Overcoming Immune Checkpoint Inhibitor Resistance with Potent, Selective Dual αvβ6/8 Inhibitors Based on Engineered Lasso Peptides.

Integrins αvβ6 and αvβ8 in the tumor microenvironment (TME) have been shown to activate immunosuppressive TGF-β, which serves as an important mechanism for immune checkpoint inhibitor resistance in a range of tumors. In this study, we demonstrate the utility of lasso peptides as versatile scaffolds for the design of new therapeutics. A series of highly potent and selective dual αvβ6/8 inhibitors were engineered through a combination of epitope scanning, computational design, and directed evolution, whereby inhibition was fine-tuned for two out of the eight related RGD-integrin receptors. NMR structures of two lasso peptide dual integrin inhibitors are provided. Facile conjugation chemistry with a small-molecule albumin binder afforded half-life extended lasso peptide analogs, including 19, which was fully characterized and shown to robustly and durably halt growth and regress anti-mPD-1-resistant ovarian and triple negative breast cancer tumors in mice when dosed in combination with the checkpoint inhibitor. These studies show that dual inhibition of αvβ6/8 integrins expressed in the TME represents an auspicious tumor-specific strategy to overcome TGF-β-driven resistance and enhance the antitumor efficacy of immune checkpoint inhibitors. Our ability to produce lasso peptides with high titers in fermenters has enabled the first detailed demonstration of their drug-like properties, including tunable in vivo pharmacokinetics and efficacy, thus paving the way for future advances using this promising modality derived from nature.