18 and older, male only, with Hemophilia B. Patients with the condition only — healthy volunteers not accepted.
Results — posted to ClinicalTrials.gov
Per-arm endpoint measurements with 95% confidence intervals where reported. Source: trial results section.
Factor IX Activity LevelsPrimary· 6 weeks post-dose
To confirm that a single dose of 2x10\^13 gc/kg AMT-061 (CSL222) resulted in factor IX activity levels of ≥5% at 6 weeks after dosing measured by the one-stage (activated partial thromboplastin \[aPTT\]-based) assay.
Group
Value
95% CI
AMT-061 (CSL222)
30.6
± 6.97
Annualized Exogenous Factor IX UsageSecondary· 52 weeks post-dose
Annualized use was calculated as the normalized amount of therapy administered per baseline weight, extrapolated where necessary from any time period less or greater than 1 year. Therapy administered included the total dosage of FIX given as prophylaxis and on-demand. Use for invasive procedures was not included.
Group
Value
95% CI
AMT-061 (CSL222)
7.1
± 6.4
Annualized Bleeding Rate (ABR)Secondary· 5 years post-dose
ABR was calculated as the ratio of the number of bleeds to the number of days in the time interval multiplied by 365.25.
All bleeds (Spontaneous + Traumatic + Joint)
Group
Value
95% CI
AMT-061 (CSL222)
0.14
Spontaneous bleeds
Group
Value
95% CI
AMT-061 (CSL222)
0.07
Traumatic bleeds
Group
Value
95% CI
AMT-061 (CSL222)
0.07
Joint bleeds
Group
Value
95% CI
AMT-061 (CSL222)
0.00
Factor IX Activity LevelsSecondary· 52 weeks post-dose
Measured by the one-stage (aPTT-based) assay.
Group
Value
95% CI
AMT-061 (CSL222)
40.8
± 9.45
Number of Participants Remaining Free of Continuous ProphylaxisSecondary· 1 year post-dose
Participants with no usage of continuous factor IX prophylaxis after AMT-061 (CSL222) treatment were considered free from continuous factor IX prophylaxis use.
Group
Value
95% CI
AMT-061 (CSL222)
3
Annualized Exogenous Factor IX Usage Post-Continuous ProphylaxisSecondary· Up to 5 years post-dose
The post-continuous-prophylaxis period began on the day after the end of continuous (routine) prophylaxis.Therapy administered included the total dosage of FIX given as prophylaxis and on-demand. Use for invasive procedures was not included.
Group
Value
95% CI
AMT-061 (CSL222)
342.1
± 592.5
Number of Participants With Treatment Emergent (TE): Adverse Events (AE), Mild, Moderate, and Severe AEs, AEs Related and Unrelated to the Study Treatment, and Serious AEsSecondary· Up to 5 years post-dose
Participant with TEAEs
Group
Value
95% CI
AMT-061 (CSL222)
3
Participant with mild TEAEs
Group
Value
95% CI
AMT-061 (CSL222)
3
Participant with moderate TEAEs
Group
Value
95% CI
AMT-061 (CSL222)
2
Participant with severe TEAEs
Group
Value
95% CI
AMT-061 (CSL222)
2
Participants with TEAEs related to study treatment
Group
Value
95% CI
AMT-061 (CSL222)
1
Participants with TEAEs unrelated to study treatment
Group
Value
95% CI
AMT-061 (CSL222)
3
Participants with serious TEAEs
Group
Value
95% CI
AMT-061 (CSL222)
1
Number of Participants With Clinically Meaningful Findings in Hematology and Serum Chemistry ParametersSecondary· Up to 5 years post-dose
Clinically meaningful findings were defined as values which were outside the standard normal reference ranges for hematology and serum chemistry parameters.
Group
Value
95% CI
AMT-061 (CSL222)
0
Number of Participants With Newly Occurring or Worsening Potentially Clinically Significant Changes in Alanine Aminotransferase (ALT) and Aspartate Aminotransferase (AST) LevelsSecondary· From baseline and up to 5 years post-dose
Post-baseline newly occurring or worsening potentially clinically significant ALT and AST levels were defined as values greater than twice the baseline value.
AST
Group
Value
95% CI
AMT-061 (CSL222)
1
ALT
Group
Value
95% CI
AMT-061 (CSL222)
1
Number of Participants Receiving Corticosteroids for AST and ALT ElevationsSecondary· Up to 5 years post-dose
Group
Value
95% CI
AMT-061 (CSL222)
0
Number of Participants Positive With AAV5 and Factor IX Neutralising Antibodies in SerumSecondary· Baseline and at 5 years post-dose
At Baseline for AAV5
Group
Value
95% CI
AMT-061 (CSL222)
3
At 5 years post dose for AAV5
Group
Value
95% CI
AMT-061 (CSL222)
3
At Baseline for FIX
Group
Value
95% CI
AMT-061 (CSL222)
0
At 5 years post dose for FIX
Group
Value
95% CI
AMT-061 (CSL222)
0
Number of Participants With AAV5 Capsid-specific T Cell ResponseSecondary· Up to Week 52
Group
Value
95% CI
AMT-061 (CSL222)
1
Adverse events — posted to ClinicalTrials.gov
Time frame: 5 years post-dose.
Reporting threshold: 5%.
Adverse-event reports describe events observed during the trial — not all are caused by the drug.
This is an open-label, single-dose, single-arm, multi-center trial, with a screening, a treatment + post-treatment follow-up phase, and a long-term follow-up phase.
The IMP AMT-061 is a recombinant adeno-associated viral vector of serotype 5 (AAV5) containing the Padua variant of a codon-optimized human FIX complementary deoxyribonucleic acid (cDNA) under the control of a liver-specific promoter. The IMP is identified as AAV5-hFIXco-Padua (AMT- 061). The pharmaceutical form of AMT-061 is a solution for intravenous infusion.
The administered dose of AMT-061 will be 2 x 10\^13 gc/kg.
Publications & conference data
8 peer-reviewed publications reference this trial (live from Europe PMC):
NCT07080905 — Phase 3, Open-label, Single-dose Study of CSL222 in Adolescent Male Subjects (≥ 12 to < 18 Years of Age) With Severe or
· Phase 3
· recruiting
NCT06727669 — Longitudinal Cohort of Thrombosis and Hemostasis Diseases
· recruiting
NCT06565481 — Measurement Properties in People with Hemophilia
· NA
· recruiting
NCT06379789 — A Study to Investigate the Safety and Effectiveness of a Coagulation Factor IX Gene Insertion Therapy (REGV131-LNP1265)
· Phase 1, PHASE2
· recruiting
NCT06399289 — Recombinant Fusion Protein Linking Coagulation Factor IX With Albumin (rIX-FP) in Chinese Subjects With Hemophilia B Pre
· Phase 3
· active not recruiting
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Publications: Europe PMC API search by NCT ID, retrieved 10 June 2026
Drug + disease cross-links: matched in real time against Drug Landscape's normalised drug + company + condition tables
Sponsor: as reported to ClinicalTrials.gov by CSL Behring
Last refreshed: 28 June 2024
Drug Landscape aggregates and links these public records for informational use only. Always verify against the primary source before clinical or regulatory decisions. Canonical URL: https://druglandscape.com/trial/NCT03489291.