Mutationally activated kinases define a clinically validated class of targets for cancer drug therapy. However, the efficacy of kinase inhibitors in patients whose tumours harbour such alleles is ...invariably limited by innate or acquired drug resistance. The identification of resistance mechanisms has revealed a recurrent theme—the engagement of survival signals redundant to those transduced by the targeted kinase. Cancer cells typically express multiple receptor tyrosine kinases (RTKs) that mediate signals that converge on common critical downstream cell-survival effectors—most notably, phosphatidylinositol-3-OH kinase (PI(3)K) and mitogen-activated protein kinase (MAPK). Consequently, an increase in RTK-ligand levels, through autocrine tumour-cell production, paracrine contribution from tumour stroma or systemic production, could confer resistance to inhibitors of an oncogenic kinase with a similar signalling output. Here, using a panel of kinase-'addicted' human cancer cell lines, we found that most cells can be rescued from drug sensitivity by simply exposing them to one or more RTK ligands. Among the findings with clinical implications was the observation that hepatocyte growth factor (HGF) confers resistance to the BRAF inhibitor PLX4032 (vemurafenib) in BRAF-mutant melanoma cells. These observations highlight the extensive redundancy of RTK-transduced signalling in cancer cells and the potentially broad role of widely expressed RTK ligands in innate and acquired resistance to drugs targeting oncogenic kinases.
Celotno besedilo
Dostopno za:
DOBA, IJS, IZUM, KILJ, KISLJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Voltage-gated sodium (Nav) channels propagate action potentials in excitable cells. Accordingly, Nav channels are therapeutic targets for many cardiovascular and neurological disorders. Selective ...inhibitors have been challenging to design because the nine mammalian Nav channel isoforms share high sequence identity and remain recalcitrant to high-resolution structural studies. Targeting the human Nav1.7 channel involved in pain perception, we present a protein-engineering strategy that has allowed us to determine crystal structures of a novel receptor site in complex with isoform-selective antagonists. GX-936 and related inhibitors bind to the activated state of voltage-sensor domain IV (VSD4), where their anionic aryl sulfonamide warhead engages the fourth arginine gating charge on the S4 helix. By opposing VSD4 deactivation, these compounds inhibit Nav1.7 through a voltage-sensor trapping mechanism, likely by stabilizing inactivated states of the channel. Residues from the S2 and S3 helices are key determinants of isoform selectivity, and bound phospholipids implicate the membrane as a modulator of channel function and pharmacology. Our results help to elucidate the molecular basis of voltage sensing and establish structural blueprints to design selective Nav channel antagonists.
FGF21 is a stress-induced hormone with potent anti-obesity, insulin-sensitizing, and hepatoprotective properties. Although proteolytic cleavage of recombinant human FGF21 in preclinical species has ...been observed previously, the regulation of endogenously produced FGF21 is not well understood. Here we identify fibroblast activation protein (FAP) as the enzyme that cleaves and inactivates human FGF21. A selective chemical inhibitor, immunodepletion, or genetic deletion of Fap stabilized recombinant human FGF21 in serum. In addition, administration of a selective FAP inhibitor acutely increased circulating intact FGF21 levels in cynomolgus monkeys. On the basis of our findings, we propose selective FAP inhibition as a potential therapeutic approach to increase endogenous FGF21 activity for the treatment of obesity, type 2 diabetes, non-alcoholic steatohepatitis, and related metabolic disorders.
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•Nav1.7 is a complex protein with multiple druggable sites.•Inhibitors of Nav1.7 are able to produce robust pain relief in preclinical models.•Highly potent and selective (>100×) of ...Nav1.7 have been recently disclosed.•More work is needed to understand PK/PD relationships of Nav1.7 inhibitors.
The voltage gated sodium channel Nav1.7 plays an essential role in the transmission of pain signals. Strong human genetic validation has motivated extensive efforts to discover potent, selective, and efficacious Nav1.7 inhibitors for the treatment of chronic pain. This digest will introduce the structure and function of Nav1.7 and highlight the wealth of recent developments on a diverse array of Nav1.7 inhibitors, including optimization of their potency, selectivity, and PK/PD relationships.
Activation of caspases-8 and -10 by FLIPL BOATRIGHT, Kelly M.; DEIS, Cristina; DENAULT, Jean-Bernard ...
Biochemical journal,
09/2004, Letnik:
382, Številka:
2
Journal Article
Recenzirano
Odprti dostop
The first step in caspase activation is transition of the latent zymogen to an active form. For the initiator caspases, this occurs through dimerization of monomeric zymogens at an activating ...complex. Recent studies have suggested that FLIPL FLICE-like inhibitory protein, long form; FLICE is FADD (Fas-associated death domain protein)-like interleukin-1β-converting enzyme, previously thought to act solely as an inhibitor of caspase-8 activation, can under certain circumstances function to enhance caspase activation. Using an in vitro induced-proximity assay, we demonstrate that activation of caspases-8 and -10 occurs independently of cleavage of either the caspase or FLIPL. FLIPL activates caspase-8 by forming heterodimeric enzyme molecules with substrate specificity and catalytic activity indistinguishable from those of caspase-8 homodimers. Significantly, the barrier for heterodimer formation is lower than that for homodimer formation, suggesting that FLIPL is a more potent activator of caspase-8 than is caspase-8 itself.
Alterations of the phosphoinositide-3 kinase (PI3K)/Akt signaling pathway occur broadly in cancer via multiple mechanisms including mutation of the PIK3CA gene, loss or mutation of phosphatase and ...tensin homolog (PTEN), and deregulation of mammalian target of rapamycin (mTOR) complexes. The dysregulation of this pathway has been implicated in tumor initiation, cell growth and survival, invasion and angiogenesis, thus, PI3K and mTOR are promising therapeutic targets for cancer. We discovered GDC-0980, a selective, potent, orally bioavailable inhibitor of Class I PI3 kinase and mTOR kinase (TORC1/2) with excellent pharmacokinetic and pharmaceutical properties. GDC-0980 potently inhibits signal transduction downstream of both PI3K and mTOR, as measured by pharmacodynamic (PD) biomarkers, thereby acting upon two key pathway nodes to produce the strongest attainable inhibition of signaling in the pathway. Correspondingly, GDC-0980 was potent across a broad panel of cancer cell lines, with the greatest potency in breast, prostate, and lung cancers and less activity in melanoma and pancreatic cancers, consistent with KRAS and BRAF acting as resistance markers. Treatment of cancer cell lines with GDC-0980 resulted in G1 cell-cycle arrest, and in contrast to mTOR inhibitors, GDC-0980 induced apoptosis in certain cancer cell lines, including those with direct pathway activation via PI3K and PTEN. Low doses of GDC-0980 potently inhibited tumor growth in xenograft models including those with activated PI3K, loss of LKB1 or PTEN, and elicited an exposure-related decrease in PD biomarkers. These preclinical data show that GDC-0980 is a potent and effective dual PI3K/mTOR inhibitor with promise for the clinic.
The discovery of 2 (GDC-0980), a class I PI3K and mTOR kinase inhibitor for oncology indications, is described. mTOR inhibition was added to the class I PI3K inhibitor 1 (GDC-0941) scaffold primarily ...through the substitution of the indazole in 1 for a 2-aminopyrimidine. This substitution also increased the microsomal stability and the free fraction of compounds as evidenced through a pairwise comparison of molecules that were otherwise identical. Highlighted in detail are analogues of an advanced compound 4 that were designed to improve solubility, resulting in 2. This compound, is potent across PI3K class I isoforms with IC50s of 5, 27, 7, and 14 nM for PI3Kα, β, δ, and γ, respectively, inhibits mTOR with a K i of 17 nM yet is highly selective versus a large panel of kinases including others in the PIKK family. On the basis of the cell potency, low clearance in mouse, and high free fraction, 2 demonstrated significant efficacy in mouse xenografts when dosed as low as 1 mg/kg orally and is currently in phase I clinical trials for cancer.
Selective block of NaV1.7 promises to produce non-narcotic analgesic activity without motor or cognitive impairment. Several NaV1.7-selective blockers have been reported, but efficacy in animal pain ...models required high multiples of the IC50 for channel block. Here, we report a target engagement assay using transgenic mice that has enabled the development of a second generation of selective Nav1.7 inhibitors that show robust analgesic activity in inflammatory and neuropathic pain models at low multiples of the IC50. Like earlier arylsulfonamides, these newer acylsulfonamides target a binding site on the surface of voltage sensor domain 4 to achieve high selectivity among sodium channel isoforms and steeply state-dependent block. The improved efficacy correlates with very slow dissociation from the target channel. Chronic dosing increases compound potency about 10-fold, possibly due to reversal of sensitization arising during chronic injury, and provides efficacy that persists long after the compound has cleared from plasma.
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•Aconitine-induced pain in IEM mice enables assay for target engagement of hNaV1.7•Acylsulfonamides inhibit pain at low multiples of the IC50 for inhibition of NaV1.7•Improvement versus arylsulfonamides correlates with longer residency time on NaV1.7•Repeat dosing of acylsulfonamides results in a 10-fold decrease in EC50 for analgesia
Bankar et al. show that acylsulfonamides produce analgesic activity at low multiples of the IC50 for inhibition of NaV1.7, in contrast to studies with arylsulfonamides that required >10 times the IC50. The improvement correlates with longer residency time on the target channels.
Using structure- and ligand-based design principles, a novel series of piperidyl chromane arylsulfonamide Nav1.7 inhibitors was discovered. Early optimization focused on improvement of potency ...through refinement of the low energy ligand conformation and mitigation of high in vivo clearance. An in vitro hepatotoxicity hazard was identified and resolved through optimization of lipophilicity and lipophilic ligand efficiency to arrive at GNE-616 (24), a highly potent, metabolically stable, subtype selective inhibitor of Nav1.7. Compound 24 showed a robust PK/PD response in a Nav1.7-dependent mouse model, and site-directed mutagenesis was used to identify residues critical for the isoform selectivity profile of 24.
The PI3K/AKT/mTOR pathway has been shown to play an important role in cancer. Starting with compounds 1 and 2 (GDC-0941) as templates, (thienopyrimidin-2-yl)aminopyrimidines were discovered as potent ...inhibitors of PI3K or both PI3K and mTOR. Structural information derived from PI3Kγ−ligand cocrystal structures of 1 and 2 were used to design inhibitors that maintained potency for PI3K yet improved metabolic stability and oral bioavailability relative to 1. The addition of a single methyl group to the optimized 5 resulted in 21, which had significantly reduced potency for mTOR. The lead compounds 5 (GNE-493) and 21 (GNE-490) have good pharmacokinetic (PK) parameters, are highly selective, demonstrate knock down of pathway markers in vivo, and are efficacious in xenograft models where the PI3K pathway is deregulated. Both compounds were compared in a PI3Kα mutated MCF7.1 xenograft model and were found to have equivalent efficacy when normalized for exposure.
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