Multicentre, randomized, open-label study of on-demand treatment with two prophylaxis regimens of recombinant coagulation factor IX in haemophilia B subjects.

Few randomized studies have reported on the use of factor IX (FIX) for secondary prophylaxis in haemophilia B patients. This study aimed to evaluate the efficacy and safety of two secondary prophylaxis regimens of recombinant coagulation FIX, nonacog alfa, compared with on-demand therapy. Male subjects aged 6-65 years with severe or moderately severe haemophilia B (FIX:C ≤ 2, n = 50) and ≥12 bleeding episodes (including ≥6 haemarthroses episodes) within 12 months of study participation were enrolled in this multicentre, randomized, open-label, four-period crossover trial. The primary measure was the annualized bleeding rate (ABR) of two prophylactic regimens vs. on-demand therapy. In the intent-to-treat group, mean ABR values were 35.1, 2.6 and 4.6 for the first on-demand period, the 50 IU kg(-1) twice-weekly period, and the 100 IU kg(-1) once-weekly period respectively. Differences in ABR between the first on-demand period and both prophylaxis regimens were significant (P < 0.0001); no significant differences were observed between prophylaxis regimens (P = 0.22). Seven serious adverse events occurred in five subjects, none related to study drug. Results demonstrated that secondary prophylaxis therapy with nonacog alfa 50 IU kg(-1) twice weekly or 100 IU kg(-1) once weekly reduced ABR by 89.4% relative to on-demand treatment. Both prophylaxis regimens demonstrated favourable safety profiles in subjects with haemophilia B.