# Pharmacokinetics of Efmoroctocog alfa by Two-Compartment Model Highlights Hemophilia A Patients with Biphasic Decay, Long Mean Residence Time, and Beta Half-Life

## TL;DR

This study shows that a new long-acting FVIII treatment for hemophilia A has better pharmacokinetics than standard treatments, with a two-compartment model revealing biphasic decay and longer half-life in most patients.

## Contribution

The study is the first to apply a two-compartment model to a large cohort of hemophilia A patients using Efmoroctocog alfa, revealing biphasic decay patterns and improved pharmacokinetics.

## Key findings

- A two-compartment model showed biphasic decay in 61% of patients receiving Efmoroctocog alfa.
- Efmoroctocog alfa had a longer Beta half-life (20.42 h) and mean residence time (25.64 h) compared to standard half-life FVIII products.
- Pharmacokinetic parameters measured by one-stage and chromogenic assays showed significant differences in Cmax and Beta half-life.

## Abstract

Background/Objectives: A compartmental pharmacokinetics (PK) analysis of new extended half-life FVIII concentrates has never been performed in a large cohort of hemophilia patients. An improved PK analysis of individual outcomes may help to tailor hemophilia replacement treatment. Methods: PK outcomes after the infusion of a standard single dose of Efmoroctocog alfa were collected from 173 patients with severe/moderately severe hemophilia A in 11 Italian hemophilia centers. Factor VIII clotting activity (FVIII:C) was measured by one-stage clotting assay (OSA) in all patients, and chromogenic substrate assay (CSA) in a subgroup (n = 52). Fifty patients underwent a comparative PK assessment with standard half-life (SHL) recombinant FVIII (rFVIII) products. Non-compartmental analysis (NCA), one compartment model (OCM), and TCM were used to analyze the decay curves of all patients, and one-way paired ANOVA to compare the PK outcomes. Results: All 173 PKs conformed to the NCA and OCM, but only 106 (61%) conformed to the TCM based on the biphasic features of their decay curves. According to the TCM, the Beta HL and MRT of rFVIIIFc were 20.42 ± 7.73 and 25.64 ± 7.61 h, respectively. ANOVA analysis of the outcomes from the three PK models showed significant differences in clearance, half-life (HL), and mean residence time (MRT) (p < 0.001 for all parameters). As anticipated, the HL and MRT of rFVIIIFc were longer than those of SHL rFVIII. Comparing OSA with CSA outcomes, Cmax resulted higher when measured by CSA (p = 0.05) and, according to TCM, Beta HL resulted longer when measured by OSA (p = 0.03). FVIII:C trough levels obtained with SHL concentrates were significantly lower than those obtained with rFVIIIFc at each post-infusion time point. Conclusions: In a large group of hemophilia A (HA) patients, three different PK models confirmed the improved pharmacokinetic (PK) characteristics of rFVIIIFc, compared with standard half-life rFVIII concentrates. The TCM only fits two-thirds of the PKs, highlighting their biphasic decay and a long Beta half-life. In these patients, the TCM would be preferable to properly evaluate individual PK features.