Coassembled Prodrug Nanoparticles Mitigating the Acquired Resistance to Protein Degradation Therapy

PROTACs (Proteolysis TArgeting Chimeras) represent an emerging class of anticancer therapeutics that induce the selective degradation of pathogenic proteins. However, the therapeutic efficacy of PROTACs is often compromised by their insufficient tumor distribution, poor bioavailability, and emergence of acquired resistance. In this study, we demonstrated that the PROTAC resistance of tumor cells is attributed to the elevated level of expression of the drug efflux pump ATP-binding cassette subfamily B member 1 (ABCB1/MDR1). We therefore innovatively developed a coassembled PROTAC nanoplatform for combating the acquired PROTAC resistance of cancer. This PROTAC nanoplatform is engineered by self-assembly of alkylated PROTAC prodrugs with human serum albumin (HSA) while simultaneously encapsulating the mTOR inhibitor rapamycin (RAPA) to inhibit extracellular PROTAC efflux. Upon cellular uptake, the PROTAC prodrug nanoparticles are hydrolyzed by intracellular esterases to restore PROTAC and ablate the protein of interest. Simultaneously, the expression of drug efflux pump MDR1 is inhibited by RAPA, thereby mitigating the MRD1-associated PROTAC resistance. The efficacy of RAPA in overcoming PROTAC resistance was validated with multiple types of PROTACs, underscoring the generality of this approach. The coassembled nanoplatform integrating the alkylated PROTAC prodrug and RAPA highly efficiently suppressed tumor growth in a mouse model of PROTAC-resistant breast cancer.