Preclinical pharmacokinetics and biodistribution of subcutaneously administered glycoPEGylated recombinant factor VIII (N8-GP) and development of a human pharmacokinetic prediction model.

Essentials N8-GP is an extended half-life recombinant factor VIII (FVIII) for the treatment of hemophilia A. Subcutaneous (SC) FVIII dosing might reduce the treatment burden of prophylaxis. SC N8-GP has a favorable PK profile in animal models and disappears from skin injection sites. Combined animal (SC) and clinical (IV) data suggest that daily SC dosing may provide prophylaxis. SUMMARY: Background N8-GP is an extended half-life recombinant factor VIII (FVIII) for the treatment of hemophilia A. Subcutaneous administration of FVIII may reduce the treatment burden of prophylaxis; however, standard FVIII products have low bioavailability after subcutaneous dosing in animals. Objective To evaluate the pharmacokinetics, effectiveness and local distribution of subcutaneously administered N8-GP in preclinical models and predict the human pharmacokinetic (PK) profile. Methods The pharmacokinetics of subcutaneously administered N8-GP were evaluated in FVIII knockout (F8-KO) mice and cynomolgus monkeys; a human PK prediction model in hemophilia A patients was developed. The hemostatic effect was evaluated in a tail vein bleeding model in F8-KO mice. The injection-site distribution and absorption of subcutaneously administered N8-GP were assessed in F8-KO mice by the use of temporal fluorescence imaging and immunohistochemistry. Results Subcutaneously administered N8-GP had a bioavailability, a first-order absorption rate and a half-life, respectively, of 24%, 0.094 h-1 and 14 h in F8-KO mice, and 26%, 0.33 h-1 and 15 h in cynomolgus monkeys. A dose-dependent effect of subcutaneously administered N8-GP on blood loss was observed in mice. A minimal amount of N8-GP was detected at the injection site 48-72 h after single or multiple dose(s) in F8-KO mice. Subcutaneously administered N8-GP was localized to the skin around the injection site, with time-dependent disappearance from the depot. PK modeling predicted that subcutaneously administered N8-GP at a daily dose of 12.5 IU kg-1 will provide FVIII trough levels of 2.5-10% in 95% of patients with severe hemophilia A. Conclusions Subcutaneously administered N8-GP may provide effective hemophilia A prophylaxis. A phase I clinical trial is underway to investigate this possibility.

Simultaneous visualization of the translocation of protein kinase Calpha-green fluorescent protein hybrids and intracellular calcium concentrations.

The alpha isoform of protein kinase C (PKCalpha) is a ubiquitous protein kinase, which, upon activation, translocates rapidly from the cytoplasm to the plasma membrane. To follow this translocation, PKCalpha was tagged with a highly fluorescent derivative of green fluorescent protein and stably expressed in baby hamster kidney cells overexpressing the muscarinic type 1 receptor. Addition of the agonist carbamylcholine triggered the onset of translocation within 1 s. Half-maximal and maximal translocation occurred after about 3 and 15 s respectively. Plasma membrane association of the fusion protein was transient and the protein returned to the cytoplasm within about 45 s. A high-resolution study showed an almost homogeneous cytoplasmic distribution of tagged PKCalpha in unstimulated cells and virtually complete translocation to the plasma membrane in response to the phorbol ester, PMA. Simultaneous visualization of intracellular calcium concentration ([Ca2+]i) and PKCalpha translocation in single cells showed a good correlation between these parameters at intermediate and high concentrations of agonist. At low agonist concentration, a small increase in [Ca2+]i was observed, without detectable translocation of PKCalpha. In contrast, PMA induced translocation of PKCalpha without any increase in [Ca2+]i. Neither cytochalasin D nor colcemid influenced the distribution or calcium-dependent translocation of tagged PKCalpha, indicating that PKCalpha translocation may be independent of both actin filaments and microtubules. The time course of PKCalpha translocation is compatible with diffusion of the protein from its cytoplasmic localization to the plasma membrane.

Cancer invasion and tissue remodeling: common themes in proteolytic matrix degradation.

Analysis of extracellular matrix degradation systems has led to the insight that in cancer invasion there is often crucial interplay between cancer cells and several types of surrounding non-neoplastic stromal cells. Likewise, in normal tissue remodeling processes, the synthesis of proteolytic components is often distributed between several cell types, and there are strong similarities between neoplastic and non-neoplastic processes in the same tissue. Thus, tissue remodeling events are excellent models for studies of extracellular proteolysis in cancer. This has become even clearer by recent analyses of genetically modified mice.