An oral proprietary P-glycoprotein (P-gp) pump inhibitor-based formulation containing the taxane docetaxel, a semisynthetic analogue of paclitaxel, and a P-gp pump inhibitor, with potential antineoplastic activity. Upon administration of oral docetaxel, the P-gp pump inhibitor moiety, which is not absorbed, binds to the P-gp pump in the gastrointestinal (GI) tract and prevents the P-gp pump-mediated efflux of docetaxel from cells the docetaxel has been internalized by back into the GI tract. This decreases P-gp-mediated excretion and enhances absorption of docetaxel. Upon absorption, docetaxel binds specifically to the beta-tubulin subunit of the microtubule, stabilizes tubulin and inhibits microtubule disassembly, which results in cell-cycle arrest at the G2/M phase and cell death. The P-gp pump inhibitor enhances the bioavailability of certain poorly bioavailable agents and thereby allows oral administration of those agents. P-gp, an efflux membrane transporter, plays a key role in active drug export, and prevents cellular uptake and accumulation of certain substances.