Pre-clinical and clinical evaluation of solution and soft gelatin capsule formulations for a BCS class 3 compound with atypical physicochemical properties.

R1481 is a sub-type selective muscarinic receptor antagonist with the potential treatment of overactive bladder. R1481 presents two challenges for drug development. The first is the viscous semi-solid nature of the active pharmaceutical ingredient (API). The second challenge is the poor oral bioavailability of this water soluble, metabolically stable compound due to low intestinal permeability, and the P-glycoprotein (P-gp) efflux mechanism. Vitamin E TPGS is reported by others to enhance bioavailability by increasing the solubility of active compounds and by inhibiting P-gp in the intestine. In this report, compatibility of R1481 in Capmul MCM-based formulations with and without vitamin E TPGS is summarized. Review of accelerated stability studies of oral formulations led to the identification of a soft gelatin capsule formulation using neat Capmul MCM as an acceptable formulation for Phase 1 clinical studies. Soft gelatin capsules (5 mg strength) were manufactured with and without the addition of vitamin E TPGS. Clinical data show that vitamin E TPGS does not improve systemic exposure of R1481 in humans.