, inhalers, eye drops) and doses this study accepts.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Hypersensitivity
An allergy, or another reaction of the immune system, to a substance. “Hypersensitivity to the study drug” means a known allergic reaction to it — not every side effect a medicine can have.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Excipients
The other ingredients in a medicine besides the active drug, such as fillers, colours or preservatives.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants will receive CSL222 as a single intravenous (IV) infusion of 2 × 10\^13 genome copies per kilogram (gc/kg) on Day 1.
Genetic: CSL222 (AAV5-hFIXco-Padua)
Administered as a single IV infusion.
Also known as: Etranacogene dezaparvovec
Annualized Bleeding Rate (ABR)
The total bleeding episodes will be analyzed. ABR is calculated as the total bleeding episodes divided by the total time at risk.
Time frame: Months 7 to 18 after CSL222 treatment
Number of participants with Treatment Emergent Adverse Events (TEAEs)
Time frame: Up to 60 months after CSL222 treatment
Percentage of participants with TEAEs
Time frame: Up to 60 months after CSL222 treatment
Number of TEAEs
Time frame: Up to 60 months after CSL222 treatment
Change in Liver ultrasound
Time frame: Up to 60 months after CSL222 treatment
Number of participants who develop Factor IX (FIX) Inhibitors
Time frame: Up to 60 months after CSL222 treatment
Percentage of participants who develop FIX Inhibitors
Time frame: Up to 60 months after CSL222 treatment
Change in hematology and biochemistry parameters
Time frame: Up to 60 months after CSL222 treatment
Number of participants with clinically significant increase in Alanine Aminotransferase (ALT) or Aspartate Aminotransferase (AST)
Time frame: Up to 60 months after CSL222 treatment
Percentage of participants with clinically significant increase in ALT or AST
Time frame: Up to 60 months after CSL222 treatment
Corticosteroid use for ALT or AST increases after CSL222 treatment
Time frame: Up to 60 months after CSL222 treatment
Number of participants with clinically significant Alpha-fetoprotein (AFP)
Time frame: Baseline and up to 60 months after CSL222 treatment
Percentage of participants with clinically significant AFP
Time frame: Baseline and up to 60 months after CSL222 treatment
Number of participants with infusion related reactions or hypersensitivity reactions
Time frame: Throughout CSL222 infusion period and up to 60 months after CSL222 treatment
Percentage of participants with infusion related reactions or hypersensitivity reactions
Time frame: Throughout CSL222 infusion period and up to 60 months after CSL222 treatment
Change in the Uncontaminated Endogenous FIX activity
Time frame: Baseline and up to Months 6, 12, and 18 after CSL222 treatment
Annualized consumption of FIX replacement therapy
Time frame: Months 7 to 18 after CSL222 treatment
Annualized infusion rate of FIX replacement therapy
Time frame: Months 7 to 18 after CSL222 treatment
Number of participants remaining free of continuous FIX prophylaxis
Time frame: Months 7 to 18 after CSL222 treatment
Percentage of participants remaining free of continuous FIX prophylaxis
Time frame: Months 7 to 18 after CSL222 treatment
ABR for spontaneous bleeding episodes
Time frame: Months 7 to 18 after CSL222 treatment
ABR for joint bleeding episodes
Time frame: Months 7 to 18 after CSL222 treatment
ABR for FIX-treated bleeding episodes
Time frame: Months 7 to 18 after CSL222 treatment
Correlation analysis of FIX activity levels with baseline AAV5 NAb titers
Time frame: Months 7 to 18 after CSL222 treatment
Number of participants with new target joints and resolved pre-existing target joints
Target joint is defined as 3 or more spontaneous bleeding episodes into a single joint.
Time frame: Months 7 to 18 after CSL222 treatment
Number of participants with zero bleeding episodes and zero FIX-treated bleeding episodes
Time frame: Months 7 to 18 after CSL222 treatment
Percentage of participants with zero bleeding episodes and zero FIX-treated bleeding episodes
Time frame: Months 7 to 18 after CSL222 treatment
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.
Time frame: Baseline and up to 18 months after CSL222 treatment
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.
Time frame: Baseline and up to 18 months after CSL222 treatment
Number of Participants with Uncontaminated Endogenous FIX Activity of Greater than or Equal to (>=) 5%
Time frame: Months 7 to 18 after CSL222 treatment
Percentage of Participants with Uncontaminated Endogenous FIX Activity of >= 5%
Time frame: Months 7 to 18 after CSL222 treatment
Plan to share: 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.
Supporting information: Study protocol, Statistical analysis plan
Time frame: Requests for IPD will generally be considered once review by major regulatory authorities (ie FDA, EMA) is complete and the primary publication is available.
Access criteria: Proposed research should seek to answer a previously unanswered important medical or scientific question. Applicable country specific privacy and other laws and regulations will be considered and may prevent sharing of IPD. If the request is approved and the researcher has executed an appropriate data sharing agreement, IPD that has been appropriately anonymized will be available.
No publications or documents are linked to this record.
Started Jan 2024 (actual). Primary completion is estimated for Oct 2028, 56 months after the start.
Of 35 industry-sponsored phase 3 interventional studies under Hemophilia B, half reached primary completion within 38 months of starting (the median), counting those still running; a quarter within 23 and three quarters within 70. This study's planned 56 months is above that.
Counting every sponsor, half of 35 studies reached it within 38 months; a quarter within 23 and three quarters within 70.
How these figures are worked out, and which studies are left out of them.
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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