Synthesis of N(4)-(substituted phenyl)-N(4)-alkyl/desalkyl-9H-pyrimido[4,5-b]indole-2,4-diamines and identification of new microtubule disrupting compounds that are effective against multidrug resistant cells.

A series of fourteen N(4)-(substituted phenyl)-N(4)-alkyl/desalkyl-9H-pyrimido[4,5-b]indole-2,4-diamines was synthesized as potential microtubule targeting agents. The synthesis involved a Fisher indole cyclization of 2-amino-6-hydrazinylpyrimidin-4(3H)-one with cyclohexanone, followed by oxidation, chlorination and displacement with appropriate anilines. Compounds 6, 14 and 15 had low nanomolar potency against MDA-MB-435 tumor cells and depolymerized microtubules. Compound 6 additionally had nanomolar GI(50) values against 57 of the NCI 60-tumor panel cell lines. Mechanistic studies showed that 6 inhibited tubulin polymerization and [(3)H]colchicine binding to tubulin. The most potent compounds were all effective in cells expressing P-glycoprotein or the ßIII isotype of tubulin, which have been associated with clinical drug resistance. Modeling studies provided the potential interactions of 6, 14 and 15 within the colchicine site.

Novel water-soluble substituted pyrrolo[3,2-d]pyrimidines: design, synthesis, and biological evaluation as antitubulin antitumor agents.

PURPOSE: To study the effects of a regioisomeric change on the biological activities of previously reported water soluble, colchicine site binding, microtubule depolymerizing agents. METHODS: Nine pyrrolo[3,2-d]pyrimidines were designed and synthesized. The importance of various substituents was evaluated. Their abilities to cause cellular microtubule depolymerization, inhibit proliferation of MDA-MB-435 tumor cells and inhibit colchicine binding to tubulin were studied. One of the compounds was also evaluated in the National Cancer Institute preclinical 60 cell line panel. RESULTS: Pyrrolo[3,2-d]pyrimidine analogs were more potent than their pyrrolo[2,3-d]pyrimidine regioisomers. We identified compounds with submicromolar potency against cellular proliferation. The structure-activity relationship study gave insight into substituents that were crucial for activity and those that improved activity. The compound tested in the NCI 60 cell line is a 2-digit nanomolar (GI(50)) inhibitor of 8 tumor cell lines. CONCLUSION: We have identified substituted pyrrolo[3,2-d]pyrimidines that are water-soluble colchicine site microtubule depolymerizing agents. These compounds serve as leads for further optimization.

Design, synthesis, and cytotoxicity of novel 3-arylidenones derived from alicyclic ketones.

Forty-four novel chalcone-inspired analogs having a 3-aryl-2-propenoyl moiety derived from alicyclic ketones were designed, synthesized, and investigated for cytotoxicity against murine B16 and L1210 cancer cell lines. The analogs belong to four structurally divergent series, three of which (series g, h, and i) contain differently substituted cyclopentanone units and the fourth (series j) contains a 3,3-dimethyl-4-piperidinone moiety. Of these, the analogs in series j showed potential cytotoxic activity against murine B16 (melanoma) and L1210 (lymphoma) cells. The most active compounds 5j, 11j, 15j, and 12h produced IC(50) values from 4.4 to 15 µm against both cell lines. A single-crystal X-ray structure analysis and molecular modeling studies confirmed that these chalcones have an E-geometry about the alkene bond and possess a slightly 'twisted' conformation similar to that of combretastatin A-4. At a concentration of 30 µm, compounds 5j, 11j, and 15j did not cause microtubule depolymerization in cells, suggesting that they have a different mechanism of action.

Synthesis and biological activities of (R)- and (S)-N-(4-Methoxyphenyl)-N,2,6-trimethyl-6,7-dihydro-5H-cyclopenta[d]pyrimidin-4-aminium chloride as potent cytotoxic antitubulin agents.

(R,S)-1 is a potent antimitotic compound. (R)-1·HCl and (S)-1·HCl were synthesized from (R)- and (S)-3-methyladipic acid. Both enantiomers were potent inhibitors of cell proliferation and caused cellular microtubule loss and mitotic arrest. They inhibited purified tubulin assembly and the binding of [(3)H]colchicine to tubulin, with (S)-1 being about twice as potent. Cytotoxicity against 60 tumor cell lines, however, indicated that the (S)-isomer was 10- to 88-fold more potent than the (R)-isomer.

A novel class of trans-methylpyrazoline analogs of combretastatins: synthesis and in-vitro biological testing.

Thirteen methylpyrazoline analogs (1a-m) of combretastatin A-4 (CA-4, 2) were synthesized. The trans-geometry of the two substituted phenyl moieties was ascertained by a single crystal X-ray diffraction study of compound 1d. The cytotoxicities of the analogs against the growth of murine B16 melanoma and L1210 lymphoma cells in culture were measured using the MTT assay. One of the derivatives, 1j, which has the same substituents as CA-4 was the most active in the series with IC(50) values of 3.3 µM and 6.8 µM against the growth of L1210 and B16 cells, respectively. The activity of this analog against human cancer cell lines was confirmed in the NCI 60 panel. The other active analogs against L1210 were 1b and 1f, which gave IC(50) values in the 6-8 µM range. Compound 1j caused microtubule depolymerization with an EC(50) value of 4.1 µM. This compound has good water solubility of 372 µM. Molecular modeling studies using DFT showed that compound 1j adopts a "twisted" conformation mimicking CA-4 that is optimal for binding to the colchicine site of tubulin.

Acetyl analogs of combretastatin A-4: synthesis and biological studies.

The combretastatins have received significant attention because of their simple chemical structures, excellent antitumor efficacy and novel antivascular mechanisms of action. Herein, we report the synthesis of 20 novel acetyl analogs of CA-4 (1), synthesized from 3,4,5-trimethoxyphenylacetone that comprises the A ring of CA-4 with different aromatic aldehydes as the B ring. Molecular modeling studies indicate that these new compounds possess a 'twisted' conformation similar to CA-4. The new analogs effectively inhibit the growth of human and murine cancer cells. The most potent compounds 6k, 6s and 6t, have IC(50) values in the sub-µM range. Analog 6t has an IC(50) of 182 nM in MDA-MB-435 cells and has advantages over earlier analogs due to its enhanced water solubility (456 µM). This compound initiates microtubule depolymerization with an EC(50) value of 1.8 µM in A-10 cells. In a murine L1210 syngeneic tumor model 6t had antitumor activity and no apparent toxicity.

Design and synthesis of novel enhanced water soluble hydroxyethyl analogs of combretastatin A-4.

Thirteen hydroxyethyl- analogs of combretastatin A-4 (CA-4) that contain the 1-(1'-hydroxyethyl)-1-(3",4",5"-trimethoxyphenyl)-2-(substituted phenyl)ethene framework were synthesized. Molecular modeling studies at the DFT level showed that compound 3j adopts a 'twisted' conformation mimicking CA-4. The cytotoxicity of the novel compounds against the growth of murine B16 melanoma and L1210 lymphoma cells in culture was measured using an MTT assay. Three analogs 3f, 3h, and 3j were active. Of these, 3j, which has the same substituents as CA-4 and IC(50) values of 16.1 and 4.1 µM against B16 and L1210 cells, respectively, was selected for further biological evaluation. The activity of 3j was verified by the NCI 60 cell line screen. Compound 3j causes microtubule depolymerization in A-10 cells with an EC(50) of 21.2 µM. Analog 3j, which has excellent water solubility of 479 µM, had antitumor activity in a syngeneic L1210 murine model.