Joint Bleeding Patterns in Patients Treated Prophylactically with an Extended Half-Life, Pegylated, Full-Length Recombinant Factor VIII (BAX 855)

BAX 855 is a pegylated full-length recombinant factor VIII (PEG rFVIII) built on ADVATE with an extended half-life and is in development for prophylaxis and treatment of bleeding in patients with hemophilia A. In a pivotal trial, 101 previously treated patients (PTPs) received BAX 855 for prophylaxis twice weekly (in the per protocol analysis set). At screening, 67/101 (66.3%) of patients had arthropathy (reported in medical history or history of joint surgery) and 69/101 (68.3%) had at least 1 target joint. A target joint was defined as a single joint (ankle, knee, hip, or elbow) with ≥ 3 spontaneous bleeding episodes in any consecutive 6-month period.

Overall, among these 101 PTPs, the mean (standard deviation) annualized joint bleeding rate (AJBR) was 1.8 (3.0) and 57.4% of patients had zero joint bleeding episodes. There were 32, 40, and 29 subjects with 0, 1-2, and ≥3 target joints, respectively, at screening. Patients with more target joints at screening experienced higher AJBRs: with mean AJBRs of 1.15, 1.84, and 2.58 for patients with 0, 1-2, and ≥3 target joints, respectively, at screening. Of the individual joints, ankle and knee joints had highest AJBRs.

BAX 855 demonstrated efficacy in the treatment of joint bleeding, with the majority of joint bleeding episodes, irrespective of target joint status, treated with 1-2 infusions: 92.8%, 91.9 % and 94.4% for patients with 0, 1-2, and ≥3 target joints, respectively, at screening. Hemostatic efficacy of BAX 855 at 24 hours was rated as excellent or good in >90% of patients, regardless of target joint status at screening.

Patients with 0 target joints at screening had 57.1% of joint bleeding episodes considered mild in severity, while patients with 1-2 or ≥3 target joints had 59.5% and 66.7% of joint bleeding episodes, respectively, rated moderate in severity. There were few joint bleeding episodes considered severe.

Similar doses per infusion of BAX 855 were used to treat joint bleeding episodes: the mean dose per BAX 855 infusion was 35, 33.8, and 36.2 IU/kg for patients with 0, 1-2, and ≥3 target joints, respectively.

In conclusion, BAX 855 demonstrated a favorable efficacy profile in the treatment of breakthrough joint bleeding episodes, and twice-weekly use was efficacious in prevention of bleeding, with the lowest overall AJBRs achieved in patients in the trial without target joints.