Rational Design of a Novel Tubulin Inhibitor with a Unique Mechanism of Action

In this study, we capitalized on our previously performed crystallographic fragment screen and developed the antitubulin small molecule Todalam with only two rounds of straightforward chemical synthesis. Todalam binds to a novel tubulin site, disrupts microtubule networks in cells, arrests cells in G2/M, induces cell death, and synergizes with vinblastine. The compound destabilizes microtubules by acting as a molecular plug that sterically inhibits the curved-to-straight conformational switch in the alpha-tubulin subunit, and by sequestering tubulin dimers into assembly incompetent oligomers. Our results describe for the first time the generation of a fully rationally designed small molecule tubulin inhibitor from a fragment, which displays a unique molecular mechanism of action. They thus demonstrate the usefulness of tubulin-binding fragments as valuable starting points for innovative antitubulin drug and chemical probe discovery campaigns.

Automated summary

This study developed an antitubulin small molecule, Todalam, through two rounds of chemical synthesis based on a crystallographic fragment screen. Todalam binds to a novel tubulin site, disrupts microtubule networks, induces cell death, and synergizes with vinblastine. It destabilizes microtubules by inhibiting the conformational switch in alpha-tubulin and sequestering tubulin dimers. This work demonstrates the importance of using tubulin-binding fragments for innovative antitubulin drug and chemical probe discovery campaigns.