Using an RNAi Signature Assay To Guide the Design of Three-Drug-Conjugated Nanoparticles with Validated Mechanisms, In Vivo Efficacy, and Low Toxicity.

Single-nanoparticle (NP) combination chemotherapeutics are quickly emerging as attractive alternatives to traditional chemotherapy due to their ability to increase drug solubility, reduce off-target toxicity, enhance blood circulation lifetime, and increase the amount of drug delivered to tumors. In the case of NP-bound drugs, that is, NP-prodrugs, the current standard of practice is to assume that the subcellular mechanism of action for each drug released from the NP mirrors that of the unbound, free-drug. Here, we use an RNAi signature assay for the first time to examine the mechanism of action of multidrug-conjugated NP prodrugs relative to their small molecule prodrugs and native drug mechanisms of action. Additionally, the effective additive contribution of three different drugs in a single-NP platform is characterized. The results indicate that some platinum(IV) cisplatin prodrugs, although cytotoxic, may not have the expected mechanism of action for cisplatin. This insight was utilized to develop a novel platinum(IV) oxaliplatin prodrug and incorporate it into a three-drug-conjugated NP, where each drug's mechanism of action is preserved, to treat tumor-bearing mice with otherwise lethal levels of chemotherapy.