The natural products colchicine and combretastatin A-4 (CA4) inspired significant world-wide drug discovery efforts targeting the colchicine binding site, which is located primarily on the beta-tubulin heterodimer. Previous studies in our laboratories resulted in the synthesis and biological evaluation of a wide variety of structurally diverse small-molecule inhibitors of tubulin polymerization that demonstrate efficient binding to the colchicine site. The most promising of these molecules function with dual mechanism of action as both potent cytotoxins (antiproliferative agents) and effective vascular disrupting agents (VDAs), which selectively impart irreversible damage to tumor-associated microvessels, ultimately leading to tumor necrosis. Two highly potent, benzosuberene-based, dual-mechanism payloads, KGP18 and KGP156, were tethered through protease-cleavable short peptides to afford corresponding drug-linker constructs that also incorporate a self-immolative <i>para</i>-aminobenzyl trigger to facilitate release of the payloads. The distal end of these drug-linker constructs terminates in a maleimidocaproyl functionality suitable for conjugation to an antibody or other tumor-targeting proteins. These constructs were designed to incorporate plasmin targeting (D-Ile-L-Phe-L-Lys) and uPA (urokinase-type plasminogen activator) targeting (Gly-Gly-L-Arg) short peptide sequences. Synthetic routes were developed for these tripeptides that facilitated ease of inclusion within the drug-linker constructs, which further included the unique benzosuberene payloads (phenolic analogue KGP18 and aniline congener KGP156). Details regarding the various synthetic routes explored to prepare these linkers in sufficient quantity, purity, and reproducibility will be discussed along with preliminary biological studies (including enzymatic and cell-based assays) to evaluate stability and release of payloads. Studies utilizing unique engineered proteins (referred to as betabodies), advanced by the Brekken Laboratory, that selectively target accessible phosphatidylserine (PS) will also be described. Though confined to the inner leaflet of the plasma membrane of healthy cells, PS is exposed on the outer leaflet of the plasma membrane of endothelial cells in tumor-associated vasculature and cancer cells, thus representing a promising target for these unique drug-linker constructs.

Synthesis of drug-linker constructs bearing dual mechanism of action payloads designed for cleavage by enzymes present in the tumor microenvironment

Where thousands of chemistry professionals meet to share ideas and advance scientific and technical knowledge. Spring 2023 abstracts, posters, and presentations will launch at the end of March.

ACS Spring 2023

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.