Jozsef Barkoczy

Targeting vascular and avascular compartments of tumors with C. novyi-NT and anti-microtubule agents.

Current approaches for treating cancer are limited, in part, by the inability of drugs to affect the poorly vascularized regions of tumors. We have found that C. novyi-NT in combination with anti-microtubule agents can cause the destruction of both the vascular and avascular compartments of tumors. The two classes of microtubule inhibitors were found to exert markedly different effects. Some agents that inhibited microtubule synthesis, such as HTI-286 and vinorelbine, caused rapid, massive hemorrhagic necrosis when used in combination with C. novyi-NT. In contrast, agents that stabilized microtubules, such as the taxanes docetaxel and MAC-321, resulted in slow tumor regressions that killed most neoplastic cells. Remaining cells in the poorly perfused regions of tumors could be eradicated by C. novyi-NT. Mechanistic studies showed that the microtubule destabilizers, but not the microtubule stabilizers, radically reduced blood flow to tumors, thereby enlarging the hypoxic niche in which C. novyi-NT spores could germinate. A single intravenous injection of C. novyi-NT plus selected anti-microtubule agents was able to cause regressions of several human tumor xenografts in nude mice in the absence of excessive toxicity.

Dolastatins 24: synthesis of (–)-dolastatin 10. X-Ray molecular structure of N,N-dimethylvalyl-valyl-dolaisoleuine tert-butyl ester

Total synthesis of the extraordinary antineoplastic constituent, dolastatin 10, from the Indian Ocean mollusc Dolabella auricularia has been summarized. The final synthetic step involved diethyl cyanophosphonate-mediated coupling of Dov-Val-Dil with Dap-Doe. Improved syntheses of these important precursors has led to a very practical synthesis of natural dolastatin 10. Important details of the HPLC and high-field (500 MHz) NMR characterization techniques employed to confirm the purity of dolastatin 10 have been recorded.

Procedures for the Analyses of Dolastatins 10 and 15 by High Performance Liquid Chromatography

Abstract A series of HPLC procedures were evaluated for assessing the purity of dolastatin 10 (1) and dolastatin 15 (2) samples. Interestingly two readily interconvertible (ambient temperature) dolastatin 10 (1) conformers were detected using a potassium dihydrogen phosphate buffered solvent (methanol-water) with a C8 reversed-phase column. A solvent system composed of acetonitrile-2-propanol-water containing sodium 1-hexanesulfonate was found especially useful for evaluating the purity of dolastatin 10 and 15 specimens. Useful HPLC procedures were also found for detecting diastereomeric isomers in the key dolastatin 10 synthetic intermediate Boc-(S, R, R)-Dap-(S)-Doe using β-cyclodextrin in 3:2 methanol-water.