IB1001, an Investigational Recombinant Factor IX, Pharmacokinetics in Pediatric Patients with Hemophilia B.

IB1001 is a recombinant factor IX product being investigated for the treatment and prevention of bleeding in individuals with hemophilia B. Pharmacokinetics (PK) in adults (>12 years) demonstrated that IB1001 had results similar to the currently available recombinant FIX with respect to parameters such as terminal phase half-life and incremental recovery.

We report the interim findings from a PK assessment in children <12 years, with severe hemophilia B (FIX <2%), >50 prior exposure days to FIX, and no history of or currently detectable inhibitor to FIX.

Non-randomized, open-label PK study with patients receiving 75±5 IU/kg of IB1001 following a washout period of ≥4 days from a previous FIX infusion. Factor IX levels were determined pre-infusion and at 15–30 minutes, 4–6, 24–26, and 68–72 hours post-infusion. Additional samples could be drawn at 1–3 and 10–14 hours.

Calculated PK parameters were: half-life (β-phase t_1/2, determined using a robust regression approach [Lee ML et al. XVI^th ISTH Congress, Florence, Italy, 1997]) but generally assuming a single compartmental model because of the small number of points, maximum plasma concentration (C_max), in vivo recovery (IVR) and AUC_(0-∞) (determined by the trapezoidal rule). In addition, the AUC_(0-t) and mean residence time (MRT) were calculated.

When compared to the findings previously reported with IB1001 in adult (≥12 years of age) subjects (Martinowitz U et al. Haemophilia, 18, 2012), the results in pediatric patients demonstrate a more rapid metabolism of factor IX as is indicated by the shorter terminal half-life (mean±SD of 19.3±7.8 h versus 29.6±18.2 h in adults) and the smaller AUC_0-∞ (mean±SD of 1059±264 versus 1668±598 in adults). In addition, the in vivo recovery was lower (mean±SD of 0.69±0.21) versus that seen in adults (mean±SD of 0.98±0.22). These results are similar to those reported by Berntorp et al (Haemophilia, 7, 2001) with nonacog alfa.

The pharmacokinetics of IB1001 has previously been shown to be non-inferior to nonacog alfa, another recombinant factor IX, in hemophilia B individuals >12 years of age. The current study is intended to provide information on children <12 and, particularly, <6 years of age. IB1001 is metabolized faster and has a lower recovery than the comparable findings in patients >12 years of age. Although the study is ongoing, these may represent important implications for the potential use of IB1001 in pediatric patients.

Gomperts:Inspiration Biopharmaceuticals Inc: Consultancy. Apte:Inspiration Biopharmacauticals Inc: Research Funding. Chaudhuri:Inspiration Biopharmaceuticals Inc: Research Funding. John:Inspiration Biopharmaceuticals Inc: Research Funding. Ramanan:Inspiration Biopharmaceuticals Inc: Research Funding. Liesner:Inspiration Biopharmaceuticals Inc: Research Funding. Shapiro:Inspiration Biopharmaceuticals Inc: Honoraria, Research Funding. Mills:Inspiration Biopharmaceuticals Inc: Employment. Lee:Inspiration Biopharmaceuticals Inc: Employment.