Synthesis of 1-benzyl-3-(5'-hydroxymethyl-2'-furyl)indazole analogues as novel antiplatelet agents

Discovery of 2,3-Dihydro[1,4]dioxino[2,3-g]benzofuran Derivatives as Protease Activated Receptor 4 (PAR4) Antagonists with Potent Antiplatelet Aggregation Activity and Low Bleeding Tendency

Patients with arterial embolic disease have benefited greatly from antiplatelet therapy. However, hemorrhage risk of antiplatelet agents cannot be ignored. Herein, we describe the discovery of 2,3-dihydro[1,4]dioxino[2,3-g]benzofuran compounds as novel PAR4 antagonists. Notably, the isomers 36 and 37 with the chemotype of phenoxyl methylene substituted on the 2,3-dihydro-1,4-dioxine ring exhibited potent in vitro antiplatelet activity (IC50 = 26.13 nM for 36 and 14.26 nM for 37) and significantly improved metabolic stability in human liver microsomes (T1/2 = 97.6 min for 36 and 11.1 min for BMS-986120). 36 also displayed good oral PK profiles (mice: T1/2 = 7.32 h and F = 45.11%). Both of them showed overall potent ex vivo antiplatelet activity at concentrations of 6 and 12 mg/kg, with no impact on the coagulation system and low bleeding liability. Our work will facilitate development of novel PAR4 antagonists as a safer therapeutic option for arterial embolism.

Synthesis and Photophysical Properties of 3-Substituted-1H-Indazoles: A Pd-Catalyzed Double C-N Bond Formation Strategy via 1,6-Conjugate Addition

A Pd-catalyzed cascade process for the direct synthesis of 3-substituted-1H-indazole employing p-quinone methide (p-QM) and arylhydrazine through Pd-catalyzed double C-N bond formation via 1,6-conjugate addition is reported. This reaction strategy affords efficient and practical access to synthetically important diverse 3-substituted-1H-indazoles in good yields. The photophysical properties of the synthesized 3-substituted-1H-indazoles are investigated, and some of them showed very good fluorescence properties with quantum yields up to 85%. Also, the synthesized 3-substituted-1H-indazole exhibits an acid-sensitive fluorescence turn-off activity.

Synthesis and in Silico Studies of Some New 1,2,3-Triazolyltetrazole Bearing Indazole Derivatives as Potent Antimicrobial Agents

1,2,3-Triazole and tetrazole derivatives bearing pyrrolidines are found to exhibit notable biological activity and have become useful scaffolds in medicinal chemistry for application in lead discovery and optimization. Novel indazole bearing 1,2,3-triazolyltetrazoles were designed as potential antimicrobial candidates. The structure of duel heterocyclics was validated by a spectroscopic technique of infrared (IR), nuclear magnetic resonance (1 H and 13 C NMR), and mass spectral data. Compounds 4b, 4c, 4d, and 4h were found to have a stronger antibacterial effect against Gram-positive (S. aureus, B. subtilis, M. Luteus) and Gram-negative (E. coli, P. aeruginosa) microorganisms with MICs ranging from 5±0.03-18±0.02 μM, respectively. Moreover, scaffolds 4a, 4h showed potent antifungal activity against A. flavus, M. gypsuem strains with MIC values of 10±0.02, 11±0.01 μM, which are similar activity that of the standard Itraconazole (MIC=8±0.02, 10±0.01 μM). The binding mode for compound 4 inside the catalytic pocket of S. aureus complexed with nicotinamide adenine dinucleotide phosphate and trimethoprim and produced a network of hydrophobic and hydrophilic interactions (3FRE). From in silico results, 4b demonstrated highly stable hydrogen binding amino acids Leu62(X) [N18…O, 2.47 Å], Arg44(X) [N17…N, 3.11 Å], Thr96(X) [N10…OG1, 3.05 Å], Gly94(X) [F7…N, 2.82 Å], and Gly43(X) [F7…N, 2.90 Å], which are plays a crucial role in ensuring efficient binding of the ligand in a crystal structure of antibacterial receptor. Furthermore, the physicochemical and ADME filtration molecular properties, estimation of toxicity, and bioactivity scores of these novel scaffolds were evaluated by using SwissADME and ADMETlab2.0 online protocols. Thus, the significant antimicrobial activity of indazole linked to duel heterocyclic compounds can be used for development of new antimicrobial agents with further modifications.

A Scalable and Metal-Free Synthesis of Indazoles from 2-Aminophenones and In Situ Generated De-Boc-Protected O-Mesitylsulfonyl Hydroxylamine Derivatives

A one-pot metal-free protocol to access indazoles from easily available 2-aminophenones and hydroxylamine derivatives has been achieved. The reaction is operationally simple, mild, and insensitive to air and moisture. A broad range of indazoles were prepared in good to excellent yield (up to 97% yield), and the reaction displayed a broad functional group tolerance. The reaction was performed at gram scale, and its synthetic application was exhibited through the rapid and efficient preparation of bioactive molecule YC-3 and FDA-approved drug axitinib.

Metal-Free Synthesis of 2H-Indazole Skeletons by Photochemistry or Thermochemistry

A simple and tuned synthesis of a 2H-indazole skeleton under metal-free conditions was developed. Under visible-light irradiation at room temperature, 2-((aryl/alkyl/H)ethynyl))aryltriazenes reacted with arylsulfinic acids to afford 3-functionalized 2H-indazoles without extra photocatalyst via an electron donor-acceptor complex. In the presence of arylsulfinic acid, 2-(ethynyl)aryltriazenes underwent an intramolecular oxidation/cyclization to provide 2H-indazole-3-carbaldehydes at 50 °C in air.

Photoredox-catalyzed trifluoromethylation of 2H-indazoles using TT-CF3+OTf- in ionic liquids

A protocol for metal and oxidant free photoredox catalyzed trifluoromethylation of 2H-indazoles was developed by using Eosin Y as the photocatalyst and recoverable ionic liquids as the solvents. A series of trifluoromethylated products were obtained in moderate to good yields in this protocol under mild conditions. The reaction proceeded via a free-radical mechanism with a broad substrate range, excellent regioselectivity, and good functional group tolerance. Furthermore, the utility of this protocol was demonstrated by the synthesis of a highly selective ligand for estrogen receptor beta (ERβ) and the drug granisetron. The protocol provides a mild and environmentally friendly solution for trifluoromethylation reaction.

A review on synthetic strategy, molecular pharmacology of indazole derivatives, and their future perspective

With different nitrogen-containing heterocyclic moieties, Indazoles earn one of the places among the top investigated molecules in medicinal research. Indazole, an important fused aromatic heterocyclic system containing benzene and pyrazole ring with a chemical formula of C₇ H₆ N₂ , is also called benzopyrazole. Indazoles consist of three tautomeric forms in which 1H-tautomers (indazoles) and 2H-tautomers (isoindazoles) exist in all phases. The tautomerism in indazoles greatly influences synthesis, reactivity, physical and even the biological properties of indazoles. The thermodynamic internal energy calculation of these tautomers points view 1H-indazole as the predominant and stable form over 2H-indazole. The natural source of indazole is limited and exists in alkaloidal nature (i.e., nigellidine, nigeglanine, nigellicine, etc.) found from Nigella plants. Some of the FDA-approved drugs like Axitinib, Entrectinib, Niraparib, Benzydamine, and Granisetron are being used to treat renal cell cancer, non-small cell lung cancer (NSCLC), epithelial ovarian cancer, chronic inflammation, chemotherapy-induced nausea, vomiting, and many more uses. Besides all these advantages regarding its biological activity, the main issue about indazoles is the less abundance in plant sources, and their synthetic derivatives also often face problems with low yield. In this review article, we discuss its chemistry, tautomerism along with their effects, different schematics for the synthesis of indazole derivatives, and their different biological activities.

Late-stage ortho-C-H alkenylation of 2-arylindazoles in aqueous medium by Manganese(i)-catalysis

Earth-abundant and water-tolerant manganese(i) catalyzed alkenylation of 2-arylindazole with alkyl and aryl alkynes through C–H bond activation is described with a unique level of E-selectivity. The reaction proceeds through the control of C3 nucleophilicity of 2-aryl indazoles. This method is applied to the late-stage functionalization of complex molecules including ethinylestradiol, norethisterone, and N-protected amino acid derivatives. The kinetic isotope studies suggest that the C–H bond activation step may not be the rate-determining step.

Earth-abundant and water-tolerant manganese(i) catalyzed alkenylation of 2-arylindazole with alkyl and aryl alkynes through C–H bond activation is described with a unique level of E-selectivity.

Discovery of Two Novel Antiplatelet Clinical Candidates (BMS-986120 and BMS-986141) That Antagonize Protease-Activated Receptor 4

Protease-activated receptor 4 (PAR4) is a G-protein coupled receptor that is expressed on human platelets and activated by the coagulation enzyme thrombin. PAR4 plays a key role in blood coagulation, and its importance in pathological thrombosis has been increasingly recognized in recent years. Herein, we describe the optimization of a series of imidazothiadiazole PAR4 antagonists to a first-in-class clinical candidate, BMS-986120 (43), and a backup clinical candidate, BMS-986141 (49). Both compounds demonstrated excellent antithrombotic efficacy and minimal bleeding time prolongation in monkey models relative to the clinically important antiplatelet agent clopidogrel and provide a potential opportunity to improve the standard of care in the treatment of arterial thrombosis.

Molecular dynamics and 3D-QSAR studies on indazole derivatives as HIF-1α inhibitors

Hypoxia-inducible factor (HIF) is a transcriptional factor which plays a crucial role in tumour metastasis thereby responsible for development of various forms of cancers. Indazole derivatives have been reported in the literature as potent HIF-1α inhibitor via interaction with key residues of the HIF-1α active site. Taking into consideration the role HIF-1α in cancer and potency of indazole derivative against HIF-1α; it was considered of interest to correlate structural features of known indazole derivatives with specified HIF-1α inhibitory activity to map pharmacophoric features through Three-dimensional quantitative structural activity relationship (3D-QSAR) and pharmacophore mapping. Field and Gaussian based 3D-QSAR studies were performed to realize the variables influencing the inhibitory potency of HIF-1α inhibitors. Field and Gaussian- based 3D-QSAR models were validated through various statistical measures generated by partial least square (PLS). The steric and electrostatic maps generated for both 3D-QSAR provide a structural framework for designing new inhibitors. Further; 3D-maps were also helpful in understanding variability in the activity of the compounds. Pharmacophore mapping also generates a common five-point pharmacophore hypothesis (A₁D₂R₃R₄R₅_4) which can be employed in combination with 3D-contour maps to design potent HIF-1α inhibitors. Molecular docking and molecular dynamics (MD) simulation of the most potent compound 39 showed good binding efficiency and was found to be quite stable in the active site of the HIF-1α protein. The developed 3D-QSAR models; pharmacophore modelling; molecular docking studies along with the MD simulation analysis may be employed to design lead molecule as selective HIF-1α inhibitors for the treatment of Cancer.

Inhibitors of protease activated receptor 4 (PAR4): a review of recent patents (2013-2021)

INTRODUCTION

Protease-activated receptor 4 (PAR4), belonging to a subfamily of G-protein-coupled receptors (GPCR), is expressed on the surface of Human platelets, and the activation of it can lead to platelets aggregation. Studies demonstrated that PAR4 inhibition protect mice from arterial/arteriolar thrombosis, pulmonary embolism and cerebral infarct, while do not affect the haemostatic responses integrity. Therefore, PAR4 has been a promising target for the development of anti-thrombotic agents.

AREAS COVERED

This review covers recent patents and literature on PAR4 and their application published between 2013 and 2021.

EXPERT OPINION

PAR4 is a promising anti-thrombotic target and PAR4 inhibitors are important biologically active compounds for the treatment of thrombosis. Most the recent patents and literature focus on PAR4 selective inhibitors, and BMS-986120 and BMS-986141, which were developed by BMS, have entered clinical trials. With the deep understanding of the crystal structures and biological functions of PAR4, we believe that many other novel types of molecules targeting PAR4 would enter the clinical studies or the market.

Unorthodox cascade reaction of arynes and N-nitrosamides leading to indazole scaffolds

An unusual cascade annulation of arynes with N-alkyl-N-nitrosamides is developed by leveraging aryne σ-insertion and C(sp³)-H bond functionalization strategies under transition-metal-free conditions at ambient temperature, offering functionalized indazoles in high yields and regioselectivity. The protocol is scalable and exhibits a broad substrate scope. The reaction mechanism is also studied with DFT calculations.

Unravelling the catalytic potential of a magnetic CoFe2O4/Cu–ABDC MOF composite in the sustainable synthesis of 2H-indazole motifs

A magnetic CoFe2O4/Cu–ABDC hybrid composite was fabricated for the synthesis of biologically active and pharmacologically significant 2H-indazole scaffolds.

Synthetic strategy and structure-activity relationship (SAR) studies of 3-(5'-hydroxymethyl-2'-furyl)-1-benzyl indazole (YC-1, Lificiguat): a review

Since 1994, YC-1 (Lificiguat, 3-(5′-hydroxymethyl-2′-furyl)-1-benzylindazole) has been synthesized, and many targets for special bioactivities have been explored, such as stimulation of platelet-soluble guanylate cyclase, indirect elevation of platelet cGMP levels, and inhibition of hypoxia-inducible factor-1 (HIF-1) and NF-κB. Recently, Riociguat®, the first soluble guanylate cyclase (sGC) stimulator drug used to treat pulmonary hypertension and pulmonary arterial hypertension, was derived from the YC-1 structure. In this review, we aim to highlight the synthesis and structure–activity relationships in the development of YC-1 analogs and their possible indications.

Since 1994, YC-1 (Lificiguat) has been synthesized, and many targets for special bioactivities have been explored, such as stimulation of platelet-soluble guanylate cyclase, indirect elevation of platelet cGMP levels, and inhibition of HIF-1 and NF-κB.

Discovery and Optimization of a Novel Series of Competitive and Central Nervous System-Penetrant Protease-Activated Receptor 4 (PAR4) Inhibitors

The detailed pharmacology and therapeutic potential of the central PAR4 receptors are poorly understood due to a lack of potent, selective, and brain-penetrant tool compounds. Despite this, robust data with biochemical and genetic tools show the therapeutic potential of PAR4 antagonists in traumatic brain injury, Alzheimer's disease, Parkinson's disease, and other neurodegenerative disorders with a neuroinflammatory component. Thus, we performed a functional HTS campaign, identified a fundamentally new PAR4 competitive inhibitor chemotype, optimized this new series (increased potency >45-fold), discovered enantiospecific activity (though opposing preference for human versus mouse PAR4), and engendered high central nervous system penetration (rat K_p's of 0.52 to 4.2 and K_p,uu's of 0.52 to 1.2).

Synthesis and evaluation of novel and potent protease activated receptor 4 (PAR4) antagonists based on a quinazolin-4(3H)-one scaffold

Protease activated receptor 4 (PAR4) is an important target in antiplatelet therapy to reduce the risk of heart attack and thrombotic complications in stroke. PAR4 antagonists can prevent harmful and stable thrombus growth, while retaining initial thrombus formation, by acting on the late diffusion stage of platelet aggregation, and may provide a safer alternative to other antiplatelet agents. To date, only two PAR4 antagonists, BMS-986120 and BMS-986141 have entered clinical trials for thrombosis. Thus, the development of a potent and selective PAR4 antagonist with a novel chemotype is highly desirable. In this study, we explored the activity of quinazolin-4(3H)-one-based PAR4 antagonists, beginning with their IDT analogues. By repeated structural optimisation, we developed a series of highly selective PAR4 antagonists with nanomolar potency on human platelets. Of these, 13 and 30g, with an 8-benzo[d]thiazol-2-yl-substituted quinazolin-4(3H)-one structure, showed optimal activity (h. PAR4-AP PRP IC₅₀ = 19.6 nM and 6.59 nM, respectively) on human platelets. Furthermore, 13 and 30g showed excellent selectivity for PAR4 versus PAR1 and other receptors (IC₅₀s > 10 μM) on human platelets. And 13 and 30g were lack of cross-reactivity for PAR1 or PAR2 (PAR1 AP FLIPR IC₅₀ > 3162 nM, PAR2 AP FLIPR IC₅₀ > 1000 nM) in the calcium mobilization assays. Metabolic stability assays and cytotoxicity tests of 13 and 30g indicated that these compounds could sever as promising drug candidates for the development of novel PAR4 antagonists. In summary, the quinazolin-4(3H)-one-based analogues are the first reported chemotypes with excellent activity and selectivity against PAR4, and, in the current study, we expanded the structural diversity of PAR4 antagonists. The two compounds, 13 and 30g, found in our study could be promising starting points with great potential for further research in antiplatelet therapy.

Potassium Persulfate Mediated Chemodivergent C-3 Functionalization of 2H-Indazoles with DMSO as C1 Source

A facile, efficient, and transition-metal-free chemodivergent C-3 functionalization of 2H-indazoles was developed under aerobic conditions using carboxylic acid and DMSO as the combined source of the carboxylic acid ester group and DMSO as the formylating agent. A series of formylated indazoles and carboxylic acid esters of indazole derivatives were produced in moderate to excellent yields. The mechanistic studies suggest that the reactions probably proceed through a radical pathway.

Fluorination of 2H-Indazoles Using N-Fluorobenzenesulfonimide

An efficient, simple, and metal-free fluorination of 2H-indazoles has been developed using N-fluorobenzenesulfonimide (NFSI) in water under ambient air. This transformation provides direct access to fluorinated indazole derivatives with broad functionalities in satisfactory yields. The experimental results suggest a radical mechanistic pathway of this protocol.

Oxidative cross-dehydrogenative coupling (CDC) via C(sp2)-H bond functionalization: tert-butyl peroxybenzoate (TBPB)-promoted regioselective direct C-3 acylation/benzoylation of 2H-indazoles with aldehydes/benzyl alcohols/styrenes

An efficient, cost-effective, transition-metal-free, oxidative C_(sp²)–H/C_(sp²)–H cross-dehydrogenative coupling via a C_(sp²)–H bond functionalization protocol for the regioselective direct C-3 acylation/benzoylation of substituted 2H-Indazoles 1a–m with substituted aldehydes 2a–q/benzyl alcohols 5a–e/styrenes 6a–e is reported. The operationally simple protocol proceeds in the presence of tert-butyl peroxybenzoate (TBPB) as an oxidant in chlorobenzene (PhCl) as a solvent at 110 °C for 24 h under an inert atmosphere, which furnished a diverse variety of substituted 3-(acyl/benzoyl)-2H-indazoles 3a–q/4a–l in up to 87% yields. The reaction involves a free-radical mechanism and proceeds via the addition of an in situ generated acyl radical (from aldehydes/benzyl alcohols/styrenes) on 2H-indazoles. The functional group tolerance, broad substrate scope, control/competitive experiments and gram-scale synthesis and its application to the synthesis of anti-inflammatory agent 11 and novel indazole-fused diazepine 13 further signify the versatile nature of the developed methodology.

An efficient transition-metal-free oxidative C_(sp²)–H/C_(sp²)–H cross-dehydrogenative coupling via C_(sp²)–H bond functionalization for regioselective C-3 acylation/benzoylation of 2H-indazoles with aldehydes/benzyl alcohols/styrenes is reported.

Protease activated receptor 4 (PAR4) antagonists: Research progress on small molecules in the field of antiplatelet agents

Protease activated receptor 4 (PAR4) is a key target in antiplatelet medication to reduce the risk of heart attack and thrombotic complications in stroke. PAR4 antagonists can prevent harmful and stable thrombus growth while retaining initial thrombus formation by acting on the late diffusion stage of platelet activation, which may provide a safer alternative than other antiplatelet agents. Currently, research on PAR4 antagonists is of increasing interest in the field of antiplatelet agents. This article provides an overview of the discovery and development of small-molecule antagonists of PAR4 as novel antiplatelet agents, including structure-activity relationship (SAR) analysis, progress of structure and bioassay optimization, and the latest structural and/or clinical information of representative small-molecule antagonists of PAR4.

Bu4NI-catalyzed, oxidative C(sp2)–C(sp3) cross dehydrogenative coupling for the regioselective direct C-3 benzylation of 2H-indazoles

A Bu₄NI-catalyzed, DTBP-promoted, regioselective C_(sp2)–C_(sp3) cross dehydrogenative coupling (CDC) protocol for the direct C-3 benzylation of 2H-indazoles is reported.

Regioselective C3-H Trifluoromethylation of 2 H-Indazole under Transition-Metal-Free Photoredox Catalysis

Trifluoromethyl-substituted heteroarenes are biologically active compounds and useful building blocks. In this sequence, we have developed a visible-light-promoted regioselective C3-H trifluoromethylation of 2 H-indazole under metal-free conditions, which proceeds via a radical mechanism. The combination of photocatalysis and hypervalent iodine reagent provides a practical approach to a library of trifluoromethylated indazoles in 35-83% yields.

Mn(III)-Mediated C-H Phosphorylation of Indazoles with Dialkyl Phosphites

A direct and efficient Mn(III) acetate-mediated phosphorylation of 2H-indazoles with dialkyl phosphites has been achieved under mild reaction conditions. A series of phosphorylated products with a wide range of functional groups were obtained in moderate to good yields. A radical mechanism has been proposed for the present protocol.

Copper nanoparticles supported on charcoal mediated one-pot three-component synthesis of N-substituted-2H-indazoles via consecutive condensation C–N and N–N bond formation

An efficient and straightforward protocol for direct synthesis of 2H-indazoles is achieved from consecutive condensation of 2-halobenzaldehydes, primary amines, and sodium azide catalyzed by heterogeneous copper nanoparticles on charcoal (Cu/C) is achieved. The recoverable heterogeneous copper nanoparticles on charcoal (Cu/C) catalyst exhibited an impressive activity for the title reaction without any additives (expensive ligands, etc.). A series of structurally diverse 2H-indazoles were prepared in good to excellent yields from easily accessible starting materials by employing this protocol.

Microwave Domino Diastereoselective Synthesis of Novel Trans-4,5-Dihydro-1H-Furo[2,3-c]Pyrazoles Using Pyridinium Salts in an Aqueous Medium

Novel fused 4,5-dihydro-1 H-furo[2,3- c]pyrazole derivatives containing both biologically active pyrazole and furan templates are synthesised by a one-pot two-step four-component domino reaction involving hydrazine hydrate, a β-keto ester, an aromatic aldehyde and a pyridinium salt catalysed by DABCO with high diastereoselectivity in H2O under microwave irradiation. To minimise the formation of byproducts, the hydrazine hydrate and ethyl acetoacetate were first irradiated until a pyrazolone was formed. Next, the aryl aldehyde, the pyridinium salt and DABCO were added and the reaction could be completed in good to excellent yields. The salient features of this eco-friendly methodology are highlighted by its short reaction time (10–12 min), high yields, high atom-economy, efficiency of producing five new bonds (2C–C, C=N, C–N and one C–O), two new rings and two stereocentres in a single operation, absence of any tedious work-up or purification and avoidance of separation of intermediates.

Pyrazole synthesis via a cascade Sonogashira coupling/cyclization of N-propargyl sulfonylhydrazones

An efficient approach for the preparation of pyrazoles via a Pd(ii)/Cu(i)-catalyzed Sonogashira coupling/cyclization of N-propargyl sulfonylhydrazones has been established.

1-(3-Chloro-6-nitro-1H-indazol-1-yl)ethan-1-one

The asymmetric unit of the title compound, C9H6ClN3O3, contains one full molecule in a general position and a half molcule sitting on a crystallographic mirror plane. In the crystal, molecules form stacks extending along theb-axis direction through a combination of offset π–π stacking between indazole units and C—Cl...π(ring) interactions with the six-membered rings of the same units. Elaboration of the C—Cl...π(ring) interactions along thea-axis direction forms slabs of molecules parallel to [001]. The stacks are joined by a combination of C—H...O and C—H...N hydrogen bonds.

The progress in the research of antiplatelet agents (1995-2017)

Antiplatelet therapy displays a critical role in the treatment and prevention of antithrombotic disorders. Many new antiplatelet agents have been developed following the emergence of various clinical limitations of classical antiplatelet drugs. This review covers mainly the recent advances in the development of P2Y₁₂ antagonists and GPIIb/IIIa antagonists. Meanwhile, it summarizes promising approaches to new platelet surface receptors such as prostanoid EP3 receptor, thromboxane A₂ prostanoid receptor, protease-activated receptors, GPIb-IX-V receptor and P-selectin. In addition, PI3K_β, a critical protein at the inside signaling pathway of platelet activation is also mentioned as an important antiplatelet target. Moreover, the development of respective drug candidates is discussed in detail.

YC-1 induces G0/G1 phase arrest and mitochondria-dependent apoptosis in cisplatin-resistant human oral cancer CAR cells

Oral cancer is a serious and fatal disease. Cisplatin is the first line of chemotherapeutic agent for oral cancer therapy. However, the development of drug resistance and severe side effects cause tremendous problems clinically. In this study, we investigated the pharmacologic mechanisms of YC-1 on cisplatin-resistant human oral cancer cell line, CAR. Our results indicated that YC-1 induced a concentration-dependent and time-dependent decrease in viability of CAR cells analyzed by MTT assay. Real-time image analysis of CAR cells by IncuCyte™ Kinetic Live Cell Imaging System demonstrated that YC-1 inhibited cell proliferation and reduced cell confluence in a time-dependent manner. Results from flow cytometric analysis revealed that YC-1 promoted G₀/G₁ phase arrest and provoked apoptosis in CAR cells. The effects of cell cycle arrest by YC-1 were further supported by up-regulation of p21 and down-regulation of cyclin A, D, E and CDK2 protein levels. TUNEL staining showed that YC-1 caused DNA fragmentation, a late stage feature of apoptosis. In addition, YC-1 increased the activities of caspase-9 and caspase-3, disrupted the mitochondrial membrane potential (AYm) and stimulated ROS production in CAR cells. The protein levels of cytochrome c, Bax and Bak were elevated while Bcl-2 protein expression was attenuated in YC-1-treated CAR cells. In summary, YC-1 suppressed the viability of cisplatin-resistant CAR cells through inhibiting cell proliferation, arresting cell cycle at G₀/G₁ phase and triggering mitochondria-mediated apoptosis. Our results provide evidences to support the potentially therapeutic application of YC-1 on fighting against drug resistant oral cancer in the future.

Ultrasound promoted mild and facile one-pot, three component synthesis of 2H-indazoles by consecutive condensation, CN and NN bond formations catalysed by copper-doped silica cuprous sulphate (CDSCS) as an efficient heterogeneous nano-catalyst

An ultrasonic promoted facile and convenient one-pot three-component procedure for the synthesis of 2H-indazole derivatives using copper-doped silica cuprous sulphate (CDSCS) as a heterogeneous nano-catalyst has been described. In this approach, ultrasonic mediated reaction of different substituted 2-bromobenzaldehydes, structurally diverse primary amines, and tetrabutylammonium azide (TBAA) as an azide source in the presence of CDSCS in DMSO at room temperature furnishes 2H-indazoles in good to excellent yields. Utilizing ultrasonic irradiation techniques provided the dramatic improvements in terms of higher yields and shorter reaction times compared with conventional heating method.

Identification of the minimum PAR4 inhibitor pharmacophore and optimization of a series of 2-methoxy-6-arylimidazo[2,1-b][1,3,4]thiadiazoles

This letter describes the further deconstruction of the known PAR4 inhibitor chemotypes (MWs 490-525 and with high plasma protein binding) to identify a minimum PAR4 pharmacophore devoid of metabolic liabilities and improved properties. This exercise identified a greatly simplified 2-methoxy-6-arylimidazo[2,1-b][1,3,4]thiadiazole scaffold that afforded nanomolar inhibition of both activating peptide and γ-thrombin mediated PAR4 stimulation, while reducing both molecular weight and the number of hydrogen bond donors/acceptors by ∼50%. This minimum PAR4 pharmacophore, with competitive inhibition, versus non-competitive of the larger chemotypes, allows an ideal starting point to incorporate desired functional groups to engender optimal DMPK properties towards a preclinical candidate.

Challenges and Opportunities in Protease-Activated Receptor Drug Development

Protease-activated receptors (PARs) are a unique class of G protein-coupled receptors (GPCRs) that transduce cellular responses to extracellular proteases. PARs have important functions in the vasculature, inflammation, and cancer and are important drug targets. A unique feature of PARs is their irreversible proteolytic mechanism of activation that results in the generation of a tethered ligand that cannot diffuse away. Despite the fact that GPCRs have proved to be the most successful class of druggable targets, the development of agents that target PARs specifically has been challenging. As a consequence, researchers have taken a remarkable diversity of approaches to develop pharmacological entities that modulate PAR function. Here, we present an overview of the diversity of therapeutic agents that have been developed against PARs. We further discuss PAR biased signaling and the influence of receptor compartmentalization, posttranslational modifications, and dimerization, which are important considerations for drug development.

Development of a Series of (1-Benzyl-3-(6-methoxypyrimidin-3-yl)-5-(trifluoromethoxy)-1H-indol-2-yl)methanols as Selective Protease Activated Receptor 4 (PAR4) Antagonists with in Vivo Utility and Activity Against γ-Thrombin

Here, we describe the development of a series of highly selective PAR4 antagonists with nanomolar potency and selectivity versus PAR1, derived from the indole-based 3. Of these, 9j (PAR4 IC50 = 445 nM, PAR1 response IC50 > 30 μM) and 10h (PAR4 IC50 = 179 nM, PAR1 response IC50 > 30 μM) maintained an overall favorable in vitro DMPK profile, encouraging rat/mouse in vivo pharmacokinetics (PK) and activity against γ-thrombin.