Antitrypanosomal Chloronitrobenzamides.

Human African trypanosomiasis (HAT), a neglected tropical disease caused by Trypanosoma brucei gambiense (Tbg) or Trypanosoma brucei rhodesiense (Tbr), remains a significant public health concern with over 55 million people at risk of infection. Current treatments for HAT face the challenges of poor efficacy, drug resistance, and toxicity. This study presents the synthesis and evaluation of chloronitrobenzamides (CNBs) against Trypanosoma species, identifying previously reported compound 52 as a potent and selective orally bioavailable antitrypanosomal agent. 52 was well tolerated in vivo and demonstrated favorable oral pharmacokinetics, maintaining plasma concentrations surpassing the cellular EC50 for over 24 h and achieving peak brain concentrations exceeding 7 µM in rodents after single oral administration (50 mg/kg). Treatment with 52 significantly extended the lifespan of mice infected with Trypanosoma congolense and T. brucei rhodesiense. These results demonstrate that 52 is a strong antitrypanosomal lead with potential for developing treatments for both human and animal African trypanosomiasis.

A small diversity library of α-methyl amide analogs of sulindac for probing anticancer structure-activity relationships.

Non-steroidal anti-inflammatory drugs (NSAIDs) have a variety of potential indications that include management of pain and inflammation as well as chemoprevention and/or treatment of cancer. Furthermore, a specific form of ibuprofen, dexibuprofen or the S-(+) form, shows interesting neurological activities and has been proposed for the treatment of Alzheimer's disease. In a continuation of our work probing the anticancer activity of small sulindac libraries, we have prepared and screened a small diversity library of α-methyl substituted sulindac amides in the profen class. Several compounds of this series displayed promising activity compared with a lead sulindac analog.

Oxazole and thiazole analogs of sulindac for cancer prevention.

AIM: Experimental and epidemiological studies and clinical trials suggest that nonsteroidal anti-inflammatory drugs possess antitumor potential. Sulindac, a widely used nonsteroidal anti-inflammatory drug, can prevent adenomatous colorectal polyps and colon cancer, especially in patients with familial adenomatous polyposis. Sulindac sulfide amide (SSA) is an amide-linked sulindac sulfide analog that showed in vivo antitumor activity in a human colon tumor xenograft model. Results/methodology: A new analog series with heterocyclic rings such as oxazole or thiazole at the C-2 position of sulindac was prepared and screened against prostate, colon and breast cancer cell lines to probe the effect of these novel substitutions on the activity of sulindac analogs. CONCLUSION: In general, replacement of the amide function of SSA analogs had a negative impact on the cell lines tested. A small number of hits incorporating rigid oxazole or thiazole groups in the sulindac scaffold in place of the amide linkage show comparable activity to our lead agent SSA.

Discovery of an Orally Bioavailable Inhibitor of Defective in Cullin Neddylation 1 (DCN1)-Mediated Cullin Neddylation.

We previously reported the discovery, validation, and structure-activity relationships of a series of piperidinyl ureas that potently inhibit the DCN1-UBE2M interaction. We demonstrated that compound 7 inhibits both the DCN1-UBE2M protein-protein interaction and DCN1-mediated cullin neddylation in biochemical assays and reduces levels of steady-state cullin neddylation in a squamous carcinoma cell line harboring DCN1 amplification. Although compound 7 exhibits good solubility and permeability, it is rapidly metabolized in microsomal models (CLint = 170 mL/min/kg). This work lays out the discovery of an orally bioavailable analogue, NAcM-OPT (67). Compound 67 retains the favorable biochemical and cellular activity of compound 7 but is significantly more stable both in vitro and in vivo. Compound 67 is orally bioavailable, well tolerated in mice, and currently used to study the effects of acute pharmacologic inhibition of the DCN1-UBE2M interaction on the NEDD8/CUL pathway.

Piperidinyl Ureas Chemically Control Defective in Cullin Neddylation 1 (DCN1)-Mediated Cullin Neddylation.

We previously discovered and validated a class of piperidinyl ureas that regulate defective in cullin neddylation 1 (DCN1)-dependent neddylation of cullins. Here, we report preliminary structure-activity relationship studies aimed at advancing our high-throughput screen hit into a tractable tool compound for dissecting the effects of acute DCN1-UBE2M inhibition on the NEDD8/cullin pathway. Structure-enabled optimization led to a 100-fold increase in biochemical potency and modestly increased solubility and permeability as compared to our initial hit. The optimized compounds inhibit the DCN1-UBE2M protein-protein interaction in our TR-FRET binding assay and inhibit cullin neddylation in our pulse-chase NEDD8 transfer assay. The optimized compounds bind to DCN1 and selectively reduce steady-state levels of neddylated CUL1 and CUL3 in a squamous cell carcinoma cell line. Ultimately, we anticipate that these studies will identify early lead compounds for clinical development for the treatment of lung squamous cell carcinomas and other cancers.

Amine Containing Analogs of Sulindac for Cancer Prevention.

BACKGROUND: Sulindac belongs to the chemically diverse family of Non-Steroidal Anti-Inflammatory Drugs (NSAIDs) that effectively prevent adenomatous colorectal polyps and colon cancer, especially in patients with familial adenomatous polyposis. Sulindac sulfide amide (SSA), an amide analog of sulindac sulfide, shows insignificant COX-related activity and toxicity while enhancing anticancer activity in vitro and demonstrating in vivo xenograft activity. OBJECTIVE: Develop structure-activity relationships in the sulindac amine series and identify analogs with promising anticancer activities. METHOD: A series of sulindac amine analogs were designed and synthesized and then further modified in a "libraries from libraries" approach to produce amide, sulfonamide and N,N-disubstituted sulindac amine sub-libraries. All analogs were screened against three cancer cell lines (prostate, colon and breast). RESULTS: Several active compounds were identified viain vitro cancer cell line screening with the most potent compound (26) in the nanomolar range. CONCLUSION: Compound 26 and analogs showing the most potent inhibitory activity may be considered for further design and optimization efforts as anticancer hit scaffolds.

Diverse amide analogs of sulindac for cancer treatment and prevention.

Sulindac is a non-steroidal anti-inflammatory drug (NSAID) that has shown significant anticancer activity. Sulindac sulfide amide (1) possessing greatly reduced COX-related inhibition relative to sulindac displayed in vivo antitumor activity that was comparable to sulindac in a human colon tumor xenograft model. Inspired by these observations, a panel of diverse sulindac amide derivatives have been synthesized and their activity probed against three cancer cell lines (prostate, colon and breast). A neutral analog, compound 79 was identified with comparable potency relative to lead 1 and activity against a panel of lymphoblastic leukemia cell lines. Several new series also show good activity relative to the parent (1), including five analogs that also possess nanomolar inhibitory potencies against acute lymphoblastic leukemia cells. Several new analogs identified may serve as anticancer lead candidates for further development.

Discovery of a Diaminopyrimidine FLT3 Inhibitor Active against Acute Myeloid Leukemia.

Profiling of the kinase-binding capabilities of an aminopyrimidine analogue detected in a cellular screen of the St. Jude small-molecule collection led to the identification of a novel series of FMS-like tyrosine kinase 3 (FLT3) inhibitors. Structure-activity relationship studies led to the development of compounds exhibiting good potency against MV4-11 and MOLM13 acute myelogenous leukemia cells driven by FLT3, regardless of their FLT3 mutation status. In vitro pharmacological profiling demonstrated that compound 5e shows characteristics suitable for further preclinical development.

Screening and Development of New Inhibitors of FtsZ from M. Tuberculosis.

A variety of commercial analogs and a newer series of Sulindac derivatives were screened for inhibition of M. tuberculosis (Mtb) in vitro and specifically as inhibitors of the essential mycobacterial tubulin homolog, FtsZ. Due to the ease of preparing diverse analogs and a favorable in vivo pharmacokinetic and toxicity profile of a representative analog, the Sulindac scaffold may be useful for further development against Mtb with respect to in vitro bacterial growth inhibition and selective activity for Mtb FtsZ versus mammalian tubulin. Further discovery efforts will require separating reported mammalian cell activity from both antibacterial activity and inhibition of Mtb FtsZ. Modeling studies suggest that these analogs bind in a specific region of the Mtb FtsZ polymer that differs from human tubulin and, in combination with a pharmacophore model presented herein, future hybrid analogs of the reported active molecules that more efficiently bind in this pocket may improve antibacterial activity while improving other drug characteristics.

Optimization of a Novel Series of Ataxia-Telangiectasia Mutated Kinase Inhibitors as Potential Radiosensitizing Agents.

We previously reported a novel inhibitor of the ataxia-telangiectasia mutated (ATM) kinase, which is a target for novel radiosensitizing drugs. While our initial lead, compound 4, was relatively potent and nontoxic, it exhibited poor stability to oxidative metabolism and relatively poor selectivity against other kinases. The current study focused on balancing potency and selectivity with metabolic stability through structural modification to the metabolized site on the quinazoline core. We performed extensive structure-activity and structure-property relationship studies on this quinazoline ATM kinase inhibitor in order to identify structural variants with enhanced selectivity and metabolic stability. We show that, while the C-7-methoxy group is essential for potency, replacing the C-6-methoxy group considerably improves metabolic stability without affecting potency. Promising analogues 20, 27g, and 27n were selected based on in vitro pharmacology and evaluated in murine pharmacokinetic and tolerability studies. Compound 27g possessed significantly improve pharmacokinetics relative to that of 4. Compound 27g was also significantly more selective against other kinases than 4. Therefore, 27g is a good candidate for further development as a potential radiosensitizer.

Potent Plasmodium falciparum gametocytocidal activity of diaminonaphthoquinones, lead antimalarial chemotypes identified in an antimalarial compound screen.

Forty percent of the world's population is threatened by malaria, which is caused by Plasmodium parasites and results in an estimated 200 million clinical cases and 650,000 deaths each year. Drug resistance has been reported for all commonly used antimalarials and has prompted screens to identify new drug candidates. However, many of these new candidates have not been evaluated against the parasite stage responsible for transmission, gametocytes. If Plasmodium falciparum gametocytes are not eliminated, patients continue to spread malaria for weeks after asexual parasite clearance. Asymptomatic individuals can also harbor gametocyte burdens sufficient for transmission, and a safe, effective gametocytocidal agent could also be used in community-wide malaria control programs. Here, we identify 15 small molecules with nanomolar activity against late-stage gametocytes. Fourteen are diaminonaphthoquinones (DANQs), and one is a 2-imino-benzo[d]imidazole (IBI). One of the DANQs identified, SJ000030570, is a lead antimalarial candidate. In contrast, 94% of the 650 compounds tested are inactive against late-stage gametocytes. Consistent with the ineffectiveness of most approved antimalarials against gametocytes, of the 19 novel compounds with activity against known anti-asexual-stage targets, only 3 had any strong effect on gametocyte viability. These data demonstrate the distinct biology of the transmission stages and emphasize the importance of screening for gametocytocidal activity. The potent gametocytocidal activity of DANQ and IBI coupled with their efficacy against asexual parasites provides leads for the development of antimalarials with the potential to prevent both the symptoms and the spread of malaria.

Dihydroquinazolinone inhibitors of proliferation of blood and liver stage malaria parasites.

Drugs that target both the liver and blood stages of malaria will be needed to reduce the disease's substantial worldwide morbidity and mortality. Evaluation of a 259-member library of compounds that block proliferation of the blood stage of malaria revealed several scaffolds--dihydroquinazolinones, phenyldiazenylpyridines, piperazinyl methyl quinolones, and bis-benzimidazoles--with promising activity against the liver stage. Focused structure-activity studies on the dihydroquinazolinone scaffold revealed several molecules with excellent potency against both blood and liver stages. One promising early lead with dual activity is 2-(p-bromophenyl)-3-(2-(diethylamino)ethyl)-2,3-dihydroquinazolin-4(1H)-one with 50% effective concentrations (EC50s) of 0.46 µM and 0.34 µM against liver stage Plasmodium berghei ANKA and blood stage Plasmodium falciparum 3D7 parasites, respectively. Structure-activity relationships revealed that liver stage activity for this compound class requires a 3-dialkyl amino ethyl group and is abolished by substitution at the ortho-position of the phenyl moiety. These compounds have minimal toxicity to mammalian cells and are thus attractive compounds for further development.

Optimization of the electrophile of chloronitrobenzamide leads active against Trypanosoma brucei.

We previously reported the phenylchloronitrobenzamides (PCNBs), a novel class of compounds active against the species of trypanosomes that cause Human African Trypanosomiasis (HAT). Herein, we explored the potential to adjust the reactivity of the electrophilic chloronitrobenzamide core. These studies identified compound 7d that potently inhibited the growth of trypanosomes (EC50=120nM for Trypanosoma b. brucei, 18nM for Trypanosoma b. rhodesiense, and 38nM for Trypanosoma b. gambiense) without significant cytotoxicity against mammalian cell lines (EC50>25µM for HepG2, HEK293, Raji, and BJ cell lines) and also had good stability in microsomal models (t1/2>4h in both human and mouse). Overall these properties indicate the compound 7d and its analogs are worth further exploration as potential leads for HAT.

Optimization of chloronitrobenzamides (CNBs) as therapeutic leads for human African trypanosomiasis (HAT).

We previously reported the discovery of the activity of chloronitrobenzamides (CNBs) against bloodstream forms of Trypanosoma brucei . Herein we disclose extensive structure-activity relationship and structure-property relationship studies aimed at identification of tractable early leads for clinical development. These studies revealed a promising lead compound, 17b, that exhibited nanomolar potency against T. brucei (EC50 = 27 nM for T. b. brucei, 7 nM for T. b. rhodesiense, and 2 nM for T. b. gambiense ) with excellent selectivity for parasite cells relative to mammalian cell lines (EC50 > 25 µM). In addition compound 17b displayed suitable physiochemical characteristics and microsomal stability (t1/2 > 4 h for human and mouse) to justify pursuing in vivo studies.

Synthesis and evaluation of methylsulfonylnitrobenzamides (MSNBAs) as inhibitors of the thyroid hormone receptor-coactivator interaction.

We previously identified the methylsulfonylnitrobenzoates (MSNBs) that block the interaction of the thyroid hormone receptor with its obligate transcriptional coactivators and prevent thyroid hormone signaling. As part of our lead optimization work we demonstrated that sulfonylnitrophenylthiazoles (SNPTs), which replace the ester linkage of MSNBs with a thiazole, also inhibited coactivator binding to TR. Here we report that replacement of the ester with an amide (methylsulfonylnitrobenzamides, MSNBA) also provides active TR antagonists.

Antimalarial activity of 10-alkyl/aryl esters and -aminoethylethers of artemisinin.

A series of n-alkyl/aryl esters were synthesized and their in vitro antiplasmodial activity was measured alongside that of previously synthesized aminoethylethers of artemisinin ozonides against various strains of Plasmodium falciparum. The cytotoxicity against human cell lines was also assessed. The esters were synthesized in a one-step reaction by derivatization on carbon C-10 of dihydroartemisinin. Both classes were active against both the 3D7 and K1 strains of P. falciparum, with all compounds being significantly more potent than artemether against both strains. The majority of compounds possessed potency either comparable or more than artesunate with a high degree of selectivity towards the parasitic cells. The 10α-n-propyl 11 and 10α-benzyl 18 esters were the most potent of all synthesized ozonides, possessing a moderate (~3-fold) and significant (22- and 12-fold, respectively) potency increases against the 3D7 and K1 strains, respectively, in comparison with artesunate.

Discovery of novel antimalarial compounds enabled by QSAR-based virtual screening.

Quantitative structure-activity relationship (QSAR) models have been developed for a data set of 3133 compounds defined as either active or inactive against P. falciparum. Because the data set was strongly biased toward inactive compounds, different sampling approaches were employed to balance the ratio of actives versus inactives, and models were rigorously validated using both internal and external validation approaches. The balanced accuracy for assessing the antimalarial activities of 70 external compounds was between 87% and 100% depending on the approach used to balance the data set. Virtual screening of the ChemBridge database using QSAR models identified 176 putative antimalarial compounds that were submitted for experimental validation, along with 42 putative inactives as negative controls. Twenty five (14.2%) computational hits were found to have antimalarial activities with minimal cytotoxicity to mammalian cells, while all 42 putative inactives were confirmed experimentally. Structural inspection of confirmed active hits revealed novel chemical scaffolds, which could be employed as starting points to discover novel antimalarial agents.

Lead optimization of antimalarial propafenone analogues.

Previously reported studies identified analogues of propafenone that had potent antimalarial activity, reduced cardiac ion channel activity, and properties that suggested the potential for clinical development for malaria. Careful examination of the bioavailability, pharmacokinetics, toxicology, and efficacy of this series of compounds using rodent models revealed orally bioavailable compounds that are nontoxic and suppress parasitemia in vivo. Although these compounds possess potential for further preclinical development, they also carry some significant challenges.

Lead optimization of 3-carboxyl-4(1H)-quinolones to deliver orally bioavailable antimalarials.

Malaria is a protozoal parasitic disease that is widespread in tropical and subtropical regions of Africa, Asia, and the Americas and causes more than 800,000 deaths per year. The continuing emergence of multidrug-resistant Plasmodium falciparum drives the ongoing need for the development of new and effective antimalarial drugs. Our previous work has explored the preliminary structural optimization of 4(1H)-quinolone ester derivatives, a new series of antimalarials related to the endochins. Herein, we report the lead optimization of 4(1H)-quinolones with a focus on improving both antimalarial potency and bioavailability. These studies led to the development of orally efficacious antimalarials including quinolone analogue 20g, a promising candidate for further optimization.

Synthesis and evaluation of sulfonylnitrophenylthiazoles (SNPTs) as thyroid hormone receptor-coactivator interaction inhibitors.

We previously identified a series of methylsulfonylnitrobenzoates (MSNBs) that block the interaction of the thyroid hormone receptor with its coactivators. MSNBs inhibit coactivator binding through irreversible modification of cysteine 298 of the thyroid hormone receptor (TR). Although MSNBs have better pharmacological features than our first generation inhibitors (ß-aminoketones), they contain a potentially unstable ester linkage. Here we report the bioisosteric replacement of the ester linkage with a thiazole moiety, yielding sulfonylnitrophenylthiazoles (SNPTs). An array of SNPTs 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 SNPTs were shown to be selective for TR relative to other nuclear hormone receptors (NRs).