Pironetin binds to α-tubulin and is an effective inhibitor of microtubule polymerization. It also has cell cycle arrest and antitumor activity. Pironetin is an α/β unsaturated lactone isolated from Streptomyces species.
Tasidotin hydrochloride, a peptide analog of the antimitotic depsipeptide dolastatin 15, is an inhibitor of microtubule assembly and microtubule dynamics.