npi-2358 and fosbretabulin

Targeting vasculature, essential in oxygen and nutrient supply, represents a new frontier in the treatment of cancer. Apart from angiogenesis inhibitors that compromise the formation of new blood vessels, a second class of vascular disrupting agents (VDAs) targets endothelial cells and pericytes of the already established tumor vasculature, resulting in tumor ischemia and necrosis. VDAs have been divided into two types: ligand-directed VDAs and small molecules. Ligand-directed VDAs consist of targeting and effector moieties that are linked together. Their clinical efficacy appears limited because of cost and a lack of specificity and toxicity. Small molecules include two classes: the synthetic flavonoids, which work through induction of local cytokine production, and the tubulin-binding agents. The aim of this review is to discuss the hypothesized molecular mechanisms of action of VDAs and their early preclinical and clinical results, emphasizing ASA404, combretastatin A-4 disodium phosphate, ABT-751, and NPI-2358, reported in the treatment of non-small cell lung cancer, which is the leading cause of cancer death worldwide, and also to discuss future developments in this cancer population.

Topics: Animals; Antineoplastic Agents; Carcinoma, Non-Small-Cell Lung; Clinical Trials as Topic; Diketopiperazines; Endothelial Cells; Humans; Imidazoles; Lung Neoplasms; Pericytes; Piperazines; Stilbenes; Sulfonamides; Xanthones

The diketopiperazine NPI-2358 is a synthetic analog of NPI-2350, a natural product isolated from Aspergillus sp., which depolymerizes microtubules in A549 human lung carcinoma cells. Although structurally different from the colchicine-binding site agents reported to date, NPI-2358 binds to the colchicine-binding site of tubulin. NPI-2358 has potent in-vitro anti-tumor activity against various human tumor cell lines and maintains activity against tumor cell lines with various multidrug-resistant (MDR) profiles. In addition, when evaluated in proliferating human umbilical vein endothelial cells (HUVECs), concentrations as low as 10 nmol/l NPI-2358 induced tubulin depolymerization within 30 min. Furthermore, NPI-2358 dose dependently increases HUVEC monolayer permeability--an in-vitro model of tumor vascular collapse. NPI-2358 was compared with three tubulin-depolymerizing agents with vascular-disrupting activity: colchicine, vincristine and combretastatin A-4 (CA4). Results showed that the activity of NPI-2358 in HUVECs was more potent than either colchicine or vincristine; the profile of CA4 approached that of NPI-2358. Altogether, our data show that NPI-2358 is a potent anti-tumor agent which is active in MDR tumor cell lines, and is able to rapidly induce tubulin depolymerization and monolayer permeability in HUVECs. These data warrant further evaluation of NPI-2358 as a vascular-disrupting agent in vivo. Currently, NPI-2358 is in preclinical development for the treatment of cancer.

Topics: Angiogenesis Inhibitors; Antineoplastic Agents; Cell Membrane Permeability; Cell Survival; Colchicine; Dextrans; Diketopiperazines; Dose-Response Relationship, Drug; Drug Resistance, Neoplasm; Endothelial Cells; Endothelium, Vascular; Fluorescein-5-isothiocyanate; HL-60 Cells; HT29 Cells; Humans; Imidazoles; Inhibitory Concentration 50; Jurkat Cells; Microtubules; Neoplasms; Piperazines; Stilbenes; Time Factors; Tubulin; Vincristine