Tubulin inhibitors(University of Stellenbosch)

Microtubule-targeting agents continue to be a cornerstone of cancer treatment; however, issues like systemic toxicity, poor metabolic stability, and multidrug resistance often restrict their effectiveness. Identifying new molecules that can overcome these limitations is crucial for enhancing therapeutic outcomes. In this work, we present a library of 12 new tubulin-binding compounds, analogues of Combretastatin A-4, incorporating a tetrazole bridge designed to preserve the cisoid disposition required for binding to the colchicine site. These compounds were assayed against a wide range of cancer cell lines, with compounds 23, 31, and 32 showing antiproliferative potencies in the low nanomolar range. The mechanism of action was assessed through microscopy experiments, which confirmed disruption of microtubule polymerization in cells. In vitro microtubule polymerization reactions with tubulin isolated from HEK-293 cells showed that compounds with drastically different inhibitory effects on polymerization dynamics elicit similar antiproliferative effects, thus questioning the usual assumption that interference with microtubule dynamics is the fundamental mechanism behind tubulin inhibitors' actions. Cell cycle and cell death assays revealed atypical behavior for antimitotic agents, showing less mitotic arrest than typically but a significant increase in apoptotic cell populations, thus suggesting that they trigger cell death in an unusual way. In silico conformational and docking studies supported binding at the colchicine site and suggested favourable pharmacokinetic profiles. Together, these results position these compounds as highly promising candidates for development as new antitumor agents, especially 23 for glioblastoma.