Simultaneous Delivery of siRNA and Paclitaxel via a Two-in-One Micelleplex Promotes Synergistic Tumor Suppression

Combination of two or more therapeutic strategies with different mechanisms can cooperatively prohibit cancer development. Combination of chemotherapy and small interfering RNA (siRNA)-based therapy represents an example of this approach. Hypothesizing that the chemotherapeutic drug and the siRNA should be simultaneously delivered to the same tumoral cell to exert their synergistic effect, the development of delivery systems that can efficiently encapsulate two drugs and successfully deliver payloads to targeted sites via systemic administration has proven to be challenging. Here, we demonstrate an innovative two-in-one micelleplex approach based on micellar nanoparticles of a biodegradable triblock copolymer poly(ethylene glycol)-b-poly(epsilon-caprolactone)-b-poly(2-aminoethyl ethylene phosphate) to systemically deliver the siRNA and chemotherapeutic drug. We show clear evidence that the micelleplex is capable of delivering siRNA and paditaxel simultaneously to the same tumoral cells both In vitro and in vivo. We further demonstrate that systemic administration of the micelleplex carrying polo-like kinase 1 (PIk1) specific siRNA and paditaxel can induce a synergistic tumor suppression effect in the MDA-MB-435s xenograft murine model, requiring a thousand-fold less paditaxel than needed for paditaxel monotherapy delivered by the micelleplex and without activation of the Innate immune response or generation of carrier-associated toxicity.