d‑α-Tocopherol Polyethylene Glycol Succinate-Based Redox-Sensitive Paclitaxel Prodrug for Overcoming Multidrug Resistance in Cancer Cells

To overcome the multidrug resistance (MDR) of P-glycoprotein (P-gp) substrate anticancer drugs, such as paclitaxel (PTX), a novel dual-functional prodrug, D-α-tocopherol polyethylene glycol succinate (TPGS) based PTX prodrug (TPGS-S-S-PTX), was synthesized here to fulfill the synergistic effect of P-gp inhibiting and intracellular redox-sensitive release. The prodrug could self-assemble into stable micelles in physiological environment with a diameter of ∼140 nm, while it disassociated in reductive condition and released PTX and TPGS active derivatives rapidly. High cell cytotoxicity in PTX-resistant human ovarian cell line A2780/T was observed with enhanced PTX accumulation due to the P-gp inhibition by the TPGS moiety. The IC₅₀ of TPGS-S-S-PTX was 55% and 91% more effective than that of Taxol (clinical formulation of PTX) and uncleavable TPGS-C-C-PTX prodrug, respectively. This was found to be related with the increased apoptosis/necrosis and cell arrest in G2/M phase. <i>In vivo</i> evaluation of the TPGS-S-S-PTX prodrug exhibited an extended half-life, increased AUC (area under the concentration–time curve), enhanced tumor distribution and significant tumor growth inhibition with reduced side effects as compared to Taxol and TPGS-C-C-PTX. This prodrug has great potential in improving efficiency in the treatment of MDR tumors