We previously identified a series of methylsulfonylnitrobenzoates (MSNB's) that block the interaction of the thyroid hormone receptor with its coactivators. MSNB's inhibits coactivator binding through irreversibly modifying cysteine 298 of thyroid hormone receptor (TR). Although MSNB's have better pharmacological features than our first generation inhibitors (β-aminoketones) they contain a potentially unstable ester linkage. Here we report the bioisosteric replacement of the ester linkage with a thiazole moiety, yielding sulfonylnitrophenylthiazoles (SNPT's). An array of SNPT's representing optimal side chains from the MSNB series was constructed using parallel chemistry and evaluated to test their antagonism of the TR-coactivator interaction. Selected active compounds were evaluated in secondary confirmatory assays including regulation of thyroid response element driven transcription in reporter constructs and native genes. In addition the selected SNPT's shown to be selective for TR relative to other nuclear hormone receptor (NR).

Propafenone, a class Ic antiarrythmic drug, inhibits growth of cultured Plasmodium falciparum. While the drug’s potency is significant, further development of propafenone as an antimalarial would require divorcing the antimalarial and cardiac activities as well as improving the pharmacokinetic profile of the drug. A small array of propafenone analogs was designed and synthesized to address the cardiac ion channel and PK liabilities. Testing of this array revealed potent inhibitors of the 3D7 (drug sensitive) and K1 (drug resistant) strains of P. falciparum that possessed significantly reduced ion channel effects and improved metabolic stability. Propafenone analogues are unusual among antimalarial leads in that they are more potent against the multi-drug resistant K1 strain of P. falciparum compared to the 3D7 strain.

Retinoblastoma is a rare childhood cancer of the retina that begins in utero and is diagnosed in the first years of life. The goals of retinoblastoma treatment are ocular salvage, vision preservation, and reduction of short-and long-term side effects without risking mortality due to tumor dissemination. To identify better chemotherapeutic combinations for the treatment of retinoblastoma, several groups have developed genetic mouse models and orthotopic xenograft models of human retinoblastoma for preclinical testing. Previous studies have implicated the MDMX protein in the suppression of the p53 pathway in retinoblastoma and shown that the MDM2/MDMX antagonist, nutlin-3a, can efficiently induce p53-mediated cell death in retinoblastoma cell lines. However, nutlin-3a cannot be administered systemically to treat retinoblastoma, because it has poor penetration across the blood-ocular barrier. Therefore, we developed an ocular formulation of nutlin-3a, nutlin-3aOC, and tested the pharmacokinetics and efficacy of this new formulation in genetic and human retinoblastoma orthotopic xenograft models of retinoblastoma. Here we show that nutlin-3aOC specifically and efficiently targets the p53 pathway and that the combination of nutlin-3aOC with systemic topotecan is a significantly better treatment for retinoblastoma than currently used chemotherapy in human orthotopic xenografts. Our studies provide a new standardized approach to evaluate and prioritize novel agents for incorporation into future clinical trials for retinoblastoma.

A library of diarylurea IGFR inhibitors was screened for activity against chloroquine-sensitive (3D7) and chloroquine-resistant (K1) strains of Plasmodium falciparum. The 4-aminoquinaldine-derived diarylureas displayed promising antimalarial potency. Further exploration of the B ring of 4-aminoquinaldinyl ureas allowed identification of several quinaldin-4-yl ureas 4{13, 39} and 4{13, 58} sufficiently potent against both 3D7 and K1 strains to qualify as bone fide leads.

Malaria is endemic in tropical and subtropical regions of Africa, Asia, and the Americas. The increasing prevalence of multi-drug-resistant Plasmodium falciparum drives the ongoing need for the development of new antimalarial drugs. In this light, novel scaffolds to which the parasite has not been exposed are of particular interest. Recently, workers at the Swiss Tropical Institute discovered two novel 4-oxo-3-carboxyl quinolones active against the intra-erythrocytic stages of P. falciparum while carrying out rationally directed low-throughput screening of potential antimalarial agents as part of an effort directed by the World Health Organization. Here we report the design, synthesis, and preliminary pharmacologic characterization of a series of analogues of 4-oxo-3-carboxyl quinolones. These studies indicate that the series has good potential for preclinical development.

A sensitive and precise LC-ESI-MS/MS method for determination of nutlin-3a in murine plasma using ketoconazole as an internal standard was developed and validated. Plasma nutlin-3a samples were prepared by either a simple protein precipitation (PP) for the high concentration range (10 – 20,000 ng/mL) or by liquid-liquid extraction (LLE) for the low concentration range (0.25 – 300 ng/mL). Nutlin-3a and ketoconazole were separated on a modified C18 analytical column (4µ, 75x2 mm) with an isocratic mobile phase (acetonitrile/5mM HCOONH4 = 70/30, v/v). The retention times of nutlin-3a and ketoconazole were 1.14 and 1.45 minutes. Detection was achieved by a tandem MS system, monitoring m/z 582/99 and m/z 532/82 for nutlin-3a and ketoconazole, respectively. The PP method was linear in a range of 10 – 20,000 ng/mL (R2 ≥0.993) and the LLE method was linear in a range of 0.25 – 300 ng/mL (R2 ≥0.992). The mean recoveries for PP and LLE were 24% and 78%, respectively. Within-day and between-day precisions were ≤ 4.5% for PP and were ≤ 4.9% for LLE. Within-day and between-day accuracies (% error) ranged from 4.8 to −7.9 for PP, and from −0.2 to −8.4 for LLE. The two extraction methods produced equivalent results, allowing use of both within the same study. This method has been applied to the measurement of nutlin-3a concentrations in murine plasma samples obtained from a preclinical pharmacokinetic study.

In an effort to discover novel anti-trypanosomal compounds, a series of podophyllotoxin analogues coupled to non-steroidal anti-inflammatory drugs (NSAIDs) has been synthesized and evaluated for activity versus Trypanosoma brucei and a panel of human cell lines, revealing compounds with low nano-molar potencies. It was discovered that coupling of NSAIDs to podophyllotoxin increased the potencies of both compounds over 1300-fold. The compounds were shown to be cytostatic in nature and seem to act via depolymerization of tubulin in a manner consistent with the known activities of podophyllotoxin. The potencies against T. brucei correlated directly with LogP values of the compounds, suggesting that the conjugates are acting as hydrophobic tags allowing podophyllotoxin to enter the cell.

Malaria caused by Plasmodium falciparum is a catastrophic disease worldwide (880,000 deaths yearly). Vaccine development has proved difficult and resistance has emerged for most antimalarials. In order to discover new antimalarial chemotypes, we have employed a phenotypic forward chemical genetic approach to assay 309,474 chemicals. Here we disclose structures and biological activity of the entire library, many of which exhibited potent in vitro activity against drug resistant strains, and detailed profiling of 172 representative candidates. A reverse chemical genetic study identified 19 new inhibitors of 4 validated drug targets and 15 novel binders among 61 malarial proteins. Phylochemogenetic profiling in multiple organisms revealed similarities between Toxoplasma gondii and mammalian cell lines and dissimilarities between P. falciparum and related protozoans. One exemplar compound displayed efficacy in a murine model. Overall, our findings provide the scientific community with new starting points for malaria drug discovery.

The trypanosomal cathepsin TbcatB is essential for parasite survival and is an attractive therapeutic target. Herein we report the structure-guided development of TbcatB inhibitors with specificity relative to rhodesain and human cathepsins B and L. Inhibitors were tested for enzymatic activity, trypanocidal activity, and general cytotoxicity. These data chemically validate TbcatB as a drug target, and demonstrate that it is possible to potently and selectively inhibit TbcatB relative to trypanosomal and human homologues.

The androgen receptor (AR), which mediates the signals of androgens, plays a crucial role in prostate related diseases. Although widely used, currently marketed anti-androgenic drugs have significant side effects. Several studies have revealed that non-steroidal anti-inflammatory drugs, like flufenamic acid, block AR transcriptional activity. Herein we describe the development of small molecule analogs of flufenamic acid that antagonize AR. This novel class of AR inhibitors binds to the hormone binding site, blocks AR transcription activity, and acts on AR target genes.

We have previously reported the discovery and preliminary structure activity relationships of a series of β-aminoketones that disrupt the binding of coactivators to TR. However, the most active compounds had moderate inhibitory potency and relatively high cytotoxicity, resulting in narrow therapeutic index. Additionally, preliminary evaluation of in vivo toxicology revealed a significant dose related cardiotoxicity. Here we describe the improvement of pharmacological properties of thyroid hormone receptor coactivator binding inhibitors. A comprehensive survey of the effects of substitutents in key areas of the molecule was carried out, based on mechanistic insight from the earlier report. This study revealed that both electron withdrawing and hydrophobic substituents on the aromatic ring led to higher potency. On the other hand, moving from an alkyl to a sulfonyl alkyl side chain led to reduced cytotoxicity. Finally, utilization of amine moieties having low pKa’s resulted in lowered ion channel activity without any loss of pharmacological activity.

Human African trypanosomiasis (HAT) is caused by the protozoan parasite Trypanosoma brucei. The cysteine proteases of T.brucei have been shown to be crucial for parasite replication and represent an attractive point for therapeutic intervention. Herein we describe the synthesis of a series of thiosemicarbazones and their activity against the trypanosomal cathepsins TbcatB and rhodesain, as well as human cathepsins L and B. The activity of these compounds was determined against cultured T.brucei, and specificity was assessed with a panel of four mammalian cell lines.