LAF389 is a synthetic analogue of bengamides, a class of marine natural products that produce inhibitory effects on tumor growth in vitro and in vivo. A proteomicsbased approach has been used to identify signaling pathways affected by bengamides. LAF389 treatment of cells resulted in altered mobility of a subset of proteins on two-dimensional gel electrophoresis. Detailed analysis of one of the proteins, 14-3-3␥, showed that bengamide treatment resulted in retention of the amino-terminal methionine, suggesting that bengamides directly or indirectly inhibited methionine aminopeptidases (MetAps). Both known MetAps are inhibited by LAF389. Short interfering RNA suppression of MetAp2 also altered amino-terminal processing of 14-3-3␥. A high resolution structure of human MetAp2 co-crystallized with a bengamide shows that the compound binds in a manner that mimics peptide substrates. Additionally, the structure reveals that three key hydroxyl groups on the inhibitor coordinate the di-cobalt center in the enzyme active site.

We have synthesized a histone deacetylase inhibitor, NVP-LAQ824, a cinnamic hydroxamic acid, that inhibited in vitro enzymatic activities and transcriptionally activated the p21 promoter in reporter gene assays. NVP-LAQ824 selectively inhibited growth of cancer cell lines at submicromolar levels after 48 -72 h of exposure, whereas higher concentrations and longer exposure times were required to retard the growth of normal dermal human fibroblasts. Flow cytometry studies revealed that both tumor and normal cells arrested in the G 2 -M phase of the cell cycle after compound treatment. However, an increased sub-G 1 population at 48 h (reminiscent of apoptotic cells) was observed only in the cancer cell line. Annexin V staining data supported our hypothesis that NVP-LAQ824 induced apoptosis in tumor and transformed cells but not in normal cells. Western blotting experiments showed an increased histone H3 and H4 acetylation level in NVP-LAQ824-treated cancer cells, suggesting that the likely in vivo target of NVP-LAQ824 was histone deacetylase(s). Finally, NVP-LAQ824 exhibited antitumor effects in a xenograft animal model. Together, our data indicated that the activity of NVP-LAQ824 was consistent with its intended mechanism of action. This novel histone deacetylase inhibitor is currently in clinical trials as an anticancer agent.

Bengamide B, a novel sponge-derived marine natural product with broad spectrum antitumor activity, was not suitable for further preclinical development because of its difficult synthesis and very poor water solubility. Bengamide B produced a 31% T/C at its solubility-limited maximum intravenous dose of 33 micromol/kg in MDA-MB-435 breast carcinoma implanted subcutaneously as a xenograft in nude mice. Compound 8a, a bengamide B analogue with three structural changes (t-Bu alkene substituent, unsubstituted lactam nitrogen, and inverted lactam 5'-myristoyloxy group), was as potent as bengamide B in vitro and more efficacious than bengamide B in vivo. A series of ester-modified analogues based on 8a were synthesized and tested in vitro and in vivo (MDA-MB-435). The cyclohexyl- and phenethyl-substituted esters, 8c and 8g, respectively, had in vitro and in vivo activities similar to that of 8a and enhanced water solubility (ca. 1 mg/mL). Consequently, 8c and 8g were tested in the MDA-MB-435 xenograft model at 100 micromol/kg and produced 29% and 57% tumor regression, respectively.