Apoptotic pathways of epothilone BMS 310705

Objective: BMS 310705 is a novel water-soluble analog of epothilone B currently in phase I clinical evaluation in the treatment of malignancies such as ovarian, renal, bladder, and lung carcinoma. Using an early passage Cell Culture model derived from the ascites of a patient clinically refractory to platinum/paclitaxel therapy, we evaluated the pathway of caspase-mediated Apoptosis.

Methods: Cells were treated for 1 h and subsequently evaluated for Apoptosis, survival, and Caspase activity. Apoptosis was determined by fluorescent microscopy. Caspase-3, -8, and -9 activities were determined by fluorometry using target tetrapeptide substrates. Mitochondrial release of cytochrome c was determined by immunoblot analysis.

Results: After treatment with BMS 310705, Apoptosis was confirmed in >25% of cells at 24 h. Survival was significantly lower (P < 0.02) in cells treated with 0.05 micro M BMS 310705 vs paclitaxel. Analysis revealed an increase of caspase-9 and -3 activity; no Caspase -8 activity was observed. Release of cytochrome c was detected at 12 h following treatment. SN-38 and topotecan failed to induce Apoptosis.

Conclusions: BMS 310705 induces significant Apoptosis, decreases survival, and utilizes the mitochondrial-mediated pathway for Apoptosis in this model.