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Prolyl hydroxylase domain oxygen sensors are dioxygenases that regulate the activity of hypoxia-inducible factor (HIF), which controls renal and hepatic erythropoietin production and coordinates erythropoiesis with iron metabolism. Small molecule inhibitors of prolyl hydroxylase domain dioxygenases (HIF-PHI [prolyl hydroxylase inhibitor]) stimulate the production of endogenous erythropoietin and improve iron metabolism resulting in efficacious anemia management in patients with CKD. Three oral HIF-PHIs-daprodustat, roxadustat, and vadadustat-have now advanced to global phase III clinical development culminating in the recent licensing of roxadustat for oral anemia therapy in China. Here, we survey current clinical experience with HIF-PHIs, discuss potential therapeutic advantages, and deliberate over safety concerns regarding long-term administration in patients with renal anemia.
Copyright © 2019 National Kidney Foundation, Inc. Published by Elsevier Inc. All rights reserved.
This letter describes the first account of the chemical optimization (SAR and DMPK profiling) of a new series of mGlu positive allosteric modulators (PAMs), leading to the identification of VU0652957 (VU2957, Valiglurax), a compound profiled as a preclinical development candidate. Here, we detail the challenges faced in allosteric modulator programs (e.g., steep SAR, as well as subtle structural changes affecting overall physiochemical/DMPK properties and CNS penetration).
Copyright © 2018 Elsevier Ltd. All rights reserved.
A classic response to systemic hypoxia is the increase in red blood cell production. This response is controlled by the prolyl hydroxylase domain/hypoxia-inducible factor (HIF) pathway, which regulates a broad spectrum of cellular functions. The discovery of this pathway as a key regulator of erythropoiesis has led to the development of small molecules that stimulate the production of endogenous erythropoietin and enhance iron metabolism. This review provides a concise overview of the cellular and molecular mechanisms that govern HIF-induced erythropoietic responses and provides an update on clinical experience with compounds that target HIF-prolyl hydroxylases for anemia therapy.
© 2017 International Society for Hemodialysis.
Although mutations in the melanocortin-4 receptor (MC4R) gene cause severe early-onset obesity, we still do not have effective approaches to correct the defects of these mutations. Several antagonists have been identified as pharmacoperones of the MC4R whereas no agonist of the MC4R has been reported. In the present study, we investigated the effect of a small molecule agonist of the MC4R, THIQ, on the cell surface expression and signaling of ten intracellularly retained MC4R mutants using different cell lines. We showed that THIQ increased the cell surface expression of three mutants (N62S, C84R, and C271Y) and two of them (N62S and C84R) had increased signaling in HEK293 cells. Interestingly, THIQ increased the signaling of two other mutants (P78L and P260Q) without increasing their cell surface expression in HEK293 cells. In neuronal cells, THIQ exhibited a more potent effect, correcting the cell surface expression and signaling of seven mutants (N62S, I69R, P78L, C84R, W174C, P260Q, and C271Y). Other mutants were not rescued by THIQ. We also showed that THIQ did not rescue MC4R mutants defective in ligand binding or signaling or one intracellularly retained mutant of the melanocortin-3 receptor. In summary, we demonstrated that a small molecule agonist acted as a pharmacoperone of the MC4R rescuing the cell surface expression and signaling of some intracellularly retained MC4R mutants.
PURPOSE - The goal of this study is to optimize the activity of trabectedin for Ewing sarcoma by developing a molecularly targeted combination therapy.
EXPERIMENTAL DESIGN - We have recently shown that trabectedin interferes with the activity of EWS-FLI1 in Ewing sarcoma cells. In this report, we build on this work to develop a trabectedin-based combination therapy with improved EWS-FLI1 suppression that also targets the drug-associated DNA damage to Ewing sarcoma cells.
RESULTS - We demonstrate by siRNA experiments that EWS-FLI1 drives the expression of the Werner syndrome protein (WRN) in Ewing sarcoma cells. Because WRN-deficient cells are known to be hypersensitive to camptothecins, we utilize trabectedin to block EWS-FLI1 activity, suppress WRN expression, and selectively sensitize Ewing sarcoma cells to the DNA-damaging effects of SN38. We show that trabectedin and SN38 are synergistic, demonstrate an increase in DNA double-strand breaks, an accumulation of cells in S-phase and a low picomolar IC50. In addition, SN38 cooperates with trabectedin to augment the suppression of EWS-FLI1 downstream targets, leading to an improved therapeutic index in vivo. These effects translate into the marked regression of two Ewing sarcoma xenografts at a fraction of the dose of camptothecin used in other xenograft studies.
CONCLUSIONS - These results provide the basis and rationale for translating this drug combination to the clinic. In addition, the study highlights an approach that utilizes a targeted agent to interfere with an oncogenic transcription factor and then exploits the resulting changes in gene expression to develop a molecularly targeted combination therapy.
Translocator Protein 18 kDa (TSPO), previously known as the peripheral-type benzodiazepine receptor (PBR), is a mitochondrial outer membrane protein that has been identified as a key player in cholesterol and porphyrin transport, apoptotic signaling, and cancer development, as well as neurological inflammation and disease. Despite a number of TSPO ligands whose effects have been studied with respect to these varied biological activities, the nature of their interactions with TSPO and the molecular mechanism of their effects remain controversial, in part because of the lack of an atomic-resolution structure. We expressed and purified the homologue of mammalian TSPO from Rhodobacter sphaeroides (RsTSPO), as well as a mutant form in a proposed drug binding loop, RsTSPOW38C. We characterized their binding behaviors with endogenous ligands and a series of compounds that affect apoptosis by using a sensitive tryptophan fluorescence quenching assay. Our results show that RsTSPO behaves as a dimer in the purified state and binds with low micromolar affinity to many of these ligands, including retinoic acid, curcumin, and a known Bcl-2 inhibitor, gossypol, suggesting a possible direct role for TSPO in their regulation of apoptosis. A computational model of the RsTSPO dimer is constructed using EM-Fold, Rosetta, and a cryo-electron microscopy density map. Binding behaviors of known ligands are discussed in the context of the model with respect to regions that may be involved in binding.
While transforming growth factor-β (TGF-β1)-induced SMAD2/3 signaling is a critical event in the progression of chronic kidney disease, the role of non-SMAD mechanisms in the orchestration of fibrotic gene changes remains largely unexplored. TGF-β1/SMAD3 pathway activation in renal fibrosis (induced by ureteral ligation) correlated with epidermal growth factor receptor(Y845) (EGFR(Y845)) and p53(Ser15) phosphorylation and induction of disease causative target genes plasminogen activator inhibitor-1 (PAI-1) and connective tissue growth factor (CTGF) prompting an investigation of the mechanistic involvement of EGFR and tumor suppressor p53 in profibrotic signaling. TGF-β1, PAI-1, CTGF, p53 and EGFR were co-expressed in the obstructed kidney localizing predominantly to the tubular and interstitial compartments. Indeed, TGF-β1 activated EGFR and p53 as well as SMAD2/3. Genetic deficiency of either EGFR or p53 or functional blockade with AG1478 or Pifithrin-α, respectively, effectively inhibited PAI-1and CTGF induction and morphological transformation of renal fibroblasts as did SMAD3 knockdown or pretreatment with the SMAD3 inhibitor SIS3. Reactive oxygen species (ROS)-dependent mechanisms initiated by TGF-β1 were critical for EGFR(Y845) and p53(Ser15) phosphorylation and target gene expression. The p22(Phox) subunit of NADPH oxidase was also elevated in the fibrotic kidney with an expression pattern similar to p53 and EGFR. EGF stimulation alone initiated, albeit delayed, c-terminal SMAD3 phosphorylation (that required the TGF-β1 receptor) and rapid ERK2 activation both of which are necessary for PAI-1 and CTGF induction in renal fibroblasts. These data highlight the extensive cross-talk among SMAD2/3, EGFR and p53 pathways essential for expression of TGF-β1-induced fibrotic target genes.
The Ewing sarcoma family of tumors or Ewing sarcoma (ES) is the second most common malignant bone tumor of childhood. The prognosis for localized Ewing sarcoma has improved through the development of intense multimodal therapy over the past several decades. Unfortunately, patients with recurrent or metastatic disease continue to have a poor prognosis. Therefore, a number of complementary approaches are being developed in both the preclinical and clinical arenas to improve these outcomes. In this review, we will discuss efforts to directly target the biologic drivers of this disease and relate these efforts to the experience with several different agents both in the clinic and under development. We will review the data for compounds that have shown excellent activity in the clinic, such as the camptothecins, and summarize the biological data that supports this activity. In addition, we will review the clinical experience with IGF1 targeted agents, ET-743 and epigenetically targeted therapies, the substantial amount of literature that supports their activity in Ewing sarcoma and the challenges remaining translating these therapies to the clinic. Finally, we will highlight recent work aimed at directly targeting the EWS-FLI1 transcription factor with small molecules in Ewing tumors.
Copyright © 2012 Elsevier Inc. All rights reserved.
Previous studies have demonstrated the feasibility of translocator protein (TSPO) imaging to visualize and quantify human breast adenocarcinoma (MDA-MB-231) cells in vivo using a TSPO-targeted near-infrared (NIR) probe (NIR-conPK11195). This study aimed to extend the use of the TSPO-targeted probe to a more biologically relevant and clinically important tumor microenvironment as well as to assess our ability to longitudinally detect the presence and progression of breast cancer cells in the brain. The in vivo biodistribution and accumulation of NIR-conPK11195 and free (unconjugated) NIR dye were quantitatively evaluated in intracranial MDA-MB-231-bearing mice and non-tumor-bearing control mice longitudinally once a week from two to five weeks post-inoculation. The in vivo time-activity curves illustrate distinct clearance profiles for NIR-conPK11195 and free NIR dye, resulting in preferential accumulation of the TSPO-targeted probe in the intracranial tumor bearing hemisphere (TBH) with significant tumor contrast over normal muscle tissue (p < 0.005 at five weeks; p < 0.01 at four weeks). In addition, the TSPO-labeled TBHs demonstrated significant contrast over the TBHs of mice injected with free NIR dye (p < 0.001 at four and five weeks) as well as over the TSPO-labeled non-tumor-bearing hemispheres (NTBHs) of control mice (p < 0.005 at four and five weeks). Overall, TSPO-targeted molecular imaging appears useful for visualizing and quantifying breast cancer xenografts propagated in the murine brain and may assist in preclinical detection, diagnosis and monitoring of metastatic disease as well as drug discovery. Furthermore, these results indicate it should be possible to perform TSPO-imaging of breast cancer cells in the brain using radiolabeled TSPO-targeted agents, particularly in light of the fact that [11C]-labeled TSPO probes such as [11C]-PK 11195 have been successfully used to image gliomas in the clinic.
BACKGROUND - The kappa opioid receptor (KOR) system contributes to the prodepressive and aversive consequences of stress and is implicated in the facilitation of conditioned fear and anxiety in rodents. Here, we sought to identify neural circuits that mediate KOR system effects on fear and anxiety in rats.
METHODS - We assessed whether fear conditioning induces plasticity in KOR or dynorphin (the endogenous KOR ligand) messenger RNA (mRNA) expression in the basolateral (BLA) and central (CeA) nuclei of the amygdala, hippocampus, or striatum. We then assessed whether microinfusions of the KOR antagonist JDTic (0-10 μg/side) into the BLA or CeA affect the expression of conditioned fear or anxiety. Finally, we examined whether fear extinction induces plasticity in KOR mRNA expression that relates to the quality of fear extinction.
RESULTS - Fear conditioning upregulated KOR mRNA in the BLA by 65% and downregulated it in the striatum by 22%, without affecting KOR levels in the CeA or hippocampus, or dynorphin levels in any region. KOR antagonism in either the BLA or CeA decreased conditioned fear in the fear-potentiated startle paradigm, whereas KOR antagonism in the BLA, but not the CeA, produced anxiolytic-like effects in the elevated plus maze. Effective fear extinction was associated with a 67% reduction in KOR mRNA in the BLA.
CONCLUSIONS - These findings suggest that fear conditioning and extinction dynamically regulate KOR expression in the BLA and provide evidence that the BLA and CeA are important neural substrates mediating the anxiolytic-like effects of KOR antagonists in models of fear and anxiety.
Copyright © 2011 Society of Biological Psychiatry. Published by Elsevier Inc. All rights reserved.