Nonlinear pharmacokinetics of factor VIII and its phosphatidylinositol lipidic complex in hemophilia A mice

Mager

et al. 2016

Biopharm & Drug Disp

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The development of inhibitory antibodies against factor VIII (FVIII) is a major challenge in hemophilia A (HA) therapy. Such antibodies develop in nearly 30% of patients receiving replacement FVIII, abrogating therapeutic efficacy. This work evaluated whether B-domain deleted FVIII encapsulated in phosphatidylinositol containing lipid nanoparticles (PI-BDD FVIII) could serve as an efficacious FVIII replacement therapy in the presence of inhibitors. The HA mice were given clinically relevant doses of FVIII to develop inhibitors. The efficacy of free and PI-BDD FVIII was studied in inhibitor-positive HA mice using a tail clip assay. Mathematical modeling of these data was conducted to evaluate the hypothesis that lipid association sterically shields the protein from inhibitor binding. The immunization protocol resulted in a mean inhibitory titer level of 198 ± 52 BU/ml. Free BDD FVIII was ineffective at controlling blood loss in inhibitor-positive HA mice as early as 2 h post dose. In contrast, PI-BDD FVIII treated animals retained partial hemostatic efficacy as long as 18 h post dose. Mathematical modeling supports the hypotheses that a greater fraction of lipid-associated FVIII remains unbound to inhibitors and that PI-BDD FVIII has lower binding affinity to inhibitors than does the free protein. In addition, the modeling approaches extend current efforts to model the impact of immunogenicity on PK and the therapeutically meaningful endpoint of efficacy, thereby addressing an important knowledge gap, particularly in the FVIII scientific literature. Clinical translation of these findings could result in a significant improvement in the quality of care of inhibitor-positive HA patients.

Section: Methodssupporting

confidence: 52%

Factor VIII associated with lipidic nanoparticles retains efficacy in the presence of anti‐factor VIII antibodies in hemophilia A mice

Mager

et al. 2016

Biopharm & Drug Disp

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“…This method combines allometry‐based scaling of PK parameters with normalized Wajima curves from preclinical species to generate human concentration–time profiles. The suitability of this method to scale PK of modified FVIII products has been previously demonstrated . Briefly, parameter estimates of V ss and CL in mice were obtained by fitting of a 1 compartment, linear clearance model to PK data.…”

Section: Methodsmentioning

confidence: 99%

“…The suitability of this method to scale PK of modified FVIII products has been previously demonstrated. 30,32 Briefly, parameter estimates of V ss and CL in mice were obtained by fitting of a 1 compartment, linear clearance model to PK data. MRT and C ss were calculated as MRT = V ss /CL and C ss = dose/V ss .…”

Section: Pk Modeling and Allometric Scalingmentioning

confidence: 99%

Soy Phosphatidylinositol Containing Nanoparticle Prolongs Hemostatic Activity of B-Domain Deleted Factor VIII in Hemophilia A Mice

Journal of Pharmaceutical Sciences

Mager

et al. 2015

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Factor VIII (FVIII) replacement therapy in Hemophilia A (HA) is complicated by a short half-life and high incidence of inhibitory antibody response against the protein. Phosphatidylinositol (PI) containing lipidic nanoparticles have previously been shown to reduce the immunogenicity and prolong the half-life of full length FVIII. It has not been established whether this prolongation in half-life improves hemostatic efficacy and whether this approach could be extended to the B-domain deleted form of FVIII (BDD FVIII). In the current study, we evaluated the pharmacokinetics (PK), hemostatic efficacy and immunogenicity of BDD FVIII associated with PI nanoparticles (PI-BDD FVIII) in HA mice. Comparative human PK was predicted using an ‘informed scaling’ approach. PI-BDD FVIII showed a ~ 1.5-fold increase in terminal half-life compared to free BDD FVIII following i.v. bolus doses of 40 IU/kg. PI-BDD FVIII treated animals retained hemostatic efficacy longer than the free FVIII treated group in a tail vein transection model of hemostasis. PI association reduced the development of inhibitory and binding antibodies against BDD FVIII after a series of i.v. injections. The combined improvements in circulating half-life and hemostatic efficacy could significantly prolong the time above clinically established therapeutic thresholds of prophylactic FVIII replacement therapy in humans.

“…However, following 4 IU/kg injections, D519V/E665V was reproducibly detected up to 2 h, but WT could not be recovered in any samples even as early as 5 min. We have previously reported that the PK of full length FVIII as well as the B-domain deleted WT protein is non-linear in the HA mice used in these studies (21,24). This is also apparent from the fact that non-compartmental analyses show an increase in clearance at lower doses (it is appropriate to acknowledge here that the PK could have been inadequately estimated at lower doses due to limited recovery of plasma FVIII levels at these doses).…”

Section: Pharmacokinetic Studiesmentioning

confidence: 99%

Effects of Replacement of Factor VIII Amino Acids Asp519 and Glu665 with Val on Plasma Survival and Efficacy In Vivo

Wakabayashi

et al. 2014

AAPS J

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Proteolytic cleavage of factor VIII (FVIII) to activated FVIIIa is required for participation in the coagulation cascade. The A2 domain is no longer covalently bound in the resulting activated heterotrimer and is highly unstable. Aspartic acid (D) 519 and glutamic acid (E) 665 at the A1-A2 and A2-A3 domain interfaces were identified as acidic residues in local hydrophobic pockets. Replacement with hydrophobic valine (V; D519V/E665V) improved the stability and activity of the mutant FVIII over the wild-type (WT) protein in several in vitro assays. In the current study, we examined the impact of mutations on secondary and tertiary structure as well as in vivo stability, pharmacokinetics (PK), efficacy, and immunogenicity in a murine model of Hemophilia A (HA). Biophysical characterization was performed with far-UV circular dichroism (CD) and fluorescence emission studies. PK and efficacy of FVIII was studied following i.v. bolus doses of 4, 10 and 40 IU/kg with chromogenic and tail clip assays. Immunogenicity was measured with the Bethesda assay and ELISA after a series of i.v. injections. Native secondary and tertiary structure was unaltered between variants. PK profiles were similar at higher doses, but at 4 IU/kg plasma survival of D519V/E665V was improved. Hemostasis at low concentrations was improved for the mutant. Immune response was similar between variants. Overall, these results demonstrate that stabilizing mutations in the A2 domain of FVIII can improve HA therapy in vivo.