Tubulysin G is a highly cytotoxic anti-microtubule toxin ( anti-microtubule toxins ) that is synthesized as an ADC cytotoxin ( ADC Cytotoxin ). Tubulysin G can be isolated from the myxobacteria Archangium geophyra and Angiococcus disciformis. Tubulysin G displays extremely potent cytotoxic activity in mammalian cells, including multidrug-resistant cell lines, with IC 50 values in the low nanomolar range. Tubulysin G inhibits microtubule/tubulin polymerization and leads to cell cycle arrest and apoptosis.