The change from baseline in FVIII activity, as measured by chromogenic substrate assay, during Weeks 49 to 52 post-BMN 270 infusion. Each subject's FVIII activity level during Week 49 to 52 is defined as the median of the values obtained during week 49-52 with the analysis window defined. Baseline: prior to BMN 270 infusion while receiving FVIII prophylaxis. The baseline value is imputed as 1 IU/dL for each subject.

The change from baseline (assuming no treatment for severe hemophilia A) in FVIII activity, as measured by chromogenic substrate assay (CSA), at Week 52 (during Weeks 49 - 52) post-BMN 270 infusion. Each participant's FVIII activity level at Week 52 is defined as the median of the values obtained within the analysis window at Weeks 49-52. The baseline value will be imputed as 1 IU/dL, since there will be no washout of severe hemophilia A participants' usual FVIII prophylaxis (in order to avoid increasing the risk of bleeding) prior to BMN 270 infusion. Post-BMN 270 infusion values for FVIII activity will be excluded from analysis if obtained within 72 hours (or 3 calendar days if time is not available) since the last infusion of exogenous FVIII replacement therapy. Baseline: prior to BMN 270 infusion while receiving FVIII prophylaxis.

Change of the FVIII activity, as measured by chromogenic substrate assay, at Week 52 post-BMN 270 infusion.

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").

Adverse events (AEs) with onset or worsening after the investigational product were included. Participants with more than one AE of the same category were counted only once for that category. Serious adverse event (SAE)

Responder/Non responder status, where a responder was defined as a participant with median FVIII activity of \>= 5 IU/dL during Week 13-16 post-BMN 270 infusion

Values for FVIII activity were excluded from analysis if obtained within 72 hours since the last infusion of exogenous FVIII replacement therapy FVIII activity levels below the Lower limit of quantitation (LLOQ) will be imputed with 0 IU/dL Q1: 25% Percentile; Q3: 75% Percentile