Preclinical safety and efficacy of a new recombinant FIX drug product for treatment of hemophilia B

Abstract

Baxter has developed a new recombinant factor IX (rFIX) drug product (BAX326) for treating patients with hemophilia B, or congenital FIX deficiency. An extensive preclinical program evaluated the pharmacokinetics, efficacy, and safety of BAX326 in different species. The efficacy of BAX326 was tested in three mouse models of primary pharmacodynamics: tail-tip bleeding, carotid occlusion, and thrombelastography. The pharmacokinetics was evaluated after a single intravenous bolus injection in mice, rats, and macaques. Toxicity was assessed in rats and macaques, safety pharmacology in rabbits and macaques, and immunogenicity in mice. BAX326 was shown to be efficacious in all three primary pharmacodynamic studies (P ≤ 0.0076). Hemostatic efficacy was dose related and similar for the three lots tested. Pharmacokinetic results showed that rFIX activity and rFIX antigen concentrations declined in a bi-phasic manner, similar to a previously licensed rFIX product. BAX326 was well tolerated in rabbits and macaques at all dose levels; no thrombogenic events and no adverse clinical, respiratory, or cardiovascular effects occurred. BAX326 was also shown to have a similar immunogenicity profile to the comparator rFIX product in mice. These results demonstrate that BAX326 has a favorable preclinical safety and efficacy profile, predictive of a comparable effect to that of the previously licensed rFIX in humans.

Fig. 1

Time to occlusion after treatment with rFIX, pdFIX, or buffer. Three lots of BAX326 (filled circle) were tested at 75 IU/kg to show lot-to-lot consistency. All lots were considered efficacious as median time to occlusion (3.3–4.8 min) was markedly reduced compared with buffer-treated animals (filled triangle >30 min = no occlusion; P = 0.00035, assessed for Lot 2 only). Median time to occlusion was 4.6 min after treatment with 75 IU/kg of the licensed rFIX (filled square) and 5.1 min after treatment with the licensed pdFIX (filled diamond)

Fig. 2

Time to clotting (R-time) of rFIX-treated and buffer-treated FIX ko mice. Median R-time in buffer-treated animals was 98.7 min. Treatment with 75 IU/kg of BAX326 led to a statistically significant reduction of time to clotting (54.5 min; P = 0.00074). Median R-time was similarly reduced to 56.2 min by treatment with 75 IU/kg of the active control item, a previously licensed rFIX

Fig. 3

Blood loss in FIX ko mice after treatment with different doses of BAX326 or buffer. Four doses of BAX326 were tested to obtain a dose–effect curve. Buffer-treated animals served as negative controls and showed a median total blood loss of 1,036 mg. Median blood loss was reduced to 927 mg by treatment with 10 IU/kg of BAX326 and to 204 mg by treatment with 25 IU/kg rFIX. Treatment with 75 IU/kg rFIX, the dose also used in the carotid occlusion and TEG studies, led to a median blood loss of 145 mg, which was shown to be statistically different from buffer (P = 0.0085). Treatment with 100 IU/kg further reduced median blood loss to 32 mg. Statistical evaluation proved a monotone dose–response relation (P = 0.0076). The higher inter-individual variation observed for 75 IU/kg than for 25 IU/kg BAX326 is consistent with published results [–15] and a known and accepted limitation of the model

Fig. 4

Pharmacokinetics of BAX326 and licensed rFIX (150 IU/kg rFIX) in macaques. The pharmacokinetic profiles of BAX326 (black) and the licensed rFIX (gray) after intravenous bolus administration of 150 IU/kg were similar for rFIX activity and rFIX antigen, declining in a generally bi-phasic manner