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

ConditionHemophilia B

Trial statusRecruiting

Trial phasePhase 3

Trial typeInterventional

Biological sexMale

Age138-206

SponsorCSL Behring

About this trial

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 criteria

This trial does not accept healthy volunteers

Qualifiers

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.

Disqualifiers

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.

Trial design

Design model

Single group

Treatments tested in this trial

CSL222 (Adeno-associated viral vector serotype 5 [AAV5]-hFIXco-Padua)
Genetic
Administered as a single IV infusion.

Treatment groups

20 Participants

are divided into 1 treatment group

Group A: CSL222Experimental treatment 1 intervention

Trial outcomes

Primary outcomes

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)

Secondary outcomes

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.

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

Mean annualized consumption (IU/year) of FIX replacement therapy (excluding FIX replacement for invasive procedures).

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)