Peptomer Linkers Enable Kinetic Control over Co-Delivery of Multiple Chemotherapeutics

Combination cancer therapies offer to minimize toxicity and alleviate patient burden, but a key challenge is independent control over the release of multiple therapeutics, especially in systems with chemotherapeutic drugs of similar size and structure. Due to MMP upregulation in cancer microenvironments, matrix metalloproteinase (MMP)-degradable linkers are often exploited for targeted release; however, their short substrates exhibit overlap with multiple proteases, which confounds kinetic control. Here, a library of MMP-responsive "peptomer" drug linkers was developed to control release on fast and slow timescales. Peptomers are hybrid molecules of peptides and non-natural peptoids (N-substituted glycines), which hinder proteolytic susceptibility. Systematic variation of peptoid substitutions within a pan-MMP-cleavable peptide sequence yielded distinct degradation kinetics to multiple MMPs. Two chemotherapeutics, doxorubicin and geldanamycin, were conjugated to peptomer linkers and incorporated into polyethylene glycol (PEG)-based hydrogels for sequential delivery. Fluorogenic and mass spectrometry-based assays demonstrated decoupled release of each drug in response to MMP-2 and MMP-9. In vitro studies using MDA-MB-231 and A549 cells showed that cell death rates correlated with the order of drug release. These findings highlight peptomers as modular, biocompatible linkers capable of kinetic control over multiple therapeutic agents, providing a versatile platform for improving the precision of combination drug delivery systems.