Search

With over 200 million cases and close to half a million deaths each year, malaria is a threat to global health, particularly in developing countries.

Treatment of tuberculosis (TB) currently takes at least 6 months. Latent Mycobacterium tuberculosis (Mtb) is phenotypically tolerant to most anti-TB drugs. A key hypothesis is that drugs that kill nonreplicating (NR) Mtb may shorten treatment when used in combination with conventional drugs. The Mtb proteasome (Mtb20S) could be such a target because its pharmacological inhibition kills NR Mtb and its genetic deletion renders Mtb unable to persist in mice. Here, we report a series of macrocyclic peptides that potently and selectively target the Mtb20S over human proteasomes, including macrocycle 6. The cocrystal structure of macrocycle 6 with Mtb20S revealed structural bases for the species selectivity. Inhibition of 20S within Mtb by 6 dose dependently led to the accumulation of Pup-tagged GFP that is degradable but resistant to depupylation and death of nonreplicating Mtb under nitrosative stress. These results suggest that compounds of this class have the potential to develop as anti-TB therapeutics.

The DEAD-box family of RNA helicases plays essential roles in both transcriptional and translational mRNA degradation; they unwind short double-stranded RNA by breaking the RNA-RNA interactions. Two DEAD-box RNA helicases, eukaryotic translation initiation factor 4A3 (eIF4A3) and DEAD-box helicase 3 (DDX3X), show high homology in the ATP-binding region and are considered key molecules for cancer progression. Several small molecules that target eIF4A3 and DDX3X have been reported to inhibit cancer cell growth; however, more potent compounds are required for cancer therapeutics, and there is a critical need for high-throughput assays to screen for RNA helicase inhibitors. In this study, we developed novel fluorescence resonance energy transfer-based high-throughput RNA helicase assays for eIF4A3 and DDX3X. Using these assays, we identified several eIF4A3 allosteric inhibitors whose inhibitory effect on eIF4A3 ATPase showed a strong correlation with inhibitory effect on helicase activity. From 102 compounds that exhibited eIF4A3 ATPase inhibition, we identified a selective DDX3X inhibitor, C1, which showed stronger inhibition of DDX3X than of eIF4A3. Small-molecule helicase inhibitors can be valuable for clarifying the molecular machinery of DEAD-box RNA helicases. The high-throughput quantitative assays established here should facilitate the evaluation of the helicase inhibitory activity of compounds.

Proteasomes of pathogenic microbes have become attractive targets for anti-infectives. Coevolving with its human host, Mycobacterium tuberculosis (Mtb) has developed mechanisms to resist host-impos...

Treatment of tuberculosis (TB) currently takes at least 6 months. Latent Mycobacterium tuberculosis (Mtb) are phenotypically tolerant to most anti-TB drugs. A key hypothesis is that drugs that kill non-replicating (NR) Mtb may shorten treatment when used in combination with conventional drugs. The Mtb proteasome (Mtb20S) could be such a target, because its pharmacological inhibition kills NR Mtb and its genetic deletion renders Mtb unable to persist in mice. Here we report a series of macrocyclic peptides that potently and selectively target the Mtb20S over human proteasomes, including macrocycle 6. The co-crystal structure of macrocycle 6 with Mtb20S revealed structural bases for the species selectivity. Inhibition of 20S within Mtb by 6 dose-dependently led to accumulation of Pup-tagged GFP that is degradable but resistant to depupylation., and death of non-replicating Mtb under nitrosative stress. These results suggest that compounds of this class have the potential to develop as anti-TB therapeutics.

[Image: see text] Tuberculosis remains a leading cause of death from a single bacterial infection worldwide. Efforts to develop new treatment options call for expansion into an unexplored target space to expand the drug pipeline and bypass resistance to current antibiotics. Lipoamide dehydrogenase is a metabolic and antioxidant enzyme critical for mycobacterial growth and survival in mice. Sulfonamide analogs were previously identified as potent and selective inhibitors of mycobacterial lipoamide dehydrogenase in vitro but lacked activity against whole mycobacteria. Here we present the development of analogs with improved permeability, potency, and selectivity, which inhibit the growth of Mycobacterium tuberculosis in axenic culture on carbohydrates and within mouse primary macrophages. They increase intrabacterial pyruvate levels, supporting their on-target activity within mycobacteria. Distinct modalities of binding between the mycobacterial and human enzymes contribute to improved potency and hence selectivity through induced-fit tight binding interactions within the mycobacterial but not human enzyme, as indicated by kinetic analysis and crystallography.

Plasmodium falciparum proteasome (Pf20S) inhibitors are active against Plasmodium at multiple stages - erythrocytic stages, gametocyte stages, liver stages and gamete activation, indicating that selective Pf20S inhibitors possess the potential to be therapeutic, prophylactic and transmission-blocking antimalarials. Starting from a reported compound, we developed a noncovalent, macrocyclic peptide inhibitor of the malarial proteasome with high species selectivity and improved pharmacokinetic properties. The compound demonstrates specific, time-dependent inhibition of the b5 subunit of the Plasmodium falciparum proteasome, kills artemisinin-sensitive and artemisinin-resistant P. falciparum isolates in vitro and reduces parasitemia in humanized, P. falciparum -infected mice.

With the aim to discover a gastric antisecretory agent more potent than the existing proton pump inhibitors, novel 3,4-dihydro-1H-spiro(naphthalene-2,2'-piperidin)-1-one derivatives, which could occupy two important lipophilic pockets (described as LP-1 and LP-2) of H+,K+-ATPase and can strongly bind to the K+-binding site, were designed based on a docking model. Among the compounds synthesized, compound 4d showed a strong H+,K+-ATPase-inhibitory activity and a high stomach concentration in rats, resulting in potent inhibitory action on histamine-stimulated gastric acid secretion in rats. Furthermore, 4d exerted significant inhibitory action on histamine-stimulated gastric-acid secretion in rats with a rapid onset and moderate duration of action after the administration. These findings may lead to a new insight into the drug design of potassium-competitive acid blockers.

Proteasomes of pathogenic microbes have become attractive targets for anti-infectives. Co-evolving with its human host, Mycobacterium tuberculosis (Mtb) has developed mechanisms to resist host-imposed nitrosative and oxidative stresses. Genetic deletion or pharmacological inhibition of the Mtb proteasome (Mtb20S) renders non-replicating Mtb susceptible to reactive nitrogen species in vitro and unable to survive in the lungs of mice, validating the Mtb proteasome as a promising target for anti-Mtb agents. Using a structure-guided and flow chemistry-enabled study of structure-activity relationships, we developed phenylimidazole-based peptidomimetics that are highly potent for Mtb20S. X-ray structures of selected compounds with Mtb20S shed light on their selectivity for mycobacterial over human proteasomes.

[Image: see text] The integrin αVβ3 receptor has been implicated in several important diseases, but no antagonists are approved for human therapy. One possible limitation of current small-molecule antagonists is their ability to induce a major conformational change in the receptor that induces it to adopt a high-affinity ligand-binding state. In response, we used structural inferences from a pure peptide antagonist to design the small-molecule pure antagonists TDI-4161 and TDI-3761. Both compounds inhibit αVβ3-mediated cell adhesion to αVβ3 ligands, but do not induce the conformational change as judged by antibody binding, electron microscopy, X-ray crystallography, and receptor priming studies. Both compounds demonstrated the favorable property of inhibiting bone resorption in vitro, supporting potential value in treating osteoporosis. Neither, however, had the unfavorable property of the αVβ3 antagonist cilengitide of paradoxically enhancing aortic sprout angiogenesis at concentrations below its IC(50), which correlates with cilengitide’s enhancement of tumor growth in vivo.

Significance Protozoal proteasome is a validated target for antimalarial drug development, but species selectivity of reported inhibitors is suboptimal. Here we identify inhibitors with improved selectivity for malaria proteasome β5 subunit over each active subunit of human proteasomes. These compounds kill the parasite in each stage of its life cycle. They interact synergistically with a β2 inhibitor and with artemisinin. Resistance to the β5 inhibitor arose through a point mutation in the nonproteolytic β6 subunit. The same mutation made the mutant strain more sensitive to a β2 inhibitor and less fit to withstand irradiation. These findings reveal complex interplay among proteasome subunits and introduce the prospect that combined inhibition of β2 and β5 subunits can afford synergy and thwart resistance., We describe noncovalent, reversible asparagine ethylenediamine (AsnEDA) inhibitors of the Plasmodium falciparum proteasome (Pf20S) β5 subunit that spare all active subunits of human constitutive and immuno-proteasomes. The compounds are active against erythrocytic, sexual, and liver-stage parasites, against parasites resistant to current antimalarials, and against P. falciparum strains from patients in Africa. The β5 inhibitors synergize with a β2 inhibitor in vitro and in mice and with artemisinin. P. falciparum selected for resistance to an AsnEDA β5 inhibitor surprisingly harbored a point mutation in the noncatalytic β6 subunit. The β6 mutant was resistant to the species-selective Pf20S β5 inhibitor but remained sensitive to the species-nonselective β5 inhibitors bortezomib and carfilzomib. Moreover, resistance to the Pf20S β5 inhibitor was accompanied by increased sensitivity to a Pf20S β2 inhibitor. Finally, the β5 inhibitor-resistant mutant had a fitness cost that was exacerbated by irradiation. Thus, used in combination, multistage-active inhibitors of the Pf20S β5 and β2 subunits afford synergistic antimalarial activity with a potential to delay the emergence of resistance to artemisinins and each other.

With the aim to find a novel long-lasting potassium-competitive acid blocker (P-CAB) that would perfectly overcome the limitations of proton pump inhibitors (PPIs), we tried various approaches based on pyrrole derivative 1b as a lead compound. As part of a comprehensive approach to identification of a new drug, we explored excellent compounds that have low lipophilicity by introducing a polar hetero-aromatic group at position 5 of the pyrrole ring. Among the compounds synthesized, fluoropyrrole derivative 37c, which has a 2-F-3-Py group at the fifth position, lower pKa, and much lower ClogP and logD values than 1b dose, showed potent gastric-acid suppressive action resulting from gastric H+,K+-ATPase inhibition in animal models. Its maximum intragastric pH elevation effect was strong in rats, and its duration of action was much longer than that of either lansoprazole or lead compound 1b in dogs. Therefore, compound 37c can be considered a promising new P-CAB with long duration of action.