F9 and hemophilia B: The orphan drugs nonacog alfa, eftrenonacog alfa and albutrepenonacog alfa (ATC: B02BD04) and the non-orphan medication nonacog gamma (ATC: B02BD04) are recombinant concentrates that replace the missing coagulation factor IX (FIX) in hemophilia B. An increasing prevalence trend was observed between 2011 and 2013, achieving a maximum of use in 2013, with values varying between 50.0% and 78.3% for most of the study period (Figure 1A).