The project is an observational, multi-central, prospective, non-interventional and open-label data collection study on secondary prophylaxis with recombinant FVIII products in adolescents and adults with severe hemophilia A (FVIII < 1%).

It will be a controlled observation of patients on secondary prophylaxis versus on-demand treatment regimen. Patients will be enrolled preferably on a 1:1 basis with regards to prophylaxis and on-demand treatment.

The patient enrollment period will be 2 years with a follow-up (observation period) of 2 years for each patient. Based on the primary effectiveness parameters (joint bleeds and overall bleeds per year) an observation period of 2 years is considered sufficient although it has to be admitted that it is rather short to assess the progression of orthopedic status. Previously treated prophylaxis patients with at least 50 exposure days and patients with continuing prophylaxis treatment will be included.

Inclusion Criteria:

• Age ≥ 18 years
• Severe hemophilia A (FVIII<1%) diagnosis
• Prior treatment or ongoing treatment with on-demand or prophylaxis regimens according to Turkish guidelines and requirements
• Previously treated patients with at least >50 exposure days
• Written informed consent signed by patient/legal representative

Exclusion Criteria:

• Currently on immune tolerance treatment
• Platelet count < 75,000/mm3
• Participation in another study
• Existence of inhibitors in the past and in the last currently available blood sample prior to study start (Bethesda titer < 0.6 BU/ml)
• Existence of inhibitor history in family members who also are diagnosed with hemophilia A
• Having been on primary prophylaxis as defined in the introduction
• Participation in another study

Adult haemophilia patients already on treatment with commercially available recombinant FVIII products.

Availability of this study's data will be determined according to Bayer's commitment to the EFPIA/PhRMA "Principles for responsible clinical trial data sharing". This pertains to scope, timepoint and process of data access. As such, Bayer commits to sharing upon request from qualified researchers patient-level clinical trial data, study-level clinical trial data, and protocols from clinical trials in patients for medicines and indications approved in the US and EU as necessary for conducting legitimate research. This applies to data on new medicines and indications that have been approved by the EU and US regulatory agencies on or after January 01, 2014. Interested researchers can use www.clinicalstudydatarequest.com to request access to anonymized patient-level data and supporting documents from clinical studies to conduct research. Information on the Bayer criteria for listing studies and other relevant information is provided in the Study sponsors section of the portal.