Pyrrole-3-carboxamides as potent and selective JAK2 inhibitors

We report herein the discovery, structure guided design, synthesis and biological evaluation of a novel class of JAK2 inhibitors. Optimization of the series led to the identification of the potent and orally bioavailable JAK2 inhibitor 28 (NMS-P953). Compound 28 displayed significant tumour growth inhibition in SET-2 xenograft tumour model, with a mechanism of action confirmed in vivo by typical modulation of known biomarkers, and with a favourable pharmacokinetic and safety profile.     

Discovery of quinolinone derivatives as potent FLT3 inhibitors

Recently some fms-like tyrosine kinase 3 (FLT3) inhibitors have shown good efficacy in acute myeloid leukemia (AML) patients. In an effort to develop anti-leukemic drugs, we investigated quinolinone derivatives as novel FLT3 inhibitors. Two substituted quinolinones, KR65367 and KR65370 were subjected to FLT3 kinase activity assay and showed potent inhibition against FLT3 kinase activity in vitro, with IC₅₀ of 2.7 and 0.57 nM, respectively. As a measure of selectivity, effects on the activity of other kinases were also tested. Both compounds have negligible activity against Met, Ron, epidermal growth factor receptor, Aurora A, Janus kinase 2, and insulin receptor; with IC₅₀ greater than 10 μM. KR compounds showed strong growth inhibition in MV4;11 AML cells and increased the apoptotic cell death in flow cytometric analyses. A decrease in STAT5 phosphorylation by KR compounds was observed in MV4;11 cells. Furthermore, in vitro evaluation of compounds structurally related to KR65367 and KR65370 showed a good structure-activity relationship.     

Comprehensive structure-activity-relationship of azaindoles as highly potent FLT3 inhibitors

Acute myeloid leukemia (AML) is characterized by fast progression and low survival rates, in which Fms-like tyrosine kinase 3 (FLT3) receptor mutations have been identified as a driver mutation in cancer progression in a subgroup of AML patients. Clinical trials have shown emergence of drug resistant mutants, emphasizing the ongoing need for new chemical matter to enable the treatment of this disease. Here, we present the discovery and topological structure-activity relationship (SAR) study of analogs of isoquinolinesulfonamide H-89, a well-known PKA inhibitor, as FLT3 inhibitors. Surprisingly, we found that the SAR was not consistent with the observed binding mode of H-89 in PKA. Matched molecular pair analysis resulted in the identification of highly active sub-nanomolar azaindoles as novel FLT3-inhibitors. Structure based modelling using the FLT3 crystal structure suggested an alternative, flipped binding orientation of the new inhibitors.     

Arylcarboxyamino-substituted diaryl ureas as potent and selective FLT3 inhibitors

A series of diaryl ureas with an amide substitution at the 4-position was prepared and found to be potent and selective FLT3 inhibitors with good oral bioavailability and efficacy in a tumor xenograft model.     

Identification of pyrrolo[2,3-d]pyrimidines as potent HCK and FLT3-ITD dual inhibitors

A series of novel pyrrolo[2,3-d]pyrimidines were synthesized by introducing 15 different amino acids to 7-cyclohexyl-5-(4-phenoxyphenyl)-7H-pyrrolo[2,3-d]pyrimidine-4-amine. Compounds with potent activities against HCK and FLT3-ITD were evaluated in viability studies with acute myeloid leukemia cell line MV4-11. Our structure activity relationship analyses lead to the identification of compound 31, which exhibited potent HCK and FLT3-ITD inhibition and activity against the MV4-11 cell line.     

Structure-based optimization of potent 4- and 6-azaindole-3-carboxamides as renin inhibitors

The control of hypertension and associated cardiovascular risk factors is possible by selective inhibition of the aspartyl protease renin due to its unique position in the renin-angiotensin system. Starting from a previously disclosed series of potent and nonchiral indole-3-carboxamides, we further explored this motif by structure-based drug design guided by X-ray crystallography in combination with efficient parallel synthesis. This resulted in the discovery of 4- or 6-azaindole derivatives with remarkable potency for renin inhibition. The best compound from these series showed an IC(50) value of 1.3 nM.     

Discovery of novel 2-aminopyridine-3-carboxamides as c-Met kinase inhibitors

A series of 2-aminopyridine-3-carboxamide derivatives against c-Met were designed and synthesized by employing bioisosteric replacement of heterocyclic moieties with the amide bond. The structure-activity relationship (SAR) at various positions of the scaffold was explored. In this study, a promising compound (S)-24o with a c-Met IC(50) of 0.022μM was identified. The compound exhibited dose-dependent inhibition of the phosphorylation of c-Met as well as downstream signaling in EBC-1 cells. Furthermore, the interactive binding model of (S)-24o with c-Met was elucidated by virtue of a molecular modeling study.     

Indirubin derivatives as potent FLT3 inhibitors with anti-proliferative activity of acute myeloid leukemic cells

Indirubin derivatives were identified as potent FLT3 tyrosine kinase inhibitors with anti-proliferative activity at acute myeloid leukemic cell lines, RS4;11 and MV4;11 which express FLT3-WT and FLT3-ITD mutation, respectively. Among several 5 and 5′-substituted indirubin derivatives, 5-fluoro analog, 13 exhibited potent inhibitory activity at FLT3 (IC₅₀ = 15 nM) with more than 100-fold selectivity versus 6 other kinases and potent anti-proliferative effect for MV4;11 cells (IC₅₀ = 72 nM) with 30-fold selectivity versus RS4;11 cells. Cell cycle analysis indicated that compound 13 induced cell cycle arrest at G₀/G₁ phase in MV4;11 cells.     

Identification of 2-oxatriazines as highly potent pan-PI3K/mTOR dual inhibitors

We recently described several highly potent, triazine (1) and triazolopyrimidine (2) scaffold-based, dual PI3K/mTOR-inhibitors (e.g., 1, PKI-587) that were efficacious in both in vitro and in vivo models. In order to further optimize these compounds we devised a novel series, the 2-oxatriazines, which also exhibited excellent potency and good metabolic stability. Some 2-oxatriazines showed promising in vivo biomarker suppression and induced apoptosis in the MDA-MB-361 breast cancer xenograft model.     

Identification of substituted 3-hydroxy-2-mercaptocyclohex-2-enones as potent inhibitors of human lactate dehydrogenase

A novel class of 3-hydroxy-2-mercaptocyclohex-2-enone-containing inhibitors of human lactate dehydrogenase (LDH) was identified through a high-throughput screening approach. Biochemical and surface plasmon resonance experiments performed with a screening hit (LDHA IC₅₀ = 1.7 μM) indicated that the compound specifically associated with human LDHA in a manner that required simultaneous binding of the NADH co-factor. Structural variation of this screening hit resulted in significant improvements in LDHA biochemical inhibition activity (best IC₅₀ = 0.18 μM). Two crystal structures of optimized compounds bound to human LDHA were obtained and explained many of the observed structure–activity relationships. In addition, an optimized inhibitor exhibited good pharmacokinetic properties after oral administration to rats (F = 45%).     

Discovery and optimization of novel benzothiophene-3-carboxamides as highly potent inhibitors of Aurora kinases A and B

Aurora kinases as regulators of cell division have become promising therapeutic targets recently. Here we report novel, low molecular weight benzothiophene-3-carboxamide derivatives designed and optimized for inhibiting Aurora kinases. The most effective compound 36 inhibits Aurora kinases in vitro in the nanomolar range and diminishes HCT 116 cell viability blocking cytokinesis and inducing apoptosis. According to western blot analysis, the lead molecule inhibits Aurora kinases equipotently to VX-680 (Tozasertib) and similarly synergizes with other targeted drugs.     

Identification and development of 2-methylimidazo[1,2-a]pyridine-3-carboxamides as Mycobacterium tuberculosis pantothenate synthetase inhibitors

In the present study, we used crystal structure of mycobacterial pantothenate synthetase (PS) bound with 2-(2-(benzofuran-2-ylsulfonylcarbamoyl)-5-methoxy-1H-indol-1-yl) acetic acid inhibitor for virtual screening of antitubercular compound database to identify new scaffolds. One of the identified lead was modified synthetically to obtain thirty novel analogues. These synthesized compounds were evaluated for Mycobacterium tuberculosis (MTB) PS inhibition study, in vitro antimycobacterial activities and cytotoxicity against RAW 264.7 cell line. Among the compounds tested, N′-(1-naphthoyl)-2-methylimidazo[1,2-a]pyridine-3-carbohydrazide (5b) was found to be the most active compound with IC₅₀ of 1.90 ± 0.12 μM against MTB PS, MIC of 4.53 μM against MTB with no cytotoxicity at 50 μM. The binding affinity of the most potent inhibitor 5b was further confirmed biophysically through differential scanning fluorimetry.     

Flavonoids as receptor tyrosine kinase FLT3 inhibitors

The Fms-like tyrosine kinase 3 (FLT3), a receptor tyrosine kinase, is involved in the proliferation, differentiation and apoptosis of hematopoietic cells. FLT3 is highly overexpressed in acute myeloid leukemia (AML) of the majority of patients. Screening for flavonoids including flavones, flavanones, flavonols, and flavanonols disclosed that luteolin was potent FLT3 enzyme inhibitor. Furthermore, luteolin suppressed cell proliferation in MV4;11 cells with constitutively activated FLT3.     

Discovery of novel N-hydroxy-2-arylisoindoline-4-carboxamides as potent and selective inhibitors of HDAC11

N-Hydroxy-2-arylisoindoline-4-carboxamides are potent and selective inhibitors of HDAC11. The discovery, synthesis, and structure activity relationships of this novel series of inhibitors are reported. An advanced analog (FT895) displays promising cellular activity and pharmacokinetic properties that make it a useful tool to study the biology of HDAC11 and its potential use as a therapeutic target for oncology and inflammation indications.     

Isoquinoline-6-carboxamides as potent and selective anti-human cytomegalovirus (HCMV) inhibitors.

Structure-activity relationship studies on our newly identified anti-HCMV compounds, the 1,6-naphthyridines led to the identification of isoquinoline-6-carboxamides as potent and selective anti-HCMV agents.     

3-Phenyl-1H-5-pyrazolylamine-based derivatives as potent and efficacious inhibitors of FMS-like tyrosine kinase-3 (FLT3)

A new class of FLT3 inhibitors has been identified based on the 3-phenyl-1H-5-pyrazolylamine scaffold. The structure-activity relationships led to the discovery of two carbamate series, and some potent compounds within these two series exhibited better growth inhibition of FLT3-mutated MOLM-13 cells than FLT3 inhibitors sorafenib (2) and ABT-869 (3). In particular, compound 8d exhibited the ability to regress tumors in mouse xenograft model using MOLM-13 cells.     

3-Benzimidazol-2-yl-1H-indazoles as potent c-ABL inhibitors

The 3-benzimidazol-2-yl-1H-indazole scaffold was developed as an alternate scaffold for our receptor tyrosine kinase (RTK) inhibitor program. In exploring the SAR of this series, it was discovered that a subset of these compounds potently inhibit the enzyme c-ABL. The SAR of these compounds is described.     

Identification of acridinyl hydrazides as potent aspartic protease inhibitors

We have identified acridinyl derivatives as potent aspartic protease inhibitors by virtual screening of in-house library of synthetic compounds. Enzyme inhibition experiments showed that both compounds inhibit human cathepsin D and Plasmodium falciparum plasmepsin-II in nanomolar ranges. The IC₅₀ values against cathepsin D and plasmepsin-II of compound-Nar103 were found to be 9.0 ± 2.0 and 4.0 ± 1.0 nM and of compound-Nar110 were 0.5 ± 0.05 and 0.13 ± 0.03 nM, respectively. Ligand docking predicted the binding of acridinyl derivatives at the substrate-binding cleft, where hydrazide part of the inhibitors interact with the S1–S1′ subsite residues including catalytic aspartates. The phenyl ring and acridinyl moiety of the inhibitors were predicted to interact with S2/S3 and S2′/S3′ subsite residues.     

Design and synthesis of 4-quinolinone 2-carboxamides as calpain inhibitors

Calpains are involved in a variety of calcium-regulated cellular processes, such as signal transduction, cell proliferation, differentiation, and apoptosis. Excessive calpain activation contributes to serious cellular damage and has been reported in many pathological conditions. 4-Quinolinone 2-carboxamide derivatives were prepared and evaluated for mu-calpain inhibitory activities. Of the compounds synthesized, 3a and 3k, which possess a primary amide and 4-methoxyphenethyl amide at P1' region, were found to most potently inhibit mu-calpain with IC50 values of 0.71+/-0.07 and 0.73+/-0.23 microM, respectively. On the other hand, the incorporation of pyridine-containing amides decreased inhibitory activity.     

2-Aminobenzimidazoles as potent Aurora kinase inhibitors

This Letter describes the discovery and key structure–activity relationship (SAR) of a series of 2-aminobenzimidazoles as potent Aurora kinase inhibitors. 2-Aminobenzimidazole serves as a bioisostere of the biaryl urea residue of SNS-314 (1c), which is a potent Aurora kinase inhibitor and entered clinical testing in patients with solid tumors. Compared to SNS-314, this series of compounds offers better aqueous solubility while retaining comparable in vitro potency in biochemical and cell-based assays; in particular, 6m has also demonstrated a comparable mouse iv PK profile to SNS-314.