The rapid clearance of factor IX (FIX) necessitates frequent intravenous IV administrations to achieve effective prophylaxis for patients with hemophilia B (HB). Subcutaneous (SC) administration would be a preferred route of administration but has been limited by low bioavailability and potency of the marketed FIX products. CB2679d/ISU304 with enhanced biological properties was developed using a rational protein design approach and has resistance to inhibition by ATIII, increased affinity for FVIIIa, increased catalytic activity and resultant 20-fold enhanced potency in vitro (clotting activity) and in vivo (the tail clip model) and 8-fold increased duration of aPTT activity in vivo compared to recombinant wild-type FIX dosed at the same mass.

ISU304 (4622 IU/mg) was injected into HB mice SC with a single dose ISU304 at 0.02, 0.05 or 0.15 mg/kg and sampled at 4, 6, 8, 24 hours. Groups of wild-type mice received ISU304 0.02, 0.05 or 0.15 mg/kg SC and BeneFIX (273 IU/mg) 0.15 mg/kg SC, and sampled at 0.25, 1, 4, 8, 24, 48, 72, and 96 hours. Daily SC injection in HB mice of ISU304 at 0.05 mg/kg was sampled at 24, 48, 72 and 96 hours. FIX antigen was measured using a sandwich ELISA and FIX activity was measured using a one-stage clotting assay on Stago Compact. Pharmacokinetics of FIX was performed using PKSolver.

There was a dose-dependent increase of plasma FIX antigen with SC ISU304. Mass-based pharmacokinetic profiles of ISU304 (t1/2, 18 hours; Tmax,8 hours, Bioavailability, 19-22%) were similar to those of BeneFIX (t1/2, 20 hours; Tmax, 8 hours, Bioavailability, 16%). Due to ISU304 high specific activity, SC dose of ISU304 yields much higher FIX activities in mouse plasma compared with the same mass dose of BeneFIX.

Daily SC dosing of ISU304 230 IU/kg reached steady-state plateau FIX 8% activity after three injections.

The bioavailability and increased potency of CB2679d/ISU304 facilitates the initiation of the Phase 1 subcutaneous dosing study in individuals with hemophilia B.

Figure 1
Figure 1.
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Table 1
Table 1.
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Figure 2
Figure 2.
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Disclosures

Hong:ISU Abxis: Employment. Levy:Catalyst Biosciences: Employment. Jung:ISU Abxis: Employment. Park:ISU Abxis: Employment. Seo:ISU Abxis: Employment. Seo:ISU Abxis: Employment. Madison:Catalyst Biosciences: Employment, Equity Ownership, Patents & Royalties.

Topics:
hemophilia b, mice, pharmacokinetics, factor ix concentrates, antigens, activated partial thromboplastin time measurement, antithrombin iii, drug administration routes, factor ix, single-dose regimen

Author notes

*

Asterisk with author names denotes non-ASH members.

© 2016 by The American Society of Hematology
2016
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