Application of mechanism-based PKPD model to identify optimal dosing regimens for future development of oraxol.

e13505 Background: Paclitaxel (PTX) is a widely used potent anticancer drug that blocks mitosis by stabilization of microtubules. Previous attempts for oral administration of PTX have been unsuccessful at least partly due to its affinity for the efflux pump, P-gp. Oraxol is an oral formulation of PTX combined with a novel potent P-gp inhibitor, HM30181A, to maximize absorption of paclitaxel without itself being systemically absorbed. A population PK/PD model was developed to characterize the temporal relationship between PTX exposure and neutropenia, and subsequently model-based simulations were utilized to determine the optimal dosing strategy for oraxol. Methods: Oraxol was administered to 68 (51M/17F) patients with various malignancies. Oraxol dose levels ranged from 60 to 420 mg/m2 QW, and 90-150 QWx2 for 3/4 weeks. Population PKPD modeling was performed with the following patient factors: [BSA (1.29-2.15 m2), ECOG PS scores (97% pts ≤ 1), age (36-81.4 yrs), CrCL (39.6-132.8 ml/min), ALB (2.3-4.8 mg/d...