Identification of N-acylhydrazone derivatives as novel lactate dehydrogenase A inhibitors

Synthesis and hLDH Inhibitory Activity of Analogues to Natural Products with 2,8-Dioxabicyclo[3.3.1]nonane Scaffold

Human lactate dehydrogenase (hLDH) is a tetrameric enzyme present in almost all tissues. Among its five different isoforms, hLDHA and hLDHB are the predominant ones. In the last few years, hLDHA has emerged as a therapeutic target for the treatment of several kinds of disorders, including cancer and primary hyperoxaluria. hLDHA inhibition has been clinically validated as a safe therapeutic method and clinical trials using biotechnological approaches are currently being evaluated. Despite the well-known advantages of pharmacological treatments based on small-molecule drugs, few compounds are currently in preclinical stage. We have recently reported the detection of some 2,8-dioxabicyclo[3.3.1]nonane core derivatives as new hLDHA inhibitors. Here, we extended our work synthesizing a large number of derivatives (42-70) by reaction between flavylium salts (27-35) and several nucleophiles (36-41). Nine 2,8-dioxabicyclo[3.3.1]nonane derivatives showed IC₅₀ values lower than 10 µM against hLDHA and better activity than our previously reported compound 2. In order to know the selectivity of the synthesized compounds against hLDHA, their hLDHB inhibitory activities were also measured. In particular, compounds 58, 62a, 65b, and 68a have shown the lowest IC₅₀ values against hLDHA (3.6-12.0 µM) and the highest selectivity rate (>25). Structure-activity relationships have been deduced. Kinetic studies using a Lineweaver-Burk double-reciprocal plot have indicated that both enantiomers of 68a and 68b behave as noncompetitive inhibitors on hLDHA enzyme.

Acylhydrazones and Their Biological Activity: A Review

Due to the structure of acylhydrazones both by the pharmacophore -CO-NH-N= group and by the different substituents present in the molecules of compounds of this class, various pharmacological activities were reported, including antitumor, antimicrobial, antiviral, antiparasitic, anti-inflammatory, immunomodulatory, antiedematous, antiglaucomatous, antidiabetic, antioxidant, and actions on the central nervous system and on the cardiovascular system. This fragment is found in the structure of several drugs used in the therapy of some diseases that are at the top of public health problems, like microbial infections and cardiovascular diseases. Moreover, the acylhydrazone moiety is present in the structure of some compounds with possible applications in the treatment of other different pathologies, such as schizophrenia, Parkinson's disease, Alzheimer's disease, and Huntington's disease. Considering these aspects, we consider that a study of the literature data regarding the structural and biological properties of these compounds is useful.

Design and Synthesis of New Pyrimidine-Quinolone Hybrids as Novel hLDHA Inhibitors

A battery of novel pyrimidine-quinolone hybrids was designed by docking scaffold replacement as lactate dehydrogenase A (hLDHA) inhibitors. Structures with different linkers between the pyrimidine and quinolone scaffolds (10-21 and 24−31) were studied in silico, and those with the 2-aminophenylsulfide (U-shaped) and 4-aminophenylsulfide linkers (24−31) were finally selected. These new pyrimidine-quinolone hybrids (24−31)(a−c) were easily synthesized in good to excellent yields by a green catalyst-free microwave-assisted aromatic nucleophilic substitution reaction between 3-(((2/4-aminophenyl)thio)methyl)quinolin-2(1H)-ones 22/23(a−c) and 4-aryl-2-chloropyrimidines (1−4). The inhibitory activity against hLDHA of the synthesized hybrids was evaluated, resulting IC50 values of the U-shaped hybrids 24−27(a−c) much better than the ones of the 1,4-linked hybrids 28−31(a−c). From these results, a preliminary structure−activity relationship (SAR) was established, which enabled the design of novel 1,3-linked pyrimidine-quinolone hybrids (33−36)(a−c). Compounds 35(a−c), the most promising ones, were synthesized and evaluated, fitting the experimental results with the predictions from docking analysis. In this way, we obtained novel pyrimidine-quinolone hybrids (25a, 25b, and 35a) with good IC50 values (<20 μM) and developed a preliminary SAR.

The Biochemical and Clinical Perspectives of Lactate Dehydrogenase: An Enzyme of Active Metabolism

BACKGROUND

Lactate dehydrogenase (LDH) is a group of oxidoreductase isoenzymes catalyzing the reversible reaction between pyruvate and lactate. The five isoforms of this enzyme, formed from two subunits, vary in isoelectric points and these isoforms have different substrate affinity, inhibition constants and electrophoretic mobility. These diverse biochemical properties play a key role in its cellular, tissue and organ specificity. Though LDH is predominantly present in the cytoplasm, it has a multi-organellar location as well.

OBJECTIVE

The primary objective of this review article is to provide an update in parallel, the previous and recent biochemical views and its clinical significance in different diseases.

METHODS

With the help of certain inhibitors, its active site three-dimensional view, reactions mechanisms and metabolic pathways have been sorted out to a greater extent. Overexpression of LDH in different cancers plays a principal role in anaerobic cellular metabolism, hence several inhibitors have been designed to employ as novel anticancer agents.

DISCUSSION

LDH performs a very important role in overall body metabolism and some signals can induce isoenzyme switching under certain circumstances, ensuring that the tissues consistently maintain adequate ATP supply. This enzyme also experiences some posttranslational modifications, to have diversified metabolic roles. Different toxicological and pathological complications damage various organs, which ultimately result in leakage of this enzyme in serum. Hence, unusual LDH isoform level in serum serves as a significant biomarker of different diseases.

CONCLUSION

LDH is an important diagnostic biomarker for some common diseases like cancer, thyroid disorders, tuberculosis, etc. In general, LDH plays a key role in the clinical diagnosis of various common and rare diseases, as this enzyme has a prominent role in active metabolism.

Discovery of a novel lactate dehydrogenase tetramerization domain using epitope mapping and peptides

Despite being initially regarded as a metabolic waste product, lactate is now considered to serve as a primary fuel for the tricarboxylic acid cycle in cancer cells. At the core of lactate metabolism, lactate dehydrogenases (LDHs) catalyze the interconversion of lactate to pyruvate and as such represent promising targets in cancer therapy. However, direct inhibition of the LDH active site is challenging from physicochemical and selectivity standpoints. However, LDHs are obligate tetramers. Thus, targeting the LDH tetrameric interface has emerged as an appealing strategy. In this work, we examine a dimeric construct of truncated human LDH to search for new druggable sites. We report the identification and characterization of a new cluster of interactions in the LDH tetrameric interface. Using nanoscale differential scanning fluorimetry, chemical denaturation, and mass photometry, we identified several residues (E62, D65, L71, and F72) essential for LDH tetrameric stability. Moreover, we report a family of peptide ligands based on this cluster of interactions. We next demonstrated these ligands to destabilize tetrameric LDHs through binding to this new tetrameric interface using nanoscale differential scanning fluorimetry, NMR water–ligand observed via gradient spectroscopy, and microscale thermophoresis. Altogether, this work provides new insights on the LDH tetrameric interface as well as valuable pharmacological tools for the development of LDH tetramer disruptors.

Small Molecule-Based Enzyme Inhibitors in the Treatment of Primary Hyperoxalurias

Primary hyperoxalurias (PHs) are a group of inherited alterations of the hepatic glyoxylate metabolism. PHs classification based on gene mutations parallel a variety of enzymatic defects, and all involve the harmful accumulation of calcium oxalate crystals that produce systemic damage. These geographically widespread rare diseases have a deep impact in the life quality of the patients. Until recently, treatments were limited to palliative measures and kidney/liver transplants in the most severe forms. Efforts made to develop pharmacological treatments succeeded with the biotechnological agent lumasiran, a siRNA product against glycolate oxidase, which has become the first effective therapy to treat PH1. However, small molecule drugs have classically been preferred since they benefit from experience and have better pharmacological properties. The development of small molecule inhibitors designed against key enzymes of glyoxylate metabolism is on the focus of research. Enzyme inhibitors are successful and widely used in several diseases and their pharmacokinetic advantages are well known. In PHs, effective enzymatic targets have been determined and characterized for drug design and interesting inhibitory activities have been achieved both in vitro and in vivo. This review describes the most recent advances towards the development of small molecule enzyme inhibitors in the treatment of PHs, introducing the multi-target approach as a more effective and safe therapeutic option.

Design, synthesis and biological evaluation of novel (E)-N-phenyl-4-(pyridine-acylhydrazone) benzamide derivatives as potential antitumor agents for the treatment of multiple myeloma (MM)

A series of novel (E)-N-phenyl-4-(pyridine-acylhydrazone) benzamide derivatives were designed, synthesized, and evaluated for their anti-proliferative activity against two different human cancer cell lines and one human normal cell line. Compound 8b had the best anti-proliferative activity (IC₅₀ = 0.12 ± 0.09 μM, RPMI8226 cells) than the other compounds. And compound 8b had lower toxicity than imatinib. Flow cytometry analysis showed that compound 8b could arrest the cell cycle at the G0/G1 phase, and induce apoptosis of RPMI8226 cells by promoting mitochondrial ROS release, thereby effectively inhibiting cell proliferation. Our findings provided a promising lead compound 8b for further structural optimization and will be instructive for the discovery of more potent antitumor drugs with high selectivity and low toxicity.

Synthesis of some new acylhydrazone compounds containing the 1,2,4-triazole structure and their neuritogenic activities in Neuro-2a cells

In the present study, a novel series of acylhydrazone compounds (A0–A10) with the structure of 1,2,4-triazole have been designed and synthesized.

Discovery of human lactate dehydrogenase 5 inhibitors (hLDH5) with anti-lung cancer activity through an in silico method and biological validation

Human lactate dehydrogenase 5 (hLDH5) is an important metabolic enzyme playing critical roles in the anaerobic glycolysis. Herein, we employed an in silico method and biological validation to identify a novel hLDH5 inhibitor with a promising cellular activity under hypoxia condition. The identified compound 9 bound to hLDH5 with a K_d value of 1.02 µM, and inhibited the enzyme with an EC₅₀ value of 0.7 µM. Compound 9 exhibited a weak potency against NCI-H1975 cell proliferation under normal condition (IC₅₀ = 36.5 µM), while dramatically increased to 5.7 µM under hypoxia condition. In line with the observation, hLDH5 expression in NCI-H1975 cell under hypoxia condition is much higher as compared to the normal oxygenated condition, indicating the hLDH5 inhibition may contribute to the cancer cell death.

Development of novel human lactate dehydrogenase A inhibitors: High-throughput screening, synthesis, and biological evaluations

Human lactate dehydrogenase A (LDHA) plays a critical role in the glycolytic process, making the enzyme an ideal of anti-cancer drug target. Herein, we report the discovery of novel potent LDHA inhibitors by screening an in-house library. The hit-to-lead modification enabled us to identify compound 24c, which inhibited LDHA activity with an EC₅₀ value of 90 nM, and reduced MiaPaCa-2 cancer cell proliferation with an IC₅₀ value of 2.1 μM. In line with the in vitro anticancer activity, 24c suppressed the tumor growth at a dose of 10 mg/kg in a MiaPaCa-2 cells xenograft model, but with little effect to the mice weight. Moreover, 24c strongly inhibited MiaPaCa-2 cell colonies formation, induced MiaPaCa-2 cell apoptosis, and arrested MiaPaCa-2 cell cycle at G2 phase. In addition, the mitochondrial bioenergetics analysis suggested that 24c could reprogram cancer cell metabolic pathways from glycolysis to oxidation phosphorylation, which verified by decreasing the extracellular acidification rates and lactate formation, and increasing oxygen consumption rate in cancer cell. All these results indicate 24c is a promising metabolic modulator for the anticancer drug development.

Discovery of potent human lactate dehydrogenase A (LDHA) inhibitors with antiproliferative activity against lung cancer cells: virtual screening and biological evaluation

Human lactate dehydrogenase A (LDHA) plays a crucial role in the promotion of glycolysis in invasive tumor cells, and recently, it has been considered as a vital therapeutic target in the field of oncology. Herein, by combining docking-based virtual screening with in vitro biochemical evaluation, we report the discovery of a potent LDHA inhibitor with antiproliferative activity. The enzymatic assay suggested that the identified compound 7 has a good inhibitory activity (IC50 = 0.36 μM) against LDHA. The in vitro cytotoxicity assay demonstrated that compound 7 reduces the growth of A549 and NCI-H1975 lung cancer cells, with EC50 values of 5.5 and 3.0 μM, respectively. These findings indicate that compound 7 could be employed as a useful probe to explore the pharmacology of LDHA.

Evaluation on the inhibition of pyrrol-2-yl ethanone derivatives to lactate dehydrogenase and anticancer activities

Lactate dehydrogenase A (LDH-A) is a potentially important metabolic target for the inhibition of the highly activated glycolysis pathway in cancer cells. In order to develop bifunctional compounds as inhibitor of LDH-A and anticancer agents, two pyrrol-2-yl methanone (or ethanone) derivatives (PM1 and PM2) were synthesized and evaluated as inhibitors of LDH-A based on the enzyme assay and cell assay by spectroscopy analysis. Fluorescence and CD spectra results demonstrated that both the change of second structure of LDH-A and the affinity interaction for compounds to LDH-A gave great effect on the activity of LDH-A. In particular, low concentration of compounds (1μμ-25μμ) could change the level of pyruvate in cancer cells. Moreover, the in vitro assay results demonstrated that pyrrol-2-yl ethanone derivatives can inhibit the proliferation of cancer cells. Therefore, pyrrol-2-yl ethanone derivatives (PM2) can be both LDH-A inhibitor and anticancer agents.

Lactate dehydrogenase inhibition: exploring possible applications beyond cancer treatment

Lactate dehydrogenase (LDH) inhibition is considered a worthwhile attempt in the development of innovative anticancer strategies. Unfortunately, in spite of the involvement of several research institutions and pharma-companies, the discovery of LDH inhibitors with drug-like properties seems a hardly resolvable challenge. While awaiting new advancements, in the present review we will examine other pathologic conditions characterized by increased glycolysis and LDH activity, which could potentially benefit from LDH inhibition. The rationale for targeting LDH activity in these contexts is the same justifying the LDH-based approach in anticancer therapy: because of the enzyme position at the end of glycolytic pathway, LDH inhibitors are not expected to hinder glucose metabolism of normal cells. Moreover, we will summarize the latest contributions in the discovery of enzyme inhibitors and try to glance over the reasons underlying the complexity of this research.

Identification of a potent inhibitor targeting human lactate dehydrogenase A and its metabolic modulation for cancer cell line

Targeting LDHA represents a promising strategy for the development of new anti-cancer agents. We report herein the identification of a potent compound as a direct LDHA inhibitor. The in vitro enzymatic assay revealed that the VS-2 had good inhibitory potency (IC50=0.25μM) to LDHA. Cytotoxic assay suggested that the VS-2 could inhibit MCF-7 cancer cell growth, with the IC50 value low to 1.54μM. The seahorse XF24 experiment validated that the VS-2 served as a modulator to reprogram MCF-7 cancer cell metabolism from glycolysis to mitochondrial respiration.