Three Small Molecule Entities (MPK18, MPK334 and YAK308) with Activity against Haemonchus contortus In Vitro.

Due to widespread multi-drug resistance in parasitic nematodes of livestock animals, there is an urgent need to discover new anthelmintics with distinct mechanisms of action. Extending previous work, here we screened a panel of 245 chemically-diverse small molecules for anti-parasitic activity against Haemonchus contortus-an economically important parasitic nematode of livestock. This panel was screened in vitro against exsheathed third-stage larvae (xL3) of H. contortus using an established phenotypic assay, and the potency of select compounds to inhibit larval motility and development assessed in dose-response assays. Of the 245 compounds screened, three-designated MPK18, MPK334 and YAK308-induced non-wildtype larval phenotypes and repeatedly inhibited xL3-motility, with IC50 values of 45.2 µM, 17.1 µM and 52.7 µM, respectively; two also inhibited larval development, with IC50 values of 12.3 µM (MPK334) and 6.5 µM (YAK308), and none of the three was toxic to human liver cells (HepG2). These findings suggest that these compounds deserve further evaluation as nematocidal candidates. Future work should focus on structure-activity relationship (SAR) studies of these chemical scaffolds, and assess the in vitro and in vivo efficacies and safety of optimised compounds against adults of H. contortus.

Isophthalic Acid-Based HDAC Inhibitors as Potent Inhibitors of HDAC8 from Schistosoma mansoni.

Schistosoma mansoni histone deacetylase 8 (SmHDAC8) has been recently identified as a new potential target for the treatment of schistosomiasis. A series of newly designed and synthesized alkoxyamide-based and hydrazide-based HDAC inhibitors were tested for inhibitory activity against SmHDAC8 and human HDACs 1, 6, and 8. The front runner compounds showed submicromolar activity against SmHDAC8 and modest preference for SmHDAC8 over its human orthologue hHDAC8. Docking studies provided insights into the putative binding mode in SmHDAC8 and allowed rationalization of the observed selectivity profile.

Assessing the Anthelmintic Candidates BLK127 and HBK4 for Their Efficacy on Haemonchus contortus Adults and Eggs, and Their Hepatotoxicity and Biotransformation.

As a widely distributed parasitic nematode of ruminants, Haemonchus contortus has become resistant to most anthelmintic classes, there has been a major demand for new compounds against H. contortus and related nematodes. Recent phenotypic screening has revealed two compounds, designated as BLK127 and HBK4, that are active against H. contortus larvae. The present study was designed to assess the activity of these compounds against H. contortus eggs and adults, hepatotoxicity in rats and sheep, as well as biotransformation in H. contortus adults and the ovine liver. Both compounds exhibited no inhibitory effect on the hatching of eggs. The benzyloxy amide BLK127 significantly decreased the viability of adults in sensitive and resistant strains of H. contortus and showed no hepatotoxic effect, even at the highest concentration tested (100 µM). In contrast, HBK4 had no impact on the viability of H. contortus adults and exhibited significant hepatotoxicity. Based on these findings, HBK4 was excluded from further studies, while BLK127 seems to be a potential candidate for a new anthelmintic. Consequently, biotransformation of BLK127 was tested in H. contortus adults and the ovine liver. In H. contortus, several metabolites formed via hydroxylation, hydrolysis and glycosidation were identified, but the extent of biotransformation was low, and the total quantity of the metabolites formed did not differ significantly between the sensitive and resistant strains. In contrast, ovine liver cells metabolized BLK127 more extensively with a glycine conjugate of 4-(pentyloxy)benzoic acid as the main BLK127 metabolite.

Total Synthesis of the Antimycobacterial Natural Product Chlorflavonin and Analogs via a Late-Stage Ruthenium(II)-Catalyzed ortho-C(sp2)-H-Hydroxylation.

The continuous, worldwide spread of multidrug-resistant (MDR) and extensively drug-resistant (XDR) tuberculosis (TB) endanger the World Health Organization's (WHO) goal to end the global TB pandemic by the year 2035. During the past 50 years, very few new drugs have been approved by medical agencies to treat drug-resistant TB. Therefore, the development of novel antimycobacterial drug candidates to combat the threat of drug-resistant TB is urgent. In this work, we developed and optimized a total synthesis of the antimycobacterial natural flavonoid chlorflavonin by selective ruthenium(II)-catalyzed ortho-C(sp2)-H-hydroxylation of a substituted 3'-methoxyflavonoid skeleton. We extended our methodology to synthesize a small compound library of 14 structural analogs. The new analogs were tested for their antimycobacterial in vitro activity against Mycobacterium tuberculosis (Mtb) and their cytotoxicity against various human cell lines. The most promising new analog bromflavonin exhibited improved antimycobacterial in vitro activity against the virulent H37Rv strain of Mtb (Minimal Inhibitory Concentrations (MIC90) = 0.78 µm). In addition, we determined the chemical and metabolic stability as well as the pKa values of chlorflavonin and bromflavonin. Furthermore, we established a quantitative structure-activity relationship model using a thermodynamic integration approach. Our computations may be used for suggesting further structural changes to develop improved derivatives.

Development of a First-in-Class Small-Molecule Inhibitor of the C-Terminal Hsp90 Dimerization.

Heat shock proteins 90 (Hsp90) are promising therapeutic targets due to their involvement in stabilizing several aberrantly expressed oncoproteins. In cancerous cells, Hsp90 expression is elevated, thereby exerting antiapoptotic effects, which is essential for the malignant transformation and tumor progression. Most of the Hsp90 inhibitors (Hsp90i) under investigation target the ATP binding site in the N-terminal domain of Hsp90. However, adverse effects, including induction of the prosurvival resistance mechanism (heat shock response or HSR) and associated dose-limiting toxicity, have so far precluded their clinical approval. In contrast, modulators that interfere with the C-terminal domain (CTD) of Hsp90 do not inflict HSR. Since the CTD dimerization of Hsp90 is essential for its chaperone activity, interfering with the dimerization process by small-molecule protein-protein interaction inhibitors is a promising strategy for anticancer drug research. We have developed a first-in-class small-molecule inhibitor (5b) targeting the Hsp90 CTD dimerization interface, based on a tripyrimidonamide scaffold through structure-based molecular design, chemical synthesis, binding mode model prediction, assessment of the biochemical affinity, and efficacy against therapy-resistant leukemia cells. 5b reduces xenotransplantation of leukemia cells in zebrafish models and induces apoptosis in BCR-ABL1+ (T315I) tyrosine kinase inhibitor-resistant leukemia cells, without inducing HSR.

3-Hydroxy-propanamidines, a New Class of Orally Active Antimalarials Targeting Plasmodium falciparum.

3-Hydroxypropanamidines are a new promising class of highly active antiplasmodial agents. The most active compound 22 exhibited excellent antiplasmodial in vitro activity with nanomolar inhibition of chloroquine-sensitive and multidrug-resistant parasite strains ofPlasmodium falciparum (with IC50 values of 5 and 12 nM against 3D7 and Dd2 strains, respectively) as well as low cytotoxicity in human cells. In addition, 22 showed strong in vivo activity in thePlasmodium berghei mouse model with a cure rate of 66% at 50 mg/kg and a cure rate of 33% at 30 mg/kg in the Peters test after once daily oral administration for 4 consecutive days. A quick onset of action was indicated by the fast drug absorption shown in mice. The new lead compound was also characterized by a high barrier to resistance and inhibited the heme detoxification machinery in P. falciparum.

Inhibition of the Yersinia pestis Methylerythritol Phosphate Pathway of Isoprenoid Biosynthesis by α-Phenyl-Substituted Reverse Fosmidomycin Analogues.

Fosmidomycin inhibits IspC (1-deoxy-d-xylulose 5-phosphate reductoisomerase), the first committed enzyme in the methylerythritol phosphate (MEP) pathway of isoprenoid biosynthesis. The MEP pathway of isoprenoid biosynthesis is essential to the causative agent of the plague, Yersinia pestis, and is entirely distinct from the corresponding mammalian pathway. To further drug development, we established structure-activity relationships of fosmidomycin analogues by assessing a suite of 17 α-phenyl-substituted reverse derivatives of fosmidomycin against Y. pestis IspC. Several of these compounds showed increased potency over fosmidomycin with IC50 values in the nanomolar range. Additionally, we performed antimicrobial susceptibility testing with Y. pestis A1122 (YpA1122). The bacteria were susceptible to several compounds with minimal inhibitory concentration (MIC) values ranging from 128 to 512 µg/mL; a correlation between the IC50 and MIC values was observed.

Phenotypic screening of the 'Kurz-box' of chemicals identifies two compounds (BLK127 and HBK4) with anthelmintic activity in vitro against parasitic larval stages of Haemonchus contortus.

BACKGROUND: Due to anthelmintic resistance problems, there is a need to discover and develop new drugs for the treatment and control of economically important and pathogenic nematodes of livestock animals. With this focus in mind, we screened 236 compounds from a library (called the 'Kurz-box') representing chemically diverse classes such as heterocyclic compounds (e.g. thiazoles, pyrroles, quinolines, pyrimidines, benzo[1,4]diazepines), hydoxamic acid-based metalloenzyme inhibitors, peptidomimetics (bis- and tris-pyrimidoneamides, alkoxyamides) and various intermediates on Haemonchus contortus, one of the most important parasitic nematodes of ruminants. METHODS: In the present study, we tested these compounds, and measured the inhibition of larval motility and development of exsheathed third-stage (xL3) and fourth-stage (L4) larvae of H. contortus using an optimised, whole-organism phenotypic screening assay. RESULTS: Of the 236 compounds, we identified two active compounds (called BLK127 and HBK4) that induced marked phenotypic changes in the worm in vitro. Compound BLK127 induced an 'eviscerated' phenotype in the xL3 stage and also inhibited L4 development. Compound HBK4 exerted a 'curved' phenotype in both xL3s and L4s. CONCLUSIONS: The findings from this study provide a basis for future work on the chemical optimisation of these compounds, on assessing the activity of optimised compounds on adult stages of H. contortus both in vitro and in vivo (in the host animal) and against other parasitic worms of veterinary and medical importance.

Novel reverse thia-analogs of fosmidomycin: Synthesis and antiplasmodial activity.

Thia analogs of fosmidomycin are potent inhibitors of the non-mevalonate isoprenoid biosynthesis enzyme 1-deoxy-d-xylulose 5-phosphate reductoisomerase (IspC, Dxr) of Plasmodium falciparum. Several new thioethers displayed antiplasmodial in vitro activity in the low nanomolar range, without apparent cytotoxic effects in HeLa cells. The (S)-(+)-enantiomer of a typical representative selectively inhibited IspC and the growth of P. falciparum in continuous culture. The inhibitor was stable at pH 7.6 and room temperature, and no racemization was observed under these conditions during a period of up to two days. Oxidation of selected thioethers to sulfones reduced antiplasmodial activity and the inhibitory activity against Escherichia coli, Mycobacterium tuberculosis and P. falciparum IspC orthologs.

3-Hydroxy-N'-arylidenepropanehydrazonamides with Halo-Substituted Phenanthrene Scaffolds Cure P. berghei Infected Mice When Administered Perorally.

Structural optimization of 3-hydroxy-N'-arylidenepropanehydrazonamides provided new analogs with nanomolar to subnanomolar antiplasmodial activity against asexual blood stages of Plasmodium falciparum, excellent parasite selectivity, and nanomolar activity against the earliest forms of gametocyte development. Particularly, derivatives with a 1,3-dihalo-6-trifluoromethylphenanthrene moiety showed outstanding in vivo properties and demonstrated in part curative activity in the Plasmodium berghei mouse model when administered perorally.