Genomically informed small-molecule drugs overcome resistance to a sustained-release formulation of an engineered death receptor agonist in patient-derived tumor models

Extrinsic pathway agonists have failed repeatedly in the clinic for three core reasons: Inefficient ligand-induced receptor multimerization, poor pharmacokinetic properties, and tumor intrinsic resistance. Here, we address these factors by (i) using a highly potent death receptor agonist (DRA), (ii) developing an injectable depot for sustained DRA delivery, and (iii) leveraging a CRISPR-Cas9 knockout screen in DRA-resistant colorectal cancer (CRC) cells to identify functional drivers of resistance. Pharmacological blockade of XIAP and BCL-X-L by targeted small-molecule drugs strongly enhanced the antitumor activity of DRA in CRC cell lines. Recombinant fusion of the DRA to a thermally responsive elastin-like polypeptide ( ELP) creates a gel-like depot upon subcutaneous injection that abolishes tumors in DRA-sensitive Colo205 mouse xenografts. Combination of ELPdepot-DRA with BCL-X-L and/or XIAP inhibitors led to tumor growth inhibition and extended survival in DRA-resistant patient-derived xenografts. This strategy provides a precision medicine approach to overcome similar challenges with other protein-based cancer therapies.