Abstract
Background Factor VIII (FVIII) products are usually dosed according to body weight (BW). This
may lead to under- or over-dosing in underweight or obese patients, respectively.
Objective This article evaluates the pharmacokinetics (PK) of recombinant FVIII concentrate,
particularly recovery, in relation to body mass index (BMI) and other body composition
descriptors.
Materials and Methods Thirty-five previously treated adults with severe haemophilia A from five BMI categories
(underweight, normal, overweight, obese class I and II/III) were included. PK was
evaluated after 50 IU per kilogram of BW single-dose recombinant FVIII (turoctocog
alfa). The body composition variable was based on measurements of weight, height,
bioimpedance analysis, and dual-energy X-ray absorptiometry. A dosing model was derived
to achieve similar peak FVIII activity levels across BMI categories.
Results A statistically significant positive association between BMI and C30min, IR30min, and AUC0–inf was observed; CL and Vss showed a significant negative association with BMI; t½ was independent of BMI and other parameters. The dosing model introduced a correction
factor ‘M’ for each BMI category, based on linear regression analysis of C30min against BMI, which ranged from 0.55 for underweight to 0.39 for obese class II/III.
This model achieved similar peak FVIII activity levels across BMI categories, estimating
an average dose adjustment of +243.3 IU (underweight) to –1,489.6 IU (obese class
II/III) to achieve similar C30min.
Conclusion BMI appears to be the best predictor of recombinant FVIII recovery; however, PK endpoints
were also dependent on other body composition variables. The model demonstrated that
dosing can be adjusted for individual BMI to achieve better FVIII predictability across
BMI categories.
Keywords
body mass index - dosing model - recombinant factor VIII - haemophilia - pharmacokinetics