Prophylaxis Study of Marstacimab in Pediatric Hemophilia Participants With or Without Inhibitors

You may be able to join if

• Participants must be male, of appropriate age, and of a minimum body weight at the time of signing the informed consent/assent as follows: •For enrollment in the first age group, participant must be ≥12 to <18 years of age with a minimum body weight of 25 kg at the time of informed consent/assent. •For enrollment in the second age group, participant must be ≥6 to <12 years of age with a minimum body weight of 19 kg at the time of informed consent/assent. •For enrollment in the third age group, participant must be ≥1 to <6 years of age at the time of informed consent/assent. The minimum body weight for this age group will be determined based on emerging data from prior enrolled age groups.
• Participants with a diagnosis of severe hemophilia A or moderately severe to severe hemophilia B (FVIII activity <1% or FIX activity ≤2%, respectively) documented by historical evidence prior to Day 1 Pre-Dose (Visit 2). If the participant’s historical factor activity is not available or documented, the severity of the participant’s hemophilia may be confirmed by a local clinical laboratory or the central laboratory for this study prior to Day 1 Pre-Dose (Visit 2).
• Participants who have at least 1 year of diary information and/or medical records available in which exogenous FVIII or FIX replacement or bypass agent infusions and hemophilic bleeding episodes were consistently documented over the 12 months prior to the time of informed consent/assent.
• 4.Participants who are enrolled into the Non-Inhibitor Cohort must also meet the following criteria: •No detectable inhibitor (≥0.6 BU/mL at the central testing lab) against FVIII or FIX prior to Day 1 Pre-Dose (Visit 2). (o)Participants who have a de novo low titer inhibitor (<5 BU/mL) at the central lab at the time of screening but have a documented absence of an inhibitor while on factor-replacement therapy at a local lab and FVIII or FIX recovery ≥60% of expected value or during Screening, and who receive a negative inhibitor result (<0.6 BU/mL, at the central lab) upon retest within 6 weeks after the initial positive result may be considered for eligibility on a case-by-case basis with discussion and agreement from the Pfizer medical monitor. •No documented history of high titer inhibitors (≥5 BU/mL or greater than the ULN for the testing laboratory) against FVIII or FIX in the 5 years prior to the time of informed consent/assent. •No low titer inhibitor (<5 BU/mL) refractory to FVIII or FIX replacement and with recovery <60% of expected in the 5 years prior to the time of informed consent/assent. •For participants who have undergone ITI, successful completion of ITI at least 5 years prior to the time of informed consent/assent and no evidence of inhibitor recurrence (permanent or temporary) as indicated by detection of an inhibitor, or FVIII or FIX recovery <60% since completing ITI. •Participants who have at least 50 documented exposure days to FVIII/FIX replacement product (recombinant, plasma-derived, or long-acting FIX product). •Participants must be on a stable routine prophylaxis regimen (defined as treatment by IV injection of factor concentrate to prevent bleeding) with FVIII/FIX replacement and have demonstrated at least 80% compliance with a stable prophylaxis regimen. a.Participants must be on a stable prophylaxis regimen during the 12 months prior to informed consent/assent. b.Exogenous FVIII/FIX replacement infusions and hemophilic bleeding episodes were documented over the previous 12 months prior to the time of informed consent/assent.
• 5.Participants who are enrolled into the Inhibitor Cohort must also meet the following criteria: •Documentation of current high titer inhibitor (≥5 BU/mL); or current low titer inhibitor (<5 BU/mL) refractory to FVIII or FIX replacement and with FVIII or FIX recovery <60% of expected within previous 12 months prior to the time of informed consent/assent. •Participants who have documented inhibitors while on factor-replacement therapy but who do not meet the high quantitative inhibitor criteria described in the prior bullet at the time of screening (eg, participant with a previously documented high-titer inhibitor ≥5 BU/mL) and whose condition precludes re-challenge with FVIII or FIX replacement) may be considered for eligibility on a case-by-case basis with discussion and agreement from the Pfizer medical monitor. •Hemophilia A participants with on-demand treatment regimen with ≥12 bleeding episodes or hemophilia B participants with on-demand treatment regimen with ≥8 bleeding episodes (spontaneous or traumatic) necessitating treatment with bypass factor in the 12 months prior to informed consent/assent. a.Participants must be on an on-demand bypass treatment regimen during the 12 months prior to informed consent/assent. b.On-demand bypass infusions and hemophilic bleeding episodes were documented over the previous 12 months prior to the time of informed consent/assent. c.Surgical bleeding episodes do not apply to this criterion. •Participants who meet the bleeding criteria noted above and who are on routine prophylaxis (defined regularly scheduled and regimented administration by IV injection of bypass factor to prevent bleeding) and have demonstrated at least 80% compliance with scheduled prophylaxis regimen during the 12 months prior to the time of informed consent/assent, may be considered for eligibility on a case-by-case basis with discussion and agreement from the Pfizer medical monitor.