Selective Mitogen-activated Protein Kinase Research Articles

REALM-DCM: A Phase 3, Multinational, Randomized, Placebo-Controlled Trial of ARRY-371797 in Patients With Symptomatic LMNA-Related Dilated Cardiomyopathy.

LMNA (lamin A/C)-related dilated cardiomyopathy is a rare genetic cause of heart failure. In a phase 2 trial and long-term extension, the selective p38α MAPK (mitogen-activated protein kinase) inhibitor, ARRY-371797 (PF-07265803), was associated with an improved 6-minute walk test at 12 weeks, which was preserved over 144 weeks. REALM-DCM (NCT03439514) was a phase 3, randomized, double-blind, placebo-controlled trial in patients with symptomatic LMNA-related dilated cardiomyopathy. Patients with confirmed LMNA variants, New York Heart Association class II/III symptoms, left ventricular ejection fraction ≤50%, implanted cardioverter-defibrillator, and reduced 6-minute walk test distance were randomized to ARRY-371797 400 mg twice daily or placebo. The primary outcome was a change from baseline at week 24 in the 6-minute walk test distance using stratified Hodges-Lehmann estimation and the van Elteren test. Secondary outcomes using similar methodology included change from baseline at week 24 in the Kansas City Cardiomyopathy Questionnaire-physical limitation and total symptom scores, and NT-proBNP (N-terminal pro-B-type natriuretic peptide) concentration. Time to a composite outcome of worsening heart failure or all-cause mortality and overall survival were evaluated using Kaplan-Meier and Cox proportional hazards analyses. REALM-DCM was terminated after a planned interim analysis suggested futility. Between April 2018 and October 2022, 77 patients (aged 23-72 years) received ARRY-371797 (n=40) or placebo (n=37). No significant differences (P>0.05) between groups were observed in the change from baseline at week 24 for all outcomes: 6-minute walk test distance (median difference, 4.9 m [95% CI, -24.2 to 34.1]; P=0.82); Kansas City Cardiomyopathy Questionnaire-physical limitation score (2.4 [95% CI, -6.4 to 11.2]; P=0.54); Kansas City Cardiomyopathy Questionnaire-total symptom score (5.3 [95% CI, -4.3 to 14.9]; P=0.48); and NT-proBNP concentration (-339.4 pg/mL [95% CI, -1131.6 to 452.7]; P=0.17). The composite outcome of worsening heart failure or all-cause mortality (hazard ratio, 0.43 [95% CI, 0.11-1.74]; P=0.23) and overall survival (hazard ratio, 1.19 [95% CI, 0.23-6.02]; P=0.84) were similar between groups. No new safety findings were observed. Findings from REALM-DCM demonstrated futility without safety concerns. An unmet treatment need remains among patients with LMNA-related dilated cardiomyopathy. URL: https://classic.clinicaltrials.gov; Unique Identifiers: NCT03439514, NCT02057341, and NCT02351856.

Distinct binding modes of a benzothiazole derivative confer structural bases for increasing ERK2 or p38α MAPK selectivity

Mitogen-activated protein kinases (MAPKs), including extracellular signal-regulated kinase 2 (ERK2) and p38α MAP kinase (p38α MAPK), regulate various cellular responses. ERK2 is a drug target for treating many diseases, such as cancer, whereas p38α has attracted much attention as a promising drug target for treating inflammatory disorders. ERK2 is a critical off-target for p38α MAPK and vice versa. In this study, an allosteric ERK2 inhibitor with a benzothiazole moiety (compound 1) displayed comparable inhibitory activity against p38α MAPK. Crystal structures of these MAPKs showed that compound 1 bound to the allosteric site of ERK2 and p38α MAPK in distinct manners. Compound 1 formed a covalent bond with Cys162 of p38α MAPK, whereas this covalent bond was absent in the ERK2 complex even though the corresponding cysteine is conserved in ERK2. Structural dissection combined with computational simulations indicated that an amino acid difference in the allosteric site is responsible for the distinct binding modes of compound 1 with ERK2 and p38α MAPK. These structural insights underline the feasibility of developing highly selective and potent ERK2 and p38α MAPK inhibitors.

New role for the anandamide metabolite prostaglandin F2α ethanolamide: Rolling preadipocyte proliferation

White adipose tissue regulation is key to metabolic health, yet still perplexing. The chief endocannabinoid anandamide metabolite, prostaglandin F2α ethanolamide (PGF2αEA), inhibits adipogenesis, that is, the formation of mature adipocytes. We observed that adipocyte progenitor cells—preadipocytes—following treatment with PGF2αEA yielded larger pellet sizes. Thus, we hypothesized that PGF2αEA might augment preadipocyte proliferation. Cell viability MTT and crystal violet assays, cell counting, and 5-bromo-2′-deoxyuridine incorporation in cell proliferation ELISA analyses confirmed our prediction. Additionally, we discovered that PGF2αEA promotes cell cycle progression through suppression of the expression of cell cycle inhibitors, p21 and p27, as shown by flow cytometry and qPCR. Enticingly, concentrations of this compound that showed no visible effect on cell proliferation or basal transcriptional activity of peroxisome proliferator-activated receptor gamma could, in contrast, reverse the anti-proliferative and peroxisome proliferator-activated receptor gamma-transcription activating effects of rosiglitazone (Rosi). MTT and luciferase reporter examinations supported this finding. The PGF2αEA pharmaceutical analog, bimatoprost, was also investigated and showed very similar effects. Importantly, we suggest the implication of the mitogen-activated protein kinase pathway in these effects, as they were blocked by the selective mitogen-activated protein kinase kinase inhibitor, PD98059. We propose that PGF2αEA is a pivotal regulator of white adipose tissue plasticity, acting as a regulator of the preadipocyte pool in adipose tissue.

Selective Inhibition of the MK2 Pathway: Data From a Phase IIa Randomized Clinical Trial in Rheumatoid Arthritis

The study objective was to evaluate the safety, tolerability, pharmacodynamics, and preliminary efficacy of ATI-450 with methotrexate in patients with rheumatoid arthritis (RA). A parallel-assignment, placebo-controlled, investigator-blinded/patient-blinded multicenter study evaluated patients with moderate-to-severe RA aged 18 to 70 years. Eligible patients were randomized (1:1) to ATI-450 50-mg oral tablets twice daily or placebo with a stable weekly dose of methotrexate for 12 weeks. The primary objective was to assess ATI-450 safety and tolerability. The secondary objectives were to assess the median percentage change from baseline high-sensitivity C-reactive protein (hs-CRP) levels, the mean change from baseline in Disease Activity Score in 28 joints based on CRP level (DAS28-CRP) and Rheumatoid Arthritis Magnetic Resonance Imaging Score hand-wrist assessments of synovitis or bone erosion at week 12, and the proportion of patients with American College of Rheumatology 20/50/70 (ACR 20/50/70) and with DAS28-CRP scores of less than 2.6. The exploratory outcomes were change from baseline in endogenous and ex vivo-stimulated cytokine levels. ATI-450 was well tolerated with no severe adverse events reported. ATI-450 reduced median hs-CRP levels by 42% or more at all posttreatment timepoints. In the ATI-450 group, a mean (median) decrease in DAS28-CRP score of 2.0 (2.1) was observed at week 12; proportions of patients with an ACR 20/50/70 response in the per-protocol population were 60%, 33%, and 20%, respectively, at week 12. Endogenous plasma levels of key inflammatory cytokines (tumor necrosis factor α, macrophage inflammatory protein 1β, interleukin 6, interleukin 8) were reduced across the 12 treatment weeks. This is the first clinical study demonstrating that selective mitogen-activated protein kinase (MAPK)-activated protein kinase 2 (MK2) pathway blockade leads to a sustained antiinflammatory effect. This suggests that targeting the MK2 pathway mitigates the tachyphylaxis observed with p38 MAPK inhibitors in RA and supports further exploration.

SP600125 Enhances Temperature-Controlled Repeated Thermal Stimulation-Induced Neurite Outgrowth in PC12-P1F1 Cells.

This study evaluated the mechanism of temperature-controlled repeated thermal stimulation (TRTS)-mediated neuronal differentiation. We assessed the effect of SP600125, a c-Jun N-terminal kinase (JNK) inhibitor, on neuronal differentiation of rat PC12-P1F1 cells, which can differentiate into neuron-like cells by exposure to TRTS or neurotrophic factors, including bone morphogenetic protein (BMP) 4. We evaluated neuritogenesis by incubating the cells under conditions of TRTS and/or SP600125. Cotreatment with SP600125 significantly enhanced TRTS-mediated neuritogenesis, whereas that with other selective mitogen-activated protein kinase (MAPK) inhibitors did not-e.g., extracellular signal-regulated kinase (ERK)1/2 inhibitor U0126, and p38 MAPK inhibitor SB203580. We tried to clarify the mechanism of SP600125 action by testing the effect of U0126 and the BMP receptor inhibitor LDN193189 on the SP600125-mediated enhancement of intracellular signaling. SP600125-enhanced TRTS-induced neuritogenesis was significantly inhibited by U0126 or LDN193189. Gene expression analysis revealed that TRTS significantly increased β3-Tubulin, MKK3, and Smad7 gene expressions. Additionally, Smad6 and Smad7 gene expressions were substantially attenuated through SP600125 co-treatment during TRTS. Therefore, SP600125 may partly enhance TRTS-induced neuritogenesis by attenuating the negative feedback loop of BMP signaling. Further investigation of the mechanisms underlying the effect of SP600125 during TRTS-mediated neuritogenesis may contribute to the future development of regenerative neuromedicine.

Scaffold modified Vemurafenib analogues as highly selective mitogen activated protein kinase kinase 4 (MKK4) inhibitors

The mitogen-activated protein kinase kinase 4 (MKK4) has recently been identified as druggable target for the treatment of acute liver failure in RNAi experiments. In these experiments MKK4 was identified to be a major regulator in hepatocyte regeneration. Inhibitors thereof may serve as medication to promote liver regeneration or reducing hepatocyte death. Just a small number of potent inhibitors with acceptable selectivity towards relevant off-targets are known up to date. Among the known potent inhibitors, selectivity is highly sensitive towards minor modifications of the molecule, which makes it necessary to carefully balance between potency and selectivity.In the herein presented study, a new class of Vemurafenib-derived inhibitors was investigated with α-carbolines as new scaffold. This new scaffold showed a remarkable intrinsic selectivity towards the chosen off-targets, without affecting potency towards MKK4 on a broad range of structural modifications.

Tracking and Inhibiting Atypical Vascular Inflammation

Mitogen‐activated protein kinase (MAPK) p38 drives the onset and progression of many clinically challenging diseases. However, three decades of research have failed to yield clinically viable, selective MAPK p38 therapeutics. The extensive and ongoing studies have principally focused on therapeutics targeting the ATP‐pocket or active site of p38. These have failed in part due to the ubiquitous expression and dichotomous role of p38, leading to blockade of both physiological and pathological signaling pathways. A promising alternative strategy is to target either the substrates of p38 or the activators that drive p38‐induced pathological signaling. Our prior studies identified an atypical mechanism for G protein‐coupled receptor mediated activation of pathological p38 signaling during vascular inflammation. Several critical problems remain: firstly, how does atypical signaling drive inflammation, and secondly how can we stop pathological p38 activity? To further define how atypical p38 signaling induces inflammation we developed a fluorescent resonance energy transfer (FRET) biosensor platform to map atypical p38 signaling. This system revealed that GPCR induced p38 signaling is initiated via an endosomal axis. Blockade of receptor internalization shifts the spatial bias to that seen for MKK3/6‐dependent signaling with enhanced nuclear p38 activity. We predict that this endosomal axis drives pathological atypical p38 activity and the progression of vasculopathic disease progression. Critically, atypical p38 activity is initiated by a direct interaction between the adaptor protein TAB1 and two binding sites on p38. Blockade of the TAB1‐p38 interaction through mutation of select residues on TAB1 can disrupt the TAB1‐p38 interaction and prevent atypical p38 signaling. Modeling studies show that small molecule inhibitors that bind to the TAB1 binding motif on p38 can block this interaction. As an alternative strategy we focused on the TAB1 peptides that directly bind to p38. Using a phage‐display library of humanized nanobodies and a yeast two‐hybrid screen we have developed an array of 40 TAB1 blocking intrabodies (IntraT‐ab’s) as the first generation of selective atypical p38 inhibitors. We show that intraT‐ab’s bind TAB1, selectively blocking GPCR induced p38 (endosomal) signaling while leaving classical MKK3/6 dependent signaling intact. IntraT‐ab’s and our FRET platform provide the first opportunity to examine in detail the specific downstream mechanisms, targets and physiological consequences of atypical p38 signaling. Intracellular delivery/expression of intraT‐ab’s could also provide a therapeutic strategy for reducing p38 signaling in multiple diseases, including acute lung injury, retinopathies and neuroinflammation.

Small-molecule IKKβ activation modulator (IKAM) targets MAP3K1 and inhibits pancreatic tumor growth

Activation of inhibitor of nuclear factor NF-κB kinase subunit-β (IKKβ), characterized by phosphorylation of activation loop serine residues 177 and 181, has been implicated in the early onset of cancer. On the other hand, tissue-specific IKKβ knockout in Kras mutation-driven mouse models stalled the disease in the precancerous stage. In this study, we used cell line models, tumor growth studies, and patient samples to assess the role of IKKβ and its activation in cancer. We also conducted a hit-to-lead optimization study that led to the identification of 39-100 as a selective mitogen-activated protein kinase kinase kinase (MAP3K) 1 inhibitor. We show that IKKβ is not required for growth of Kras mutant pancreatic cancer (PC) cells but is critical for PC tumor growth in mice. We also observed elevated basal levels of activated IKKβ in PC cell lines, PC patient-derived tumors, and liver metastases, implicating it in disease onset and progression. Optimization of an ATP noncompetitive IKKβ inhibitor resulted in the identification of 39-100, an orally bioavailable inhibitor with improved potency and pharmacokinetic properties. The compound 39-100 did not inhibit IKKβ but inhibited the IKKβ kinase MAP3K1 with low-micromolar potency. MAP3K1-mediated IKKβ phosphorylation was inhibited by 39-100, thus we termed it IKKβ activation modulator (IKAM) 1. In PC models, IKAM-1 reduced activated IKKβ levels, inhibited tumor growth, and reduced metastasis. Our findings suggests that MAP3K1-mediated IKKβ activation contributes to KRAS mutation-associated PC growth and IKAM-1 is a viable pretherapeutic lead that targets this pathway.

Expanding the Toolkit of Fluorescent Biosensors for Studying Mitogen Activated Protein Kinases in Plants

Mitogen-activated protein kinases (MAPKs) are key regulators of numerous biological processes in plants. To better understand the mechanisms by which these kinases function, high resolution measurement of MAPK activation kinetics in different biological contexts would be beneficial. One method to measure MAPK activation in plants is via fluorescence-based genetically-encoded biosensors, which can provide real-time readouts of the temporal and spatial dynamics of kinase activation in living tissue. Although fluorescent biosensors have been widely used to study MAPK dynamics in animal cells, there is currently only one MAPK biosensor that has been described for use in plants. To facilitate creation of additional plant-specific MAPK fluorescent biosensors, we report the development of two new tools: an in vitro assay for efficiently characterizing MAPK docking domains and a translocation-based kinase biosensor for use in plants. The implementation of these two methods has allowed us to expand the available pool of plant MAPK biosensors, while also providing a means to generate more specific and selective MAPK biosensors in the future. Biosensors developed using these methods have the potential to enhance our understanding of the roles MAPKs play in diverse plant signaling networks affecting growth, development, and stress response.

The discovery and development of binimetinib for the treatment of melanoma

ABSTRACT Introduction Binimetinib is an uncompetitive, small-molecule inhibitor of selective mitogen-activated protein kinase (MEK1/2) and was recently approved in 2018 in combination with encorafenib for the treatment of metastatic melanomas. Preclinical and clinical trial data on the drug demonstrate its potent efficacy in cancers, especially melanomas with BRAF and NRAS mutations. Areas covered The authors review the preclinical as well as clinical Phase 1, 2 and 3 trial data leading to its FDA approval in 2018 for metastatic melanoma. Phase 3 data in combination with encorafenib demonstrated double the PFS (14.9 months) compared to vemurafenib alone (7.3 months) in patients with BRAF-mutated metastatic melanoma. Expert opinion No longer-term data is available yet to demonstrate any durable complete responses to therapy with binimetinib or improvements in overall survival compared to other FDA-approved therapies including immunotherapy or vemurafenib. Treatment approaches to patients with BRAF-mutated metastatic melanoma should be individualized and binimetinib in combination with encorafenib is a reasonable oral strategy with a reasonably tolerated toxicity profile. The cost of treatment and durability of response should be incorporated into the discussion as part of the overall medical decision-making.

Mitogen-Activated Protein Kinase Pathway Inhibition for Redifferentiation of Radioiodine Refractory Differentiated Thyroid Cancer: An Evolving Protocol.

Background: Some patients with metastatic differentiated thyroid cancer (DTC) lack iodine avidity and are therefore unsuitable for radioactive iodine (RAI) therapy. Limited experience suggests that single-agent selective mitogen-activated protein kinase (MAPK) pathway inhibitors can restore expression of the sodium-iodide symporter rendering RAI refractory (RAIR) DTC patients amenable to RAI therapy. The aim of this study was to assess the feasibility of mutation-guided MAPK-pathway blockade combined with thyroid hormone withdrawal (THW) for redifferentiation. Methods: This is a retrospective review of metastatic RAIR DTC and driver mutation in MAPK pathway, treated on a redifferentiation protocol. All patients had metastatic disease that had never been RAI-avid and/or imaging and biochemical progression despite treatment with RAI within the past 12 months. Patients with tumors harboring an NRAS mutation were treated with an MEK inhibitor (trametinib), and tumors with a BRAFV600E mutation with combined BRAF and MEK inhibition (dabrafenib and trametinib; or vemurafenib and cobimetinib) for four weeks. Thyrotropin stimulation was performed by THW for four weeks. Restoration of RAI uptake was determined by 124I positron emission tomography/computed tomography imaging. The response was assessed at least three months post-RAI. Results: From 2015 to 2017, six patients (age 45-70, four females) received redifferentiation therapy. Three patients had an NRAS mutation; two with follicular thyroid carcinoma (FTC) and one with a poorly differentiated thyroid carcinoma (PDTC); and three patients had a BRAFV600E mutation and papillary thyroid carcinoma (PTC). One NRAS and all BRAFV600E mutation cases demonstrated restoration of RAI uptake and proceeded to RAI therapy with a median follow-up of 16.6 months (range 13.5-42.3 months). The patient with an NRAS mutation and two of three patients with a BRAFV600E demonstrated partial imaging response beyond a three-month follow-up. Grade 3 adverse events (acneiform rash) were observed in two patients with NRAS mutations. Conclusions: Mutation-guided MAPK pathway inhibition with MEK inhibitor or a combination of BRAF inhibitor and MEK inhibitor under concurrent THW is a feasible and a promising strategy to redifferentiate RAIR DTC, thereby rendering them suitable for RAI therapy with satisfactory retention following treatment.

Pharmacological, Mechanistic, and Pharmacokinetic Assessment of Novel Melatonin-Tamoxifen Drug Conjugates as Breast Cancer Drugs.

Tamoxifen is used to prevent and treat estrogen receptor-positive (ER+) breast cancer (BC); however, its chronic use can increase uterine cancer risk and induce tamoxifen resistance. Novel melatonin-tamoxifen drug conjugates may be promising to treat BC and may help offset the adverse effects of tamoxifen usage alone due to the presence of melatonin. We synthesized and screened five drug conjugates (C2, C4, C5, C9, and C15 linked) for their effects on BC cell (MCF-7, tamoxifen-resistant MCF-7, mouse mammary carcinoma, MDA-MB-231, and BT-549) viability, migration, and binding affinity to melatonin receptor 1 (MT1R) and estrogen receptor 1 (ESR1). C4 and C5 demonstrated the most favorable pharmacological characteristics with respect to binding profiles (affinity for ESR1 and MT1R) and their potency/efficacy to inhibit BC cell viability and migration in four phenotypically diverse invasive ductal BC cell lines. C4 and C5 were further assessed for their actions against tamoxifen-resistant MCF-7 cells and a patient-derived xenograft triple-negative BC cell line (TU-BcX-4IC) and for their mechanisms of action using selective mitogen-activated protein kinase kinase MEK1/2, MEK5, and phosphoinositide 3-kinase (PI3K) inhibitors. C4 and C5 inhibited tamoxifen-resistant MCF-7 cells with equal potency (IC50 = 4-8 μM) and efficacy (∼90% inhibition of viability and migration) but demonstrated increased potency (IC50 = 80-211 μM) and efficacy (∼140% inhibition) to inhibit migration versus cell viability (IC50 = 181-304 mM; efficacy ∼80% inhibition) in TU-BcX-4IC cells. Unique pharmacokinetic profiles were observed, with C4 having greater bioavailability than C5. Further assessment of C4 and C5 demonstrates that they create novel pharmacophores within each BC cell that is context specific and involves MEK1/2/pERK1/2, MEK5/pERK5, PI3K, and nuclear factor κB. These melatonin-tamoxifen drug conjugates show promise as novel anticancer drugs and further preclinical and clinical evaluation is warranted.

Synthesis and Biological Evaluation of 3-Arylindazoles as Selective MEK4 Inhibitors.

Herein we report the discovery of a novel series of highly potent and selective mitogen-activated protein kinase kinase 4 (MEK4) inhibitors. MEK4 is an upstream kinase in MAPK signaling pathways that phosphorylates p38 MAPK and JNK in response to mitogenic and cellular stress queues. MEK4 is overexpressed and induces metastasis in advanced prostate cancer lesions. However, the value of MEK4 as an oncology target has not been pharmacologically validated because selective chemical probes targeting MEK4 have not been developed. Optimization of this series via structure-activity relationships and molecular modeling led to the identification of compound 6 ff (4-(6-fluoro-2H-indazol-3-yl)benzoic acid), a highly potent and selective MEK4 inhibitor. This series of inhibitors is the first of its kind in both activity and selectivity and will be useful in further defining the role of MEK4 in prostate and other cancers.

An isoform-selective p38α mitogen-activated protein kinase inhibitor rescues early entorhinal cortex dysfunctions in a mouse model of Alzheimer's disease.

Neuroinflammation is a fundamental mechanism in Alzheimer's disease (AD) progression. The stress-induced activation of the p38α mitogen-activated protein kinase (MAPK) leads to increased production of proinflammatory cytokines and neurodegeneration. We investigated the effects of an isoform selective p38α MAPK inhibitor, MW01-18-150SRM (MW150), administered at 2.5mg/kg/d (i.p.; 14days) on early entorhinal cortex (EC) alterations in an AD mouse model carrying human mutations of the amyloid precursor protein (mhAPP). We used electrophysiological analyses with long-term potentiation induction in EC-containing brain slices and EC-relevant associative memory tasks. We found that MW150 was capable of rescuing long-term potentiation in 2-month old mhAPP mice. Acute delivery of MW150 to brain slices was similarly effective in rescuing long-term potentiation, with a comparable efficacy to that of the widely used multikinase inhibitor SB203580. MW150-treated mhAPP mice demonstrated improved ability to discriminate novel associations between objects and their position/context. Our findings suggest that the selective inhibition of the stress-activated p38α MAPK with MW150 can attenuate the EC dysfunctions associated with neuroinflammation in an early stage of AD progression.

Optimization of Selective Mitogen-Activated Protein Kinase Interacting Kinases 1 and 2 Inhibitors for the Treatment of Blast Crisis Leukemia.

Chronic myeloid leukemia (CML) is a myeloproliferative disease caused by bcr-abl1, a constitutively active tyrosine kinase fusion gene responsible for an abnormal proliferation of leukemic stem cells (LSCs). Inhibition of BCR-ABL1 kinase activity offers long-term relief to CML patients. However, for a proportion of them, BCR-ABL1 inhibition will become ineffective at treating the disease, and CML will progress to blast crisis (BC) CML with poor prognosis. BC-CML is often associated with excessive phosphorylated eukaryotic translation initiation factor 4E (eIF4E), which renders LSCs capable of proliferating via self-renewal, oblivious to BCR-ABL1 inhibition. In vivo, eIF4E is exclusively phosphorylated on Ser209 by MNK1/2. Consequently, a selective inhibitor of MNK1/2 should reduce the level of phosphorylated eIF4E and re-sensitize LSCs to BCR-ABL1 inhibition, thus hindering the proliferation of BC LSCs. We report herein the structure-activity relationships and pharmacokinetic properties of a selective MNK1/2 inhibitor clinical candidate, ETC-206, which in combination with dasatinib prevents BC-CML LSC self-renewal in vitro and enhances dasatinib antitumor activity in vivo.

Structure-based Design of Pyridone-Aminal eFT508 Targeting Dysregulated Translation by Selective Mitogen-activated Protein Kinase Interacting Kinases 1 and 2 (MNK1/2) Inhibition.

Dysregulated translation of mRNA plays a major role in tumorigenesis. Mitogen-activated protein kinase interacting kinases (MNK)1/2 are key regulators of mRNA translation integrating signals from oncogenic and immune signaling pathways through phosphorylation of eIF4E and other mRNA binding proteins. Modulation of these key effector proteins regulates mRNA, which controls tumor/stromal cell signaling. Compound 23 (eFT508), an exquisitely selective, potent dual MNK1/2 inhibitor, was designed to assess the potential for control of oncogene signaling at the level of mRNA translation. The crystal structure-guided design leverages stereoelectronic interactions unique to MNK culminating in a novel pyridone-aminal structure described for the first time in the kinase literature. Compound 23 has potent in vivo antitumor activity in models of diffuse large cell B-cell lymphoma and solid tumors, suggesting that controlling dysregulated translation has real therapeutic potential. Compound 23 is currently being evaluated in Phase 2 clinical trials in solid tumors and lymphoma. Compound 23 is the first highly selective dual MNK inhibitor targeting dysregulated translation being assessed clinically.

Structural and Dynamic Insights into the Mechanism of Allosteric Signal Transmission in ERK2-Mediated MKP3 Activation.

The mitogen-activated protein kinases (MAPKs) are key components of cellular signal transduction pathways, which are down-regulated by the MAPK phosphatases (MKPs). Catalytic activity of the MKPs is controlled both by their ability to recognize selective MAPKs and by allosteric activation upon binding to MAPK substrates. Here, we use a combination of experimental and computational techniques to elucidate the molecular mechanism for the ERK2-induced MKP3 activation. Mutational and kinetic study shows that the 334FNFM337 motif in the MKP3 catalytic domain is essential for MKP3-mediated ERK2 inactivation and is responsible for ERK2-mediated MKP3 activation. The long-term molecular dynamics (MD) simulations further reveal a complete dynamic process in which the catalytic domain of MKP3 gradually changes to a conformation that resembles an active MKP catalytic domain over the time scale of the simulation, providing a direct time-dependent observation of allosteric signal transmission in ERK2-induced MKP3 activation.

Comparison of the Pharmacokinetics of the Phase II and Phase III Capsule Formulations of Selumetinib and the Effects of Food on Exposure: Results From Two Randomized Crossover Trials in Healthy Male Subjects

PurposeSelumetinib (AZD6244, ARRY-142886), an oral, potent, and highly selective mitogen-activated protein kinase 1/2 inhibitor with a short half-life, has shown activity across various tumor types. Before initiation of Phase III trials, the site, scale, and color (hypromellose shell from white [Phase II] to blue [Phase III]) of the selumetinib 25mg capsule manufacture was changed. We present 2 crossover trials evaluating Phase III capsules in healthy subjects. MethodsThe relative bioavailability trial was a Phase I, open-label, randomized, 3-treatment, 4-period, 6-sequence crossover trial in healthy male subjects (aged 18–55 years). Subjects received selumetinib 75mg (3 × 25 mg) Phase II or Phase III capsules, or a 35mg oral solution, during 4 dosing periods in 1 of 6 randomized treatment sequences. The food effect trial was a Phase I, open-label, randomized, 2-period crossover trial in healthy male subjects (aged 18–45 years). Subjects were randomized to 1 of 2 sequences to receive selumetinib 75mg (3 × 25 mg) Phase III capsules. In sequence 1, subjects received selumetinib after 10 hours of fasting. Following a washout period, selumetinib was administered after a high-fat meal. In sequence 2, subjects received selumetinib in the fed state, before the fasted state. Pharmacokinetic parameters were determined from serial blood sampling. FindingsTwenty-seven subjects were randomized to the relative bioavailability trial; 26 completed all dosing periods. Mean selumetinib AUC was unchanged (geometric least squares mean ratio [GLSMR], 90.01% [90% CI, 81.74–99.11]). Cmax was 18% lower with the Phase III capsules (GLSMR, 81.97% [90% CI, 69.01–97.36]). A post hoc exploratory statistical analysis excluding outlying observations with later Tmax showed that Phase II and III capsules produced similar exposure in terms of Cmax and AUC. High intrasubject variability for Cmax attributed to the pharmacokinetic sampling schedule was judged to have impacted on the estimated GLSMR. In the food effect trial, 34 subjects completed both study periods. A high-fat meal reduced selumetinib Cmax compared with the fasted state (GLSMR, 49.76% [90% CI, 43.82–56.51]); AUC was minimally changed (GLSMR, 84.08% [90% CI, 80.72–87.59]). Median Tmax was prolonged by 1.49 hours. No deaths or serious adverse events were reported. ImplicationsSelumetinib 75mg (3 × 25 mg) Phase III capsules are being used in ongoing pivotal Phase III trials and should be administered in the fasted state. Based on findings from the relative bioavailability trial, pharmacokinetic sampling frequency was increased for healthy subject trials, including the food effect trial. ClinicalTrials.gov identifiers: NCT01635023 (relative bioavailability) and NCT01974349 (food effect).

Targeting of multiple senescence-promoting genes and signaling pathways by triptonide induces complete senescence of acute myeloid leukemia cells

Leukemia cells aberrantly overexpress senescence-suppression telomerase reverse transcriptase (TERT) and down-regulate key senescence-promoting genes to escape complete senescence, resulting in immortalization and malignant progression. Accordingly, induction of complete senescence is a sensible strategy for anti-leukemia therapy. However, effective senescence-based anti-leukemia drugs with low toxicity are currently lacking. In this study, we found that triptonide (chemical name diterpene triepoxide), a small molecule derived from the herb Tripterygium wilfordii Hook, strongly induced complete senescence in cultured acute myeloid leukemia (AML) cell lines, and potently inhibited growth and colony formation of U937 and HL-60 AML cell line with IC50 values of 7.5 and 12nM, respectively. Strikingly, triptonide (4mg/kg) nearly completely suppressed human leukemia cell tumorigenicity (>99%) without obvious toxicity in a mouse xenograft model. Mechanistic studies showed that triptonide induced senescence followed by apoptosis mainly by suppressing transcription of TERT and oncogenic c-Myc, while concomitantly promoting transcription of senescence-promoting genes p16 and p21 and the pro-apoptotic gene encoding DNA damage-inducible transcript 3. These effects of triptonide are mediated by selective mitogen-activated protein kinase kinase-3/p38 signaling pathway activation. Our study provides a conceptual framework for inducing complete senescence as an effective anti-leukemia therapeutic strategy through a “multiple-hits” model and supports further development of triptonide as an anti-cancer agent.

Explore the variation of MMP3, JNK, p38 MAPKs, and autophagy at the early stage of osteoarthritis.

Osteoarthritis is a chronic disease characterized by cartilage degeneration and chondrocyte apoptosis. Mitogen-activated protein kinase (MAPK) signaling pathway plays a key role in regulating OA process. Autophagy has an important effect on the OA process, and it is believed to be regulated by MAPKs. To reveal the mechanism and the effect of JNK and p38 MAPKs on matrix metalloproteinase 3 (MMP3) and autophagy in OA, the study established OA model in rabbits, used the measurement of the Osteoarthritis Research Society International scoring system to evaluate OA model, and conducted general observation, histological observation, and Western blotting of JNK, phosphorylate-JNK (P-JNK), p38, phosphorylate-p38 (P-p38), MMP3, and light-chain 3 (LC3)-II/LC3-I to explore the variation of JNK, p38 MAPKs, and autophagy at the early stage of OA. With OA progressing at the early stage, MMP3, P-p38, and P-JNK were gradually upregulated from the baseline to the peak in study groups when compared with the control group; JNK and p38 variated of turbulence without statistical difference; and LC3-II/LC3-I had a decreasing tendency from the 0- to 15-day group. This study identifies that compromised autophagy may be related to the OA progress and that JNK and p38 MAPKs have positive regulation on MMP3 and negative regulation on autophagy. It also implicates a new therapeutic strategy for OA and other degenerate diseases based on selective MAPK inhibitors, reduction of MMP3, and autophagy.