Rational Evolution of a Novel Type of Potent and Selective Proviral Integration Site in Moloney Murine Leukemia Virus Kinase 1 (PIM1) Inhibitor from a Screening-Hit Compound

Comprehensive Insights that Targeting PIM for Cancer Therapy: Prospects and Obstacles

Proviral integration sitea for Moloney-murine leukemia virus (PIM) kinases are a family of highly conserved serine/tyrosine kinases consisting of three members, PIM-1, PIM-2, and PIM-3. These kinases regulate a wide range of substrates through phosphorylation and affect key cellular processes such as transcription, translation, proliferation, apoptosis, and energy metabolism. Several PIM inhibitors are currently undergoing clinical trials, such as a phase I clinical trial of Uzanserti (5) for the treatment of relapsed diffuse large B-cell lymphoma that has been completed. The current focus encompasses the structural and biological characterization of PIM, ongoing research progress on small-molecule inhibitors undergoing clinical trials, and evaluation analysis of persisting challenges in this field. Additionally, the design and discovery of small-molecule inhibitors targeting PIM in recent years have been explored, with a particular emphasis on medicinal chemistry, aiming to provide valuable insights for the future development of PIM inhibitors.

Targeting Death-Associated Protein Kinases for Treatment of Human Diseases: Recent Advances and Future Directions

The death-associated protein kinase (DAPK) family is a member of the calcium/calmodulin-regulated serine/threonine protein kinase family, and studies have shown that its role, as its name suggests, is mainly to regulate cell death. The DAPK family comprises five members, including DAPK1, DAPK2, DAPK3, DRAK1 and DRAK2, which show high homology in the common N-terminal kinase domain but differ in the extra-catalytic domain. Notably, previous research has suggested that the DAPK family plays an essential role in both the development and regulation of human diseases. However, only a few small-molecule inhibitors have been reported. In this Perspective, we mainly discuss the structure, biological function, and role of DAPKs in diseases and the currently discovered small-molecule inhibitors, providing valuable information for the development of the DAPK field.

Recent Research Advances in Small-Molecule Pan-PIM Inhibitors

PIM kinase is consequently emerging as a promising target for cancer therapeutics and immunomodulation. PIM kinases are overexpressed in a variety of hematological malignancies and solid tumors, and their inhibition has become a strong therapeutic interest. Currently, some pan-PIM kinase inhibitors are being developed under different phases of clinical trials. Based on the different scaffold structures, they can be classified into various subclasses. The X-ray structure of the kinase complex outlines the rationale of hit compound confirmation in the early stage. Structure–activity relationships allow us to rationally explore chemical space and further optimize multiple physicochemical and biological properties. This review focuses on the discovery and development of small-molecule pan-PIM kinase inhibitors in the current research, and hopes to provide guidance for future exploration of the inhibitors.

Bioactive Aurones, Indanones, and Other Hemiindigoid Scaffolds: Medicinal Chemistry and Photopharmacology Perspectives

Hemiindigoids comprise a range of natural and synthetic scaffolds that share the same aromatic hydrocarbon backbone as well as promising biological and optical properties. The encouraging therapeutic potential of these scaffolds has been unraveled by many studies over the past years and uncovered representants with inspiring pharmacophoric features such as the acetylcholinesterase inhibitor donezepil and the tubulin polymerization inhibitor indanocine. In this review, we summarize the last advances in the medicinal potential of hemiindigoids, with a special attention to molecular design, structure-activity relationship, ligand-target interactions, and mechanistic explanations covering their effects. As their strong fluorogenic potential and photoswitch behavior recently started to be highlighted and explored in biology, giving rise to the development of novel fluorescent probes and photopharmacological agents, we also discuss these properties in a medicinal chemistry perspective.

Contribution of Knoevenagel Condensation Products towards Development of Anticancer Agents: An Updated Review

Knoevenagel condensation is an entrenched, prevailing, prominent arsenal following greener principles in the generation of α, β-unsaturated ketones/carboxylic acids by involving carbonyl functionalities and active methylenes. This reaction has proved to be a major driving force in many multicomponent reactions indicating the prolific utility towards the development of biologically fascinating molecules. This eminent reaction was acclimatised on different pharmacophoric aldehydes (benzimidazole, β-carboline, phenanthrene, indole, imidazothiadiazole, pyrazole etc.) and active methylenes (oxindole, barbituric acid, Meldrum's acid, thiazolidinedione etc.) to generate the library of chemical compounds. Their potential was also explicit to understand the significance of functionalities involved, which thereby evoke further developments in drug discovery. Furthermore, most of these reaction products exhibited remarkable anticancer activity in nanomolar to micromolar ranges by targeting different cancer targets like DNA, microtubules, Topo-I/II, and kinases (PIM, PARP, NMP, p300/CBP) etc. This review underscores the efficiency of the Knoevenagel condensation explored in the past six-year to generate molecules of pharmacological interest, predominantly towards cancer. The present review also provides the aspects of structure-activity relationships, mode of action and docking study with possible interaction with the target protein.

Discovery of AS-0141, a Potent and Selective Inhibitor of CDC7 Kinase for the Treatment of Solid Cancers

CDC7, a serine-threonine kinase, plays conserved and important roles in regulation of DNA replication and has been recognized as a potential anticancer target. We report here the optimization of a series of furanone analogues starting from compound 1 with a focus on ADME properties suitable for clinical development. By replacing the 2-chlorobenzene moiety in 1 with various aliphatic groups, we identified compound 24 as a potent CDC7 inhibitor with excellent kinase selectivity and favorable oral bioavailability in multiple species. Oral administration of 24 demonstrated robust in vivo antitumor efficacy in a colorectal cancer xenograft model. Compound 24 (AS-0141) is currently in phase I clinical trials for the treatment of solid cancers.

Therapeutic targeting of PIM KINASE signaling in cancer therapy: Structural and clinical prospects

BACKGROUND

PIM kinases are well-studied drug targets for cancer, belonging to Serine/Threonine kinases family. They are the downstream target of various signaling pathways, and their up/down-regulation affects various physiological processes. PIM family comprises three isoforms, namely, PIM-1, PIM-2, and PIM-3, on alternative initiation of translation and they have different levels of expression in different types of cancers. Its structure shows a unique ATP-binding site in the hinge region which makes it unique among other kinases.

SCOPE OF REVIEW

PIM kinases are widely reported in hematological malignancies along with prostate and breast cancers. Currently, many drugs are used as inhibitors of PIM kinases. In this review, we highlighted the physiological significance of PIM kinases in the context of disease progression and therapeutic targeting. We comprehensively reviewed the PIM kinases in terms of their expression and regulation of different physiological roles. We further predicted functional partners of PIM kinases to elucidate their role in the cellular physiology of different cancer and mapped their interaction network.

MAJOR CONCLUSIONS

A deeper mechanistic insight into the PIM signaling involved in regulating different cellular processes, including transcription, apoptosis, cell cycle regulation, cell proliferation, cell migration and senescence, is provided. Furthermore, structural features of PIM have been dissected to understand the mechanism of inhibition and subsequent implication of designed inhibitors towards therapeutic management of prostate, breast and other cancers.

GENERAL SIGNIFICANCE

Being a potential drug target for cancer therapy, available drugs and PIM inhibitors at different stages of clinical trials are discussed in detail.

Exploration of 7-azaindole-coumaranone hybrids and their analogues as protein kinase inhibitors

7-Azaindole has been labelled a privileged scaffold for the design of new potent inhibitors of protein kinases. In this paper, we determined the inhibition profiles of novel mono- and disubstituted derivatives of 7-azaindole-coumaranone hybrids on various disease-related protein kinases. Eight hit compounds were identified, including a potent Haspin inhibitor with an IC₅₀ value of 0.15 μM. An interesting observation was that all active monosubstituted compounds displayed dual inhibition for Haspin and GSK-3β, while disubstituted derivatives inhibited GSK-3β and LmCK1 from Leishmania major parasite. Analyses of structure activity relationships (SARs) also revealed that mono-substitution with para-fluorobenzyloxy ring produced an equipotent inhibition of Haspin and GSK-3β. Haspin and GSK-3β are relevant targets for developing new anticancer agents while LmCK1 is an innovative target for leishmanicidal drugs. Novel compounds reported in this paper constitute promising starting points for the development of new anticancer and leishmanicidal drugs.

Structure-Based Virtual Screening and De Novo Design of PIM1 Inhibitors with Anticancer Activity from Natural Products

BACKGROUND

the proviral insertion site of Moloney murine leukemia (PIM) 1 kinase has served as a therapeutic target for various human cancers due to the enhancement of cell proliferation and the inhibition of apoptosis.

METHODS

to identify effective PIM1 kinase inhibitors, structure-based virtual screening of natural products of plant origin and de novo design were carried out using the protein-ligand binding free energy function improved by introducing an adequate dehydration energy term.

RESULTS

as a consequence of subsequent enzyme inhibition assays, four classes of PIM1 kinase inhibitors were discovered, with the biochemical potency ranging from low-micromolar to sub-micromolar levels. The results of extensive docking simulations showed that the inhibitory activity stemmed from the formation of multiple hydrogen bonds in combination with hydrophobic interactions in the ATP-binding site. Optimization of the biochemical potency by chemical modifications of the 2-benzylidenebenzofuran-3(2H)-one scaffold led to the discovery of several nanomolar inhibitors with antiproliferative activities against human breast cancer cell lines.

CONCLUSIONS

these new PIM1 kinase inhibitors are anticipated to serve as a new starting point for the development of anticancer medicine.

Exploration of nitrogen heterocycle scaffolds for the development of potent human neutrophil elastase inhibitors

Human neutrophil elastase (HNE) is a potent protease that plays an important physiological role in many processes but is also involved in a variety of pathologies that affect the pulmonary system. Thus, compounds able to inhibit HNE proteolytic activity could represent effective therapeutics. We present here a new series of pyrazolopyridine and pyrrolopyridine derivatives as HNE inhibitors designed as modifications of our previously synthesized indazoles and indoles in order to evaluate effects of the change in position of the nitrogen and/or the insertion of an additional nitrogen in the scaffolds on biological activity and chemical stability. We obtained potent HNE inhibitors with IC₅₀ values in the low nanomolar range (10-50 nM), and some compounds exhibited improved chemical stability in phosphate buffer (t_1/2 > 6 h). Molecular modeling studies demonstrated that inhibitory activity was strictly dependent on the formation of a Michaelis complex between the OH group of HNE Ser195 and the carbonyl carbon of the inhibitor. Moreover, in silico ADMET calculations predicted that most of the new compounds would be optimally absorbed, distributed, metabolized, and excreted. Thus, these new and potent HNE inhibitors represent novel leads for future therapeutic development.

Discovery of SARxxxx92, a pan-PIM kinase inhibitor, efficacious in a KG1 tumor model

N-substituted azaindoles were discovered as potent pan-PIM inhibitors. Lead optimization, guided by structure and focused on physico-chemical properties allowed us to solve inherent hERG and permeability liabilities, and provided compound 27, which subsequently impacted KG-1 tumor growth in a mouse model.

Pim kinase inhibitors in cancer: medicinal chemistry insights into their activity and selectivity

The oncogenic Pim kinase proteins (Pim-1/2/3) regulate tumorigenesis through phosphorylating essential proteins that control cell cycle and proliferation. Pim kinase is a potential chemotherapeutic target in cancer and its inhibition is currently the focus of intensive drug design and development efforts. The distinctive presence of proline amino acids in the hinge region provides an opportunity to inhibit Pim kinase while conserving the physiological functions of other kinases and reducing the toxicity profiles of the inhibitors. Various Pim kinase inhibitors have been clinically evaluated for the treatment of hematological cancers, yet none has reached the clinic. In this review, we discuss the design and development of selective and potent Pim inhibitors with novel chemotypes focusing on structural features essential for high potency and selectivity.

A serine/threonine protein PIM kinase as a biomarker of cancer and a target for anti-tumor therapy

The PIM Kinases belong to the family of a proto-oncogene that essentially phosphorylates the serine/threonine residues of the target proteins. They are primarily categorized into three types PIM-1, PIM-2, PIM-3 which plays an indispensable regulatory role in signal transduction cascades, by promoting cell survival, proliferation, and drug resistance. These kinases are overexpressed in several solid as well as hematopoietic tumors which supports in vitro and in vivo malignant cell growth along with survival by regulating cell cycle and inhibiting apoptosis. They lack regulatory domain which makes them constitutively active once transcribed. PIM kinases usually appear to be important downstream effectors of oncoproteins which overexpresses and helps in mediating drug resistance to available agents, such as rapamycin. Structural studies of PIM kinases revealed that they have unique hinge regions where two Proline resides and makes ATP binding unique, by offering a target for an increasing number of potent PIM kinase inhibitors. Preclinical studies of those inhibitory compounds in various cancers indicate that these novel agents show promising activity and some of them currently being under examination. In this review, we have outlined PIM kinases molecular mechanism and signaling pathways along with matriculation in various cancer and list of inhibitors often used.

Saccharomonosporine A inspiration; synthesis of potent analogues as potential PIM kinase inhibitors

Saccharomonosporine A was recently reported as a natural anti-cancer agent working through inhibition of a Proviral integration site for Moloney murine leukemia virus-1 (PIM-1) kinase. Structural bioisosteres of this natural product were synthesized and tested against PIM kinase enzymes. They showed potent inhibitory activity against all the known PIM kinases (PIM-1, 2 and 3) with IC₅₀ values ranging from 0.22 to 2.46 μM. Compound 5 was the most potent pan-inhibitor with IC₅₀ values of 0.37, 0.41, and 0.3 μM, against PIM-1, 2, 3 respectively. Compounds 4–6 were tested for their cytotoxic activities against 3 cell lines: H1650, HT-29, and HL-60. Compound 5 exhibited significant cytotoxic activity against human colon adenocarcinoma HT-29 and the human promyelocytic leukemia HL-60, with IC₅₀ μM values of 1.4 and 1.7 respectively. Molecular docking and homology modeling studies were carried out to confirm the affinity of these synthesized compounds to the three different PIM kinases. Additionally, a number of in silico predictions, ADME/Tox, were adopted to evaluate their drug-likeness.

The E isomer of compound 5 exhibited a potent inhibitory effect against PIM kinase isoforms of IC₅₀s 0.30–0.41 μM.

Off-target toxicity is a common mechanism of action of cancer drugs undergoing clinical trials

Ninety-seven percent of drug-indication pairs that are tested in clinical trials in oncology never advance to receive U.S. Food and Drug Administration approval. While lack of efficacy and dose-limiting toxicities are the most common causes of trial failure, the reason(s) why so many new drugs encounter these problems is not well understood. Using CRISPR-Cas9 mutagenesis, we investigated a set of cancer drugs and drug targets in various stages of clinical testing. We show that-contrary to previous reports obtained predominantly with RNA interference and small-molecule inhibitors-the proteins ostensibly targeted by these drugs are nonessential for cancer cell proliferation. Moreover, the efficacy of each drug that we tested was unaffected by the loss of its putative target, indicating that these compounds kill cells via off-target effects. By applying a genetic target-deconvolution strategy, we found that the mischaracterized anticancer agent OTS964 is actually a potent inhibitor of the cyclin-dependent kinase CDK11 and that multiple cancer types are addicted to CDK11 expression. We suggest that stringent genetic validation of the mechanism of action of cancer drugs in the preclinical setting may decrease the number of therapies tested in human patients that fail to provide any clinical benefit.

Catalytic enantioselective Michael addition of 2-substituted benzofuran-3-ones to 2-enoyl pyridines

An organocatalytic diastereo- and enantioselective synthesis of 2,2'-disubstituted benzofuran-3-ones bearing adjacent quaternary and tertiary stereocenters has been achieved through Michael addition of 2-substituted benzofuran-3-ones to 2-enoyl pyridines. Both the enantiomeric forms of the major diastereomer were obtained using l-proline derived squaramide and quinine derived bis squaramide with excellent yield (up to 98%) and stereoselectivities (up to 97 : 3 dr and 98% ee). The control experiment revealed that the presence and position of nitrogen atoms in the 2-enoylpyridine have played a crucial role in the stereochemical outcome of the product.

Design and synthesis of 4β-Acetamidobenzofuranone-podophyllotoxin hybrids and their anti-cancer evaluation

A new series of amide derivatives of 4β-Acetamidobenzofuranone-podophyllotoxin hybrids (14a-g) were synthesized and their chemical structures were confirmed by ¹H, ¹³C NMR and mass spectral data. Further, all the synthesized Acetamidobenzofuranone-podophyllotoxin hybrids were evaluated for in vitro cytotoxic activity against a panel of four human cancer cell lines i.e., human breast (MCF-7, MDA MB-231), lung (A549), and prostrate (DU-145). Among benzofuranone-podophyllotoxin hybrid compounds, 14b and 14e were exhibited more potent activity than standard drug and 14c and 14f were showed anticancer activity equivalent to etoposide.

A review on PIM kinases in tumors

The Proviral Integration site for Moloney murine leukemia virus (PIM) kinases is serine/threonine kinases that promote growth and survival in multiple cell types, implicated in the pathogenesis of various diseases. Over expression of Pim-1 experimentally leads to tumor formation in mice, whereas there is no observable phenotype concerning the complete knockout of the protein. When it is over expressed it may lead to cancer development by three major ways; by inhibiting apoptosis, by promoting cell proliferation and also through promoting genomic instability. Expression in normal tissues is nearly undetectable. Recent improvements in the development of novel inhibitors of PIMs have been reviewed. Significant progress in the design of PIMs inhibitors, in which it displays selectivity versus other kinases, has been achieved within the last years. However, the development of isoform-selective PIM inhibitors is still an open task. As Pim-1 possesses oncogenic functions and is over expressed in various kinds of cancer diseases, its inhibition provides a new option in cancer therapy. A PubMed literature search was performed to review the currently available data on Pim-1 expression, regulation, and targets; its implication in different types of cancer and its impact on prognosis is described. Consequently, designing new inhibitors of PIMs is now a very active area of research in academic and industrial laboratories.

Discovery of N-substituted 7-azaindoles as Pan-PIM kinases inhibitors - Lead optimization - Part III

N-substituted azaindoles were discovered as promising pan-PIM inhibitors. Lead optimization is described en route toward the identification of a clinical candidate. Modulation of physico-chemical properties allowed to solve inherent hERG and permeability liabilities. Compound 17 showed tumor growth inhibition in a KG1 tumor-bearing mouse model.

New Pim-1 Kinase Inhibitor From the Co-culture of Two Sponge-Associated Actinomycetes

Saccharomonospora sp. UR22 and Dietzia sp. UR66, two actinomycetes derived from the Red Sea sponge Callyspongia siphonella, were co-cultured and the induced metabolites were monitored by HPLC-DAD and TLC. Saccharomonosporine A (1), a novel brominated oxo-indole alkaloid, convolutamydine F (2) along with other three known induced metabolites (3-5) were isolated from the EtOAc extract of Saccharomonospora sp. UR22 and Dietzia sp. UR66 co-culture. Additionally, axenic culture of Saccharomonospora sp. UR22 led to isolation of six known microbial metabolites (6-11). A kinase inhibition assay results showed that compounds 1 and 3 were potent Pim-1 kinase inhibitors with an IC₅₀ value of 0.3 ± 0.02 and 0.95 ± 0.01 μM, respectively. Docking studies revealed the binding mode of compounds 1 and 3 in the ATP pocket of Pim-1 kinase. Testing of compounds 1 and 3 displayed significant antiproliferative activity against the human colon adenocarcinoma HT-29, (IC₅₀ 3.6 and 3.7 μM, respectively) and the human promyelocytic leukemia HL-60, (IC₅₀ 2.8 and 4.2 μM, respectively). These results suggested that compounds 1 and 3 act as potential Pim-1 kinase inhibitors that mediate the tumor cell growth inhibitory effect. This study highlighted the co-cultivation approach as an effective strategy to increase the chemical diversity of the secondary metabolites hidden in the genomes of the marine actinomycetes.

Pim1 promotes cell proliferation and regulates glycolysis via interaction with MYC in ovarian cancer

Background

Ovarian cancer (OC) is the leading cause of death among women with gynecologic malignancies. Recent studies have highlighted the role of Pim1, which belongs to a group of constitutively activated serine/threonine kinases, in cancer development. However, the effect of Pim1 in OC is largely unclear.

Methods

OC cell lines with Pim1 overexpression or knockdown were constructed with len-tivirus transduction. Cell Counting Kit-8, colony formation, glycolysis stress test and in vivo mice models were carried out to assess the effect of Pim1 on OC biological functions. Co-immunoprecipitation assay coupled with western blot were performed to explore the intrinsic mechanisms of Pim1 in OC. Bioinformatic analysis was then performed to evaluate the expression and prognostic value of Pim1.

Results

We present the first evidence that silencing or overexpressing Pim1 can suppress or promote, respectively, OC cell proliferation. Furthermore, we demonstrated that Pim1 can significantly enhance glycolysis in OC cells. In vivo experiments further confirmed that knockdown of Pim1 inhibits the growth of tumors derived from the SKOV3 cell line. To search for the underlying molecular mechanism, we examined the effect of Pim1 on MYC, a pivotal gene in glycolysis, and observed that Pim1-mediated phosphorylation of c-Myc activated the expression of glycolysis-associated key genes such as PGK1 and LDHA. Moreover, we found that the Pim1 inhibitor SMI4a induced chemosensitization to cisplatin. Clinically, Pim1 was also overexpressed in OC and correlated with poor overall survival by bioinformatics analysis.

Conclusion

Together, these results suggest that Pim1 contributes to proliferation and gly-colysis in OC via interaction with MYC and may serve as a potential target in the treatment of OC patients.

N-Heterocyclic Carbene/Palladium Cascade Catalysis: Construction of 2,2-Disubstitiuted Benzofuranones from the Reaction of 3-(2-Formylphenoxy)propenoates with Allylic Esters

The cascade catalysis involving N-heterocyclic carbene (NHC) and palladium/ligand was demonstrated. In the presence of a triazolium salt, palladium catalyst, and base, the reaction of 3-(2-formylphenoxy)propenoates and allylic esters proceeded efficiently under mild conditions to afford 2-allylbenzofuran-3-one-2-acetates in moderated to good yields. An asymmetric cascade catalysis was achieved when (R)-BINAP was employed as a chiral ligand, producing enantiomerically enriched 2,2-disubstitiuted benzofuran-3-one derivatives with an ee up to 81%.

Theoretical Analysis of Activity Cliffs among Benzofuranone-Class Pim1 Inhibitors Using the Fragment Molecular Orbital Method with Molecular Mechanics Poisson-Boltzmann Surface Area (FMO+MM-PBSA) Approach

Significant activity changes due to small structural changes (i.e., activity cliffs) of serine/threonine kinase Pim1 inhibitors were studied theoretically using the fragment molecular orbital method with molecular mechanics Poisson-Boltzmann surface area (FMO+MM-PBSA) approach. This methodology enables quantum-chemical calculations for large biomolecules with solvation. In the course of drug discovery targeting Pim1, six benzofuranone-class inhibitors were found to differ only in the position of the indole-ring nitrogen atom. By comparing the various qualities of complex structures based on X-ray, classical molecular mechanics (MM)-optimized, and quantum/molecular mechanics (QM/MM)-optimized structures, we found that the QM/MM-optimized structures provided the best correlation (R² = 0.85) between pIC₅₀ and the calculated FMO+MM-PBSA binding energy. Combining the classical solvation energy with the QM binding energy was important to increase the correlation. In addition, decomposition of the interaction energy into various physicochemical components by pair interaction energy decomposition analysis suggested that CH-π and electrostatic interactions mainly caused the activity differences.

Discovery of N-substituted 7-azaindoles as PIM1 kinase inhibitors - Part I

Novel N-substituted azaindoles have been discovered as PIM1 inhibitors. X-ray structures have played a significant role in orienting the chemistry effort in the initial phase of hit confirmation. Disclosure of an unconventional binding mode for 1 and 2, as demonstrated by X-ray crystallography, is presented and was an important factor in selecting and advancing a lead series.

Discovery of N-substituted 7-azaindoles as Pan-PIM kinase inhibitors - Lead series identification - Part II

N-Substituted azaindoles have been discovered as pan-PIM kinase inhibitors. Initial SAR, early ADME and PK/PD data of a series of compounds is described and led to the identification of promising pan-PIM inhibitors which validated our interest in the 7-azaindole scaffold and led us to pursue the identification of a clinical candidate.

Design and Synthesis of Potent and Selective PIM Kinase Inhibitors by Targeting Unique Structure of ATP-Binding Pocket

In the development of kinase inhibitors, one of the major concerns is selectivity. An effective strategy to achieve high selectivity is to utilize structural differences among kinases to inform inhibitor design. Here, we set out to improve the PIM (proviral integration site for Moloney murine leukemia virus) kinase-inhibitory selectivity of our previously reported 7-azaindole derivative 2, which has promising ADMET properties, by targeting a unique bulge in the ATP-binding pocket. 6-Substituted 7-azaindoles, especially the 6-chlorinated derivatives, proved to be potent and selective PIM kinase inhibitors and appear to be promising lead compounds for future drug discovery.

Discovery of novel furanone derivatives as potent Cdc7 kinase inhibitors

Cdc7 is a serine-threonine kinase and plays a conserved and important role in DNA replication, and it has been recognized as a potential anticancer target. Herein, we report the design, synthesis and structure-activity relationship of novel furanone derivatives as Cdc7 kinase inhibitors. Compound 13 was identified as a strong inhibitor of Cdc7 with an IC₅₀ value of 0.6 nM in the presence of 1 mM ATP and showed excellent kinase selectivity. In addition, it exhibited slow off-rate characteristics, which may offer advantages over known Cdc7 inhibitors in its potential to yield prolonged inhibitory effects in vivo. Compound 13 potently inhibited Cdc7 activity in cancer cells, and effectively induced cell death.

Aberrant expression of pim-3 promotes proliferation and migration of ovarian cancer cells

Pim kinase-3(Pim-3), a member of serine/threonine protein kinases, has been implicated in multiple human cancers and involved in Myc-induced tumorigenesis. However, little is known regarding its expression and biological function in human ovarian cancer. In this study we showed that the clinical significance and biological functions of Pim-3 in ovarian cancer and found that higher Pim-3 mRNA level are detected in ovarian cancer tissues than those in normal ovarian tissues. There are significant correlations between higher Pim-3 expression levels with the FIGO stage, histopathological subtypes, and distant metastasis in ovarian cancer patients. Lentivirus-mediated gene overexpression of Pim-3 significantly promotes the proliferation and migration of SKOV3 cell lines. Furthermore, MACC1 and Pim-3 expression were significantly correlated in human ovarian cancer cells, and overexpression of Pim-3 in ovary cancer cells increased MACC1 mRNA and protein expression. The data indicate that Pim-3 acts as a putative oncogene in ovary cancer and could be a viable diagnostic and therapeutic target for ovarian cancer.

Design and synthesis of an in vivo-efficacious PIM3 kinase inhibitor as a candidate anti-pancreatic cancer agent

Serine/threonine kinase PIM3 is a potential therapeutic target for pancreatic cancer. Here, we describe the evolution of our previous PIM1 inhibitor 1 into PIM3 inhibitor 11 guided by use of the crystal structure of PIM1 as a surrogate to provide a basis for rational modification. Compound 11 potently inhibits PIM3 kinase activity, as well as growth of several pancreatic cancer cell lines. In a mouse xenograft model, 11 inhibited growth of human pancreatic cancer cell line PCI66 with negligible body weight loss. Thus, 11 appears to be a promising lead compound for further optimization to develop new anti-pancreatic cancer agents.

Rh(iii)-catalyzed 7-azaindole synthesis via C–H activation/annulative coupling of aminopyridines with alkynes

An efficient Rh(iii)-catalyzed 7-azaindole synthesis was developed via C–H activation/annulative coupling of aminopyridines with alkynes.

Design, synthesis and biological evaluation of novel C3-functionalized oxindoles as potential Pim-1 kinase inhibitors

A novel series of C3-functionalized oxindoles, 3-(2-oxo-4-phenylbut-3-en-1-ylidene) indolin-2-ones as potential Pim-1 kinase inhibitors, were designed, synthesized and investigated for inhibition of human cancer-cell proliferation.

The discovery of novel 3-(pyrazin-2-yl)-1H-indazoles as potent pan-Pim kinase inhibitors

The three Pim kinases are a small family of serine/threonine kinases regulating several signaling pathways that are fundamental to tumorigenesis. As such, the Pim kinases are a very attractive target for pharmacological inhibition in cancer therapy. Herein, we describe our efforts toward the development of a potent, pan-Pim inhibitor. The synthesis and hit-to-lead SAR development from a 3-(pyrazin-2-yl)-1H-indazole derived hit 2 to the identification of a series of potent, pan-Pim inhibitors such as 13o are described.

The azaindole framework in the design of kinase inhibitors

This review article illustrates the growing use of azaindole derivatives as kinase inhibitors and their contribution to drug discovery and innovation. The different protein kinases which have served as targets and the known molecules which have emerged from medicinal chemistry and Fragment-Based Drug Discovery (FBDD) programs are presented. The various synthetic routes used to access these compounds and the chemical pathways leading to their synthesis are also discussed. An analysis of their mode of binding based on X-ray crystallography data gives structural insights for the design of more potent and selective inhibitors.

Practical, modular, and general synthesis of 3-coumaranones through gold-catalyzed intermolecular alkyne oxidation strategy

A gold-catalyzed intermolecular alkyne oxidation for the preparation of 3-coumaranones has been developed. Using 8-isopropylquinoline N-oxides as oxidants, the reactions of o-ethynylanisoles afford versatile 3-coumaranones in moderate to good isolated yields. The synthetic utility of this chemistry is also indicated by the synthesis of the natural product sulfuretin.

Kinase crystal identification and ATP-competitive inhibitor screening using the fluorescent ligand SKF86002

The small kinase inhibitor SKF86002 lacks intrinsic fluorescence but becomes fluorescent upon binding to the ATP-binding sites of p38 mitogen-activated protein kinase (p38α). It was found that co-crystals of this compound with various kinases were distinguishable by their strong fluorescence. The co-crystals of SKF86002 with p38α, Pim1, ASK1, HCK and AMPK were fluorescent. Addition of SKF86002, which binds to the ATP site, to the co-crystallization solution of HCK promoted protein stability and thus facilitated the production of crystals that otherwise would not grow in the apo form. It was further demonstrated that the fluorescence of SKF86002 co-crystals can be applied to screen for candidate kinase inhibitors. When a compound binds competitively to the ATP-binding site of a kinase crystallized with SKF86002, it displaces the fluorescent SKF86002 and the crystal loses its fluorescence. Lower fluorescent signals were reported after soaking SKF86002-Pim1 and SKF86002-HCK co-crystals with the inhibitors quercetin, a quinazoline derivative and A-419259. Determination of the SKF86002-Pim1 and SKF86002-HCK co-crystal structures confirmed that SKF86002 interacts with the ATP-binding sites of Pim1 and HCK. The structures of Pim1-SKF86002 crystals soaked with the inhibitors quercetin and a quinazoline derivative and of HCK-SKF86002 crystals soaked with A-419259 were determined. These structures were virtually identical to the deposited crystal structures of the same complexes. A KINOMEscan assay revealed that SKF86002 binds a wide variety of kinases. Thus, for a broad range of kinases, SKF86002 is useful as a crystal marker, a crystal stabilizer and a marker to identify ligand co-crystals for structural analysis.

Small molecule inhibitors of PIM1 kinase: July 2009 to February 2013 patent update

INTRODUCTION

The proviral insertion in murine (PIM) lymphoma proteins for which three isoforms, PIM1, PIM2 and PIM3 have been identified, belonging to the family of serine/threonine kinases has emerged recently as an important therapeutic target for the development of selective inhibitors as the new drugs for treating hematological malignancies and solid tumors. The small molecules developed by academia and the pharmaceutical industry have steadily increased in the last few years. Several drug discovery groups focus on treating disorders, such as cancer mediated by PIM kinase, have provided preclinical evidence suggesting that PIM inhibitor provides anti-apoptotic activity, inhibit cell survival and cell proliferation.

AREAS COVERED

This article discloses recent reviews on research and advances published in the patent literature and scientific publications from July 2009 to February 2013, highlighting discoveries on PIM1 kinase.

EXPERT OPINION

Several PIM1 kinase small molecule inhibitors are now at the pre-clinical research stage, development and testing. Though nearly 40 patents emerged in the last 3 years, greater efforts towards additional designs and medicinal chemistry continues for developing clinically efficacious PIM1 inhibitors, due to the significance of the target for cancer and the potential for novel and diverse inhibitors as drug candidates.