Bioequivalence, Heat Stability and Reconstitution of Room Temperature Stable Recombinant Activated Factor VII (rFVIIa-RT)

Recombinant FVIIa (rFVIIa) is a well-established treatment for bleeding episodes in patients with congenital or acquired hemophilia A or B with inhibitors to factors VIII and IX and patients with FVII deficiency. rFVIIa bypasses the need for clotting factors VIII and IX and promotes local hemostasis where tissue factor is exposed and activated platelets are present. At pharmacologic doses, rFVIIa can directly activate factor X on the surface of activated platelets, forming a stable haemostatic plug. In FVII deficiency, rFVIIa provides FVII as replacement. The original rFVIIa product had to be refrigerated for storage of up to 3 years.

rFVIIa-RT is a recombinant coagulation factor VIIa that is room temperature stable, with recommended storage between 2–25°C for up to two years prior to reconstitution and up to 3 hours following reconstitution. Room temperature stability was achieved through the addition of 2 new excipients to the lyophilized powder (sucrose, a stabilizer, and methionine, an antioxidant) and the use of a diluent containing histidine in sterile water. This abstract summarizes three studies regarding key pharmacokinetic bioequivalence between this product and its predecessor, rFVIIa, its heat stability, and reconstitution data with various diluents.

Pharmacokinetic equivalence of rFVIIa-RT with original rFVIIa was examined in a randomized, double blind, cross-over study by Bysted et al. Twenty-five healthy subjects were randomized to receive a single 90 mcg/kg dose of rFVIIa-RT or original rFVIIa and then crossed over to receive the other treatment after a 2–3 week washout. The specific activities of FVIIa were nearly identical over time for both products. The mean ratio rFVIIa-RT/original rFVIIa for the area under the plasma activity-time curve from time 0 to last quantifiable activity was 0.93 (90% CI: [0.89–0.96]) and met the study’s predefined bioequivalence criteria. All other pharmacokinetic parameters were comparable, as were the coagulation parameter profiles. No serious adverse events were reported and no FVIIa antibodies were detected.

The in vitro stability of lyophilized and reconstituted rFVIIa-RT was tested in various storage conditions by Nedergaard et al. For the lyophilized product, FVIIa specific activity was maintained for 24 months at 5°C and 25°C, for 12 months at 30°C (86°F), and for 6 months when stored sequentially at 40°C followed by 12 months at 25°C. Activity was also maintained when product was stored at higher temperatures (30°C, 50°C, 60°C, and 70°C) for 12 hours, as temperature excursions might be encountered by patients during routine transport. To simulate likely practice, in which the product may be stored both in and out of refrigeration, rFVIIa-RT was cycled from 5°C to 25°C once daily for 5 days, with no observed loss of activity. For reconstituted product, the specific activity remained stable for 6 hours at 25°C and for 24 hours at 5°C.

The in vitro stability of rFVIIa-RT was tested after reconstitution with appropriate volumes of inappropriate solvent (sterile water for injection or physiologic saline) or the appropriate histidine solvent, and with inappropriate volumes of saline, histidine solvent, or a mixture of saline and histidine solvent (Petersson et al.). The product remained chemically and physically stable for up to 6 hours of storage at 25°C or for up to 24 hours of storage at 5°C when reconstituted with an inappropriate type or volume of solvent.

rFVIIa-RT provides a convenient formulation that is stable and maintains its activity profile at temperatures up to 25°C and under various ‘real world’ conditions, thereby removing the need for refrigerated storage and transportation of factor and potentially improving the convenience of treatment of hemophilia patients with inhibitors.