Tasidotin hydrochloride is a peptide analog of the antimitotic depsipeptide dolastatin 15. Tasidotin hydrochloride is an inhibitor of microtubule assembly and microtubule dynamics.

The greatest difference in sensitivity to Tasidotin is between the more sensitive MDA-MB-435 line and the less sensitive HS 578-T line of the remaining lines. The IC50 values in the two lines are 4 and 200 nM, respectively. The IC50 in Ewing's sarcoma, rhabdomyosarcoma, osteosarcoma, and synovial sarcoma lines ranges from 2 to 320 nM. Tasidotin induces a G2-M arrest that persists for 48 h after Tasidotin is washed from the cells in the SK-ES1 and RH30 cell lines. In vitro, more than half the cells are in the early or late phase of apoptosis 48 h after treatment with Tasidotin. Following treatment for 24 h with 160 nM Tasidotin, the RH30 line, and SK-ES1 line each shows an accumulation of cells in the G2-M phase. At hour 24, nearly all the RH30 cells are in the G2-M phase [1][2].

Tasidotin (90 mg/kg/d, mice) treatment has a mean weight loss of <16% following each 5-day treatment of Tasidotin. In vivo, a significant increase in apoptotic nuclei is apparent in xenograft tumors harvested within 24 h after a 5-day course of Tasidotin. Mice treated with 100 mg/kg have a mean weight loss of >20% with no return to their baseline starting weight, and one mouse dies before the second treatment course [2].