BAY 94–9027, a PEGylated Recombinant Human FVIII, Shows Less Immunogenicity Compared to Un-PEGylated Recombinant FVIII

BAY 94–9027, a recombinant FVIII candidate containing a single, large, branched polyethylene glycol (PEG) molecule conjugated to a specific amino acid, is intended for replacement therapy in hemophilia A. It has been demonstrated to have extended efficacy due to prolonged half life compared to un-PEGylated FVIII in preclinical models(Mei et al. Blood, 2010 118(2) 270–279). This may allow less frequent treatment than with current FVIII products.

Binding (bAB) and activity neutralizing antibodies (nAB) were measured in 3 animal models: hemophilia A mice (FVIII deficient), normal rats and normal rabbits, both with a normal coagulation system. Male hemophilia A mice received once weekly intravenous (IV) injections of BAY 94–9027 for 5 weeks. An un-PEGylated rFVIII molecule (rFVIII) was injected as comparator at the same frequency to give comparable exposure by AUC or dose. Normal rats and rabbits were dosed IV every other day for 2 weeks and blood samples were analyzed for antibodies during treatment and after the end of treatment. Analysis of bABs was based on an ELISA assay. The analysis of nABs was based on a modified FVIII Chromogenic assay (Coatest SP FVIII, Dia Pharma) assay. nAB titers were defined as 50% inhibition of 1 IU/mL rFVIII (in accordance to the definition of FVIII Bethesda units).

Previous nonclinical experiments show that animals are likely to have a much higher frequency of anti-FVIII antibody formation than is seen in humans due to the foreignness of this human protein in animals. As expected, antibodies to BAY 94–9027 or rFVIII developed in hemophilia A mice, rats and rabbits since the human protein acts as antigen. In the day 21 and day 36 mouse samples, bABs and nABs against BAY 94–9027 and rFVIII were detected in a time- and dose-dependent manner. By day 21 (after 3 administrations), mice treated with rFVIII showed statistically higher mean titers and more mice had measurable antibodies compared to animals treated with BAY 94–9027 at the same dose. By day 36 (after 5 administrations), animals treated with rFVIII showed statistically higher mean titers than those treated with BAY 94–9027 when comparing both, doses or overall exposure (AUC). At the end of the study, 17/36 mice (47%) treated with BAY 94–9027 had bAB titers, of which 8 (47% of animals with binding antibodies or 22% of all mice treated with BAY 94–9027) showed neutralizing (inhibitory) potential. Whereas, 20/24 (83%) mice treated with rFVIII (un-PEGylated comparator) had detectable bAB titer, of which 18 (90% of animals with binding antibodies or 75% of all animals treated with rFVIII) showed neutralizing potential. In normal rats and rabbits anti-drug bAB and nABs were assessed on days 7, 9 and 15 during treatment and twice after the end of the 2 week treatment. Results confirmed the findings in Hemophilia A mice that, generally more animals responded with bAB and nABs to rFVIII than with BAY 94–9027, the PEGylated protein.

The results indicate that BAY 94–9027, which has the same acute efficacy and prolonged duration of protection from bleeding, as seen in hemophilia A mouse efficacy studies (Mei et al. Blood, 2010 118(2) 270–279), was significantly less immunogenic in hemophilia A mice, normal rats and normal rabbits when compared to un-PEGylated rFVIII. This confirms findings with other PEGylated proteins, which indicate that specially branched PEGs may shield antigenic epitopes on the protein surface and can make it less immunogenic (BN Novicov et al. J Control Release, 2010. doi:10.1016/j.jconrel.2010. 06.003). Clinical studies need to assess if these findings can be confirmed in humans.

Ivens: Bayer HealthCare Pharmaceuticals: Employment, Equity Ownership. Zierz: Bayer Schering Pharma: Employment, Equity Ownership. Haaning: Bayer HealthCare Pharmaceuticals: Employment, Equity Ownership. McDonald: Bayer HealthCare Pharmaceuticals: Employment, Equity Ownership.