Potential Use of Selective and Nonselective Pim Kinase Inhibitors for Cancer Therapy

Combining machine learning and structure-based approaches to develop oncogene PIM kinase inhibitors

Introduction: PIM kinases are targets for therapeutic intervention since they are associated with a number of malignancies by boosting cell survival and proliferation. Over the past years, the rate of new PIM inhibitors discovery has increased significantly, however, new generation of potent molecules with the right pharmacologic profiles were in demand that can probably lead to the development of Pim kinase inhibitors that are effective against human cancer.

Method: In the current study, a machine learning and structure based approaches were used to generate novel and effective chemical therapeutics for PIM-1 kinase. Four different machine learning methods, namely, support vector machine, random forest, k-nearest neighbour and XGBoost have been used for the development of models. Total, 54 Descriptors have been selected using the Boruta method.

Results: SVM, Random Forest and XGBoost shows better performance as compared to k-NN. An ensemble approach was implemented and, finally, four potential molecules (CHEMBL303779, CHEMBL690270, MHC07198, and CHEMBL748285) were found to be effective for the modulation of PIM-1 activity. Molecular docking and molecular dynamic simulation corroborated the potentiality of the selected molecules. The molecular dynamics (MD) simulation study indicated the stability between protein and ligands.

Discussion: Our findings suggest that the selected models are robust and can be potentially useful for facilitating the discovery against PIM kinase.

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.

Nicotinonitrile-derived apoptotic inducers: Design, synthesis, X-ray crystal structure and Pim kinase inhibition

Although a plethora of targeted anticancer small molecule drugs became available, the low response rate and drug resistance imply the continuous need for expanding the anticancer chemical space. In this study, a novel series of nicotinonitrile derivatives was designed, synthesized and evaluated for cytotoxic activities in HepG2 and MCF-7 cells. All derivatives showed high to moderate cytotoxic activity against both cell lines, with cell-type and chemotype-dependent cytotoxic potential. The normal HEK-293 T cells were ca. 50-fold less susceptible to the cytotoxic effect of the inhibitors. The in vitro enzyme inhibitory activity of selected active cytotoxic derivatives 8c, 8e, 9a, 9e and 12 showed that they have sub- to one digit micromolar 50 % inhibitory concentration (IC₅₀) against the three Pim kinase isoforms, with 8e being the most potent (IC₅₀ ≤ 0.28 μM against three Pim kinases), comparable to the pan kinase inhibitor, Staurosporine. In HepG2, 8e induced cell cycle arrest at the G2/M phase. Apoptotic mechanistic studies with 8c and 8e in HepG2 cells, indicated a significant upregulation in both P53 and caspase-3 relative gene expression, as well as increased Bax/Bcl-2 protein expression level. Further, docking studies combined with molecular dynamic simulation showed a stable complex with high binding affinity of 8e to Pim-1 kinase; exploiting a negative electrostatic potential surface interaction with the added dimethyl amino group in the new compounds. Moreover, in silico ADME profile prediction indicated that all compounds are orally bioavailable and most of them can penetrate the blood-brain barrier. This study presents novel nicotinonitrile derivatives as auspicious hits for further optimization as antiproliferative agents against liver cancer cells and promising pan Pim kinase inhibitors at submicromolar concentrations.

Development of novel cyanopyridines as PIM-1 kinase inhibitors with potent anti-prostate cancer activity: Synthesis, biological evaluation, nanoparticles formulation and molecular dynamics simulation

Recently, inhibition of PIM-1 enzyme is found as an effective route in the fight against proliferation of cancer. Herein, new cyano pyridines that target PIM-1 kinase were designed, synthesized, and biologically evaluated. Two prostate cell lines were used to examine each of the new compounds in vitro for anticancer activity, namely, PC-3 and DU-145. The cyanopyridine derivatives 2b, 3b, 4b, and 5b with an N,N-dimethyl phenyl group at the pyridine ring's 4-position showed considerable antitumor effect on the tested cell lines. Additionally, the high selectivity index revealed that these compounds were less cytotoxic to normal WI-38 cells. Furthermore, they exhibited strong inhibitory effect on PIM-1 having IC₅₀ = 0.248, 0.13, 0.326 and 0.245 μM, respectively. The most powerful derivatives2b, 3b, 4b, and 5b, were chosen for further examination of their inhibitory potential on both kinases (PIM-2 and PIM-3). Interestingly, upon loading compound 3b in a cubosomes formulation with nanometric size, improvements in cytotoxicity and inhibitory effect on PIM-1 kinase were observed. In silico ADME parameters study revealed that compound 3b is orally bioavailable without penetration to the blood-brain barrier. Further, the docking simulations revealed the ability of our potent compounds to well accommodate the PIM-1 kinase active site forming stable complexes. In a 150 ns MD simulation, the most powerful PIM-1 inhibitor 3b produced stable complex with the PIM-1 enzyme (RMSD = 1.76). Furthermore, the 3b-PIM-1 complex has the low binding free energy (-242.2 kJ/mol) according to the MM-PBSA calculations.

The Role of PIM Kinases in Pediatric Solid Tumors

PIM kinases have been identified as potential therapeutic targets in several malignancies. Here, we provide an in-depth review of PIM kinases, including their structure, expression, activity, regulation, and role in pediatric carcinogenesis. Also included is a brief summary of the currently available pharmaceutical agents targeting PIM kinases and existing clinical trials.

Utilization of cyanopyridine in design and synthesis of first-in-class anticancer dual acting PIM-1 kinase/HDAC inhibitors

Herein, we report design and synthesis of twenty-one dual PIM-1/HDAC inhibitors utilizing 3-cyanopyridines as a novel cap moiety linked with aliphatic /aromatic linker bearing carboxylic acid 3a-g, hydroxamic acid 4a-g or 2-aminoanilide moieties 5a-g as zinc-binding group. Most of the target hybrids revealed promising growth inhibition according to one dose NCI protocol against 60 cancer cell lines. Meanwhile, hydroxamic acids 4b, 4d and 4e displayed strong and broad-spectrum activity against nine tumor subpanels tested (GI₅₀ 0.176-8.87 μM); 4d displayed strong antiproliferative activity with GI₅₀ ≤ 3 μM against different cancer cell lines (GI₅₀ range from 0.325 to 2.9 μM). Furthermore, 4a, 4d-4g and 5f manifested a high inhibitory activity against HDACs 1 and 6 isozymes; 4g, displayed potent HDAC 1 and 6 inhibitory activity (45.01 ± 2.1 and 19.78 ± 1.1 nM) more than the reference SAHA (51.54 ± 2.4 and 21.38 ± 1.2 nM, respectively), while 4f was more potent (30.09 ± 1.4 nM) than SAHA against HDAC 1 and less potent (30.29 ± 1.7 nM) than SAHA against HDAC 6. Hybrids 4b, 4d, 4e and 4f exhibited potent PIM-1 inhibitory activity; 4d showed comparable activity to quercetin (IC₅₀ of 343.87 ± 16.6 and 353.76 ± 17.1 nM, respectively); it exhibited pre G1 apoptosis and arrest cell cycle at G2/M phase. Moreover, it revealed good binding into pocket of HDACs 1,6 and PIM-1 kinase enzymes with good correlation with biological results. Moreover, 4b, 4d and 4e had reasonable drug-likeness properties according to Lipinski's rule. However, multitarget inhibitor of PIM-1/HDAC is a promising strategy in anticancer drug discovery; the most potent hybrids require further in vivo and clinical investigations.

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.

New cyanopyridine-based scaffold as PIM-1 inhibitors and apoptotic inducers: Synthesis and SARs study

Two novel series of 6-(4-benzamido-/4-phthalimido)-3-cyanopyridine derivatives were designed and synthesized as inhibitors of PIM-1 kinase. Based on cytotoxicity results via MTT assay against prostate carcinoma PC3, human hepatocellular carcinoma HepG2 and breast adenocarcinoma MCF-7 cell lines, the most potent cytotoxic cyanopyridine hits, 6, 7, 8, 12 and 13 were 1.5-3.3 times more inhibitor of cell proliferation than the reference standard, 5-FU. Selectivity profile of the latter compounds on normal human cells (WI-38), was executed, indicating that they are highly selective (IC₅₀ > 145 μM) in their cytotoxic effect. The promising compounds were further evaluated as PIM-1 kinase inhibitors. These compounds elicited remarkable inhibition of PIM-1 kinase (76.43-53.33%). Extensive studies on apoptosis were conducted for these compounds; they enhanced caspase-3 and boosted the Bax/Bcl-2 ratio 27-folds in comparison to the control. Molecular docking study of the most potent compound, 13 in PIM-1 kinase active site was consistent with the in vitro activity. Finally, prediction of chemo-informatic properties released compound 13 as the most promising ligand.

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.

In Vitro and In Vivo Anti-Breast Cancer Activities of Some Newly Synthesized 5-(thiophen-2-yl)thieno-[2,3-d]pyrimidin-4-one Candidates

In this study, some of new thiophenyl thienopyrimidinone derivatives 2–15 were prepared and tested as anti-cancer agents by using thiophenyl thieno[2,3-d]pyrimidinone derivative 2 as a starting material, which was prepared from cyclization of ethyl ester derivative 1 with formamide. Treatment of 2 with ethyl- chloroacetate gave thienopyrimidinone N-ethylacetate 3, which was reacted with hydrazine hydrate or anthranilic acid to afford acetohydrazide 4 and benzo[d][1,3]oxazin-4-one 5, respectively. Condensation of 4 with aromatic aldehydes or phenylisothiocyanate yielded Schiff base derivatives 6,7, and thiosemicarbazise 10, which were treated with 2-mercaptoacetic acid or chloroacetic acid to give the corresponding thiazolidinones 8, 9, and phenylimino-thiazolidinone 11, respectively. Treatment of 4 with ethylacetoacetate or acetic acid/acetic anhydride gave pyrazole 12 and acetyl acetohydrazide 13 derivatives, respectively. The latter compound 13 was reacted with ethyl cycno-acetate or malononitrile to give 14 and 15, respectively. In this work, we have studied the anti-cancer activity of the synthesized thienopyrimidinone derivatives against MCF-7 and MCF-10A cancer cells. Furthermore, in vivo experiments showed that the synthesized compounds significantly reduced tumor growth up to the 8^th day of treatment in comparison to control animal models. Additionally, the synthesized derivatives showed potential inhibitory effects against pim-1 kinase activities.

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.

Design, synthesis and biological evaluation of N-arylsulfonyl carbazoles as novel anticancer agents

In this work, a set of structurally diverse synthetic carbazoles was screened for their anticancer activities. According to structure–activity relationship studies, carbazoles with an N-substituted sulfonyl group exhibited better anticancer activity. Moreover, compound 8h was discovered to show the most potent anticancer effects on Capan-2 cells by inducing apoptosis and cell cycle arrest in G2/M phase. Finally, the in vivo study demonstrated that 8h prevented the tumor growth in PANC-1 and Capan-2 xenograft models without apparent toxicity.

In this work, a set of structurally diverse synthetic carbazoles was screened for their anticancer activities.

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.

Synthesis of new pyridothienopyrimidinone derivatives as Pim-1 inhibitors

Four series of pyridothienopyrimidin-4-one derivatives were designed and prepared to improve the pim-1 inhibitory activity of the previously reported thieno[2,3-b]pyridines. Significant improvement in the pim-1 inhibition and cytotoxic activity was achieved using structure rigidification strategy via ring closure. Six compounds (6c, 7a, 7c, 7d, 8b and 9) showed highly potent pim-1 inhibitory activity with IC₅₀ of 4.62, 1.18, 1.38, 1.97, 8.83 and 4.18 μM, respectively. Four other compounds (6b, 6d, 7b and 8a) showed moderate pim-1 inhibition. The most active compounds were tested for their cytotoxic activity on three cell lines [MCF7, HCT116 and PC3]. Compounds 7a [the 2-(2-chlorophenyl)-2,3-dihydro derivative] and 7d [the 2-(2-(trifluoromethyl)-phenyl)-2,3-dihydro derivative] displayed the most potent cytotoxic effect on the three cell lines tested consistent with their highest estimated pim-1 IC₅₀ values.

Thiazolidine derivatives as potent and selective inhibitors of the PIM kinase family

The PIM family of serine/threonine kinases have become an attractive target for anti-cancer drug development, particularly for certain hematological malignancies. Here, we describe the discovery of a series of inhibitors of the PIM kinase family using a high throughput screening strategy. Through a combination of molecular modeling and optimization studies, the intrinsic potencies and molecular properties of this series of compounds was significantly improved. An excellent pan-PIM isoform inhibition profile was observed across the series, while optimized examples show good selectivity over other kinases. Two PIM-expressing leukemic cancer cell lines, MV4-11 and K562, were employed to evaluate the in vitro anti-proliferative effects of selected inhibitors. Encouraging activities were observed for many examples, with the best example (44) giving an IC₅₀ of 0.75μM against the K562 cell line. These data provide a promising starting point for further development of this series as a new cancer therapy through PIM kinase inhibition.

Discovery of imidazopyridazines as potent Pim-1/2 kinase inhibitors

High levels of Pim expression have been implicated in several hematopoietic and solid tumor cancers, suggesting that inhibition of Pim signaling could provide patients with therapeutic benefit. Herein, we describe our progress towards this goal using a screening hit (rac-1) as a starting point. Modification of the indazole ring resulted in the discovery of a series of imidazopyridazine-based Pim inhibitors exemplified by compound 22m, which was found to be a subnanomolar inhibitor of the Pim-1 and Pim-2 isoforms (IC₅₀ values of 0.024nM and 0.095nM, respectively) and to potently inhibit the phosphorylation of BAD in a cell line that expresses high levels of all Pim isoforms, KMS-12-BM (IC₅₀=28nM). Profiling of Pim-1 and Pim-2 expression levels in a panel of multiple myeloma cell lines and correlation of these data with the potency of compound 22m in a proliferation assay suggests that Pim-2 inhibition would be advantageous for this indication.

Discovery and Optimization of Macrocyclic Quinoxaline-pyrrolo-dihydropiperidinones as Potent Pim-1/2 Kinase Inhibitors

The identification of Pim-1/2 kinase overexpression in B-cell malignancies suggests that Pim kinase inhibitors will have utility in the treatment of lymphoma, leukemia, and multiple myeloma. Starting from a moderately potent quinoxaline-dihydropyrrolopiperidinone lead, we recognized the potential for macrocyclization and developed a series of 13-membered macrocycles. The structure-activity relationships of the macrocyclic linker were systematically explored, leading to the identification of 9c as a potent, subnanomolar inhibitor of Pim-1 and -2. This molecule also potently inhibited Pim kinase activity in KMS-12-BM, a multiple myeloma cell line with relatively high endogenous levels of Pim-1/2, both in vitro (pBAD IC50 = 25 nM) and in vivo (pBAD EC50 = 30 nM, unbound), and a 100 mg/kg daily dose was found to completely arrest the growth of KMS-12-BM xenografts in mice.

Synthesis of new thieno[2,3-b]pyridine derivatives as pim-1 inhibitors

Three series of 5-bromo-thieno[2,3-b]pyridines bearing amide or benzoyl groups at position 2 were prepared as pim-1 inhibitors. All the prepared compounds were tested for their pim-1 enzyme inhibitory activity. Two compounds (3c and 5b) showed moderate pim-1 inhibitory activity with IC50 of 35.7 and 12.71 μM, respectively. Three other compounds (3d, 3g and 6d) showed poor pim-1 inhibition. The most active compounds were tested for their cytotoxic activity on five cell lines [MCF7, HEPG2, HCT116, A549 and PC3]. Compound 3g was the most potent cytotoxic agent on almost all the cell lines tested.

Design and synthesis of substituted pyrido[3,2-d]-1,2,3-triazines as potential Pim-1 inhibitors

A novel series of substituted pyrido[3,2-d]-1,2,3-triazines were designed and synthesized as Pim-1 inhibitors through scaffold hopping. Most of the derivatives showed potent in vitro Pim-1 inhibitory activities and anti-proliferative effects toward prostate cancer cells. Among them, 6b, 6h and 6m showed the best Pim-1 inhibitory activity with IC50 values of 0.69, 0.60 and 0.80 μM, respectively. Furthermore, compounds 6b, 6i, 6j and 6m showed strong inhibitory activity to human prostate cancer LNcap and PC-3 cell lines with IC50 values at low micromolar level. Structure-activity relationship analysis revealed that appropriate substitutions at C-6 positions contributed to the kinase inhibition and antiproliferative effects. Moreover, western blot assay suggested that 6j could decrease the levels of p-BAD and p-4E-BP1 in a dose-dependent manner in PC-3 cells. Docking studies showed that 3-N of the scaffold formed a hydrogen bond with Lys67, aromatic 4-aniline formed a key π-π stack with Phe49. Taken together, this study might provide the first sight for developing the pyrido[3,2-d]-1,2,3-triazine scaffold as novel Pim-1 inhibitors.

Efficient synthesis of novel disubstituted pyrido[3,4-b]pyrazines for the design of protein kinase inhibitors

Urea and aniline derivatives were active at low micromomolar IC₅₀ values against a panel of seven cancer-related protein kinases.

Targeting Pim kinases for cancer treatment: opportunities and challenges

Pim oncogenes are highly expressed in many types of hematological and solid cancers. Pim kinases regulate the network of signaling pathways that are critical for tumorigenesis and development, making Pim kinases the attractive drug targets. Currently, two approaches have been employed in designing Pim kinase inhibitors: ATP-mimetics and non-ATP mimetics; but all target the ATP-binding pocket and are ATP-competitive. In this review, we summarize the current progress in understanding the Pim-related structure and biology, and provide insights into the binding modes of some prototypical Pim-1 inhibitors. The challenges as well as opportunities are highlighted for development of Pim kinase inhibitors as potential anticancer agents.

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.

PIM kinases as potential therapeutic targets in a subset of peripheral T cell lymphoma cases

Currently, there is no efficient therapy for patients with peripheral T cell lymphoma (PTCL). The Proviral Integration site of Moloney murine leukemia virus (PIM) kinases are important mediators of cell survival. We aimed to determine the therapeutic value of PIM kinases because they are overexpressed in PTCL patients, T cell lines and primary tumoral T cells. PIM kinases were inhibited genetically (using small interfering and short hairpin RNAs) and pharmacologically (mainly with the pan-PIM inhibitor (PIMi) ETP-39010) in a panel of 8 PTCL cell lines. Effects on cell viability, apoptosis, cell cycle, key proteins and gene expression were evaluated. Individual inhibition of each of the PIM genes did not affect PTCL cell survival, partially because of a compensatory mechanism among the three PIM genes. In contrast, pharmacological inhibition of all PIM kinases strongly induced apoptosis in all PTCL cell lines, without cell cycle arrest, in part through the induction of DNA damage. Therefore, pan-PIMi synergized with Cisplatin. Importantly, pharmacological inhibition of PIM reduced primary tumoral T cell viability without affecting normal T cells ex vivo. Since anaplastic large cell lymphoma (ALK+ ALCL) cell lines were the most sensitive to the pan-PIMi, we tested the simultaneous inhibition of ALK and PIM kinases and found a strong synergistic effect in ALK+ ALCL cell lines. Our findings suggest that PIM kinase inhibition could be of therapeutic value in a subset of PTCL, especially when combined with ALK inhibitors, and might be clinically beneficial in ALK+ ALCL.

PIM and AKT kinase inhibitors show synergistic cytotoxicity in acute myeloid leukaemia that is associated with convergence on mTOR and MCL1 pathways

PIM kinases (PIM1, 2 and 3) are involved in cell proliferation and survival signalling and are emerging targets for the therapy of various malignancies. We found that a significant proportion of primary acute myeloid leukaemia (AML) samples showed PIM1 and PIM2 expression by quantitative reverse transcription polymerase chain reaction. Therefore, we investigated the effects of a novel ATP-competitive pan-PIM inhibitor, AZD1897, on AML cell growth and survival. PIM inhibition showed limited single agent activity in AML cell lines and primary AML cells, including those with or without FLT3-internal tandem duplication (ITD) mutation. However, significant synergy was seen when AZD1897 was combined with the Akt inhibitor AZD5363, a compound that is in early-phase clinical trials. AML cells from putative leukaemia stem cell subsets, including CD34+38- and CD34+38+ fractions, were equivalently affected by dual PIM/Akt inhibition when compared with bulk tumour cells. Analysis of downstream signalling pathways showed that combined PIM/Akt inhibition downregulated mTOR outputs (phosphorylation of 4EBP1 and S6) and markedly reduced levels of the anti-apoptotic protein MCL1. The combination of PIM and Akt inhibition holds promise for the treatment of AML.

PIM inhibitors target CD25-positive AML cells through concomitant suppression of STAT5 activation and degradation of MYC oncogene

CD25 is a predictive biomarker for sensitivity to PIM inhibitors in AML cells. PIM inhibitors may prolong overall/relapse-free survival through attenuating STAT5 activation and destabilizing MYC in CD25+ AML cells.

Discovery of (7-aryl-1,5-naphthyridin-2-yl)ureas as dual inhibitors of ERK2 and Aurora B kinases with antiproliferative activity against cancer cells

A novel series of (7-aryl-1,5-naphthyridin-2-yl)ureas was discovered as dual ERK2 and Aurora B kinases inhibitors. Several analogues were active at micromolar and submicromolar range against ERK2 and Aurora B, associated with very promising antiproliferative activity toward various cancer cell lines. Synthesis, structure activity relationship and docking study are reported. In vitro ADME properties and safety data are also discussed.

Stochastic detection of Pim protein kinases reveals electrostatically enhanced association of a peptide substrate

In stochastic sensing, the association and dissociation of analyte molecules is observed as the modulation of an ionic current flowing through a single engineered protein pore, enabling the label-free determination of rate and equilibrium constants with respect to a specific binding site. We engineered sensors based on the staphylococcal α-hemolysin pore to allow the single-molecule detection and characterization of protein kinase-peptide interactions. We enhanced this approach by using site-specific proteolysis to generate pores bearing a single peptide sensor element attached by an N-terminal peptide bond to the trans mouth of the pore. Kinetics and affinities for the Pim protein kinases (Pim-1, Pim-2, and Pim-3) and cAMP-dependent protein kinase were measured and found to be independent of membrane potential and in good agreement with previously reported data. Kinase binding exhibited a distinct current noise behavior that forms a basis for analyte discrimination. Finally, we observed unusually high association rate constants for the interaction of Pim kinases with their consensus substrate Pimtide (~10(7) to 10(8) M(-1) · s(-1)), the result of electrostatic enhancement, and propose a cellular role for this phenomenon.

Discovery and optimization of pyrrolo[1,2-a]pyrazinones leads to novel and selective inhibitors of PIM kinases

A novel series of PIM inhibitors was derived from a combined effort in natural product-inspired library generation and screening. The novel pyrrolo[1,2-a]pyrazinones initial hits are inhibitors of PIM isoforms with IC50 values in the low micromolar range. The application of a rational optimization strategy, guided by the determination of the crystal structure of the complex in the kinase domain of PIM1 with compound 1, led to the discovery of compound 15a, which is a potent PIM kinases inhibitor exhibiting excellent selectivity against a large panel of kinases, representative of each family. The synthesis, structure-activity relationship studies, and pharmacokinetic data of compounds from this inhibitor class are presented herein. Furthermore, the cellular activities including inhibition of cell growth and modulation of downstream targets are also described.