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PI3Kα is highly mutated in cancer resulting in hyperactivation of lipid kinase activity and downstream AKT signaling. H1047 is the most common site of oncogenic mutation and occurs in ~14% of all breast cancers. Initial therapeutic benefit of targeting PI3Kα was established with alpelisib, an alpha-selective PI3K inhibitor that is equipotent against wild-type and mutant forms. However, wild-type PI3Kα inhibition results in frequent dose-limiting toxicities including hyperglycemia, restricting the full potential of this drug. Selective targeting of H1047X-mutant PI3Kα is expected to both improve anti-tumor activity and reduce toxicity. STX-478 is an allosteric, CNS-penetrant, selective PI3Kα H1047X inhibitor, having excellent drug-like properties and exceptional kinome selectivity. STX-478 demonstrated minimal inhibition of CYP enzymes in vitro, supporting the potential for combinations with a wide range of therapeutics in breast cancer and a variety of other tumor types. STX-478 selectivity extended to the inhibition of other activating kinase domain mutations in biochemical assays. In a diverse panel of PI3Kα H1047X mutant cell lines, STX-478 selectively reduced the cellular levels of pAKT (S473) with a strong correlation between pAKT inhibition and cell viability (R = 0.8). In a high-throughput viability screen of 467 cancer cell lines, the presence of PIK3CA H1047X and other kinase domain mutations were the single strongest predictor of STX-478 sensitivity with potency superior to alpelisib. STX-478 also selectively inhibited the proliferation of cell lines with PI3Kα helical domain mutations, potentially due to the selective dependency of these cells on mutant PI3Kα. When combined with fulvestrant, lapatinib, or abemaciclib, STX-478 demonstrated synergistic anti-proliferative activity in cell lines with relevant ER/HER2 status. Unlike alpelisib, STX-478 did not impair glucose metabolism or cause insulin resistance at efficacious doses. In the T47D (PI3Kα H1047R) breast cancer model, STX-478 (100 mg/kg) monotherapy caused tumor regression whereas alpelisib caused only stasis. STX-478 combination with fulvestrant was well-tolerated, with more consistent and deeper tumor regression. Similar results were observed in a PI3Kα H1047R mutant ER+/HER2- PDX model, where fulvestrant monotherapy showed minimal activity, while combination with STX-478 yielded tumor regressions. In an ER+/HER2+ PDX model (PI3Kα H1047R/R108H), palbociclib and STX-478 (100 mg/kg) monotherapy resulted in similar efficacy while the combination was well tolerated and yielded tumor regression. Together these data indicate robust STX-478 monotherapy activity that was well tolerated and improved when dosed in combination with fulvestrant or CDK4/6 inhibitors. Finally, we investigated the effect of STX-478 treatment in an ER+ PDX model carrying a helical domain mutation. STX-478 treatment resulted in tumor growth inhibition at doses that did not result in metabolic dysfunction, suggesting that STX-478 may also be efficacious in treating PIK3CA mutant tumors with helical domain mutations. In summary, STX-478 efficacy was superior to alpelisib at a dose level that exceeds the clinically relevant exposure in mice without causing metabolic dysfunction. STX- 478 has a predicted low human dose, CNS exposure, low risk of DDI, and a predicted long half-life with minimal variation in peak-to-trough plasma concentrations which further supports a favorable therapeutic index. STX-478 has the potential to provide a best-in-class profile to improve outcomes in patients harboring tumors with prevalent PI3Kα H1047X mutations as well as other kinase and helical domain mutant tumors. The significant CNS exposure of STX-478 is expected to enable this treatment for patients with brain tumors and brain metastases not afforded by existing options. STX-478 is currently in IND enabling studies and is expected to enter human clinical trials in 2023. Citation Format: Leonard Buckbinder, David J. St. Jean, Brendon Ladd, Trang Tieu, Philip Jonsson, Jacob Alltucker, Samantha Manimala, Weixue Wang, Angel Guzman-Perez, Darrin D. Stuart, Gregory Dowdell. STX-478, a mutant-selective PI3Kα H1047X inhibitor clinical candidate with a best-in-class profile: Pharmacology and therapeutic activity as monotherapy and in combination in breast cancer xenograft models [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-07-04.

Myeloperoxidase (MPO) is a highly oxidative, pro-inflammatory enzyme involved in post-myocardial infarction (MI) injury and is a potential therapeutic target. While multiple MPO inhibitors have been developed, the lack of an imaging reporter to select appropriate patients and assess therapeutic efficacy has hampered clinical development. Thus, a translational imaging method to detect MPO activity non-invasively would help to better understand the role MPO plays in MI and facilitate novel therapy development and clinical validation. Interestingly, many MPO inhibitors affect both intracellular and extracellular MPO, but previous MPO imaging methods can only report extracellular MPO activity. In this study, we found that an MPO-specific PET imaging agent (18F-MAPP) can cross cell membranes to report intracellular MPO activity. We showed that 18F-MAPP can track the treatment effect of an MPO inhibitor (PF-2999) at different doses in experimental MI. The imaging results were corroborated by ex vivo autoradiography and gamma counting data. Furthermore, extracellular and intracellular MPO activity assays revealed that 18F-MAPP imaging can report the changes induced by PF-2999 on both intracellular and extracellular MPO activities. These findings support 18F-MAPP as a translational candidate to noninvasively report MPO activity and accelerate drug development against MPO and other related inflammatory targets.

ObjectiveHeart failure with preserved ejection fraction (HFpEF) is a heterogeneous syndrome. We aimed to derive HFpEF phenotype-based groups ('phenogroups') based on clinical and echocardiogram data using machine learning, and to compare clinical characteristics, proteomics and outcomes across the phenogroups.MethodsWe applied model-based clustering to 32 echocardiogram and 11 clinical and laboratory variables collected in stable condition from 320 HFpEF outpatients in the Karolinska-Rennes cohort study (56% female, median 78 years (IQR: 71–83)). Baseline proteomics and the composite end point of all-cause mortality or heart failure (HF) hospitalisation were used in secondary analyses.ResultsWe identified six phenogroups, for which significant differences in the prevalence of concomitant atrial fibrillation (AF), anaemia and kidney disease were observed (pConclusionsUsing machine learning we identified distinct HFpEF phenogroups with differential characteristics and outcomes, as well as differential levels of inflammatory and cardiovascular proteins.

Oncogenic PIK3CA mutations are found in 14% of all cancers and most frequently occur at amino acids E542/E545 and H1047, involving the helical and kinase domains, respectively (Zhang 2017). Alpelisib is a PI3Kα isoform-selective, orthosteric kinase inhibitor, having equivalent activity on wild-type (wt) and mutant (mt) forms and was approved to treat PI3Kα mt, HR+/HER2- breast cancer in combination with fulvestrant, nearly doubling progression-free survival (Andre 2019). Hyperglycemia with insulin resistance is an on-target result of wt PI3Kα inhibition, leading to frequent alpelisib dose reductions, interruptions, and discontinuations. H1047X is the most common PIK3CA alteration, found in ~14% of all breast cancer patients (Martínez-Sáez 2020). We considered that selectively targeting this mutant could improve patient outcomes by sparing metabolic dysfunction related to wt inhibition. We have validated this therapeutic concept preclinically with the discovery of ST-814, an allosteric, CNS-penetrant, mutant selective PI3KαH1047X inhibitor, displaying excellent drug-like properties. ST-814 was 14-fold selective for PI3KαH1047R vs PI3Kαwt in biochemical assays (IC50 11 vs 146 nM) with exquisite isoform and kinome selectivity. Cell-based activity and selectivity were characterized in T47D (PI3KαH1047R) and SKBR3 (PI3KαWT) tumor cells grown in 10% FBS, with 8-fold mut-selectivity observed in target engagement (pAKT EC50 38 vs 304 nM) and 11-fold selectivity in viability (GI50 153 vs 1683 nM). ST-814 has robust anti-tumor activity in PI3KαH1047X in xenografts, with efficacy similar or superior to alpelisib dosed at 50 mg/kg (Table 1). To achieve this level of mouse efficacy, alpelisib exposure exceeded that in patients >200% (mouse vs human AUC0-24, 74,000 vs 33,224 ng*hr/mL). As such, repeat dosing of alpelisib at 50 mg/kg, caused profound elevations in serum insulin 1 hr post-dose (*p Table 1. CAL33 H1047R Oral Sq Cell Carcinoma Xenograft Alpelisib TGI% 50 mg/kg ST-814 TGI% 100 mg/kg Alpelisib ΔInsulin ng/mL ST-814 ΔInsulin ng/mL 79% 82% 4.42* 0.40 Citation Format: Leonard Buckbinder, David J. St. Jean, Trang Tieu, Weixue Wang, Gregory Kryukov, Philip Jonsson, Jacob Alltucker, Samantha Manimala, Brendon Ladd, Angel Guzman-Perez, Darrin Stuart. Discovery and characterization of a mutant selective PI3KαH1047Xinhibitor with a best-in-class profile [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr LB194.

The propensity for CYP3A4 induction by 2-(6-(5-chloro-2-methoxyphenyl)-4-oxo-2-thioxo-3,4-dihydropyrimidin-1(2H)-yl)acetamide (PF-06282999), an irreversible inactivator of myeloperoxidase, was examined in the present study. Studies using human hepatocytes revealed moderate increases in CYP3A4 mRNA and midazolam-1'-hydroxylase activity in a PF-06282999 dose-dependent fashion. At the highest tested concentration of 300 μM, PF-06282999 caused maximal induction in CYP3A4 mRNA and enzyme activity ranging from 56% to 86% and 47% t0 72%, respectively, of rifampicin response across the three hepatocyte donor pools. In a clinical drug-drug interaction (DDI) study, the mean midazolam Cmax and area under the curve (AUC) values following 14-day treatment with PF-06282999 decreased in a dose-dependent fashion with a maximum decrease in midazolam AUC0-inf and Cmax of ∼57.2% and 41.1% observed at the 500 mg twice daily dose. The moderate impact on midazolam pharmacokinetics at the 500 mg twice daily dose of PF-06282999 was also reflected in statistically significant changes in plasma 4β-hydroxycholesterol/cholesterol and urinary 6β-hydroxycortisol/cortisol ratios. Changes in plasma and urinary CYP3A4 biomarkers did not reach statistical significance at the 125 mg three times daily dose of PF-06282999, despite a modest decrease in midazolam systemic exposure. Predicted DDI magnitude based on the in vitro induction parameters and simulated pharmacokinetics of perpetrator (PF-06282999) and victim (midazolam) using the Simcyp (Simcyp Ltd., Sheffield, United Kingdom) population-based simulator were in reasonable agreement with the observed clinical data. Since the magnitude of the 4β-hydroxycholesterol or 6β-hydroxycortisol ratio change was generally smaller than the magnitude of the midazolam AUC change with PF-06282999, a pharmacokinetic interaction study with midazolam ultimately proved important for assessment of DDI via CYP3A4 induction.

Visual Abstract, Highlights • The inflammatory enzyme MPO is a potential therapeutic target in cardiovascular diseases. • PF-1355 is an orally bioavailable mechanism-based inhibitor of MPO enzymatic activity. PF-1355 treatment successfully inhibited MPO in mouse models of myocardial infarction and ischemia reperfusion injury. • Short duration oral drug treatment for 7 days attenuated inflammation and cardiac dilation during early infarct healing. However, MPO-containing cells persisted beyond 7 days. • Prolonged 21-day treatment improved ejection fraction (∼44%) and decreased end-diastolic volume (∼53%) and left ventricular mass (∼33%) compared with untreated control subjects. • Better therapeutic effect was also achieved when treatment was started early (at 1 h) after the initial ischemic insult., Summary PF-1355 is an oral myeloperoxidase (MPO) inhibitor that successfully decreased elevated MPO activity in mouse myocardial infarction models. Short duration PF-1355 treatment for 7 days decreased the number of inflammatory cells and attenuated left ventricular dilation. Cardiac function and remodeling improved when treatment was increased to 21 days. Better therapeutic effect was further achieved with early compared with delayed treatment initiation (1 h vs. 24 h after infarction). In conclusion, PF-1355 treatment protected a mouse heart from acute and chronic effects of MI, and this study paves the way for future translational studies investigating this class of drugs in cardiovascular diseases.

Heart failure (HF) is a leading cause of morbidity and mortality worldwide1. A small proportion of HF cases are attributable to monogenic cardiomyopathies and existing genome-wide association studies (GWAS) have yielded only limited insights, leaving the observed heritability of HF largely unexplained2–4. We report the largest GWAS meta-analysis of HF to-date, comprising 47,309 cases and 930,014 controls. We identify 12 independent variant associations with HF at 11 genomic loci, all of which demonstrate one or more associations with coronary artery disease (CAD), atrial fibrillation, or reduced left ventricular function suggesting shared genetic aetiology. Expression quantitative trait analysis of non-CAD-associated loci implicate genes involved in cardiac development (MYOZ1, SYNPO2L), protein homeostasis (BAG3), and cellular senescence (CDKN1A). Using Mendelian randomisation analysis we provide new evidence supporting previously equivocal causal roles for several HF risk factors identified in observational studies, and demonstrate CAD-independent effects for atrial fibrillation, body mass index, hypertension and triglycerides. These findings extend our knowledge of the genes and pathways underlying HF and may inform the development of new therapeutic approaches.

Myeloperoxidase (MPO) is a critical proinflammatory enzyme implicated in cardiovascular, neurological, and rheumatological diseases. Emerging therapies targeting inflammation have raised interest in tracking MPO activity in patients. We describe 18 F-MAPP, an activatable MPO activity radioprobe for positron emission tomography (PET) imaging. The activated radioprobe binds to proteins and accumulates at sites of MPO activity. The radioprobe 18 F-MAPP has a short blood half-life, remains stable in plasma, does not demonstrate cytotoxicity, and crosses the intact blood–brain barrier. The 18 F-MAPP imaging detected sites of elevated MPO activity in living mice embedded with human MPO and in mice induced with chemical inflammation or myocardial infarction. The 18 F-MAPP PET imaging noninvasively differentiated varying amounts of MPO activity, competitive inhibition, and MPO deficiency in living animals, confirming specificity and showing that the radioprobe can quantify changes in in vivo MPO activity. The radiosynthesis has been optimized and automated, an important step in translation. These data indicate that 18 F-MAPP is a promising translational candidate to noninvasively monitor MPO activity and inflammation in patients.

Myeloperoxidase (MPO) is a highly abundant protein within the neutrophil that is associated with lipoprotein oxidation, and increased plasma MPO levels are correlated with poor prognosis after myocardial infarct. Thus, MPO inhibitors have been developed for the treatment of heart failure and acute coronary syndrome in humans. 2-(6-(5-Chloro-2-methoxyphenyl)-4-oxo-2-thioxo-3,4-dihydropyrimidin-1(2H)-yl)acetamide PF-06282999 is a recently described selective small molecule mechanism-based inactivator of MPO. Here, utilizing PF-06282999, we investigated the role of MPO to regulate atherosclerotic lesion formation and composition in the Ldlr-/- mouse model of atherosclerosis. Though MPO inhibition did not affect lesion area in Ldlr-/- mice fed a Western diet, reduced necrotic core area was observed in aortic root sections after MPO inhibitor treatment. MPO inhibition did not alter macrophage content in and leukocyte homing to atherosclerotic plaques. To assess non-invasive monitoring of plaque inflammation, [18F]-Fluoro-deoxy-glucose (FDG) was administered to Ldlr-/- mice with established atherosclerosis that had been treated with clinically relevant doses of PF-06282999, and reduced FDG signal was observed in animals treated with a dose of PF-06282999 that corresponded with reduced necrotic core area. These data suggest that MPO inhibition does not alter atherosclerotic plaque area or leukocyte homing, but rather alters the inflammatory tone of atherosclerotic lesions; thus, MPO inhibition could have utility to promote atherosclerotic lesion stabilization and prevent atherosclerotic plaque rupture.

N1-Substituted-6-arylthiouracils, represented by compound 1 [6-(2,4-dimethoxyphenyl)-1-(2-hydroxyethyl)-2-thioxo-2,3-dihydropyrimidin-4(1H)-one], are a novel class of selective irreversible inhibitors of human myeloperoxidase. The present account is a summary of our in vitro studies on the facile oxidative desulfurization in compound 1 to a cyclic ether metabolite M1 [5-(2,4-dimethoxyphenyl)-2,3-dihydro-7H-oxazolo[3,2-a]pyrimidin-7-one] in NADPH-supplemented rats (t1/2 [half-life = mean ± S.D.] = 8.6 ± 0.4 minutes) and dog liver microsomes (t1/2 = 11.2 ± 0.4 minutes), but not in human liver microsomes (t1/2 > 120 minutes). The in vitro metabolic instability also manifested in moderate-to-high plasma clearances of the parent compound in rats and dogs with significant concentrations of M1 detected in circulation. Mild heat deactivation of liver microsomes or coincubation with the flavin-containing monooxygenase (FMO) inhibitor imipramine significantly diminished M1 formation. In contrast, oxidative metabolism of compound 1 to M1 was not inhibited by the pan cytochrome P450 inactivator 1-aminobenzotriazole. Incubations with recombinant FMO isoforms (FMO1, FMO3, and FMO5) revealed that FMO1 principally catalyzed the conversion of compound 1 to M1. FMO1 is not expressed in adult human liver, which rationalizes the species difference in oxidative desulfurization. Oxidation by FMO1 followed Michaelis-Menten kinetics with Michaelis-Menten constant, maximum rate of oxidative desulfurization, and intrinsic clearance values of 209 μM, 20.4 nmol/min/mg protein, and 82.7 μl/min/mg protein, respectively. Addition of excess glutathione essentially eliminated the conversion of compound 1 to M1 in NADPH-supplemented rat and dog liver microsomes, which suggests that the initial FMO1-mediated S-oxygenation of compound 1 yields a sulfenic acid intermediate capable of redox cycling to the parent compound in a glutathione-dependent fashion or undergoing further oxidation to a more electrophilic sulfinic acid species that is trapped intramolecularly by the pendant alcohol motif in compound 1.

Studies have linked the serine-threonine kinase MAP4K4 to the regulation of a number of biological processes and/or diseases, including diabetes, cancer, inflammation, and angiogenesis. With a majority of the members of our lead series (e.g., 1) suffering from time-dependent inhibition (TDI) of CYP3A4, we sought design avenues that would eliminate this risk. One such approach arose from the observation that carboxylic acid-based intermediates employed in our discovery efforts retained high MAP4K4 inhibitory potency and were devoid of the TDI risk. The medicinal chemistry effort that led to the discovery of this central nervous system-impaired inhibitor together with its preclinical safety profile is described.

Myeloperoxidase (MPO) is a heme peroxidase that catalyzes the production of hypochlorous acid. Clinical evidence suggests a causal role for MPO in various autoimmune and inflammatory disorders including vasculitis and cardiovascular and Parkinson's diseases, implying that MPO inhibitors may represent a therapeutic treatment option. Herein, we present the design, synthesis, and preclinical evaluation of N1-substituted-6-arylthiouracils as potent and selective inhibitors of MPO. Inhibition proceeded in a time-dependent manner by a covalent, irreversible mechanism, which was dependent upon MPO catalysis, consistent with mechanism-based inactivation. N1-Substituted-6-arylthiouracils exhibited low partition ratios and high selectivity for MPO over thyroid peroxidase and cytochrome P450 isoforms. N1-Substituted-6-arylthiouracils also demonstrated inhibition of MPO activity in lipopolysaccharide-stimulated human whole blood. Robust inhibition of plasma MPO activity was demonstrated with the lead compound 2-(6-(5-chloro-2-methoxyphenyl)-4-oxo-2-thioxo-3,4-dihydropyrimidin-1(2H)-yl)acetamide (PF-06282999, 8) upon oral administration to lipopolysaccharide-treated cynomolgus monkeys. On the basis of its pharmacological and pharmacokinetic profile, PF-06282999 has been advanced to first-in-human pharmacokinetic and safety studies.

Recent studies in adipose tissue, pancreas, muscle, and macrophages suggest that MAP4K4, a serine/threonine protein kinase may be a viable target for antidiabetic drugs. As part of the evaluation of MAP4K4 as a novel antidiabetic target, a tool compound, 16 (PF-6260933) and a lead 17 possessing excellent kinome selectivity and suitable properties were delivered to establish proof of concept in vivo. The medicinal chemistry effort that led to the discovery of these lead compounds is described herein together with in vivo pharmacokinetic properties and activity in a model of insulin resistance.

A significant improvement in agonist activity of the previously described 2-aryloctahydrophenanthrene-2,3,7-triol series of dissociated glucocorticoid receptor agonists (DAGRs) was achieved by modifying the substitution at C3 from (S)-3-hydroxy to (R)-3-hydroxy-3-methyl. The IC50 of the prototype 13 in the efficacy assay measuring repression of IL-1 induced MMP-13 expression was 3.5 nM, exhibiting 87% of the maximal effect of dexamethasone (DEX). It displayed a dissociated profile by exhibiting 42% of the maximal effect of DEX in a mouse mammary tumor virus (MMTV) luciferase reporter transactivation assay. Compound 13 and analogues containing heterocyclic replacements for the C2 phenyl and modified B rings showed high repression of TNFα production in human whole blood, with IC50 values (43-167 nM) approaching the level of DEX (21 nM). On the basis of X-ray structures and force field calculations, the overall potency of this series was attributed to a favorable conformation of the C2α phenyl, induced by the neighboring C3α methyl.

Small vessel vasculitis is a life-threatening condition and patients typically present with renal and pulmonary injury. Disease pathogenesis is associated with neutrophil accumulation, activation, and oxidative damage, the latter being driven in large part by myeloperoxidase (MPO), which generates hypochlorous acid among other oxidants. MPO has been associated with vasculitis, disseminated vascular inflammation typically involving pulmonary and renal microvasculature and often resulting in critical consequences. MPO contributes to vascular injury by 1) catabolizing nitric oxide, impairing vasomotor function; 2) causing oxidative damage to lipoproteins and endothelial cells, leading to atherosclerosis; and 3) stimulating formation of neutrophil extracellular traps, resulting in vessel occlusion and thrombosis. Here we report a selective 2-thiouracil mechanism-based MPO inhibitor (PF-1355 [2-(6-(2,5-dimethoxyphenyl)-4-oxo-2-thioxo-3,4-dihydropyrimidin-1(2H)-yl)acetamide) and demonstrate that MPO is a critical mediator of vasculitis in mouse disease models. A pharmacokinetic/pharmacodynamic response model of PF-1355 exposure in relation with MPO activity was derived from mouse peritonitis. The contribution of MPO activity to vasculitis was then examined in an immune complex model of pulmonary disease. Oral administration of PF-1355 reduced plasma MPO activity, vascular edema, neutrophil recruitment, and elevated circulating cytokines. In a model of anti-glomerular basement membrane disease, formerly known as Goodpasture disease, albuminuria and chronic renal dysfunction were completely suppressed by PF-1355 treatment. This study shows that MPO activity is critical in driving immune complex vasculitis and provides confidence in testing the hypothesis that MPO inhibition will provide benefit in treating human vasculitic diseases.

Signalling pathways that control endothelial cell (EC) permeability, leukocyte adhesion and inflammation are pivotal for atherosclerosis initiation and progression. Here we demonstrate that the Sterile-20-like mitogen-activated protein kinase kinase kinase kinase 4 (MAP4K4), which has been implicated in inflammation, is abundantly expressed in ECs and in atherosclerotic plaques from mice and humans. On the basis of endothelial-specific MAP4K4 gene silencing and gene ablation experiments in Apoe−/− mice, we show that MAP4K4 in ECs markedly promotes Western diet-induced aortic macrophage accumulation and atherosclerotic plaque development. Treatment of Apoe−/− and Ldlr−/− mice with a selective small-molecule MAP4K4 inhibitor also markedly reduces atherosclerotic lesion area. MAP4K4 silencing in cultured ECs attenuates cell surface adhesion molecule expression while reducing nuclear localization and activity of NFκB, which is critical for promoting EC activation and atherosclerosis. Taken together, these results reveal that MAP4K4 is a key signalling node that promotes immune cell recruitment in atherosclerosis., Atherosclerosis is an inflammatory disease with limited therapeutic options. Here, the authors show that protein kinase MAP4K4 regulates vascular inflammation underlying atherosclerotic plaque development and that its inhibition prevents the disease and promotes lesion regression in mice, proposing a new atherosclerosis treatment.

Angiogenesis is regulated by both soluble growth factors and cellular interactions with the extracellular matrix (ECM). While cell adhesion via integrins has been shown to be required for angiogenesis, the effects of quantitative changes in cell adhesion and spreading against the ECM remain less clear. Here, we show that angiogenic sprouting in natural and engineered three-dimensional matrices exhibited a biphasic response, with peak sprouting when adhesion to the matrix was limited to intermediate levels. Examining changes in global gene expression to determine a genetic basis for this response, we demonstrate a vascular endothelial growth factor (VEGF)-induced upregulation of genes associated with vascular invasion and remodeling when cell adhesion was limited, whereas cells on highly adhesive surfaces upregulated genes associated with proliferation. To explore a mechanistic basis for this effect, we turned to focal adhesion kinase (FAK), a central player in adhesion signaling previously implicated in angiogenesis, and its homologue, proline-rich tyrosine kinase 2 (Pyk2). While FAK signaling had some impact, our results suggested that Pyk2 can regulate both gene expression and endothelial sprouting through its enhanced activation by VEGF in limited adhesion contexts. We also demonstrate decreased sprouting of tissue explants from Pyk2-null mice as compared to wild type mice as further confirmation of the role of Pyk2 in angiogenic sprouting. These results suggest a surprising finding that limited cell adhesion can enhance endothelial responsiveness to VEGF and demonstrate a novel role for Pyk2 in the adhesive regulation of angiogenesis.

This work addresses the link between selectivity and an unusual, folded conformation for the P-loop observed initially for MAP4K4 and subsequently for other kinases. Statistical and computational analyses of our crystal structure database demonstrate that inhibitors that induce the P-loop folded conformation tend to be more selective, especially if they take advantage of this specific conformation by interacting more favorably with a conserved Tyr or Phe residue from the P-loop.

The PYK2 tyrosine kinase is a negative regulator of bone formation, but aside from the requirement for PYK2 kinase activity there has been little progress toward understanding of the molecular mechanism involved in this function. To gain insight into the signaling pathways modulated by PYK2 we sought to identify PYK2 substrates. Challenges inherent to a quantitative phosphoproteomic analysis for non-receptor tyrosine kinases were overcome by employing an inducible PYK2 overexpression system in NIH3T3 cells in combination with a selective PYK2 inhibitor. The identification of a number of known PYK2 substrates and interacting partners validated the methodology. Results of the inducible cell system were extended to a cell model of osteogenesis, examining the effect of the PYK2 inhibitor on the phosphorylation state of targets identified in the phosphoproteomic study. Consistent with phosphoproteomic analysis, increased osteogenesis associated with a selective PYK2 inhibitor was accompanied by reduced phosphorylation of paxillin, Gab1 and p130Cas, along with reduction of phosphorylation levels of the Met activation loop. These results further confirmed the utility of the methodology and point to a previously unknown bi-directional activation pathway between PYK2 and Met.

Signaling by the B cell receptor (BCR) promotes integrin-mediated adhesion and cytoskeletal reorganization. This results in B cell spreading, which enhances the ability of B cells to bind antigens and become activated. Proline-rich tyrosine kinase (Pyk2) and focal adhesion kinase (FAK) are related cytoplasmic tyrosine kinases that regulate cell adhesion, cell morphology, and cell migration. In this report we show that BCR signaling and integrin signaling collaborate to induce the phosphorylation of Pyk2 and FAK on key tyrosine residues, a modification that increases the kinase activity of Pyk2 and FAK. Activation of the Rap GTPases is critical for BCR-induced integrin activation as well as for BCR- and integrin-induced reorganization of the actin cytoskeleton. We now show that Rap activation is essential for BCR-induced phosphorylation of Pyk2 and for integrin-induced phosphorylation of Pyk2 and FAK. Moreover Rap-dependent phosphorylation of Pyk2 and FAK required an intact actin cytoskeleton as well as actin dynamics, suggesting that Rap regulates Pyk2 and FAK via its effects on the actin cytoskeleton. Importantly B cell spreading induced by BCR/integrin co-stimulation or by integrin engagement was inhibited by short hairpin RNA-mediated knockdown of either Pyk2 or FAK expression and by treatment with PF-431396, a chemical inhibitor that blocks the kinase activities of both Pyk2 and FAK. Thus Pyk2 and FAK are downstream targets of the Rap GTPases that play a key role in regulating B cell morphology.

The synthesis, in vitro properties, and in vivo pharmacokinetics for a series of sulfoximine-substituted trifluoromethylpyrimidines as inhibitors of proline-rich tyrosine kinase, a target for the possible treatment of osteoporosis, are described. These compounds were prepared as surrogates of the corresponding sulfone compound 1. Sulfone 1 was an attractive PYK2 lead compound; however, subsequent studies determined this compound possessed high dofetilide binding, which is an early indicator of cardiovascular safety. Surprisingly, the corresponding sulfoximine analogs displayed significantly lower dofetilide binding, which, for N-methylsulfoximine (S)-14a, translated to lower activity in a patch clamp hERG K(+) ion channel screen. In addition, compound (S)-14a shows good oral exposure in a rat pharmacokinetic model.

As exemplified by the lead compound 2, octahydrophenanthrene-2,7-diol analogues exhibit the profile of a pathway-selective or "dissociated" agonist of the glucocorticoid receptor (GR), retaining the potent activity that glucocorticoids have for transrepression (as measured by inhibition of IL-1 induced MMP-13 expression) but showing an attenuated capacity for transactivation (as measured in an MMTV luciferase reporter assay). With the guidance of a homology model of the GR ligand binding domain, structural modifications to 2 were carried out that were successful in replacing the allyl and propynyl side chains with groups likely to be more chemically stable and less likely to produce toxic metabolites. Key to success was the introduction of an additional hydroxyl group onto the tricyclic carbon framework of the series.

Mitogen-activated protein kinase 4 (MAP4K4) regulates the MEK kinase cascade and is implicated in cytoskeletal rearrangement and migration; however, identifying MAP4K4 substrates has remained a challenge. To ascertain MAP4K4-dependent phosphorylation events, we combined phosphoproteomic studies of MAP4K4 inhibition with in vitro assessment of its kinase specificity. We identified 235 phosphosites affected by MAP4K4 inhibition in cells and found that pTP and pSP motifs were predominant among them. In contrast, in vitro assessment of kinase specificity showed that MAP4K4 favors a pTL motif. We showed that MAP4K4 directly phosphorylates and coimmunoprecipitates with FERM, RhoGEF, and pleckstrin domain-containing protein 1 (FARP1). MAP4K4 inhibition in SH-SY5Y cells increases neurite outgrowth, a process known to involve FARP1. As FARP1 and MAP4K4 both contribute to cytoskeletal rearrangement, the results suggest that MAP4K4 exerts some of its effects on the cytoskeleton via phosphorylation of FARP1.

The nuclear functions of NF-kappaB p50/RelA heterodimers are regulated in part by posttranslational modifications of its RelA subunit, including phosphorylation and acetylation. Acetylation at lysines 218, 221, and 310 differentially regulates RelA's DNA binding activity, assembly with IkappaBalpha, and transcriptional activity. However, it remains unclear whether the acetylation is regulated or simply due to stimulus-coupled nuclear translocation of NF-kappaB. Using anti-acetylated lysine 310 RelA antibodies, we detected p300-mediated acetylation of RelA in vitro and in vivo after stimulation of cells with tumor necrosis factor alpha (TNF-alpha). Coexpression of catalytically inactive mutants of the catalytic subunit of protein kinase A/mitogen- and stress-activated kinase 1 or IKK1/IKK2, which phosphorylate RelA on serine 276 or serine 536, respectively, sharply inhibited RelA acetylation on lysine 310. Furthermore, phosphorylation of RelA on serine 276 or serine 536 increased assembly of phospho-RelA with p300, which enhanced acetylation on lysine 310. Reconstitution of RelA-deficient murine embryonic fibroblasts with RelA S276A or RelA S536A decreased TNF-alpha-induced acetylation of lysine 310 and expression of the endogenous NF-kappaB-responsive E-selectin gene. These findings indicate that the acetylation of RelA at lysine 310 is importantly regulated by prior phosphorylation of serines 276 and 536. Such phosphorylated and acetylated forms of RelA display enhanced transcriptional activity.

Stretch of vascular smooth muscle stimulates growth and proliferation as well as contraction and expression of contractile/cytoskeletal proteins, all of which are also regulated by calcium‐dependent signals. We studied the role of the calcium‐ and integrin‐activated proline‐rich tyrosine kinase 2 (PYK2) in stretch‐induced responses of the rat portal vein loaded by a hanging weight ex vivo. PYK2 phosphorylation at Tyr‐402 was increased both by a 10‐min stretch and by organ culture with load over several days. Protein and DNA synthesis were reduced by the novel PYK2 inhibitor PF‐4594755 (0.5–1 μmol/L), while still sensitive to stretch. In 3‐day organ culture, PF‐4594755 caused maintained myogenic spontaneous activity but did not affect contraction in response to high‐K+ (60 mmol/L) or to α1‐adrenergic stimulation by cirazoline. Basal and stretch‐induced PYK2 phosphorylation in culture were inhibited by PF‐4594755, closely mimicking inhibition of non‐voltage‐dependent calcium influx by 2‐APB (30 μmol/L). In contrast, the L‐type calcium channel blocker, nifedipine (1 μmol/L) eliminated stretch‐induced but not basal PYK2 phosphorylation. Stretch‐induced Akt and ERK1/2 phosphorylation was eliminated by PF‐4594755. PYK2 inhibition had no effect on mRNA expression of several smooth muscle markers, and stretch‐sensitive SM22α synthesis was preserved. Culture of portal vein with the Ang II inhibitor losartan (1 μmol/L) eliminated stretch sensitivity of PYK2 and Akt phosphorylation, but did not affect mRNA expression of smooth muscle markers. The results suggest that PYK2 signaling functionally distinguishes effects of voltage‐ and non‐voltage‐dependent calcium influx. A small‐molecule inhibitor of PYK2 reduces growth and DNA synthesis but does not affect contractile differentiation of vascular smooth muscle., We studied the role of the calcium‐ and integrin‐activated proline‐rich tyrosine kinase 2 (PYK2) in stretch‐induced responses of the rat portal ex vivo. PYK2 phosphorylation at Tyr‐402 was increased both by a 10‐min stretch and by organ culture under stretch for 3 days. Protein and DNA synthesis were reduced by the novel PYK2 inhibitor PF‐4594755 (0.5–1 μmol/L), but contractile differentiation was not affected. Basal and stretch‐induced PYK2 phosphorylation in culture were inhibited by PF‐4594755, closely mimicking inhibition of non‐voltage‐dependent calcium influx by 2‐APB (30 μmol/L). In contrast, the L‐type calcium channel blocker, nifedipine (1 μmol/L) eliminated stretch‐induced but not basal PYK2 phosphorylation. The results suggest that PYK2 signaling functionally distinguishes effects of voltage‐ and non‐voltage‐dependent calcium influx.

Exposure of mammalian cells to hypoxia, radiation and certain chemotherapeutic agents promotes cell cycle arrest and/or apoptosis. Activation of p53 responsive genes is believed to play an important role in mediating such responses. In this study we identified a novel gene, PA26, which maps to chromosome 6q21 and encodes at least three transcript isoforms, of which two are differentially induced by genotoxic stress (UV, gamma-irradiation and cytotoxic drugs) in a p53-dependent manner. A functional p53-responsive element was identified in the second intron of the PA26 gene, in consistance with a mechanism of transcriptional induction of the PA26 gene by p53. No clues to its functions were revealed by sequence analysis, although pronounced negative regulation by serum factors argues for a potential role of PA26 in growth regulation. Immunological analysis suggests that PA26 protein(s) is localized to the cell nucleus. Our results suggest that the PA26 gene is a novel p53 target gene with properties common to the GADD family of growth arrest and DNA damage-inducible stress-response genes, and, thus, a potential novel regulator of cellular growth.

Thionamides such as propylthiouracil (PTU) and methimazole (MMI) have been used for more than 50 years to treat the more common causes of thyrotoxicosis/hyperthyroidism such as Graves’ disease. Serious adverse effects associated with thionamides in humans include idiosyncratic liver damage, agranulocytosis, aplastic anemia, and vasculitis. Both prospective and retrospective clinical studies with these drugs have failed to identify predictive biomarker for these adverse effects. To assess whether rat is a good model for predicting drug-related adverse events in the liver and in the bone marrow, we conducted a comprehensive study in male rats with multiple doses of PTU and MMI. As expected, euthyroid animals became hypothyroid along with several secondary changes associated with hypothyroidism. There were slight reductions in red blood cell parameters along with some marginal effects on the bone marrow elements. However, there was no evidence of significant neutropenia and liver injury in both PTU-treated and MMI-treated cohorts. MMI-related effects were noted in the seminiferous tubules of the testes. Overall, 1-month daily treatment of euthyroid rats with PTU or MMI resulted in hypothyroidism, minor bone marrow effects, and several secondary effects associated with hypothyroidism, but without any evidence of adverse effects reported in humans including liver injury and agranulocytosis.

Previous drug discovery efforts identified classical PYK2 kinase inhibitors such as 2 and 3 that possess selectivity for PYK2 over its intra-family isoform FAK. Efforts to identify more kinome-selective chemical matter that stabilize a DFG-out conformation of the enzyme are described herein. Two sub-series of PYK2 inhibitors, an indole carboxamide-urea and a pyrazole-urea have been identified and found to have different binding interactions with the hinge region of PYK2. These leads proved to be more selective than the original classical inhibitors.

The ability of the p53 protein to act as a sequence-specific transcriptional activator suggests that genes induced by p53 may encode critical mediators of p53 tumor suppression. Using a tetracycline-regulated p53 expression system and cDNA library subtraction procedure, we identified several p53-induced gene transcripts in human Saos-2 osteosarcoma cells that are novel on the basis of their size, regulation, and low abundance. Wild-type p53-dependent induction of these transcripts was observed in cells that are growth arrested by p53, as well as in cells that undergo apoptosis upon expression of an inducible wild-type p53 transgene. These results show that p53 activates the expression of numerous response genes and suggest that multiple effectors may play a role in mediating cellular functions of p53.

B-lymphocytes produce protective antibodies but also contribute to autoimmunity. In particular, marginal zone (MZ) B cells recognize both microbial components and self-antigens. B cell trafficking is critical for B cell activation and is controlled by chemoattactants such as CXCL13 and sphingosine 1-phosphate (S1P). The related tyrosine kinases focal adhesion kinase (FAK) and proline-rich tyrosine kinase (Pyk2) regulate cell migration and adhesion but their roles in B cells are not fully understood. Using a novel Pyk2-selective inhibitor described herein (PF-719), as well as a FAK-selective inhibitor, we show that both Pyk2 and FAK are important for CXCL13- and S1P-induced migration of B-2 cells and MZ B cells. In contrast, LFA-1-mediated adhesion required only Pyk2 whereas activation of the Akt pro-survival kinase required FAK but not Pyk2. Thus Pyk2 and FAK mediate critical processes in B cells and these inhibitors can be used to further elucidate their functions in B cells.

Greater than 120 genes are up-regulated in Xenopus laevis limb buds within the first 24 h after induction of metamorphosis by thyroid hormone. Fourteen of these have been isolated and characterized. Four encode heat shock proteins. The identified regulated genes have in common a relatedness with cell growth as exemplified by the serum response of quiescent fibroblasts. Some of the genes respond directly to hormone. However, the majority appear to be secondary response genes judging from their delayed kinetics and cycloheximide sensitivity. This indicates that there are at least two periods of gene expression change in the first 24 h. DNA replication increases in the second 24 h. Growth of the limb bud occurs for several days before the genes that characterize terminal differentiation of its cell types are up-regulated.

The synthesis and SAR for a series of diaminopyrimidines as PYK2 inhibitors are described. Using a combination of library and traditional medicinal chemistry techniques, a FAK-selective chemical series was transformed into compounds possessing good PYK2 potency and 10- to 20-fold selectivity against FAK. Subsequent studies found that the majority of the compounds were positive in a reactive metabolite assay, an indicator for potential toxicological liabilities. Based on the proposed mechanism for bioactivation, as well as a combination of structure-based drug design and traditional medicinal chemistry techniques, a follow-up series of PYK2 inhibitors was identified that maintained PYK2 potency, FAK selectivity and HLM stability, yet were negative in the RM assay.

Bone is accrued and maintained primarily through the coupled actions of bone-forming osteoblasts and bone-resorbing osteoclasts. Cumulative in vitro studies indicated that proline-rich tyrosine kinase 2 (PYK2) is a positive mediator of osteoclast function and activity. However, our investigation of PYK2−/− mice did not reveal evidence supporting an essential function for PYK2 in osteoclasts either in vivo or in culture. We find that PYK2−/− mice have high bone mass resulting from an unexpected increase in bone formation. Consistent with the in vivo findings, mouse bone marrow cultures show that PYK2 deficiency enhances differentiation and activity of osteoprogenitor cells, as does expressing a PYK2-specific short hairpin RNA or dominantly interfering proteins in human mesenchymal stem cells. Furthermore, the daily administration of a small-molecule PYK2 inhibitor increases bone formation and protects against bone loss in ovariectomized rats, an established preclinical model of postmenopausal osteoporosis. In summary, we find that PYK2 regulates the differentiation of early osteoprogenitor cells across species and that inhibitors of the PYK2 have potential as a bone anabolic approach for the treatment of osteoporosis.

Synthetic glucocorticoids are among the most effective anti-inflammatory drugs available. The activity of this drug class is mediated by the glucocorticoid receptor, a nuclear steroid receptor whose endogenous ligand is the adrenal hormone cortisol. Chronic glucocorticoid treatment is accompanied by serious side-effects, reflecting the symptoms of cortisol excess seen in Cushing's syndrome patients. During the past 50 years advances to this drug class have been limited largely to reducing systemic exposure through inhaled delivery and increasing glucocorticoid receptor selectivity. However, a safer oral drug for the treatment of conditions such as rheumatoid arthritis, inflammatory bowel disease, and transplant rejection, still represents a major unmet medical need. Over the past 20 years, mechanisms of glucocorticoid receptor action have been elucidated. Before the gene was even cloned, the glucocorticoid receptor was known to be a ligand-induced DNA binding protein. Identification of hormone response elements in the promoters of metabolic target genes in the liver provided a model for its broad activities. It was since revealed that much of its anti-inflammatory activity is not DNA-dependent after all, but instead is the result of a complex set of protein-protein interactions which lead to transcriptional inhibition of pro-inflammatory targets. Thus, a glucocorticoid receptor ligand that dissociates the DNA binding and protein interaction mediated activities is expected to show improved safety. This review will focus on the scientific advances, which impact the development of this hypothesis and will present a survey of current preclinical drug candidates employing this strategy.

Objective : The Sox9 transcription factor has emerged as an important determinant of chondrocyte differentiation, including the regulation of type II collagen (Col2) and aggrecan gene expression. We sought to identify a human cell line model that conserves the Sox9 regulatory pathways identified in the mouse. Design : The SW1353 chondrosarcoma cell line was considered to be a candidate for Sox9 studies. The activity of a Sox9 regulated Col2a1 enhancer reporter gene was analyzed in response to treating cells with known regulators of murine Sox9 expression/activity. The effect of treatment on expression of the endogenous Sox9 gene was analyzed by real-time PCR and Western blot. Results : Col2 enhancer activity was stimulated by fibroblast growth factors (FGF-1 and -2) and repressed by inflammatory cytokines (IL-1β and TNFα) in SW1353 cells. These effects correlated with changes in Sox9 mRNA and protein levels. In addition, FGF-9 was shown to stimulate enhancer activity and Sox9 expression. Cotreatment studies demonstrated that FGFs functionally antagonize the cytokine-mediated repression of Sox9 expression and Col2 enhancer activity. Conclusions : SW1353 cells represent a useful human cell model as they conserve many Sox9 signaling pathways previously demonstrated in mouse chondrocytes. We identify FGF-9 as a particularly potent Sox9 agonist. The antagonism between FGFs and cytokines on Sox9 expression and Col2 enhancer activity suggests that Sox9 integrates the opposing activities of FGFs and cytokines. We also find that SW1353 cells respond to very low doses of IL-1 with Col2 enhancer activation, while increasing doses lead to repression.

The loss or functional inactivation of tumor suppressor genes appears to be one of the most fundamental genetic mechanisms of tumorigenesis, and rational insights into the signaling pathways of tumor suppressor genes have emerged as a successful strategy of identifying novel drug discovery targets downstream of the tumor suppressor protein itself. Elucidation of novel pathways downstream of p53 have established a link between this important tumor suppressor gene and the insulin-like growth factor-1 receptor (IGF-1r), either via direct regulation of IGF-1 receptor levels, or modulation of IGFs via transactivation of the insulin-like growth factor-binding protein 3 (IGF-BP3) gene. Binding of IGF-BP3 to IGFs inhibits both their mitogenic and cell survival functions, highlighting a novel pathway whereby p53 may regulate apoptosis in tumor cells.

Heterotrimeric G proteins transduce multiple growth-factor-receptor-initiated and intracellular signals that may lead to activation of the mitogen-activated or stress-activated protein kinases. Herein we report on the identification of a novel p53 target gene (A28-RGS14) that is induced in response to genotoxic stress and encodes a novel member of a family of regulators of G protein signaling (RGS) proteins with proposed GTPase-activating protein activity. Overexpression of A28-RGS14p protein inhibits both Gi- and Gq-coupled growth-factor-receptor-mediated activation of the mitogen-activated protein kinase signaling pathway in mammalian cells. Thus, through the induction of A28-RGS14, p53 may regulate cellular sensitivity to growth and/or survival factors acting through G protein-coupled receptor pathways.

TRANSCRIPTIONAL activation of target genes represents an important component of the tumour-suppressor function of p53 and provides a functional link between p53 and various growth-regulatory processes, including cell cycle progression (p21/WAF1)1a¤-3, DNA repair (GADD45)4 and apoptosis (bax)5. Here we use a differential cloning approach to identify the gene encoding insulin-like growth factor binding protein 3 (IGF-BP3) as a novel p53-regulated target gene. Induction of IGF-BP3 gene expression by wild-type but not mutant p53 is associated with enhanced secretion of an active form of IGF-BP3 capable of inhibiting mitogenic signalling by the insulin-like growth factor IGF-1. Our results indicate that IGF-BP3 may link p53 to potential novel autocrine/paracrine signalling pathways and to processes regulated by or dependent on IGF(s), such as cellular growth, transformation and survival.

The cDNAs encoding Xenopus laevis prolactin (PRL) and the alpha and beta subunits of thyroid-stimulating hormone (TSH alpha and TSH beta, respectively) have been cloned from a pituitary library. Results of developmental RNA blot analysis contradict the long-held biological role for PRL as a juvenilizing hormone in amphibia. The pituitary gland of a premetamorphic tadpole expresses PRL mRNA at very low levels. The abundance of PRL mRNA increases late in metamorphosis as a response to thyroid hormone (TH), suggesting that PRL is more likely to have a function in the frog than in the tadpole. TSH alpha and -beta mRNA levels increase through prometamorphosis; this rise does not appear to be regulated directly by TH. At climax, both TH and TSH mRNA levels drop. The sequential morphological changes that characterize prometamorphosis depend upon the gradual increase of endogenous TH, which peaks at climax. This increase in TH in turn depends upon the lack of a traditional thyroid-pituitary negative-feedback loop throughout prometamorphosis.

Highly purified RNA polymerase II was found to be able to weakly recognize the initiator (Inr) present in the adenovirus IVa2 and major late promoters. The association of RNA polymerase II with the Inr was enhanced by the general transcription factors. The Inr was capable of directing the formation of a DNA-protein complex. Transcription competent complexes on the adenovirus major late and IVa2 promoters appear to be formed by alternative pathways mediated through the Inr and/or "TATA" motif. The presence of both motifs, however, is required for efficient transcription utilizing a discrete start site. Complexes formed at either site required transcription factor TFIID, the TATA binding protein. Consistent with this observation, a TFIID requirement was demonstrated for transcription from a mutant adenovirus major late promoter construct lacking a functional TATA motif.

The isolation of a cellular factor that was specifically required for transcription from the promoter of the adenovirus early gene iv, an EIa-activated promoter, is described. This factor (EivF) was purified from HeLa cells using a functional transcription assay and identified as a 72,000- to 65,000-dalton protein. DNase I footprinting experiments demonstrated that purified EivF bound to the sequence 5'-GT(G/T)ACGT-3' present two times upstream of the Eiv TATA box. Nuclear extracts prepared from HeLa cells contained more than one factor capable of binding to the EivF recognition site. Previous studies have indicated that a sequence similar to the EivF-binding site was recognized by a 43,000-dalton protein and participated in the cAMP response of the somatostatin promoter. The purified and transcriptionally active EivF also bound to DNA sequence elements present in the somatostatin and alpha-gonadotropin promoters shown previously to be responsive to cAMP.