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Novel dihydroalkoxybenzyloxopyrimidine (S-DABO) derivatives targeting the non-nucleoside inhibitor (NNI) binding site of human immunodeficiency virus (HIV) reverse transcriptase (RT) have been synthesized using a novel computer model for the NNI binding pocket and tested for their RT inhibitory activity in cell-free assays using purified recombinant HIV RT as well as for their anti-HIV activity in HTL VIIIB-infected peripheral blood mononuclear cells. Our computational approach allowed the identification of several ligand derivatization sites for the generation of more potent S-DABO derivatives. Our lead S-DABO derivative, 5-isopropyl-2-[(methylthiomethyl)thio]-6-(benzyl)-pyrimidin-4-(1H)-one (compound 3), elicited potent anti-HIV activity with an IC50 value of less than 1nM for inhibition of HIV replication without any evidence of cytotoxicity and an unprecedented selectivity index of > 100,000.

We have replaced the pyridyl ring of trovirdine with an alicyclic cyclohexenyl, adamantyl or cis -myrtanyl ring. Only the cyclohexenyl-containing thiourea compound N-[2-(1-cyclohexenyl)ethyl]-N′-[2-(5-bromopyridyl)]-thiourea (HI-346) (as well as its chlorine-substituted derivative N-[2-(1-cyclohexenyl)ethyl]-N′-[2-(5-chloropyridyl)]- thiourea/HI-445) showed RT inhibitory activity. HI-346 and HI-445 effectively inhibited recombinant RT with better IC 50 values than other anti-HIV agents tested. The ranking order of efficacy in cell-free RT inhibition assays was: HI-346 (IC 50 = 0.4 μM) > HI-445 (IC 50 = 0.5 μM) > trovirdine (IC 50 = 0.8 μM) > MKC-442 (IC 50 = 0.8 μM) = delavirdine (IC 50 = 1.5μM) > nevirapine (IC 50 = 23 μM). In accord with this data, both compounds inhibited the replication of the drug-sensitive HIV-1 strain HTLV IIIB with better IC 50 values than other anti-HIV agents tested. The ranking order of efficacy in cellular HIV-1 inhibition assays was: HI-445 = HI-346 (IC 50 = 3 nM) > MKC-442 (IC 50 = 4 nM) = AZT (IC 50 = 4 nM) > trovirdine (IC 50 = 7 nM) > delavirdine (IC 50 = 9 nM) > nevirapine (IC 50 = 34 nM). Surprisingly, the lead compounds HI-346 and HI-445 were 3-times more effective against the multidrug resistant HIV-1 strain RT-MDR with a V106A mutation (as well as additional mutations involving the RT residues 74V,41L, and 215Y) than they were against HTLV IIIB with wild-type RT. HI-346 and HI-445 were 20-times more potent than trovirdine, 200-times more potent than AZT, 300-times more potent than MKC-442, 400-times more potent than delavirdine, and 5000-times more potent than nevirapine against the multidrug resistant HIV-1 strain RT-MDR. HI-445 was also tested against the RT Y181C mutant A17 strain of HIV-1 and found to be >7-fold more effective than trovirdine and >1,400-fold more effective than nevirapine or delavirdine. Similarly, both HI-346 and HI-445 were more effective than trovirdine, nevirapine, and delavirdine against the problematic NNI-resistant HIV-1 strain A17-variant with both Y181C and K103N mutations in RT, although their activity was markedly reduced against this strain. Neither compound exhibited significant cytotoxicity at effective concentrations (CC 50 > 100 μM). These findings establish the lead compounds HI-346 and HI-445 as potent inhibitors of drug-sensitive as well as multidrug-resistant stains of HIV-1.

The thiophene-ethyl thiourea (TET) compound N′-[2-(2-thiophene)ethyl]-N′-[2-(5-bromopyridyl)]-thiourea (compound HI-443 ) was five times more potent than trovirdine, 1250 times more potent than nevirapine, 100 times more potent than delavirdine, 75 times more potent than MKC-442, and 50 times more potent than AZT against the multidrug resistant HIV-1 strain RT-MDR with a V106A mutation. HI-443 was almost as potent against the NNI-resistant HIV-1 strain A17 with a Y181C mutation as it was against HTLV IIIB . The activity of HI-443 against A17 was ten times more potent than that of trovirdine, 2083 times more potent than that of nevirapine, and 1042 times more potent than that of delavirdine. HI-443 inhibited the replication of the NNI-resistant HIV-1 strain A17 variant with Y181C plus K103N mutations in RT with an IC 50 value of 3.3 μM, whereas the IC 50 values of trovirdine, nevirapine, and delavirdine were all >100 μM. These findings establish the novel thiophene containing thiourea compound HI-443 as a novel NNI with potent antiviral activity against NNI-sensitive, NNI-resistant and multidrug-resistant strains of HIV-1.

We report here the synthesis and X-ray structure of a novel spiroketal pyran, SPIKET-P1, as a pharmocophore for the tubulin-depolymerizing marine natural product spongistatin 1. Following its retro-synthetic analysis, SPIKET-P1 was prepared using a versatile 11-step synthetic scheme in a stereocontrolled fashion.

SPIKET-P, a novel synthetic spiroketal pyran, was rationally designed as a pharmocophore for the tubulin depolymerizing marine natural product Spongistatin 1. SPIKET-P was prepared from the commercially available benzyl (R)-(-)-glycidyl ether using a versatile 11-step synthetic scheme in a stereocontrolled fashion. At nanomolar concentrations, SPIKET-P caused tubulin depolymerization in cell-free turbidity assays and exhibited potent cytotoxic activity against cancer cells as evidenced by destruction of microtubule organization, and prevention of mitotic spindle formation in human breast cancer cells.

A novel mono-THF containing synthetic anticancer drug (WHI-261) was designed for targeting a previously unrecognized unique narrow binding cavity on the surface of tubulin. The anti-cancer activity of WHI-261 was confirmed using MTT assays. The structure-based design, synthesis, and biological activity of WHI-261 are reported.

Several thiazolyl thiourea derivatives were designed and synthesized as non-nucleoside inhibitors (NNRTI) of HIV-1 reverse transcriptase. Six lead compounds were identified that showed subnanomolar IC50 values for the inhibition of HIV replication, were minimally toxic to human peripheral blood mononuclear cells (PBMC) with CC50 values ranging from 28 to >100 μM, and showed remarkably high selectivity indices ranging from 28,000 to >100,000. The most promising compound was N-[1-(1-furoylmethyl)]-N′-[2-(thiazolyl)]thiourea (compound 6), which showed potency against two NNRTI-resistant HIV-1 isolates (A17 and A17 variant) at nanomolar to low micromolar concentrations, exhibited much greater potency against both wild-type as well as NNRTI-resistant HIV-1 than nevirapine, delavirdine, HI-443, and HI-244, was minimally toxic to PBMC, and had a selectivity index of >100,000. The potency and minimal cytotoxicity of these aromatic/heterocyclic thiourea compounds suggest that they may be potentially useful as anti-AIDS drugs.

Chiral derivatives of two cyclohexylethyl halopyridyl thiourea compounds (HI-509 and HI-510), two α-methyl benzyl halopyridyl compounds (HI-511 and HI-512), and a cyclohexyl ethyl thiazolyl thiourea compound (HI-513) were synthesized as nonnucleoside inhibitors (NNI) of human immunodeficiency virus (HIV) reverse transcriptase (RT). The R stereoisomers of all five compounds inhibited the recombinant RT in vitro with 100-fold lower IC 50 values. HI-509 R , HI-510 R , HI-511 R , HI-512 R and HI-513 R were active anti-HIV agents and inhibited HIV-1 replication in human peripheral blood mononuclear cells at nanomolar concentrations, whereas their enantiomers were inactive. Each of these five compounds was also active against NNI-resistant HIV-1 strains, with HI-511 R being the most active agent. When tested against the NNI-resistant HIV-1 strain A17 with a Y181C mutation in RT, HI-511 R was found to be 10,000-times more active than nevirapine, 5000-times more active than delavirdine, and 50-times more active than trovirdine. HI-511 R inhibited the HIV-strain A17 variant, containing RT mutations Y181C plus K103N, with an IC 50 value of 2.7 μM, whereas the IC 50 values of nevirapine, delavirdine, and trovirdine against this highly NNI-resistant HIV-1 strain were >100 μM.

A novel mono-THF containing synthetic anticancer drug, COBRA-1, was designed for targeting a previously unrecognized unique narrow binding cavity on the surface of α-tubulin. COBRA-1 inhibited GTP-induced tubulin polymerization in cell-free tubulin turbidity assays. Treatment of human breast cancer and brain tumor (glioblastoma) cells with COBRA-1 caused destruction of microtubule organization and apoptosis. Like other microtubule-interfering agents, COBRA-1 activated the pro-apoptotic c-Jun N-terminal kinase (JNK) signal transduction pathway, as evidenced by rapid induction of c-jun expression.