All bleeds comprises both treated and non-treated bleeds. In this definition, all bleeds are included, irrespective of treatment with coagulation factors, with the following exception: bleeds due to surgery/procedure are excluded. All bleeds are any reported bleeding events regardless of the use of FVIII or other treatments.

ABR for all bleeds= Number of bleeding episodes for all bleeds during the calculation period / total number of days during the calculation period * 365.25.

Baseline: prior to BMN 270 infusion while receiving FVIII prophylaxis.

EEP: From Week 5 post-BMN 270 infusion (Study Day 33) or the end of FVIII prophylaxis plus the washout period (3 days for products of standard half-life or plasma-derived and 5 days for products of extended half-life), whichever is later, to last visit by the data cut-off for the 2-year analysis, hereafter referred to as "Post FVIII Prophylaxis to Last Visit").

Rollover Population (n=112): Subjects who completed approximately 6 months participation in the non-interventional study 270-902 before enrolling in 270-301, were HIV-negative at study screening, and received BMN 270 infusion in 270-301.

ABR for treated bleeds=Number of bleeding episodes for treated bleeds during the calculation period/total number of days during the calculation period * 365.25

Bleeds that were treated with FVIII replacement therapy (recorded as "treatment for bleed") within 72 hours and were not associated with surgery or a procedure were included.

Baseline: prior to BMN 270 infusion while receiving FVIII prophylaxis.

EEP: From Week 5 post-BMN 270 infusion (Study Day 33) or the end of FVIII prophylaxis plus the washout period (3 days for products of standard half-life or plasma-derived and 5 days for products of extended half-life), whichever is later, to last visit by the data cut-off for the 2-year analysis, hereafter referred to as "Post FVIII Prophylaxis to Last Visit").

Rollover Population

The change from baseline (assuming no treatment for severe hemophilia A) in FVIII activity, as measured by chromogenic substrate assay, at Weeks 104 post-BMN 270 infusion.

Each subject's FVIII activity level at Week 104 is defined as the median of the values obtained at Week 104 with the analysis window defined. The baseline value is imputed as 1 IU/dL for each subject.

Note: One of the subject's wk104 duplicate data issue was corrected in the 3 year analysis per which the mean (standard deviation) values are reported in outcome measure table.

Baseline: prior to BMN 270 infusion while receiving FVIII prophylaxis.

Modified Intent-to-Treat (mITT) Population (n=132): All HIV-negative subjects at study screening who were dosed in 270-301.

The change from baseline in the annualized utilization (IU/kg/year) of exogenous FVIII replacement therapy in the Post FVIII Prophylaxis to Last Visit in the EEP.

The annualized utilization (IU/kg/year) of exogenous FVIII replacement therapy is defined as Sum of FVIII use (IU/kg) during calculation period/Total number of days during the calculation period ×365.25.

Baseline: prior to BMN 270 infusion while receiving FVIII prophylaxis.

EEP: From Week 5 post-BMN 270 infusion (Study Day 33) or the end of FVIII prophylaxis plus the washout period (3 days for products of standard half-life or plasma-derived and 5 days for products of extended half-life), whichever is later, to last visit by the data cut-off for the 2-year analysis, hereafter referred to as "Post FVIII Prophylaxis to Last Visit").

Rollover population

The change from baseline(assuming no treatment for severe hemophilia A) in Haemo-Qol-A score, at wk104 post-BMN 270 infusion.The Haemo-Qol-A questionnaire is a fit for purpose hemophilia-specific health related quality of life(HRQoL)questionnaire for adults consisting of 41 items covering 6 domains(Physical Functioning,Role Functioning,Worry,Consequences of Bleeding,Emotional Impact &Treatment Concerns). The Haemo-Qol-A items are answered on a 6-point Likert scale ranging from 0(none of the time)to 5 (all of the time).The recall period for the Haemo-Qol-A is one month (4-weeks).

The Haemo-QoL-A domain(physical functioning, role functioning, worry, consequences of bleeding, emotional impact, treatment concern) scores range from 0 to 5 and the total score is derived by summing each domain score (range, 0 to 30). Domain and total scores are transformed to a 0 (minimum) to 100 (maximum) scale with higher scores indicating a better or less impaired haemophilia related quality of life.

mITT Population: Modified Intent-to-Treat Population - all HIV-negative subjects dosed in 270-301.

Change from baseline was based on the subjects with available measurements at both time points.

The change from baseline (assuming no treatment for severe hemophilia A) in Haemo-Qol-A score, at week 104 post-BMN 270 infusion. The Haemo-Qol-A questionnaire is a fit for purpose hemophilia-specific health related quality of life (HRQoL) questionnaire for adults consisting of 41 items covering six domains (Physical Functioning, Role Functioning, Worry, Consequences of Bleeding, Emotional Impact and Treatment Concerns).The Haemo-Qol-A items are answered on a 6-point Likert scale ranging from 0 (none of the time) to 5 (all of the time).The recall period for the Haemo-Qol-A is one month (4-weeks).

The Haemo-Qol-A physical functioning domain score is an average of each item value within a domain.The range of domain scores is 0 to 5; higher scores mean better HRQoL or less impairment for the domain. The physical functioning domain score is transformed to a 0 (minimum) to 100 (maximum) scale with higher scores indicating a better or less impaired haemophilia-related physical functioning

mITT population

Change from baseline was based on the subjects with available measurements at both time points.

The change from baseline(assuming no treatment for severe hemophilia A)in Haemo-Qol-A score, at week 104 post-BMN 270 infusion. The Haemo-Qol-A questionnaire is a fit for purpose hemophilia-specific health related quality of life(HRQoL)questionnaire for adults consisting of 41 items covering 6 domains(Physical Functioning,Role Functioning,Worry,Consequences of Bleeding,Emotional Impact and Treatment Concerns). The Haemo-Qol-A items are answered on a 6-point Likert scale ranging from 0(none of the time) to 5(all of the time). The recall period for the Haemo-Qol-A is one month (4-wks).

The Haemo-Qol-A consequences of bleeding domain score is an average of each item value within a domain. The range of domain scores is 0 to 5; higher scores mean better HRQoL or less impairment for the domain. The consequences of bleeding domain score is transformed to a 0 (minimum) to 100 (maximum) scale with higher scores indicating a better or less impaired haemophilia-related consequences of bleeding

mITT population.

Change from baseline was based on the subjects with available measurements at both time points.

The change from baseline (assuming no treatment for severe hemophilia A) in Haemo-Qol-A score, at week 104 post-BMN 270 infusion. The Haemo-Qol-A questionnaire is a fit for purpose hemophilia-specific health related quality of life (HRQoL) questionnaire for adults consisting of 41 items covering six domains (Physical Functioning, Role Functioning, Worry, Consequences of Bleeding, Emotional Impact and Treatment Concerns).The Haemo-Qol-A items are answered on a 6-point Likert scale ranging from 0 (none of the time) to 5 (all of the time). The recall period for the Haemo-Qol-A is one month (4-weeks).

The Haemo-Qol-A role functioning domain score is an average of each item value within a domain. The range of domain scores is 0 to 5; higher scores mean better HRQoL or less impairment for the domain. The role functioning domain score is transformed to a 0 (minimum) to 100 (maximum) scale with higher scores indicating a better or less impaired haemophilia-related role functioning.

mITT population

Change from baseline was based on the subjects with available measurements at both time points.