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1.  Substituted 2-Phenyl-Imidazopyridines: A New Class of Drug Leads for Human African Trypanosomiasis 
Journal of medicinal chemistry  2014;57(3):828-835.
A phenotypic screen of a compound library for antiparasitic activity on Trypanosoma brucei, the causative agent of human African trypanosomiasis, led to the identification of substituted 2-(3-aminophenyl) oxazolopyridines as a starting point for hit-to-lead medicinal chemistry. A total of 110 analogues were prepared, which led to the identification of 64, a substituted 2-(3-aminophenyl) imidazopyridine. This compound showed antiparasitic activity in vitro with an EC50 of 2 nM and displayed reasonable drug-like properties when tested in a number of in vitro assays. The compound was orally bioavailable and displayed good plasma and brain exposure in mice. Compound 64 cured mice infected with Trypanosoma brucei when dosed orally down to 2.5 mg/kg. Given its potent anti-parasitic properties and its ease of synthesis, compound 64 represents a new lead for the development of drugs to treat human African trypanosomiasis.
PMCID: PMC3962778  PMID: 24354316
2.  The Protein Farnesyltransferase Inhibitor Tipifarnib as a new Lead for the Development of Drugs against Chagas Disease 
Journal of Medicinal Chemistry  2005;48(17):5415-5418.
Tipifarnib (R115777), an inhibitor of human protein farnesyltransferase (PFT), is shown to be a highly potent inhibitor of Trypanosoma cruzi growth (ED50 = 4 nM). Surprisingly, this is due to the inhibition of cytochrome P450 sterol 14-demethylase (CYP51, EC Homology models of the T. cruzi CYP51 were used for the prediction of the binding modes of the substrate lanosterol and of Tipifarnib, providing a basis for the design of derivatives with selectivity for TcCYP51 over human PFT.
PMCID: PMC3265986  PMID: 16107140
3.  Second Generation Analogs of the Cancer Drug Clinical Candidate Tipifarnib for Anti-Chagas Disease Drug Discovery 
Journal of medicinal chemistry  2010;53(10):3887-3898.
We previously reported that the cancer drug clinical candidate tipifarnib kills the causative agent of Chagas disease, Trypanosoma cruzi, by blocking ergosterol biosynthesis at the level of inhibition of lanosterol 14α-demethylase. Tipifarnib is an inhibitor of human protein farnesyltransferase. We synthesized tipifarnib analogs that no longer bind to protein farnesyltransferase and display increased potency for killing parasites. This was achieved in a structure-guided fashion by changing the substituents attached to the phenyl group at the 4-position of the quinoline ring of tipifarnib and by replacing the amino group by OMe. Several compounds that kill Trypanosoma cruzi at sub-nanomolar concentrations and are devoid of protein farnesyltransferase inhibition were discovered. The compounds are shown to be advantageous over other lanosterol 14α-demethylase inhibitors in that they show only modest potency for inhibition of human cytochrome P450 (3A4). Since tipifarnib displays high oral bioavailability and acceptable pharmacokinetic properties, the newly discovered tipifarnib analogs are ideal leads for the development of drugs to treat Chagas disease.
PMCID: PMC2877169  PMID: 20429511
cytochrome P450; Chagas disease; drug discovery; sterol biosynthesis; structure-based drug design
4.  Potent, Plasmodium-Selective Farnesyltransferase Inhibitors That Arrest the Growth of Malaria Parasites: Structure—Activity Relationships of Ethylenediamine-Analogue Scaffolds and Homology Model Validation 
Journal of medicinal chemistry  2008;51(17):5176-5197.
New chemotherapeutics are urgently needed to combat malaria. We previously reported on a novel series of antimalarial, ethylenediamine-based inhibitors of protein farnesyltransferase (PFT). In the current study, we designed and synthesized a series of second generation inhibitors, wherein the core ethylenediamine scaffold was varied in order to examine both the homology model of Plasmodium falciparum PFT (PfPFT) and our predicted inhibitor binding mode. We identified several PfPFT inhibitors (PfPFTIs) that are selective for PfPFT versus the mammalian isoform of the enzyme (up to 136-fold selectivity), that inhibit the malarial enzyme with IC50 values down to 1 nM, and that block the growth of P. falciparum in infected whole cells (erythrocytes) with ED50 values down to 55 nM. The structure–activity data for these second generation, ethylenediamine-inspired PFT inhibitors were rationalized by consideration of the X-ray crystal structure of mammalian PFT and the homology model of the malarial enzyme.
PMCID: PMC3049929  PMID: 18686940
5.  Structure-Based Design and Synthesis of Potent, Ethylenediamine-Based, Mammalian Farnesyltransferase Inhibitors as Anticancer Agents 
Journal of medicinal chemistry  2010;53(19):6867-6888.
A potent class of anticancer, human farnesyltransferase (hFTase) inhibitors has been identified by “piggy-backing” on potent, antimalarial inhibitors of Plasmodium falciparum farnesyltransferase (PfFTase). On the basis of a 4-fold substituted ethylenediamine scaffold, the inhibitors are structurally simple and readily derivatized, facilitating the extensive structure–activity relationship (SAR) study reported herein. Our most potent inhibitor is compound 1f, which exhibited an in vitro hFTase IC50 value of 25 nM and a whole cell H-Ras processing IC50 value of 90 nM. Moreover, it is noteworthy that several of our inhibitors proved highly selective for hFTase (up to 333-fold) over the related prenyltransferase enzyme geranylgeranyltransferase-I (GGTase-I). A crystal structure of inhibitor 1a co-crystallized with farnesyl pyrophosphate (FPP) in the active site of rat FTase illustrates that the para-benzonitrile moiety of 1a is stabilized by a π–π stacking interaction with the Y361β residue, suggesting a structural explanation for the observed importance of this component of our inhibitors.
PMCID: PMC3045627  PMID: 20822181
6.  Highly Specific and Broadly Potent Inhibitors of Mammalian Secreted Phospholipases A2 
Journal of medicinal chemistry  2008;51(15):4708-4714.
We report a series of inhibitors of secreted phospholipases A2 (sPLA2s) based on substituted indoles, 6,7-benzoindoles, and indolizines derived from LY315920, a well-known indole-based sPLA2 inhibitor. Using the human group X sPLA2 crystal structure, we prepared a highly potent and selective indole-based inhibitor of this enzyme. Also, we report human and mouse group IIA and IIE specific inhibitors and a substituted 6,7-benzoindole that inhibits nearly all human and mouse sPLA2s in the low nanomolar range.
PMCID: PMC2965735  PMID: 18605714
7.  The First Potent Inhibitor of Mammalian Group X Secreted Phospholipase A2: Elucidation of Sites for Enhanced Binding 
Journal of medicinal chemistry  2006;49(10):2858-2860.
Using the X-ray structure of human group X secreted phospholipase A2 (hGX), we carried out structure-based design of indole-based inhibitors and prepared the compounds using a new synthetic route. The most potent compound inhibited hGX and the mouse orthologue with an IC50 of 75 nM. This compound is the most potent hGX inhibitor reported to date and was also found to inhibit a subset of the other mouse and human sPLA2s.
PMCID: PMC2963729  PMID: 16686528
8.  Adenosine Analogues as Selective Inhibitors of Glyceraldehyde-3-phosphate Dehydrogenase of Trypanosomatidae via Structure-Based Drug Design 
Journal of medicinal chemistry  2001;44(13):2080-2093.
In our continuation of the structure-based design of anti-trypanosomatid drugs, parasite-selective adenosine analogues were identified as low micromolar inhibitors of glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Crystal structures of Trypanosoma brucei, Trypanosoma cruzi, Leishmania mexicana, and human GAPDH’s provided details of how the adenosyl moiety of NAD+ interacts with the proteins, and this facilitated the understanding of the relative affinities of a series of adenosine analogues for the various GAPDH’s. From exploration of modifications of the naphthalenemethyl and benzamide substituents of a lead compound, N6-(1-naphthalenemethyl)-2′-deoxy-2′-(3-methoxybenzamido)adenosine (6e), N6-(substituted-naphthalenemethyl)-2′-deoxy-2′-(substituted-benzamido)adenosine analogues were investigated. N6-(1-Naphthalenemethyl)-2′-deoxy-2′-(3,5-dimethoxybenzamido)adenosine (6m), N6-[1-(3-hydroxy-naphthalene)methyl]-2′-deoxy-2′-(3,5-dimethoxybenzamido)adenosine (7m), N6-[1-(3-methoxy-naphthalene)methyl]-2′-deoxy-2′-(3,5-dimethoxybenzamido)adenosine (9m), N6-(2-naphthalene-methyl)-2′-deoxy-2′-(3-methoxybenzamido)adenosine (11e), and N6-(2-naphthalenemethyl)-2′-deoxy-2′-(3,5-dimethoxybenzamido)adenosine (11m) demonstrated a 2- to 3-fold improvement over 6e and a 7100- to 25000-fold improvement over the adenosine template. IC50’s of these compounds were in the range 2–12 μM for T. brucei, T. cruzi, and L. mexicana GAPDH’s, and these compounds did not inhibit mammalian GAPDH when tested at their solubility limit. To explore more thoroughly the structure–activity relationships of this class of compounds, a library of 240 N6-(substituted)-2′-deoxy-2′-(amido)adenosine analogues was generated using parallel solution-phase synthesis with N6 and C2′ substituents chosen on the basis of computational docking scores. This resulted in the identification of 40 additional compounds that inhibit parasite GAPDH’s in the low micromolar range. We also explored adenosine analogues containing 5′-amido substituents and found that 2′,5′-dideoxy-2′-(3,5-dimethoxy-benzamido)-5′-(diphenylacetamido)adenosine (49) displays an IC50 of 60–100 μM against the three parasite GAPDH’s.
PMCID: PMC2957370  PMID: 11405646
9.  Second Generation Tetrahydroquinoline-Based Protein Farnesyltransferase Inhibitors as Antimalarials 
Journal of medicinal chemistry  2007;50(19):4585-4605.
Substituted tetrahydroquinolines (THQs) have been previously identified as inhibitors of mammalian protein farnesyltransferase (PFT). Previously we showed that blocking PFT in the malaria parasite led to cell death and that THQ-based inhibitors are the most potent among several structural classes of PFT inhibitors (PFTIs). We have prepared 266 THQ-based PFTIs and discovered several compounds that inhibit the malarial enzyme in the sub- to low-nanomolar range and that block the growth of the parasite (P. falciparum) in the low-nanomolar range. This body of structure–activity data can be rationalized in most cases by consideration of the X-ray structure of one of the THQs bound to mammalian PFT together with a homology structural model of the malarial enzyme. The results of this study provide the basis for selection of antimalarial PFTIs for further evaluation in preclinical drug discovery assays.
PMCID: PMC2894570  PMID: 17722901
10.  Structurally Simple Inhibitors of Lanosterol 14α-Demethylase Are Efficacious In a Rodent Model of Acute Chagas Disease 
Journal of medicinal chemistry  2009;52(12):3703-3715.
We report structure-activity studies of a large number of dialkyl imidazoles as inhibitors of Trypanosoma cruzi lanosterol-14α-demethylase (L14DM). The compounds have a simple structure compared to posaconazole, another L14DM inhibitor that is an anti-Chagas drug candidate. Several compounds display potency for killing T. cruzi amastigotes in vitro with values of EC50 in the 0.4–10 nM range. Two compounds were selected for efficacy studies in a mouse model of acute Chagas disease. At oral doses of 20–50 mg/kg given after establishment of parasite infection, the compounds reduced parasitemia in the blood to undetectable levels, and analysis of remaining parasites by PCR revealed a lack of parasites in the majority of animals. These dialkyl imidazoles are substantially less expensive to produce than posaconazole and are appropriate for further development toward an anti-Chagas disease clinical candidate.
PMCID: PMC2771698  PMID: 19463001

Results 1-10 (10)