In vitro stability of recombinant human factor VIII (Recombinate((TM)))

Factor VIII (FVIII) is currently administered in diverse settings and by a range of methods, and it is important that the stability of specific FVIII preparations be documented for these varying uses. This study of Recombinat e(TM) recombinant human FVIII (rhFVIII) evaluated: (i) thermostability; (ii ) photostability; (iii) stability during simulated continuous infusion; and (iv) stability after dilution. This evaluation was conducted over a range of initial rhFVIII potencies and under differing conditions of temperature, light exposure, dilution and heparin usage. FVIII biological activity was measured by one-stage and chromogenic substrate assays. Microbiological ass essment was also performed. Lyophilized rhFVIII was found to be highly ther mostable, as evidenced by an energy of activation (E-a) of 16.2 kcal mol(-1 ) and recovery of 99.3% of initial activity after incubation for 6 months a t 40 degrees C and 93.8% at 60 degrees C for 2 months. No significant loss of activity could be detected after accelerated simulated natural daylight exposure of lyophilized rhFVIII, although partial activity loss was observe d after similar exposure of reconstituted rhFVIII. Shielding in foil wrap e ffectively prevented such photodegradation of reconstituted rhFVIII. Based upon these results, exposure of lyophilized rhFVIII to sunlight is unlikely to affect stability adversely. Activity of reconstituted rhFVIII (22-106 I U mL(-1)) remained stable during simulated continuous infusion for 96 h at ambient (20-25 degrees C) and elevated (28-32 degrees C) temperature, and i n the presence or absence of 1 U mL(-1) heparin. After dilution of reconsti tuted rhFVIII, an immediate 14-42% loss of expected rhFVIII activity was ob served depending upon diluent composition. Accordingly, potential partial l oss of rhFVIII activity should be taken into account when dilution is being considered. rhFVIII remained sterile at least 96 h during simulated contin uous infusion. rhFVIII is a robust preparation exhibiting biological stabil ity under a wide array of clinically relevant conditions.