Metabolomics reveals the phytotoxicity mechanisms of foliar spinach exposed to bulk and nano sizes of PbCO3.

PbCO3 is an ancient raw material for Pb minerals and continues to pose potential risks to the environment and human health through mining and industrial processes. However, the specific effects of unintentional PbCO3 discharge on edible plants remain poorly understood. This study unravels how foliar application of PbCO3 induces phytotoxicity by potentially influencing leaf morphology, photosynthetic pigments, oxidative stress, and metabolic pathways related to energy regulation, cell damage, and antioxidant defense in Spinacia oleracea L. Additionally, it quantifies the resultant human health risks. Plants were foliarly exposed to PbCO3 nanoparticles (NPs) and bulk products (BPs), as well as Pb2+ at 0, 5, 10, 25, 50, and 100 mg·L-1 concentrations once a day for three weeks. The presence and localization of PbCO3 NPs inside the plant cells were confirmed by TEM-EDS analysis. The maximum accumulation of total Pb was recorded in the root (2947.77 mg·kg-1 DW for ion exposure), followed by the shoot (942.50 mg·kg-1 DW for NPs exposure). The results revealed that PbCO3 and Pb2+ exposure had size- and dose-dependent inhibitory effects on spinach length, biomass, and photosynthesis attributes, inducing impacts on the antioxidase activity of CAT, membrane permeability, and nutrient elements absorption and translocation. Pb2+ exhibited pronounced toxicity in morphology and chlorophyll; PbCO3 BP exposure accumulated the most lipid peroxidation products of MDA and H2O2; and PbCO3 NPs triggered the largest cell membrane damage. Furthermore, PbCO3 NPs at 10 and 100 mg·L-1 induced dose-dependent metabolic reprogramming in spinach leaves, disturbing the metabolic mechanisms related to amino acids, antioxidant defense, oxidative phosphorylation, fatty acid cycle, and the respiratory chain. The spinach showed a non-carcinogenic health risk hierarchy: Pb2+ > PbCO3 NPs > PbCO3 BPs, with children more vulnerable than adults. These findings enhance our understanding of PbCO3 particle effects on food security, emphasizing the need for further research to minimize their impact on human dietary health.

D-1553: A novel KRASG12C inhibitor with potent and selective cellular and in vivo antitumor activity.

D-1553 is a small molecule inhibitor selectively targeting KRASG12C and currently in phase II clinical trials. Here, we report the preclinical data demonstrating antitumor activity of D-1553. Potency and specificity of D-1553 in inhibiting GDP-bound KRASG12C mutation were determined by thermal shift assay and KRASG12C -coupled nucleotide exchange assay. In vitro and in vivo antitumor activity of D-1553 alone or in combination with other therapies were evaluated in KRASG12C mutated cancer cells and xenograft models. D-1553 showed selective and potent activity against mutated GDP-bound KRASG12C protein. D-1553 selectively inhibited ERK phosphorylation in NCI-H358 cells harboring KRASG12C mutation. Compared to the KRAS WT and KRASG12D cell lines, D-1553 selectively inhibited cell viability in multiple KRASG12C cell lines, and the potency was slightly superior to sotorasib and adagrasib. In a panel of xenograft tumor models, D-1553, given orally, showed partial or complete tumor regression. The combination of D-1553 with chemotherapy, MEK inhibitor, or SHP2 inhibitor showed stronger potency on tumor growth inhibition or regression compared to D-1553 alone. These findings support the clinical evaluation of D-1553 as an efficacious drug candidate, both as a single agent or in combination, for patients with solid tumors harboring KRASG12C mutation.

MK-8325: A silyl proline-containing NS5A inhibitor with pan-genotype activity for treatment of HCV.

HCV NS5A inhibitors have shown impressive in vitro potency profiles in HCV replicon assays thus making them attractive components for inclusion in an all oral fixed dose combination regimen. Herein, we describe the discovery and characterization of silyl proline-containing HCV NS5A inhibitor MK-8325 with good pan-genotype activity and acceptable pharmacokinetic properties.

Alternative core development around the tetracyclic indole class of HCV NS5A inhibitors.

Herein, we describe our research efforts to develop unique cores in molecules which function as HCV nonstructural protein 5A (NS5A) inhibitors. In particular, various fused tetracyclic cores were identified which showed genotype and mutant activities comparable to the indole-based tetracyclic core.

Matched and mixed cap derivatives in the tetracyclic indole class of HCV NS5A inhibitors.

A matched and mixed capping SAR study was conducted on the tetracyclic indole class of HCV NS5A inhibitors to examine the influence of modifications of this region on the overall HCV virologic resistance profiles.

Alkyl substituted aminal derivatives of HCV NS5A inhibitor MK-8742.

HCV NS5A inhibitors have demonstrated impressive in vitro potency profiles in HCV replicon assays and robust HCV RNA titer reduction in the clinic making them attractive components for inclusion in an all oral fixed dose combination regimen for the treatment of HCV infection. Herein we describe our continued research efforts around the alkyl "Z group" modification of the tetracyclic indole-based NS5A inhibitor MK-8742, which led to the discovery of a series of potent NS5A inhibitors. Compounds 10 and 19 are of particular interests since they are as potent as our previous leads and have much improved rat pharmacokinetic profiles.

Discovery of potent macrocyclic HCV NS5A inhibitors.

HCV NS5A inhibitors have demonstrated impressive in vitro virologic profiles in HCV replicon assays and robust HCV RNA titer reduction in the clinic making them attractive components for inclusion in an all oral fixed-dose combination (FDC) regimen for the treatment of HCV infection. Merck's effort in this area identified MK-4882 and MK-8325 as early development leads. Herein, we describe the discovery of potent macrocyclic NS5A inhibitors bearing the MK-8325 or MK-4882 core structure.

Discovery of fused tricyclic core containing HCV NS5A inhibitors with pan-genotype activity.

HCV NS5A inhibitors have demonstrated impressive in vitro potency profiles in HCV replicon assays and robust HCV RNA titer reduction in the clinic making them attractive components for inclusion in an all oral fixed dose combination regimen for the treatment of HCV infection. Herein, we describe research efforts that led to the discovery of a series of fused tricyclic core containing HCV NS5A inhibitors such as 24, 39, 40, 43, and 44 which have pan-genotype activity and are orally bioavailable in the rat.

Discovery of silyl proline containing HCV NS5A inhibitors with pan-genotype activity: SAR development.

HCV NS5A inhibitors have shown impressive in vitro potency profiles in HCV replicon assays thus making them attractive components for inclusion in an all oral fixed dose combination treatment regimen. Herein we describe the research efforts that led to the discovery of silyl proline containing HCV NS5A inhibitors such as 7e and 8a with pan-genotype activity profile and acceptable pharmacokinetic properties.

Discovery of SCH 900188: A Potent Hepatitis C Virus NS5B Polymerase Inhibitor Prodrug As a Development Candidate.

Starting from indole-based hepatitis C virus (HCV) NS5B polymerase inhibitor lead compound 1, structure modifications were performed at multiple indole substituents to improve potency and pharmacokinetic (PK) properties. Bicyclic quinazolinone was found to be the best substituent at indole nitrogen, while 4,5-furanylindole was identified as the best core. Compound 11 demonstrated excellent potency. Its C2 N,N-dimethylaminoethyl ester prodrug 12 (SCH 900188) demonstrated significant improvement in PK and was selected as the development candidate.

IV. Discovery of CXCR3 antagonists substituted with heterocycles as amide surrogates: improved PK, hERG and metabolic profiles.

The structure-human CXCR3 binding affinity relationship of a series of pyridyl/pyrazinyl-piperazinyl-piperidine derivatives were explored with a focus to improve PK, hERG and metabolic profiles. Several small heterocycles were identified as amide surrogates, which minimized many potential metabolite issues. During the course of SAR development, we have observed the additive effect of desirable functional groups to improve hERG and PK profiles which lead to the discovery of many clinically developable CXCR3 antagonists with excellent overall profile.

Optimization of potency and pharmacokinetics of tricyclic indole derived inhibitors of HCV NS5B polymerase. Identification of ester prodrugs with improved oral pharmacokinetics.

HCV infections are the leading causes for hepatocellular carcinoma and liver transplantation in the United States. Recent advances in drug discovery have identified direct acting antivirals which have significantly improved cure rates in patients. Current efforts are directed towards identification of novel direct acting antiviral targeting different mechanism of actions which could become part of all oral therapies. We recently disclosed the identification of a novel tricyclic indole derived inhibitors of HCV NS5B polymerase that bound to the enzyme close to the active site. In this manuscript we describe further optimization of potency and pharmacokinetics (PK) of these inhibitors to identify compounds in low nM potency against gt-1b. These analogs also demonstrate excellent PK in rats and monkeys when administered as a dimethyl ethyl amino ester prodrug.

Discovery of an irreversible HCV NS5B polymerase inhibitor.

The discovery of lead compound 2e was described. Its covalent binding to HCV NS5B polymerase enzyme was investigated by X-ray analysis. The results of distribution, metabolism and pharmacokinetics were reported. Compound 2e was demonstrated to be potent (replicon GT-1b EC50 = 0.003 µM), highly selective, and safe in in vitro and in vivo assays.

Synthesis and SAR studies of benzimidazolone derivatives as histamine H3-receptor antagonists.

A novel series of benzimidazolone-containing histamine H3-receptor antagonists were prepared and their structure-activity relationship was explored. These benzimidazolone analogs demonstrate potent H3-receptor binding affinities, no P450 enzyme inhibition, and strong H3 functional activity. Compound 1o exhibits the best overall profile with H3Ki=0.95nM and rat AUC=12.9µMh.

Discovery of novel tricyclic indole derived inhibitors of HCV NS5B RNA dependent RNA polymerase.

The characterization of HCV genome has identified various vital functional proteins involved in the life cycle of hepatitis C virus. This has resulted in many novel enzymatic targets that are potential for development of therapeutic agents. The HCV RNA dependent RNA polymerase (HCV NS5B) is one such essential enzyme for HCV replication that has been well characterized and studied by various groups to develop novel therapies for hepatitis C. In this paper, we describe our efforts towards the identification and structure-activity relationship (SAR) of novel tricyclic indole derivatives that bind close to the palm site of the NS5B polymerase. X-ray crystal structure of an inhibitor bound to the polymerase is also described.

A novel class of highly potent irreversible hepatitis C virus NS5B polymerase inhibitors.

Starting from indole-based C-3 pyridone HCV NS5B polymerase inhibitor 2, structure-activity relationship (SAR) investigations of the indole N-1 benzyl moiety were performed. This study led to the discovery of irreversible inhibitors with p-fluoro-sulfone- or p-fluoro-nitro-substituted N-1 benzyl groups which achieved breakthrough replicon assay potency (EC(50) = 1 nM). The formation of a covalent bond with adjacent cysteine-366 thiol was was proved by mass spectroscopy and X-ray crystal structure studies. The C-5 ethyl C-2 carboxylic acid derivative 47 had an excellent oral area-under-the-curve (AUC) of 18 µM·h (10 mg/kg). Its oral exposure in monkeys and dogs was also very good. The NMR ALARM assay, mass spectroscopy experiments, in vitro counter screening, and toxicology assays demonstrated that the covalent bond formation between compound 47 and the protein was highly selective and specific. The overall excellent profile of 47 made it an interesting candidate for further investigation.

Structure-activity relationship (SAR) development and discovery of potent indole-based inhibitors of the hepatitis C virus (HCV) NS5B polymerase.

Starting with the indole-based C-3 pyridone lead HCV polymerase inhibitor 2, extensive SAR studies were performed at different positions of the indole core. The best C-5 groups were found to be compact and nonpolar moieties and that the C-6 attachments were not affecting potency. Limited N-1 benzyl-type substituent studies indicated that the best substitutions were fluoro or methyl groups at 2' or 5' positions of the benzyl group. To improve pharmacokinetic (PK) properties, acylsulfonamides were incorporated as acid isosteres at the C-2 position. Further optimization of the combination at N-1, C-2, C-5, and C-6 resulted in the identification of compound 56, which had an excellent potency in both NS5B enzyme (IC(50) = 0.008 µM) and cell-based replicon (EC(50) = 0.02 µM) assays and a good oral PK profile with area-under-the curve (AUC) of 14 and 8 µM·h in rats and dogs, respectively. X-ray structure of inhibitor 56 bound to the enzyme was also reported.

II. Novel HCV NS5B polymerase inhibitors: discovery of indole C2 acyl sulfonamides.

Development of SAR at the C2 position of indole lead 1, a palm site inhibitor of HCV NS5B polymerase (NS5B IC(50)=0.053µM, replicon EC(50)=4.8µM), is described. Initial screening identified an acyl sulfonamide moiety as an isostere for the C2 carboxylic acid group. Further SAR investigation resulted in identification of acyl sufonamide analog 7q (NS5B IC(50)=0.039µM, replicon EC(50)=0.011µM) with >100-fold improved replicon activity.

III. Identification of novel CXCR3 chemokine receptor antagonists with a pyrazinyl-piperazinyl-piperidine scaffold.

The SAR of a novel pyrazinyl-piperazinyl-piperidine scaffold with CXCR3 receptor antagonist activity was explored. Optimization of the DMPK profile and reduction of hERG inhibition is described. Compound 16e with single-digit CXCR3 affinity, good rat PK and hERG profiles has been identified as a lead for further study.

I. Novel HCV NS5B polymerase inhibitors: discovery of indole 2-carboxylic acids with C3-heterocycles.

SAR development of indole-based palm site inhibitors of HCV NS5B polymerase exemplified by initial indole lead 1 (NS5B IC(50)=0.9 µM, replicon EC(50)>100 µM) is described. Structure-based drug design led to the incorporation of novel heterocyclic moieties at the indole C3-position which formed a bidentate interaction with the protein backbone. SAR development resulted in leads 7q (NS5B IC(50)=0.032 µM, replicon EC(50)=1.4 µM) and 7r (NS5B IC(50)=0.017 µM, replicon EC(50)=0.3 µM) with improved enzyme and replicon activity.