Eptacog Beta in Glanzmann's (HeT_LFB-Strength-Study_FID531)

Proportion of acute bleeding events successfully treated with EB within 24 hours of the first EB administration based on an "excellent or good" response on a 4-point hemostatic efficacy scale and without rebleeding before 36 hours.

Hemostatic Efficacy Scale:

None = No effect; bleeding unchanged or worsened; continued treatment needed.

Moderate = Some effect (e.g., pain decreased, bleeding signs improved) but bleeding continued; further treatment needed.

Good = Bleeding symptoms are largely reduced but not completely resolved; no further EB infusions are needed.

Excellent = Full relief of bleeding symptoms; no additional EB infusion required.

The number of bleeding events occurring while receiving routine EB prophylaxis will be compared with the number of bleeding events that occurred during on-demand therapy.

*This outcome applies only to the optional interventional prophylaxis phase.

Safety of EB will be measured by the number of treatment-emergent adverse events, treatment-emergent serious adverse events, and treatment-emergent potentially clinically significant laboratory values reported during the interventional phases compared to those reported during the non-interventional observational phase.

The EQ-5D-Y-5L is a child-friendly, five-dimension, five-level instrument assessing: Mobility, Looking After Myself, Doing Usual Activities, Having Pain or Discomfort, and Feeling Worried, Sad, or Unhappy.

Each dimension has five response levels (1 = no problems to 5 = extreme problems/unable to do). Respondents select one statement per dimension describing their health on the assessment day, forming a 5-digit profile summarizing their health state. For example, code 11234 indicates no problems with mobility or looking after myself, slight problems doing usual activities, some pain or discomfort, and feeling very worried, sad, or unhappy. Higher scores reflect greater severity.

*15 months applies to the optional phase only.

The EuroQol 5 Dimension 5 Level (EQ-5D-5L) is a self-report survey that measures quality of life across 5 domains: mobility, self-care, usual activities, pain/discomfort, and anxiety/depression. It captures how people feel across five dimensions, each of which has five levels: 1 = no problems to 5 = extreme problems/unable to do. The five answers produce a unique 5-digit health state, for example, 11234, that describes the young person's health state. For example, the code 11234 describes a health state where there are no problems with walking about (mobility) or looking after myself, a little bit of a problem with doing usual activities, some pain or discomfort, and feeling really worried, sad, or unhappy.

*15 months applies to the optional phase only.

The PROMIS Fatigue item banks assess a range of self-reported symptoms, from mild subjective feelings of tiredness to an overwhelming, debilitating, and sustained sense of exhaustion that likely decreases one's ability to execute daily activities and function normally in family or social roles. Fatigue is divided into the experience of fatigue (frequency, duration, and intensity) and the impact of fatigue on physical, mental, and social activities. The fatigue short forms are universal and assess fatigue over the past seven days. PROMIS measures use a T-score metric in which 50 is the mean of a relevant reference population and 10 is the standard deviation (SD) of that population. On the T-score metric:

A score of 40 is one SD lower than the mean of the reference population. A score of 60 is one SD higher than the mean of the reference population. Higher scores equal more fatigue.

*15 months applies to the optional phase only.

The PROMIS Pediatric Fatigue Short Form will be used to assess fatigue based on age: self-report (ages 8-17) and parent-proxy (ages 5-17). It measures fatigue symptoms and their impact on physical, mental, and social activities over the past 7 days. Items reflect both the frequency and severity of fatigue. Scores are reported as T-scores (mean = 50, SD = 10) based on a reference population. A higher T-score indicates greater fatigue (e.g., 60 = 1 SD above the mean). This measure captures the participant's ability to carry out daily activities and participate in usual roles.

*15 months applies to the optional phase only.

The MIQ was developed to assess the effect of heavy menstrual bleeding (menorrhagia) on various aspects of a woman's quality of life (QoL). It is a brief, 6-item patient-reported outcome measure that focuses on: Perceived amount of blood loss, limitations in work, physical and social activities, and changes due to treatment. Each item is rated on a 6-point scale, indicating the severity of impact (e.g., 0 = no effect, up to 5 = severe effect).

Total Score = Sum of all 6 items (range 0-30), with higher scores reflecting a greater negative impact of menorrhagia on daily life.

ETP concentration following ex vivo spiking in various concentrations of EB. Samples will be compared to baseline participants and healthy control samples.

Lag time and time to peak thrombin following ex vivo spiking in various concentrations of EB. Samples will be compared to baseline participants and healthy control samples.

Peak thrombin levels following ex vivo spiking in various concentrations of EB. Samples will be compared to baseline participants and healthy control samples.

ETP thrombin levels at 30 and 60 minutes following in vivo infusion of EB. Samples will be compared to pre-infusion baseline participant and healthy control samples.

Lag time and time to peak thrombin at 30 and 60 minutes following in vivo infusion of EB. Samples will be compared to pre-infusion baseline patient PRP and healthy control samples.

Peak thrombin at 30 and 60 minutes following in vivo infusion of EB. Samples will be compared to pre-infusion baseline patient platelet-rich plasma (PRP) and healthy control samples.

CT and CFT will be measured using rotational thromboelastometry following ex vivo spiking with various concentrations of EB. Samples will be compared to baseline samples and healthy control samples.

MCF will be measured using rotational thromboelastometry following ex vivo spiking with various concentrations of EB. Samples will be compared to baseline samples and healthy control samples.

The alpha angle will be measured using rotational thromboelastometry following ex vivo spiking with various concentrations of EB. Samples will be compared to baseline samples and healthy control samples.