Design and synthesis of indole-based analogues of OXi8006 as inhibitors of tubulin polymerization and their incorporation as payloads in drug-linker constructs.

OXi8006, originally designed and synthesized by the Pinney Research Group at Baylor University, exhibited potent inhibition of tubulin polymerization and strong cytotoxicity against human various cancer cell lines. In previous studies, OXi8007, the phosphate prodrug of OXi8006, demonstrated vascular disrupting activity within 2 hours of administration by targeting tumor vasculature. OXi8006 binds to the colchicine site on α,β-tubulin heterodimers, inducing a conformation shift from a straight to a curved structure. This conformational change inhibits tubulin polymerization, leading to cell cycle arrest and apoptosis. To gain a deeper understanding of the interaction of OXi8006 with the colchicine site, a structure-activity relationship (SAR) study was conducted by replacing the carbonyl moiety with various one-atom and two-atom bridging functionalities. Among the analogues synthesized, compounds bearing a sulfide bridge (KGP555) and a methylene bridge (KGP608) demonstrated potent biological activity, including a strong inhibition of tubulin polymerization, a high affinity for the colchicine site, and significant cytotoxicity against cancer cell lines such as MCF-7, MDA-MB-231, and PANC-1. Encouraged by these results, phosphate prodrugs of KGP555 and KGP608 were synthesized to enhance water solubility. However, these prodrugs proved unsuccessful in achieving the desired solubility improvements. To overcome this limitation, an aniline-based congener, KGP681, was developed to broaden prodrug options, including ւ-serinamide and glycinamide derivatives. These analogues were incorporated as payloads in drug-linker constructs featuring a valine-citrulline (Val-Cit) dipeptide linker for potential use in antibody-drug conjugates (ADCs). The goal is to facilitate selective payload delivery to the tumor microenvironment, where the linker will undergo cleavage by cathepsin B, an enzyme overexpressed in many tumors, thus releasing the payload site-specific to the tumor. As a preliminary assessment of efficacy, KGP619, a drug linker construct incorporating the phenolic payload KGP555 and N,N’-dimethylethylenediamine (DMED) as a spacer, exhibited a 27% payload release upon exposure to cathepsin B. In another example, the drug-linker construct KGP682, when treated with cathepsin B, released its payload, KGP681, with more efficiency (52%). Inspired by this enhancement, further modifications to KGP682 were investigated, which included the optimization of an attachment group, a dipeptide linker, a self-immolative spacer, and the payload.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Doctoral

Grantor

Baylor University.

Year dc:date.issued

2025

Author dc:creator

• Wong, Molly Ching (Yu Ching), 1993-

Advisor dc:contributor.advisor

• Pinney, Kevin G.

• OXi8006.
• Tubulin-binding molecules.
• Inhibition of tubulin polyermization.
• Antibody-drug conjugates (ADCs)
• Drug-linker constructs.

Statement dc:rights

• Baylor University works are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. Contact libraryquestions@baylor.edu for inquiries about permission.

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/2104/13925

OAI identifier oai:identifier

oai:baylor-ir.tdl.org:2104/13925