Small molecule kinase inhibitors approved by the FDA from 2000 to 2011: a systematic review of preclinical ADME data

Recent advances in chemometric modelling of inhibitors against SARS-CoV-2

The outbreak of the novel coronavirus disease 2019 (COVID-19), caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), has caused great harm to all countries worldwide. This disease can be prevented by vaccination and managed using various treatment methods, including injections, oral medications, or aerosol therapies. However, the selection of suitable compounds for the research and development of anti-SARS-CoV-2 drugs is a daunting task because of the vast databases of available compounds. The traditional process of drug research and development is time-consuming, labour-intensive, and costly. The application of chemometrics can significantly expedite drug R&D. This is particularly necessary and important for drug development against pandemic public emergency diseases, such as COVID-19. Through various chemometric techniques, such as quantitative structure-activity relationship (QSAR) modelling, molecular docking, and molecular dynamics (MD) simulations, compounds with inhibitory activity against SARS-CoV-2 can be quickly screened, allowing researchers to focus on the few prioritised candidates. In addition, the ADMET properties of the screened candidate compounds should be further explored to promote the successful discovery of anti-SARS-CoV-2 drugs. In this case, considerable time and economic costs can be saved while minimising the need for extensive animal experiments, in line with the 3R principles. This paper focuses on recent advances in chemometric modelling studies of COVID-19-related inhibitors, highlights current limitations, and outlines potential future directions for development.

Pharmacokinetics and Pharmacodynamics of Ruxolitinib: A Review

BACKGROUND AND OBJECTIVE

Ruxolitinib is a tyrosine kinase inhibitor targeting the Janus kinase (JAK) and signal transducer and activator of transcription (STAT) pathways. Ruxolitinib is used to treat myelofibrosis, polycythemia vera and steroid-refractory graft-versus-host disease in the setting of allogeneic stem-cell transplantation. This review describes the pharmacokinetics and pharmacodynamics of ruxolitinib.

METHODS

Pubmed, EMBASE, Cochrane Library and web of Science were searched from the time of database inception to march 15, 2021 and was repeated on November 16, 2021. Articles not written in English, animal or in vitro studies, letters to the editor, case reports, where ruxolitinib was not used for hematological diseases or not available as full text were excluded.

RESULTS

Ruxolitinib is well absorbed, has 95% bio-availability, and is bound to albumin for 97%. Ruxolitinib pharmacokinetics can be described with a two-compartment model and linear elimination. Volume of distribution differs between men and women, likely related to bodyweight differences. Metabolism is mainly hepatic via CYP3A4 and can be altered by CYP3A4 inducers and inhibitors. The major metabolites of ruxolitinib are pharmacologically active. The main route of elimination of ruxolitinib metabolites is renal. Liver and renal dysfunction affect some of the pharmacokinetic variables and require dose reductions. Model-informed precision dosing might be a way to further optimize and individualize ruxolitinib treatment, but is not yet advised for routine care due to lack of information on target concentrations.

CONCLUSION

Further research is needed to explain the interindividual variability of the ruxolitinib pharmacokinetic variables and to optimize individual treatment.

Identification of 1,2,4-Oxadiazoles-Based Novel EGFR Inhibitors: Molecular Dynamics Simulation-Guided Identification and in vitro ADME Studies

Background

In this work, we have identified heterocyclic derivatives with 1,2,4 oxadiazole scaffold mimicking the functions of tyrosine kinase inhibitors. Fourteen molecules that displayed the best fit were picked from the library of compounds and studied under in-silico and in-vitro conditions. Four compounds were selected for further cytotoxicity and ADME (Absorption, Distribution, Metabolism, Elimination) profiling showing IC₅₀ (from 8–13 µM) values against EGFR positive cancer cell line (MCF7).

Methods

A molecular dynamics simulation study was performed to understand the correlation of non-covalent binding energies with biological activity. The drug-like properties of the selected four compounds (7a, 7b, 7e, and 7m) were evaluated by in-vitro ADME studies. Compounds 7a, 7b, and 7m were the active compounds in the molecular dynamics simulations study. Further, EGFR binding activity was confirmed with EGFR^WT and EGFR^T790M kinase assay using a luminescence-based method.

Results

These compounds (7a, 7b, and 7m) showed activity against EGFR^WT and mutant EGFR^T790M, exhibiting IC₅₀ values of <10 and <50 micromolar, respectively. These compounds also possess moderate aqueous solubility in 40–70 µg/mL at pH 7.4 and 30–100 µg/mL at pH 4.0. Further, 7a, 7b, and 7m showed balanced lipophilicity with Log D values ranging from 1–3. They demonstrated a good correlation in Caco-2 permeability with Apparent permeability (Papp) 1 to 5 × 10⁻⁶ cm/s in comparison with 7e, which was found to be highly lipophilic (Log D >5) and showed high permeability (Papp 17 × 10⁻⁶ cm/s). Lastly, all these compounds were moderately stable in liver microsomes at alkaline pH with a half-life of 30–60 min, while at a highly acidic pH (2.0), the compounds were stable up to 15–20 min.

Conclusion

Overall, in-vitro ADME results of these molecules showed good drug-like properties, which are well correlated with the in-silico ADME data, making them ideal for developing an oral drug delivery formulation.

Organometallic small molecule kinase inhibitors - direct incorporation of Re and 99mTc into Opaganib®

[(η5-Cp)Re^I(CO)₃] was incorporated into the kinase inhibitor Opaganib®. The resulting bioorganometallic complex showed a similar anti-cancer activity to Opaganib® against PC-3 cancer cells. The IC₅₀ value for the kinase SK2 is 30x higher than that of Opaganib®. The ^99mTc homologue was synthesized, completing a matched-pair for molecular theranostics.

Replacing an adamantyl unit in the protein kinase inhibitor Opaganib® with an integrated [(η⁵-Cp)M(CO)₃] (M = Re, ^99mTc) unit retains the lead's bioactivity and yields a true matched-pair pharmacomimetic.

Drug-Encapsulated Cyclodextrin Nanosponges

To date, a number of nanocarriers, either inorganic or organic, have been developed to improve the delivery and therapeutic efficacy of various drugs. Drug delivery systems have attempted to overcome the undesirable pharmacokinetic problems encountered. Among the various nanomaterials that have been designed as potential nanocarriers, cyclodextrin-based polymers are of particular interest in this review.Cyclodextrins (CD) are a class of cyclic glucopyranose oligomers, obtained from starch by enzymatic action, with a characteristic toroidal shape that forms a truncated cone-shaped lipophilic cavity. The main common native cyclodextrins are named α, β, and γ which comprise six, seven, and eight glucopyranose units, respectively. Cyclodextrins have the capability to include compounds whose size and polarity are compatible with those of their cavity.Cyclodextrin-based cross-linked polymers, often referred to as "cyclodextrin nanosponges" (CDNSs), attract great attention from researchers for solving major bioavailability problems such as inadequate solubility, poor dissolution rate, and limited stability of some agents, as well as increasing their effectiveness and decreasing unwanted side effects.Registered patents about this novel system in various fields, different pharmaceutical applications, and classes of drugs encapsulated by CDNSs are detailed. The features outlined make CDNSs a promising platform for the development of innovative and advanced delivery systems.

Assessing OATP1B1- and OATP1B3-Mediated Drug-Drug Interaction Potential of Vemurafenib Using R-Value and Physiologically-Based Pharmacokinetic Models

Organic anion transporting polypeptides (OATP) 1B1 and OATP1B3 are important determinants of transporter-mediated drug-drug interactions (DDIs). Current studies assessed the OATP1B1 and OATP1B3-mediated DDI potential of vemurafenib, a kinase inhibitor drug with high protein binding and low aqueous solubility, using R-value and physiologically-based pharmacokinetic (PBPK) models. The total half-maximal inhibitory concentration (IC50,total) values of vemurafenib against OATP1B1 and OATP1B3 were determined in 100% human plasma in transporter-overexpressing human embryonic kidney 293 stable cell lines. The unbound fraction of vemurafenib in human plasma before (fu,plasma) and after addition into the uptake assay plate (fu,plasma,inc) were determined by rapid equilibrium dialysis. There was no statistically significant difference between fu,plasma and fu,plasma,inc. Vemurafenib IC50,total values against OATP1B1 and OATP1B3 are 175 ± 82 and 231 ± 26 μM, respectively. The R-values [R = 1 + fu,plasma × Iin,max/(fu,plasma,inc × IC50,total)] were then simplified as R = 1+Iin,max/IC50,total, and were 1.76 and 1.57 for OATP1B1 and OATP1B3, respectively. The simulated pravastatin AUC ratio was 1.28 when a single dose of pravastatin (40 mg) was co-administered with vemurafenib (960 mg, twice daily) at steady-state, compared to pravastatin alone. Both R-value and PBPK models predict that vemurafenib has the potential to cause OATP1B1- and OATP1B3-mediated DDIs.

Extension of the Mechanistic Tissue Distribution Model of Rodgers and Rowland by Systematic Incorporation of Lysosomal Trapping: Impact on Unbound Partition Coefficient and Volume of Distribution Predictions in the Rat

Physiologically based pharmacokinetic modeling has become a standard tool to predict drug distribution in early stages of drug discovery; however, this does not currently encompass lysosomal trapping. For basic lipophilic compounds, lysosomal sequestration is known to potentially influence intracellular as well as tissue distribution. The aim of our research was to reliably predict the lysosomal drug content and ultimately integrate this mechanism into pharmacokinetic prediction models. First, we further validated our previously presented method to predict the lysosomal drug content (Schmitt et al., 2019) for a larger set of compounds (n = 41) showing a very good predictivity. Using the lysosomal marker lipid bis(monoacylglycero)phosphate, we estimated the lysosomal volume fraction for all major tissues in the rat, ranging from 0.03% for adipose up to 5.3% for spleen. The pH-driven lysosomal trapping was then estimated and fully integrated into the mechanistic distribution model published by Rodgers et al. (2005) Predictions of Kpu improved for all lysosome-rich tissues. For instance, Kpu increased for nicotine 4-fold (spleen) and 2-fold (lung and kidney) and for quinidine 1.8-fold (brain), although for most other drugs the effects were much less (≤7%). Overall, the effect was strongest for basic compounds with a lower lipophilicity, such as nicotine, for which the unbound volume of distribution at steady-state prediction changed from 1.34 to 1.58 l/kg. For more lipophilic (basic) compounds or those that already show strong interactions with acidic phospholipids, the additional contribution of lysosomal trapping was less pronounced. Nevertheless, lysosomal trapping will also affect intracellular distribution of such compounds. SIGNIFICANCE STATEMENT: The estimation of the lysosomal content in all body tissues facilitated the incorporation of lysosomal sequestration into a general physiologically based pharmacokinetic model, leading to improved predictions as well as elucidating its influence on tissue and subcellular distribution in the rat.

Understanding the mechanism of action of pyrrolo[3,2-b]quinoxaline-derivatives as kinase inhibitors

Two novel quinoxaline-based EphA3 tyrosine kinase inhibitors have been designed and characterized in vivo in a relevant lymphoma model, showing high efficacy in the control of tumor size.

The X-ray structure of the catalytic domain of the EphA3 tyrosine kinase in complex with a previously reported type II inhibitor was used to design two novel quinoxaline derivatives, inspired by kinase inhibitors that have reached clinical development. These two new compounds were characterized by an array of cell-based assays and gene expression profiling experiments. A global chemical proteomics approach was used to generate the drug-protein interaction profile, which suggested suitable therapeutic indications. Both inhibitors, studied in the context of angiogenesis and in vivo in a relevant lymphoma model, showed high efficacy in the control of tumor size.

Pre-Clinical Pharmacokinetics, Tissue Distribution and Physicochemical Studies of CLBQ14, a Novel Methionine Aminopeptidase Inhibitor for the Treatment of Infectious Diseases

INTRODUCTION

CLBQ14, a derivative of 8-hydroxyquinoline, exerts its chemotherapeutic effect by inhibiting methionine aminopeptidase (MetAP), the enzyme responsible for the post-translational modification of several proteins and polypeptides. MetAP is a novel target for infectious diseases. CLBQ14 is selective and highly potent against replicating and latent Mycobacterium tuberculosis making it an appealing lead for further development.

METHODS

The physicochemical properties (solubility, pH stability and lipophilicity), in vitro plasma stability and metabolism, pre-clinical pharmacokinetics, plasma protein binding and tissue distribution of CLBQ14 in adult male Sprague-Dawley rats were characterized.

RESULTS

At room temperature, CLBQ14 is practically insoluble in water (<0.07 mg/mL) but freely soluble in dimethyl acetamide (>80 mg/mL); it has a log P value of 3.03 ± 0.04. CLBQ14 exhibits an inverse Z-shaped pH decomposition profile; it is stable at acidic pH but is degraded at a faster rate at basic pH. It is highly bound to plasma proteins (>91%), does not partition to red blood cells (B/P ratio: 0.83 ± 0.03), and is stable in mouse, rat, monkey and human plasma. CLBQ14 exhibited a bi-exponential pharmacokinetics after intravenous administration in rats, bioavailability of 39.4 and 90.0%, respectively from oral and subcutaneous route. We observed a good correlation between predicted and observed rat clearance, 1.90 ± 0.17 L/kg/h and 1.67 ± 0.08 L/kg/h, respectively. Human hepatic clearance predicted from microsomal stability data and from the single species scaling were 0.80 L/hr/kg and 0.69 L/h/kg, respectively. CLBQ14 is extensively distributed in rats; following a 5 mg/kg intravenous administration, lowest and highest concentrations of 15.6 ± 4.20 ng/g of heart and 405.9 ± 77.11 ng/g of kidneys, respectively, were observed. In vitro CYP reaction phenotyping demonstrates that CLBQ14 is metabolized primarily by CYP 1A2.

CONCLUSION

CLBQ14 possess appealing qualities of a drug candidate. The studies reported herein are imperative to the development of CLBQ14 as a new chemical entity for infectious diseases.

Use of roller compaction and fines recycling process in the preparation of erlotinib hydrochloride tablets

This study focuses on improving the manufacturing process for a generic immediate-release tablet containing erlotinib hydrochloride by adding a fines recycling process during roller compaction. Due to the large fraction of small-sized API particles, the starting powder mixture was inconsistently fed into the roller compactor. Consequently, poorly flowing granules with a high ratio of fines were produced. A fines recycling step was, therefore, added to the existing roller compaction process to minimize the risks caused by the poor granule flow. A laboratory scale roller compactor and a tablet simulator were used to prepare granules at various process conditions. The effect of dry granulation parameters on size distribution, API distribution, powder flow, compaction properties, and dissolution profile was evaluated. The granule batch after fines recycling had markedly improved size distribution and flowability while maintaining acceptable tablet tensile strength and rapid dissolution profile. The application of the fines recycling process at commercial scale resulted in reliable dissolution performance and batch-to-batch consistency, which were further confirmed by bioequivalence to the reference product. Understanding how granule properties are impacted by the fines recycling process may enable fine-tuning of the dry granulation process for optimal product quality.

Discovery of a JAK1/3 Inhibitor and Use of a Prodrug To Demonstrate Efficacy in a Model of Rheumatoid Arthritis

The four members of the Janus family of nonreceptor tyrosine kinases play a significant role in immune function. The JAK family kinase inhibitor, tofacitinib 1, has been approved in the United States for use in rheumatoid arthritis (RA) patients. A number of JAK inhibitors with a variety of JAK family selectivity profiles are currently in clinical trials. Our goal was to identify inhibitors that were functionally selective for JAK1 and JAK3. Compound 22 was prepared with the desired functional selectivity profile, but it suffered from poor absorption related to physical properties. Use of the phosphate prodrug 32 enabled progression to a murine collagen induced arthritis (CIA) model. The demonstration of a robust efficacy in the CIA model suggests that use of phosphate prodrugs may resolve issues with progressing this chemotype for the treatment of autoimmune diseases such as RA.

An in silico design of bioavailability for kinase inhibitors evaluating the mechanistic rationale in the CYP metabolism of erlotinib

Soft spot analysis helps evaluate the site of the metabolic lability that impacts the bio-availability of the drug. However, given its laborious and time consuming experimentation, we propose a reliable and cheap in silico strategy. In this context, we hypothesized a mechanistic rationale for metabolism of erlotinib by the CYP3A4 enzyme. The comparison of the 3D conformations of the target CYP class of enzymes using MD simulations with GROMACS helped evaluate its impact on the metabolism. The molecular docking studies using Autodock-Vina ascertained the explicit role of the Fe ion present in the Heme moiety in this process. This mechanism was confirmed with respect to 13 other popular approved FDA kinase inhibitors using ab initio DFT calculations using Gaussian 09 (G09), molecular docking studies with Autodock-Vina, and MD simulations with GROMACS. We then developed a quantitative (Q-Met) metabolic profile of these soft spots in the molecules and demonstrated the lack of a linear relationship between the extent of metabolism and drug efficacy. We thus propose an economic in silico strategy for the early prediction of the lability in kinase inhibitors to help model their bio-availability and activity simultaneously, prior to clinical testing.

Assessment of Transporter-Mediated and Passive Hepatic Uptake Clearance Using Rifamycin-SV as a Pan-Inhibitor of Active Uptake

The use of in vitro data for the quantitative prediction of transporter-mediated clearance is critical. Central to this evaluation is the use of hepatocytes, since they contain the full complement of transporters and metabolic enzymes. In general, uptake clearance (CL_uptake) is evaluated by measuring the appearance of compound in the cell. Passive clearance (CL_pd) is often determined by conducting parallel studies at 4 °C or by attempting to saturate uptake pathways. Both approaches have their limitations. Recent studies have proposed the use of Rifamycin-SV (RFV) as a pan-inhibitor of hepatic uptake pathways. In our studies, we confirm that transport activity of all major hepatic uptake transporters is inhibited significantly by RFV at 1 mM (OATP1B1, 1B3, and 2B1 = NTCP (80%), OCT1 (65%), OAT2 (60%)). Under these incubation conditions, we found that the free intracellular concentration of RFV is ∼175 μM and that several major CYPs and UGTs can be reversibly inhibited. Using this approach, we also determined CL_uptake and CL_pd of nine known OATP substrates across three different lots of human hepatocytes. The scaling factors generated for these compounds at 37 °C with RFV and 4 °C were found to be similar. The CL_pd of passively permeable compounds like metoprolol and semagacestat were found to be higher at 37 °C compared to 4 °C, indicating a temperature effect on these compounds. In addition, our data also suggests that incorporation of medium concentrations into CL_uptake and CL_pd calculations may be critical for highly protein bound and highly lipophilic drugs. Overall, our data indicate that RFV, instead of 4 °C, can be reliably used to measure CL_uptake and CL_pd of drugs.

Editor's Highlight: PlacentalDisposition and Effects of Crizotinib: An Ex Vivo Study in the Isolated Dual-Side Perfused Human Cotyledon

Tyrosine kinase inhibitors (TKIs) play an important role in cancer pharmacotherapy, yet there is limited data on their use during pregnancy. We studied placental disposition and placental toxicity of crizotinib, a TKI used to treat nonsmall cell lung cancer. Term placentas were perfused for 3 h with crizotinib (1 µM) using the ex vivo dual-side cotyledon perfusion technique. Interference of TKIs with trophoblast viability was studied using BeWo cells. Expression of P-glycoprotein (P-gp) and Breast Cancer Resistance Protein (BCRP) in placental tissue was assessed by immunohistochemistry and inhibition of these transporters was determined in vitro by transport studies with membrane vesicles overexpressing human P-gp or BCRP. We found that crizotinib rapidly and strongly accumulates in cotyledon perfusion experiments, reaching a concentration of 3.1 ± 0.4 µM in placental tissue. Final drug concentrations in the maternal and foetal reservoirs were 0.2 ± 0.05 and 0.08 ± 0.01 µM, respectively. Furthermore, crizotinib inhibited BeWo cell viability (IC50: 234 nM, 95% CI: 167-328 nM) 10 times more potently than other TKIs tested. In vitro transport studies revealed that crizotinib is a potent inhibitor of the transport activities of BCRP (IC50: 5.7 µM, 95% CI: 2.7-11.8 µM) and P-gp (IC50: 7.8 µM, 95% CI: 3.4-18.0 µM). In conclusion, crizotinib strongly accumulated in placental tissue at clinically relevant concentrations. IC50 values for transporter inhibition and trophoblast cell viability were similar to the tissue concentrations reached, suggesting that crizotinib can inhibit placental BCRP and P-gp function and possibly affect trophoblast viability.

Protein-Protein Interactions (PPIs) as an Alternative to Targeting the ATP Binding Site of Kinase

Most of the developed kinase inhibitor drugs are ATP competitive and suffer from drawbacks such as off-target kinase activity, development of resistance due to mutation in the ATP binding pocket and unfavorable intellectual property situations. Besides the ATP binding pocket, protein kinases have binding sites that are involved in Protein-Protein Interactions (PPIs); these PPIs directly or indirectly regulate the protein kinase activity. Of recent, small molecule inhibitors of PPIs are emerging as an alternative to ATP competitive agents. Rational design of inhibitors for kinase PPIs could be carried out using molecular modeling techniques. In silico tools available for the prediction of hot spot residues and cavities at the PPI sites and the means to utilize this information for the identification of inhibitors are discussed. Moreover, in silico studies to target the Aurora B-INCENP PPI sites are discussed in context. Overall, this chapter provides detailed in silico strategies that are available to the researchers for carrying out structure-based drug design of PPI inhibitors.

A Systematic Analysis of Physicochemical and ADME Properties of All Small Molecule Kinase Inhibitors Approved by US FDA from January 2001 to October 2015

BACKGROUND

During lead identification and optimization, the advancement criteria may be driven based on scientific principles, prior experiences, and/or by examining the path paved by approved drugs. However, accessing the discovery data on physicochemical and ADME properties of the approved kinase inhibitors is a monumental task as these are either scattered in the literature or have not been published.

OBJECTIVE

Our goals were: 1) To compile the relevant data on all kinase inhibitors approved prior to 2016 for easy access by the biopharmaceutical community, 2) To provide a retrospective analysis to highlight trends and attributes which may have contributed to the "developability" of these drugs, and 3) To ignite focused debates on what constitutes "actionable", "nice-to-have", and unnecessary data. Such debates bring about more clarity on stage appropriateness of different types of information and prevent confusion due to abundance of unnecessary data, leading to more efficient and less costly drug discovery programs.

METHODS

A careful and thorough analysis of different bodies of data such as published manuscripts, and available regulatory documents were employed.

RESULTS

We were able to assemble a large body of data on the first thirty kinase inhibitors approved by US FDA since 2001.

CONCLUSION

In conclusion, we have compiled physicochemical and ADME data on the first 30 approved kinase inhibitors and provided our retrospective analysis, which we hope is helpful in constructing advancement criteria in discovery programs. The examination of this data provides an opportunity to develop an opinion on data prioritization and stage appropriateness of assays.

Resisting resistance: is there a solution for malaria?

INTRODUCTION

Currently, widely used antimalarial drugs have a limited clinical lifespan due to parasite resistance development. With resistance continuously rising, antimalarial drug discovery requires strategies to decrease the time of delivering a new antimalarial drug while simultaneously increasing the drug's therapeutic lifespan. Lessons learnt from various chemotherapeutic resistance studies in the fields of antibiotic and cancer research offer potentially useful strategies that can be applied to antimalarial drug discovery.

AREAS COVERED

In this review the authors discuss current strategies to circumvent resistance in malaria and alternatives that could be employed.

EXPERT OPINION

Scientists have been 'beating back' the malaria parasite with novel drugs for the past 49 years but the constant rise in antimalarial drug resistance is forcing the drug discovery community to explore alternative strategies. Avant-garde anti-resistance strategies from alternative fields may assist our endeavors to manage, control and prevent antimalarial drug resistance to progress beyond beating the resistant parasite back, to stopping it dead in its tracks.

Synthesis of 6,8,9 poly-substituted purine analogue libraries as pro-apoptotic inducers of human leukemic lymphocytes and DAPK-1 inhibitors

A 18-member library of 6,8,9-poly-substituted purines was prepared from pyrimidines, primary alcohols, and N,N-dimethylamides under basic conditions via a novel one-pot synthetic pathway controlled by amide sizes and the novel analogues were tested against two leukemia cell lines: Jurkat (acute T cell leukemia) and K562 (chronic erythroleukemia) cells. Compounds having a benzoxy group at C6 position of the aromatic ring exhibited antiproliferative activity in Jurkat cells whereas all compounds induced a lower effect on K562 cells. Analysis of cell cycle, Annexin-V staining, and cleavage of initiator caspases assays showed that the active purine analogues induce cell death by apoptosis. Based on these results, a new purine derivative was synthesized, 6-benzyloxy-9-tert-butyl-8-phenyl-9H-purine (6d), which displayed the highest activity of the series against Jurkat cell lines. Finally, (33)P-radiolabeled kinase assays using 96 recombinant human kinases known to be involved in apoptotic events were performed. Just one of the kinases tested, DAPK-1, was inhibited 50% or more by the phenotypic hits at 10 μM, suggesting that the inhibition of this target could be responsible for the induction of cell death by apoptosis. In agreement with the phenotypic results, the most active antiproliferative agent, 6d, displayed also the lowest IC50 value against recombinant DAPK1 (2.5 μM), further supporting the potential role of this protein on the observed functional response. DAPK-1 inhibition led by 6d together with its pro-apoptotic properties against the Jurkat line makes it an interesting candidate to further investigate the role of DAPK1 kinase in triggering apoptosis in cancer cells, a role which is attracting recent interest.

Potential of erlotinib cyclodextrin nanosponge complex to enhance solubility, dissolution rate, in vitro cytotoxicity and oral bioavailability

The present study was envisaged to evaluate the effect of erlotinib β-cyclodextrin nanosponge (ERL-NS) on the solubility, dissolution, in vitro cytotoxicity and oral bioavailability of erlotinib (ERL). Preliminary studies were conducted to select the optimized stoichiometry concentration of ERL and NS. The drug nanosponge complex comprising of 1:4 proportions of ERL and NS was prepared by freeze drying. ERL-NS formed nanoparticles of 372 ± 31 nm size with narrow size distribution (0.21 ± 0.07 PDI) and high zeta potential (-32.07 ± 4.58 mV). The complexation phenomenon was confirmed by DSC, SEM, PXRD, FTIR, and TEM studies. In vitro dissolution studies revealed an increased dissolution rate (2-folds) with an enhanced dissolution efficiency of the nanosponge complex in comparison to pure drug. In vitro cytotoxicity study and apoptosis assay in pancreatic cell lines (MIA PaCa-2 and PANC-1) indicates the increased toxicity of ERL-NS. Both, quantitative and qualitative cell uptake studies unveiled the higher uptake efficiency of ERL-NS than free drug. ERL-NS showed enhanced oral bioavailability with 1.8-fold higher Cmax (78.98 ± 6.2 vs. 42.36 ± 1.75 μg/ml), and ∼ 2-fold AUC0-∞ (1079.95 ± 41.38 vs. 580.43 ± 71.91), in comparison to pure ERL. Therefore, we conclude that the formation of a complex of nanosponge with ERL is a successful approach to increase its solubility, dissolution and oral bioavailability which may ultimately result in reduction in dose and dose related side-effects.

Small-molecule kinase inhibitors: an analysis of FDA-approved drugs

Small-molecule kinase inhibitors (SMKIs), 28 of which are approved by the US Food and Drug Administration (FDA), have been actively pursued as promising targeted therapeutics. Here, we assess the key structural and physicochemical properties, target selectivity and mechanism of function, and therapeutic indications of these approved inhibitors. Our analysis showed that >30% of approved SMKIs have a molecule weight (MW) exceeding 500 and all have a total ring count of between three and five. The assumption that type II inhibitors tend to be more selective than type I inhibitors has been proved to be unreliable. Although previous SMKI research was concentrated on tyrosine kinase inhibitors for cancer treatment, recent progress indicates diversification of SMKI research in terms of new targets, mechanistic types, and therapeutic indications.

Highly efficient and selective phosphorylation of amino acid derivatives and polyols catalysed by 2-aryl-4-(dimethylamino)pyridine-N-oxides--towards kinase-like reactivity

The chemoselective phosphorylation of hydroxyl containing amino acid derivatives and polyols by phosphoryl chlorides catalyzed by 2-aryl-4-(dimethylamino)pyridine-N-oxides is described.

HER2-signaling pathway, JNK and ERKs kinases, and cancer stem-like cells are targets of Bozepinib small compound

Identification of novel anticancer drugs presenting more than one molecular target and efficacy against cancer stem-like cells (CSCs) subpopulations represents a therapeutic need to combat the resistance and the high risk of relapse in patients. In the present work we show how Bozepinib [(RS)-2,6-dichloro-9-[1-(p-nitrobenzenesulfonyl)-1,2,3,5-tetrahydro-4,1-benzoxazepin-3-yl]-9H-purine], a small anti-tumor compound, demonstrated selectivity on cancer cells and showed an inhibitory effect over kinases involved in carcinogenesis, proliferation and angiogenesis. The cytotoxic effects of Bozepinib were observed in both breast and colon cancer cells expressing different receptor patterns. Bozepinib inhibited HER-2 signaling pathway and JNK and ERKs kinases. In addition, Bozepinib has an inhibitory effect on AKT and VEGF together with anti-angiogenic and anti-migratory activities. Moreover, the modulation of pathways involved in tumorigenesis by Bozepinib was also evident in microarrays analysis. Interestingly, Bozepinib inhibited both mamo- and colono-spheres formation and eliminated ALDH+ CSCs subpopulations at a low micromolar range similar to Salinomycin. Bozepinib induced the down-regulation of c-MYC, β-CATENIN and SOX2 proteins and the up-regulation of the GLI-3 hedgehog-signaling repressor. Finally, Bozepinib shows in vivo anti-tumor and anti-metastatic efficacy in xenotransplanted nude mice without presenting sub-acute toxicity. These findings support further studies on the therapeutic potential of Bozepinib in cancer patients.

Targeting human central nervous system protein kinases: An isoform selective p38αMAPK inhibitor that attenuates disease progression in Alzheimer's disease mouse models

The first kinase inhibitor drug approval in 2001 initiated a remarkable decade of tyrosine kinase inhibitor drugs for oncology indications, but a void exists for serine/threonine protein kinase inhibitor drugs and central nervous system indications. Stress kinases are of special interest in neurological and neuropsychiatric disorders due to their involvement in synaptic dysfunction and complex disease susceptibility. Clinical and preclinical evidence implicates the stress related kinase p38αMAPK as a potential neurotherapeutic target, but isoform selective p38αMAPK inhibitor candidates are lacking and the mixed kinase inhibitor drugs that are promising in peripheral tissue disease indications have limitations for neurologic indications. Therefore, pursuit of the neurotherapeutic hypothesis requires kinase isoform selective inhibitors with appropriate neuropharmacology features. Synaptic dysfunction disorders offer a potential for enhanced pharmacological efficacy due to stress-induced activation of p38αMAPK in both neurons and glia, the interacting cellular components of the synaptic pathophysiological axis, to be modulated. We report a novel isoform selective p38αMAPK inhibitor, MW01-18-150SRM (=MW150), that is efficacious in suppression of hippocampal-dependent associative and spatial memory deficits in two distinct synaptic dysfunction mouse models. A synthetic scheme for biocompatible product and positive outcomes from pharmacological screens are presented. The high-resolution crystallographic structure of the p38αMAPK/MW150 complex documents active site binding, reveals a potential low energy conformation of the bound inhibitor, and suggests a structural explanation for MW150’s exquisite target selectivity. As far as we are aware, MW150 is without precedent as an isoform selective p38MAPK inhibitor or as a kinase inhibitor capable of modulating in vivo stress related behavior.

Plasmodium IspD (2-C-Methyl-D-erythritol 4-Phosphate Cytidyltransferase), an Essential and Druggable Antimalarial Target

As resistance to current therapies spreads, novel antimalarials are urgently needed. In this work, we examine the potential for therapeutic intervention via the targeting of Plasmodium IspD (2-C-methyl-D-erythritol 4-phosphate cytidyltransferase), the second dedicated enzyme of the essential methylerythritol phosphate (MEP) pathway for isoprenoid biosynthesis. Enzymes of this pathway represent promising therapeutic targets because the pathway is not present in humans. The Malaria Box compound, MMV008138, inhibits Plasmodium falciparum growth, and PfIspD has been proposed as a candidate intracellular target. We find that PfIspD is the sole intracellular target of MMV008138 and characterize the mode of inhibition and target-based resistance, providing chemical validation of this target. Additionally, we find that the Pf ISPD genetic locus is refractory to disruption in malaria parasites, providing independent genetic validation for efforts targeting this enzyme. This work provides compelling support for IspD as a druggable target for the development of additional, much-needed antimalarial agents.

A Comprehensive Structural Overview of p38α MAPK in Complex with Type I Inhibitors

p38α mitogen-activated protein kinase (MAPK) is a well-recognized therapeutic target for the treatment of autoimmune and inflammatory diseases. Over the past two decades, tremendous efforts have been focused on the discovery and development of small-molecule p38α MAPK inhibitors, although currently no drugs targeting this protein are clinically available. Therefore, the identification of novel chemotypes that are able to inhibit p38α MAPK function is still of great therapeutic significance. With the objective to support drug discovery programs aimed at identifying new immunomodulators acting on p38α MAPK, herein we present a complete overview of the available crystal structures of this protein in complex with ATP-site type I inhibitors. The 85 available complexes are classified by chemotype and experimental binding mode, and the ligand-protein interactions are discussed using the most representative inhibitors. The type and frequency of key inhibitor features are analyzed to give a final summary of the chemical requirements of promising p38α MAPK inhibitors. The proposed pharmacophore can be exploited to enhance the opportunities to identify novel type I inhibitors of p38α MAPK.

An integrated flow and microwave approach to a broad spectrum protein kinase inhibitor

The protein kinase inhibitor CTx-0152960 and the piperazinyl analogue CTx-0294885 were prepared using a hybrid flow and microwave approach.

Drug repurposing and human parasitic protozoan diseases

Parasitic diseases have an enormous health, social and economic impact and are a particular problem in tropical regions of the world. Diseases caused by protozoa and helminths, such as malaria and schistosomiasis, are the cause of most parasite related morbidity and mortality, with an estimated 1.1 million combined deaths annually. The global burden of these diseases is exacerbated by the lack of licensed vaccines, making safe and effective drugs vital to their prevention and treatment. Unfortunately, where drugs are available, their usefulness is being increasingly threatened by parasite drug resistance. The need for new drugs drives antiparasitic drug discovery research globally and requires a range of innovative strategies to ensure a sustainable pipeline of lead compounds. In this review we discuss one of these approaches, drug repurposing or repositioning, with a focus on major human parasitic protozoan diseases such as malaria, trypanosomiasis, toxoplasmosis, cryptosporidiosis and leishmaniasis.