ROS-Activated Peptide-Based Prodrug for Chemoselective Covalent Targeting in Cancer Cells

The development of covalent drugs has renewed interest in strategies that achieve high selectivity while minimizing off-target reactivity. Herein, we report IRS1, a peptide-based prodrug comprising an integrin-targeting RGD motif, an ROS-responsive thiomorpholine unit, and a chlorambucil-derived covalent warhead for efficient cancer inhibition. Under physiological conditions, IRS1 self-assembles into nanoparticles and preferentially accumulates in uveal melanoma (UM) cells via integrin-mediated targeting. Within the tumor microenvironment, ROS-triggered oxidation of thiomorpholine induces a hydrophobic-to-hydrophilic transition, driving the nanoparticle-to-nanofibril transformation and exposing the chlorambucil moiety. This enables covalent conjugation with the thiol groups of DR4/DR5 on the cell membrane. IRS1 effectively disrupts membrane integrity, activates extrinsic apoptosis, and induces cancer cell death <i>in vitro</i>. In UM xenograft models, IRS1 shows potent antitumor efficacy with reduced systemic toxicity, highlighting a peptide-reconfiguration strategy for tumor-selective covalent therapeutics.