Hit-to-lead optimization and kinase selectivity of imidazo[1,2-a]quinoxalin-4-amine derived JNK1 inhibitors

As the result of a rhJNK1 HTS, the imidazo[1,2-a]quinoxaline 1 was identified as a 1.6 μM rhJNK1 inhibitor. Optimization of this compound lead to AX13587 (rhJNK1 IC₅₀ = 160 nM) which was co-crystallized with JNK1 to identify key molecular interactions. Kinase profiling against 125+ kinases revealed AX13587 was an inhibitor of JNK, MAST3, and MAST4 whereas its methylene homolog AX14373 (native JNK1 IC₅₀ = 47 nM) was a highly specific JNK inhibitor.     

Discovery of a novel series of 4-quinolone JNK inhibitors

A novel series of highly selective JNK inhibitors based on the 4-quinolone scaffold was designed and synthesized. Structure based drug design was utilized to guide the compound design as well as improvements in the physicochemical properties of the series. Compound (13c) has an IC₅₀ of 62/170 nM for JNK1/2, excellent kinase selectivity and impressive efficacy in a rodent asthma model.     

Development of amino-pyrimidine inhibitors of c-Jun N-terminal kinase (JNK): Kinase profiling guided optimization of a 1,2,3-benzotriazole lead

A series of amino-pyrimidines was developed based upon an initial kinase cross-screening hit from a CDK2 program. Kinase profiling and structure-based drug design guided the optimization from the initial 1,2,3-benzotriazole hit to a potent and selective JNK inhibitor, compound 24f (JNK1 and 2 IC₅₀ = 16 and 66 nM, respectively), with bioavailability in rats and suitable for further in vivo pharmacological evaluation.     

Design and synthesis of spirocyclic compounds as HCV replication inhibitors by targeting viral NS4B protein

Two novel series of spirocyclic piperidine analogs appended to a pyrazolo[1,5-a]pyridine core were designed, synthesized and evaluated for their anti-HCV activity. A series of piperidine ketals afforded dispiro 6p which showed excellent in vitro anti-HCV activities (EC₅₀ of 1.5 nM and 1.2 nM against genotype 1a and 1b replicons, respectively). A series of piperidine oxazolidinones afforded 27c which showed EC₅₀’s of 10.9 nM and 6.1 nM against 1a and 1b replicons, respectively. Both compounds 6p and 27c bound directly to non-structural NS4B protein in vitro (IC₅₀’s = 10.2 and 30.4 nM, respectively) and exhibited reduced potency in replicons containing resistance mutations encoding changes in the NS4B protein.     

Synthesis and biological evaluation of novel 3,4-diaryl lactam derivatives as triple reuptake inhibitors

A series of 3,4-diarylpyrrolidin-2-one was designed, prepared and evaluated as triple reuptake inhibitors for antidepressant. Most compounds exhibited comparable in vitro efficacy as norepinephrine and dopamine transporter reuptake inhibitors. Especially, 2i showed better potency than GBR-12909 (IC₅₀ = 14 nM) which was used as reference compound for dopamine transporter. In addition, 2a and 2b showed inhibition (5.17 μM–85.6 nM) for three transporters.     

Discovery of novel HCV inhibitors: Synthesis and biological activity of 6-(indol-2-yl)pyridine-3-sulfonamides targeting hepatitis C virus NS4B

A novel series of 6-(indol-2-yl)pyridine-3-sulfonamides was prepared and evaluated for their ability to inhibit HCV RNA replication in the HCV replicon cell culture assay. Preliminary optimization of this series furnished compounds with low nanomolar potency against the HCV genotype 1b replicon. Among these, compound 8c has identified as a potent HCV replicon inhibitor (EC₅₀ = 4 nM) with a selectivity index with respect to cellular GAPDH of more than 2500. Further, compound 8c had a good pharmacokinetic profile in rats with an IV half-life of 6 h and oral bioavailability (F) of 62%. Selection of HCV replicon resistance identified an amino acid substitution in HCV NS4B that confers resistance to these compounds. These compounds hold promise as a new chemotype with anti-HCV activity mediated through an underexploited viral target.     

The optimization of aminooxadiazoles as orally active inhibitors of Cdc7

A series of aminooxadiazoles was optimized for inhibition of Cdc7. Early lead isoquinoline 1 suffered from modest cell potency (cellular IC₅₀ = 0.71 μM measuring pMCM2), low selectivity against structurally related kinases, and high IV clearance in rats (CL = 18 L/h/kg). Extensive optimization resulted in azaindole 26 (Cdc7 IC₅₀ = 1.1 nM, pMCM2 IC₅₀ = 32 nM) that demonstrated robust lowering of pMCM2 in a mouse pharmacodynamic (PD) model when dosed orally. Modifications to improve the pharmacokinetic profile of this series were guided by trapping experiments with glutathione in rat hepatocytes.     

The discovery of potent and selective 4-aminothienopyridines as B-Raf kinase inhibitors

A series of novel, potent 4-aminothienopyridine B-Raf kinase inhibitors was designed and synthesized using knowledge-based design. Compounds 5f, and 6k exhibited not only excellent potency in both enzyme assay (IC₅₀ = 5.1, 16.6 nM) and cellular assay (IC₅₀ = 0.2, 0.2 μM), but also had an outstanding selectivity profile against other kinases.     

Discovery and optimization of a series of imidazo[4,5-b]pyrazine derivatives as highly potent and exquisitely selective inhibitors of the mesenchymal–epithelial transition factor (c-Met) protein kinase

Aberrant c-Met activation has been implicated in multiple tumor oncogenic processes and drug resistance. In this study, a series of imidazo[4,5-b]pyrazine derivatives was designed and synthesized, and their inhibitory activities were evaluated in vitro. Structure–activity relationship (SAR) was investigated systematically and docking analysis was performed to elucidate the binding mode, leading to the identification of the most promising compound 1D-2 which exhibited significant inhibitory effect on both enzymatic (IC₅₀ = 1.45 nM) and cellular (IC₅₀ = 24.7 nM in H1993 cell line) assays, as well as exquisite selectivity and satisfactory metabolic stability in human and rat liver microsomes.     

Evaluation of N-substitution in 6,7-benzomorphan compounds

6,7-Benzomorphan derivatives, exhibiting different μ, δ, and κ receptor selectivity profiles depending on the N-substituent, represent a useful skeleton for the synthesis of new and better analgesic agents. In this work, an aromatic ring and/or alkyl residues have been used with an N-propanamide or N-acetamide spacer for the synthesis of a new series of 5,9-dimethyl-2′-hydroxy-6,7-benzomorphan derivatives (12–22). Data obtained by competition binding assays showed that the μ opioid receptor seems to prefer an interaction with the 6,7-benzomorphan ligands having an N-substituent with a propanamide spacer and less hindered amide. Highly stringent features are required for δ receptor interaction, while an N-acetamide spacer and/or bulkier amide could preferentially lead to κ receptor selectivity. In the propanamide series, compound 12 (named LP1) displayed high μ affinity (K_i = 0.83 nM), good δ affinity (K_i = 29 nM) and low affinity for the κ receptor (K_i = 110 nM), with a selectivity ratio δ/μ and κ/μ of 35.1 and 132.5, respectively. Further, in the adenylyl cyclase assay, LP1 displayed a μ/δ agonist profile, with IC₅₀ values of 4.8 and 12 nM at the μ and δ receptors, respectively. The antinociceptive potency of LP1 in the tail-flick test after sc administration in rat was comparable with the potency of morphine (ED₅₀ = 2.03 and 2.7 mg/kg, respectively), and was totally reversed by naloxone. LP1, possessing a μ/δ agonist profile, could represent a lead in further developing benzomorphan-based ligands with potent in vivo analgesic activity and a reduced tendency to induce side effects.     

Novel potent inhibitors of hepatitis C virus (HCV) NS3 protease with cyclic sulfonyl P3 cappings

Extensive SAR studies of the P3 capping group led to the discovery of a series of potent inhibitors with sultam and cyclic sulfonyl urea moieties as the P3 capping. The bicyclic thiophene-sultam or phenyl-sultam cappings were selected for further SAR development. Modification at the P3 side chain determined that the tert-butyl group was the best choice at that position. Optimization of P1 residue significantly improved potency and selectivity. The combination of optimal moieties at all positions led to the discovery of compound 33. This compound had the best overall profile in potency and PK profile: excellent K_i¹ of 5.3 nM and activity in replicon (EC₉₀) of 80 nM, extremely high selectivity of 6100, and a good rat PO AUC of 1.43 μM h.     

Discovery of new [1,4]dioxino[2,3-f]quinazoline-based inhibitors of EGFR including the T790M/L858R mutant

A novel series of 2,3-dihydro-[1,4]dioxino[2,3-f]quinazoline derivatives were designed, synthesized and evaluated as reversible and noncovalent epidermal growth factor receptor (EGFR) inhibitors. Most of the compounds exhibited good potency against EGFR^wt and some showed moderate to excellent potency against EGFR^T790M/L858R mutant. The half-maximal inhibitory concentration (IC₅₀) values of twenty-one compounds against EGFR^wt were less than 50 nM, and those of six compounds were less than 10 nM. The IC₅₀ values of eleven compounds against EGFR^T790M/L858R were less than 100 nM. Among these, compound b1 displayed the most potent inhibitory activity against EGFR^wt (IC₅₀ = 2.0 nM) and EGFR^T790M/L858R (IC₅₀ = 6.9 nM). Compounds with excellent inhibitory activities against EGFR^wt and EGFR^T790M/L858R kinase inhibitory activities showed good antiproliferative activities against H358 and A549 cells. Docking study was performed to position compound b1 into the EGFR active pocket to determine the probable binding conformation.     

Synthesis of 9-anilinoacridine triazines as new class of hybrid antimalarial agents

There is challenge and urgency to synthesize cost-effective chemotherapeutic agents for treatment of malaria after the widespread development of resistance to CQ. In the present study, we synthesized a new series of hybrid 9-anilinoacridine triazines using the cheap chemicals 6,9-dichloro-2-methoxy acridine and cyanuric chloride. The series of new hybrid 9-anilinoacridine triazines were evaluated in vitro for their antimalarial activity against CQ-sensitive 3D7 strain of Plasmodium falciparum and their cytotoxicity were determined on VERO cell line. Of the evaluated compounds, two compounds 17 (IC₅₀ = 4.21 nM) and 22 (IC₅₀ = 4.27 nM) displayed two times higher potency than CQ (IC₅₀ = 8.15 nM). Most of the compounds showed fairly high selectivity index. The compounds 13 and 29 displayed >96.59% and 98.73% suppression, respectively, orally against N-67 strain of Plasmodium yoelii in swiss mice at dose 100 mg/kg for four days.     

Isoquinoline derivatives as potent CRTH2 antagonists: Design,synthesis and SAR

In this study, we describe the synthesis and structure–activity relationship (SAR) of a series of isoquinoline chemoattractant receptor–homologous molecule expressed on Th2 cells (CRTH2) antagonists. TASP0376377 (15-20), one of the most potent compounds, showed a potent binding affinity (IC₅₀ = 19 nM) in addition to the excellent functional antagonist activity (IC₅₀ = 13 nM). Moreover, the efficacy of this compound in a chemotaxis assay (IC₅₀ = 23 nM) was in good agreement with its potency as a CRTH2 antagonist. In addition, 15-20 exhibited greater selectivity in binding to CRTH2 than to the DP1 prostanoid receptor (IC₅₀ >1 μM) or the enzymes COX-1 and COX-2 (IC₅₀ >10 μM).     

Lactam and oxazolidinone derived potent 5-hydroxytryptamine 6 receptor antagonists

Lactam and oxazolidinone derived potent 5-hydroxytryptamine 6 (5-HT₆) receptor antagonists have been disclosed. One potent member from the lactam series, racemic compound 14 (K_i of 2.6 nM in binding assay, IC₅₀ of 15 nM in functional cAMP antagonism assay) was separated into corresponding enantiomers that displayed the effect of chirality on binding potency (K_i of 1.6 nM and 3000 nM, respectively). The potent enantiomer displayed an IC₅₀ of 8 nM in cAMP antagonism assay, selectivity against a number of family members as well as brain permeability in rats after 6 h post oral administration.     

Quinoline-3-carboxamide containing sulfones as liver X receptor (LXR) agonists with binding selectivity for LXRβ and low blood–brain penetration

A series of quinoline-3-carboxamide containing sulfones was prepared and found to have good binding affinity for LXRβ and moderate binding selectivity over LXRα. The 8-Cl quinoline analog 33 with a high TPSA score, displayed 34-fold binding selectivity for LXRβ over LXRα (LXRβ IC₅₀ = 16 nM), good activity for inducing ABCA1 gene expression in a THP macrophage cell line, desired weak potency in the LXRα Gal4 functional assay, and low blood–brain barrier penetration in rat.     

C-3 benzoic acid derivatives of C-3 deoxybetulinic acid and deoxybetulin as HIV-1 maturation inhibitors

A series of C-3 phenyl- and heterocycle-substituted derivatives of C-3 deoxybetulinic acid and C-3 deoxybetulin was designed and synthesized as HIV-1 maturation inhibitors (MIs) and evaluated for their antiviral activity and cytotoxicity in cell culture. A 4-subsituted benzoic acid moiety was identified as an advantageous replacement for the 3′3′-dimethylsuccinate moiety present in previously disclosed MIs that illuminates new aspects of the topography of the pharmacophore. The new analogs exhibit excellent in vitro antiviral activity against wild-type (wt) virus and a lower serum shift when compared with the prototypical HIV-1 MI bevirimat (1, BVM), the first MI to be evaluated in clinical studies. Compound 9a exhibits comparable cell culture potency toward wt virus as 1 (WT EC₅₀ = 16 nM for 9a compared to 10 nM for 1). However, the potency of 9a is less affected by the presence of human serum, while the compound displays a similar pharmacokinetic profile in rats to 1. Hence 9a, the 4-benzoic acid derivative of deoxybetulinic acid, represents a new starting point from which to explore the design of a 2nd generation MI.     

Identification of 3,6-disubstituted dihydropyrones as inhibitors of human lactate dehydrogenase

A series of 3,6-disubstituted dihydropyrones were identified as inhibitors of human lactate dehydrogenase (LDH)-A. Structure activity relationships were explored and a series of 6,6-spiro analogs led to improvements in LDHA potency (IC₅₀ <350 nM). An X-ray crystal structure of an improved compound bound to human LDHA was obtained and it illustrated additional opportunities to enhance the potency of these compounds, resulting in the identification of 51 (IC₅₀ = 30 nM).     

Synthesis of 4-(3-biaryl)quinoline sulfones as potent liver X receptor agonists

A series of 4-(3-biaryl)quinolines with sulfone substituents on the terminal aryl ring (8) was prepared as potential LXR agonists. High affinity LXRβ ligands with generally modest binding selectivity over LXRα and excellent agonist potency in LXR functional assays were identified. Many compounds had LXRβ binding IC₅₀ values <10 nM while the most potent had EC₅₀ values <1.0 nM in an ABCA1 mRNA induction assay in J774 mouse cells with efficacy comparable to T0901317. Sulfone 8a was further evaluated in LDL (?/?) mice and shown to reduce atherosclerotic lesion progression.     

New class of azaheptapyridine FPT inhibitors as potential cancer therapy agents

Tertiary hydroxyl class of C-imidazole bridgehead azaheptapyridine FPT inhibitors were prepared in an attempt to block in vivo oxidation of secondary hydroxyl series. One representative compound 5a exhibited potent enzyme (IC₅₀ = 1.4 nM) and cellular activities (soft agar IC₅₀ = 1.3 nM) with excellent oral pharmacokinetic profiles in rats, mice, monkeys and dogs. The in vivo study in wap-ras TG mouse models showed dose dependent tumor growth inhibition and regression.