A Conformation Selective Mode of Inhibiting SRC Improves Drug Efficacy and Tolerability.

Despite the approval of several multikinase inhibitors that target SRC and the overwhelming evidence of the role of SRC in the progression and resistance mechanisms of many solid malignancies, inhibition of its kinase activity has thus far failed to improve patient outcomes. Here we report the small molecule eCF506 locks SRC in its native inactive conformation, thereby inhibiting both enzymatic and scaffolding functions that prevent phosphorylation and complex formation with its partner FAK. This mechanism of action resulted in highly potent and selective pathway inhibition in culture and in vivo. Treatment with eCF506 resulted in increased antitumor efficacy and tolerability in syngeneic murine cancer models, demonstrating significant therapeutic advantages over existing SRC/ABL inhibitors. Therefore, this mode of inhibiting SRC could lead to improved treatment of SRC-associated disorders. SIGNIFICANCE: Small molecule-mediated inhibition of SRC impairing both catalytic and scaffolding functions confers increased anticancer properties and tolerability compared with other SRC/ABL inhibitors.

Alkali Metal Adducts of an Iron(0) Complex and Their Synergistic FLP-Type Activation of Aliphatic C-X Bonds.

We report the formation and full characterization of weak adducts between Li+ and Na+ cations and a neutral iron(0) complex, [Fe(CO)3(PMe3)2] (1), supported by weakly coordinating [BArF20] anions, [1·M][BArF20] (M = Li, Na). The adducts are found to synergistically activate aliphatic C-X bonds (X = F, Cl, Br, I, OMs, OTf), leading to the formation of iron(II) organyl compounds of the type [FeR(CO)3(PMe3)2][BArF20], of which several were isolated and fully characterized. Stoichiometric reactions with the resulting iron(II) organyl compounds show that this system can be utilized for homocoupling and cross-coupling reactions and the formation of new C-E bonds (E = C, H, O, N, S). Further, we utilize [1·M][BArF20] as a catalyst in a simple hydrodehalogenation reaction under mild conditions to showcase its potential use in catalytic reactions. Finally, the mechanism of activation is probed using DFT and kinetic experiments that reveal that the alkali metal and iron(0) center cooperate to cleave C-X via a mechanism closely related to intramolecular FLP activation.

Sublingual immunotherapy vs placebo in the management of grass pollen-induced allergic rhinitis in adults: A systematic review and meta-analysis.

INTRODUCTION: Allergic rhinitis (AR) is a common inflammatory condition of the nasal mucosa affecting approximately 20% of the population worldwide. Current therapies include intranasal antihistamines, corticosteroids, subcutaneous and sublingual immunotherapy (SLIT). This review and meta-analysis assess the efficacy of SLIT in the management of grass pollen-induced AR in adults. METHODS: Ovid EMBASE, Ovid EBM Reviews, Cochrane Central Register of Controlled Trials, Ovid MedLine and PubMed were searched using the following terms: 'sublingual immunotherapy', 'SLIT', 'rhinitis', 'allergic rhinitis', 'rhinosinusitis' and 'rhino-conjunctivitis'. All included studies were double-blind, placebo-controlled and randomised trials. Primary outcome was symptom score and secondary outcome included quality of life and safety profile. Meta-analysis of symptom improvement was carried out. RESULTS: Six studies were identified with 979 subjects randomly allocated to SLIT and 992 to a placebo control. All studies reported an improvement in symptoms with SLIT, with five reaching statistical significance (P < .05). Four studies reported statistically significant improvement in quality of life (P < .05). Oral pruritus was the most common adverse event reported. The overall risk of bias was high in 50% of the studies. CONCLUSIONS: Sublingual immunotherapy was a safe and effective treatment for grass pollen-induced AR in adults, and therefore, consideration should be given to its use for moderate-to-severe disease in the UK-wide population.

Zero valent iron complexes as base partners in frustrated Lewis pair chemistry.

The prototypical iron(0) complex [Fe(CO)3(PMe3)2] (1) forms a frustrated Lewis pair (FLP) with B(C6F5)3 (BCF). In this FLP, the iron complex acts as the Lewis base partner, and the borane as the Lewis acid partner. This FLP is able to cleave H-H, H-Cl, H-O and H-S bonds in H2, HCl, H2O and HSPh. The FLP 1/BCF is shown to catalyze the hydrogenation of alkenes under mild conditions, where terminal alkenes are preferentially reduced. Mechanistic studies using D2 gas suggest that a branched intermediate in an alkene insertion cycle or an ionic cycle is favored for this catalytic reaction.

Pyrazolopyrimide library screening in glioma cells discovers highly potent antiproliferative leads that target the PI3K/mTOR pathway.

The search for novel targeted inhibitors active on glioblastoma multiforme is crucial to develop new treatments for this unmet clinical need. Herein, we report the results from a screening campaign against glioma cell lines using a proprietary library of 100 structurally-related pyrazolopyrimidines. Data analysis identified a family of compounds featuring a 2-amino-1,3-benzoxazole moiety (eCF309 to eCF334) for their antiproliferative properties in the nM range. These results were validated in patient-derived glioma cells. Available kinase inhibition profile pointed to blockade of the PI3K/mTOR pathway as being responsible for the potent activity of the hits. Combination studies demonstrated synergistic activity by inhibiting both PI3Ks and mTOR with selective inhibitors. Based on the structure activity relationships identified in this study, five new derivatives were synthesized and tested, which exhibited potent activity against glioma cells but not superior to the dual PI3K/mTOR inhibitor and lead compound of the screening eCF324.

Stable Carbocation Generated via 2,5-Cyclohexadien-1-one Protonation.

Protonation of a substituted cyclohexadien-1-one (1) leads to the generation of carbocation [3]+, capable of effecting hydride abstraction and oxidation reactions. The molecular structure of [3]+ shows it to be structurally similar to [(p-MeO-C6H4)Ph2C]+. The ability to easily access [3]+ from stable and available precursors, such as 1 and commercially available acids, may allow a wider application of the growing number of trityl-based reactions in organic syntheses.

Rapid Discovery and Structure-Activity Relationships of Pyrazolopyrimidines That Potently Suppress Breast Cancer Cell Growth via SRC Kinase Inhibition with Exceptional Selectivity over ABL Kinase.

Novel pyrazolopyrimidines displaying high potency and selectivity toward SRC family kinases have been developed by combining ligand-based design and phenotypic screening in an iterative manner. Compounds were derived from the promiscuous kinase inhibitor PP1 to search for analogs that could potentially target a broad spectrum of kinases involved in cancer. Phenotypic screening against MCF7 mammary adenocarcinoma cells generated target-agnostic structure-activity relationships that biased subsequent designs toward breast cancer treatment rather than to a particular target. This strategy led to the discovery of two potent antiproliferative leads with phenotypically distinct anticancer mode of actions. Kinase profiling and further optimization resulted in eCF506, the first small molecule with subnanomolar IC50 for SRC that requires 3 orders of magnitude greater concentration to inhibit ABL. eCF506 exhibits excellent water solubility, an optimal DMPK profile and oral bioavailability, halts SRC-associated neuromast migration in zebrafish embryos without inducing life-threatening heart defects, and inhibits SRC phosphorylation in tumor xenografts in mice.

Identification of novel pathways linking epithelial-to-mesenchymal transition with resistance to HER2-targeted therapy.

Resistance to human epidermal growth factor receptor 2 (HER2)-targeted therapies in the treatment of HER2-positive breast cancer is a major clinical problem. To identify pathways linked to resistance, we generated HER2-positive breast cancer cell lines which are resistant to either lapatinib or AZD8931, two pan-HER family kinase inhibitors. Resistance was HER2 independent and was associated with epithelial-to-mesenchymal transition (EMT), resulting in increased proliferation and migration of the resistant cells. Using a global proteomics approach, we identified a novel set of EMT-associated proteins linked to HER2-independent resistance. We demonstrate that a subset of these EMT-associated genes is predictive of prognosis within the ERBB2 subtype of human breast cancers. Furthermore, targeting the EMT-associated kinases Src and Axl potently inhibited proliferation of the resistant cells, and inhibitors to these kinases may provide additional options for the treatment of HER2-independent resistance in tumors.

Protonolysis and thermolysis reactions of functionalised NHC-carbene boranes and borates.

A set of ß-ketoimidazolium and ß-ketoimidazolinium salts of the general formula [R(1)C(O)CH2{CH[NCR(3)CR(3)N(R(2))]}]X (R(1) = (t)Bu, naphth; R(2) = (i)Pr, Mes, (t)Bu; R(3) = H, Me, (H)2; X = Cl, Br) show contrasting reactivity with superhydride bases MHBEt3; two are reduced to chiral ß-alcohol carbene-boranes R(1)CH(OH)CH2{C(BEt3)[NCR(3)CR(3)N(R(2))]} 2 (R(1) = (t)Bu; R(2) = (i)Pr, Mes; R(3) = H), two with bulky R(2) substituents are reduced to chiral ß-borate imidazolium salts [R(1)CH(OBEt3)CH2{CH[NCR(3)CR(3)N(R(2))]}]X 3 (R(1) = (t)Bu, naphth; R(2) = Mes, (t)Bu; R(3) = H, Me; X = Cl, Br), and the two saturated heterocycle derivatives remain unreduced but form carbene-borane adducts R(1)C(O)CH2{C(BEt3)[NCR(3)CR(3)N(R(2))]} 4 (R(1) = (t)Bu, naphth; R(2) = Mes; R(3) = (H)2). Heating solutions of the imidazolium borates 3 results in the elimination of ethane, in the first example of organic borates functioning as Brønsted bases and forming carbene boranes R(1)CH(OBEt2)CH2{C[NCR(3)CR(3)N(R(2))]} 5 (R(1) = naphth; R(2) = Mes; R(3) = Me). The 'abnormal' carbene borane of the form 2 R(1)CH(OH)CH2{CH[NC(BEt3)CR(3)N(R(2))]} (R(1) = (t)Bu; R(2) = (t)Bu; R(3) = H), is also accessible by thermolysis of 3, suggesting that the carbene-borane alcohol is a more thermodynamically stable combination than the zwitterionic imidazolium borate. High-temperature thermolysis also can result in complete cleavage of the alcohol arm, eliminating tert-butyloxirane and forming the B-N bound imidazolium borate 7. The strong dependence of reaction products on the steric and electronic properties of each imidazole precursor molecule is discussed.

N-alkynyl derivatives of 5-fluorouracil: susceptibility to palladium-mediated dealkylation and toxigenicity in cancer cell culture.

Palladium-activated prodrug therapy is an experimental therapeutic approach that relies on the unique chemical properties and biocompatibility of heterogeneous palladium catalysis to enable the spatially-controlled in vivo conversion of a biochemically-stable prodrug into its active form. This strategy, which would allow inducing local activation of systemically administered drug precursors by mediation of an implantable activating device made of Pd(0), has been proposed by our group as a way to reach therapeutic levels of the active drug in the affected tissue/organ while reducing its systemic toxicity. In the seminal study of such an approach, we reported that propargylation of the N1 position of 5-fluorouracil suppressed the drug's cytotoxic properties, showed high stability in cell culture and facilitated the bioorthogonal restoration of the drug's pharmacological activity in the presence of extracellular Pd(0)-functionalized resins. To provide additional insight on the properties of this system, we have investigated different N1-alkynyl derivatives of 5-fluorouracil and shown that the presence of substituents near the triple bond influence negatively on its sensitivity to palladium catalysis under biocompatible conditions. Comparative studies of the N1- vs. the N3-propargyl derivatives of 5-fluorouracil revealed that masking each or both positions equally led to inactive derivatives (>200-fold reduction of cytotoxicity relative to the unmodified drug), whereas the depropargylation process occurred faster at the N1 position than at the N3, thus resulting in greater toxigenic properties in cancer cell culture.

Development and bioorthogonal activation of palladium-labile prodrugs of gemcitabine.

Bioorthogonal chemistry has become one of the main driving forces in current chemical biology, inspiring the search for novel biocompatible chemospecific reactions for the past decade. Alongside the well-established labeling strategies that originated the bioorthogonal paradigm, we have recently proposed the use of heterogeneous palladium chemistry and bioorthogonal Pd(0)-labile prodrugs to develop spatially targeted therapies. Herein, we report the generation of biologically inert precursors of cytotoxic gemcitabine by introducing Pd(0)-cleavable groups in positions that are mechanistically relevant for gemcitabine's pharmacological activity. Cell viability studies in pancreatic cancer cells showed that carbamate functionalization of the 4-amino group of gemcitabine significantly reduced (>23-fold) the prodrugs' cytotoxicity. The N-propargyloxycarbonyl (N-Poc) promoiety displayed the highest sensitivity to heterogeneous palladium catalysis under biocompatible conditions, with a reaction half-life of less than 6 h. Zebrafish studies with allyl, propargyl, and benzyl carbamate-protected rhodamines confirmed N-Poc as the most suitable masking group for implementing in vivo bioorthogonal organometallic chemistry.

Extracellular palladium-catalysed dealkylation of 5-fluoro-1-propargyl-uracil as a bioorthogonally activated prodrug approach.

A bioorthogonal organometallic reaction is a biocompatible transformation undergone by a synthetic material exclusively through the mediation of a non-biotic metal source; a selective process used to label biomolecules and activate probes in biological environs. Here we report the in vitro bioorthogonal generation of 5-fluorouracil from a biologically inert precursor by heterogeneous Pd(0) catalysis. Although independently harmless, combined treatment of 5-fluoro-1-propargyl-uracil and Pd(0)-functionalized resins exhibits comparable antiproliferative properties to the unmodified drug in colorectal and pancreatic cancer cells. Live-cell imaging and immunoassay studies demonstrate that the cytotoxic activity of the prodrug/Pd(0)-resin combination is due to the in situ generation of 5-fluorouracil. Pd(0)-resins can be carefully implanted in the yolk sac of zebrafish embryos and display excellent biocompatibility and local catalytic activity. The in vitro efficacy shown by this masking/activation strategy underlines its potential to develop a bioorthogonally activated prodrug approach and supports further in vivo investigations.