Physiology-based pharmacokinetics of caspofungin for adults and paediatrics.

Purpose: Caspofungin (CAS) is an antifungal agent for intravenous application in adults and children. Our aim was the development and validation of a physiology-based pharmacokinetic (PBPK) model in order to predict the pharmacokinetics in different patient populations, particularly in paediatrics.

Methods: A PBPK model for adults was built and validated with raw data of the two clinical trials CASLAMB and CASMTD. Afterwards, the model was scaled for paediatric patients under the consideration of known biochemical differences between adults and paediatrics.

Results: The simulated results of the PBPK model were in good agreement with the observed values of the CASLAMB and CASMTD trial. Patients of the CASLAMB trial received CAS in combination with cyclosporine A (CsA), which leads to an increased AUC0-24h of CAS hypothetically due to an inhibition of the hepatic transport protein OATP1B1 by CsA. However, there was no difference in the transport rate of OATP1B1 between CASLAMB and CASMTD patients in the PBPK model, suggesting that CsA might not influence OATP1B1. Furthermore, the model was able to sufficiently predict the pharmacokinetics of paediatric patients compared to published data.

Conclusion: The final PBPK model of CAS without individualized parameter is able to predict the pharmacokinetics in different patient populations correctly. Thus, the model provides a basis for investigators to choose doses and sampling times for special populations such as infants and small children.