Alessandro Boezio

Discovery and Optimization of Triazolopyridazines as Potent and Selective Inhibitors of the c-Met Kinase.

Tumorigenesis is a multistep process in which oncogenes play a key role in tumor formation, growth, and maintenance. MET was discovered as an oncogene that is activated by its ligand, hepatocyte growth factor. Deregulated signaling in the c-Met pathway has been observed in multiple tumor types. Herein we report the discovery of potent and selective triazolopyridazine small molecules that inhibit c-Met activity.

Pharmacological effects of nonselective and subtype-selective nicotinic acetylcholine receptor agonists in animal models of persistent pain.

&NA; Nicotinic acetylcholine receptors (nAChRs) are longstanding targets for a next generation of pain therapeutics, but the nAChR subtypes that govern analgesia remain unknown. We tested a series of nicotinic agonists, including many molecules used or tried clinically, on a panel of cloned neuronal nAChRs for potency and selectivity using patch‐clamp electrophysiology and a live cell‐based fluorescence assay. Nonselective nicotinic agonists as well as compounds selective either for &agr;4&bgr;2 or for &agr;7 nAChRs were then tested in the formalin and complete Freunds adjuvant models of pain. Nonselective nAChR agonists ABT‐594 and varenicline were effective analgesics. By contrast, the selective &agr;4&bgr;2 agonist ispronicline and a novel &agr;4&bgr;2‐selective potentiator did not appear to produce analgesia in either model. &agr;7‐selective agonists reduced the pain‐related endpoint, but the effect could be ascribed to nonspecific reduction of movement rather than to analgesia. Neither selective nor nonselective &agr;7 nicotinic agonists affected the release of pro‐inflammatory cytokines in response to antigen challenge. Electrophysiological recordings from spinal cord slice showed a strong nicotine‐induced increase in inhibitory synaptic transmission that was mediated partially by &agr;4&bgr;2 and only minimally by &agr;7 subtypes. Taken with previous studies, the results suggest that agonism of &agr;4&bgr;2 nAChRs is necessary but not sufficient to produce analgesia, and that the spinal cord is a key site where the molecular action of nAChRs produces analgesia.

Structure-Based Design of Novel Class II c-Met Inhibitors: 2. SAR and Kinase Selectivity Profiles of the Pyrazolone Series

As part of our effort toward developing an effective therapeutic agent for c-Met-dependent tumors, a pyrazolone-based class II c-Met inhibitor, N-(4-((6,7-dimethoxyquinolin-4-yl)oxy)-3-fluorophenyl)-1,5-dimethyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazole-4-carboxamide (1), was identified. Knowledge of the binding mode of this molecule in both c-Met and VEGFR-2 proteins led to a novel strategy for designing more selective analogues of 1. Along with detailed SAR information, we demonstrate that the low kinase selectivity associated with class II c-Met inhibitors can be improved significantly. This work resulted in the discovery of potent c-Met inhibitors with improved selectivity profiles over VEGFR-2 and IGF-1R that could serve as useful tools to probe the relationship between kinase selectivity and in vivo efficacy in tumor xenograft models. Compound 59e (AMG 458) was ultimately advanced into preclinical safety studies.

Discovery and optimization of potent and selective triazolopyridazine series of c-Met inhibitors

Deregulation of the receptor tyrosine kinase c-Met has been implicated in several human cancers and is an attractive target for small molecule drug discovery. We previously showed that O-linked triazolopyridazines can be potent inhibitors of c-Met. Herein, we report the discovery of a related series of N-linked triazolopyridazines which demonstrate nanomolar inhibition of c-Met kinase activity and display improved pharmacodynamic profiles. Specifically, the potent time-dependent inhibition of cytochrome P450 associated with the O-linked triazolopyridazines has been eliminated within this novel series of inhibitors. N-linked triazolopyridazine 24 exhibited favorable pharmacokinetics and displayed potent inhibition of HGF-mediated c-Met phosphorylation in a mouse liver PD model. Once-daily oral administration of 24 for 22days showed significant tumor growth inhibition in an NIH-3T3/TPR-Met xenograft mouse efficacy model.

Discovery and optimization of substituted piperidines as potent, selective, CNS-penetrant α4β2 nicotinic acetylcholine receptor potentiators

The discovery of a series of small molecule alpha4beta2 nAChR potentiators is reported. The structure-activity relationship leads to potent compounds selective against nAChRs including alpha3beta2 and alpha3beta4 and optimized for CNS penetrance. Compounds increased currents through recombinant alpha4beta2 nAChRs, yet did not compete for binding with the orthosteric ligand cytisine. High potency and efficacy on the rat channel combined with good PK properties will allow testing of the alpha4beta2 potentiator mechanism in animal models of disease.

Chemical Reactivity of Methoxy 4-O-Aryl Quinolines: Identification of Glutathione Displacement Products in Vitro and in Vivo

AMG 458 {1-(2-hydroxy-2-methylpropyl)-N-[5-(7-methoxyquinolin-4-yloxy)pyridin-2-yl]-5-methyl-3-oxo-2-phenyl-2,3-dihydro-1H-pyrazole-4-carboxamide} is a potent, selective inhibitor of c-Met, a receptor tyrosine kinase that is often deregulated in cancer. AMG 458 was observed to bind covalently to liver microsomal proteins from rats and humans in the absence of NADPH. When [(14)C]AMG 458 was incubated with liver microsomes in the presence of glutathione and N-acetyl cysteine, thioether adducts were detected by radiochromatography and LC/MS/MS analysis. These adducts were also formed upon incubation of AMG 458 with glutathione and N-acetyl cysteine in buffers at pH 7.4. In vivo, the thioether adducts were detected in bile and urine of bile duct-cannulated rats dosed with [(14)C]AMG 458. The two adducts were isolated, and their structures were determined by MS/MS and NMR analysis. The identified structures resulted from a thiol displacement reaction to yield a quinoline thioether structure and the corresponding hydroxyaryl moiety. The insights gained from elucidating the mechanism of adduct formation led to the design of AMG 458 analogues that exhibited eliminated or reduced glutathione adduct formation in vitro and in vivo.

Discovery of triazine-benzimidazoles as selective inhibitors of mTOR.

mTOR is part of the PI3K/AKT pathway and is a central regulator of cell growth and survival. Since many cancers display mutations linked to the mTOR signaling pathway, mTOR has emerged as an important target for oncology therapy. Herein, we report the discovery of triazine benzimidazole inhibitors that inhibit mTOR kinase activity with up to 200-fold selectivity over the structurally homologous kinase PI3Kα. When tested in a panel of cancer cell lines displaying various mutations, a selective inhibitor from this series inhibited cellular proliferation with a mean IC(50) of 0.41 μM. Lead compound 42 demonstrated up to 83% inhibition of mTOR substrate phosphorylation in a murine pharmacodynamic model.

Discovery and optimization of potent and selective imidazopyridine and imidazopyridazine mTOR inhibitors

mTOR is a critical regulator of cellular signaling downstream of multiple growth factors. The mTOR/PI3K/AKT pathway is frequently mutated in human cancers and is thus an important oncology target. Herein we report the evolution of our program to discover ATP-competitive mTOR inhibitors that demonstrate improved pharmacokinetic properties and selectivity compared to our previous leads. Through targeted SAR and structure-guided design, new imidazopyridine and imidazopyridazine scaffolds were identified that demonstrated superior inhibition of mTOR in cellular assays, selectivity over the closely related PIKK family and improved in vivo clearance over our previously reported benzimidazole series.

Sulfonamides as Selective NaV1.7 Inhibitors: Optimizing Potency and Pharmacokinetics While Mitigating Metabolic Liabilities

Several reports have recently emerged regarding the identification of heteroarylsulfonamides as NaV1.7 inhibitors that demonstrate high levels of selectivity over other NaV isoforms. The optimization of a series of internal NaV1.7 leads that address a number of metabolic liabilities including bioactivation, PXR activation, as well as CYP3A4 induction and inhibition led to the identification of potent and selective inhibitors that demonstrated favorable pharmacokinetic profiles and were devoid of the aforementioned liabilities. The key to achieving this within a series prone to transporter-mediated clearance was the identification of a small range of optimal cLogD values and the discovery of subtle PXR SAR that was not lipophilicity dependent. This enabled the identification of compound 20, which was advanced into a target engagement pharmacodynamic model where it exhibited robust reversal of histamine-induced scratching bouts in mice.

Sulfonamides as Selective NaV1.7 Inhibitors: Optimizing Potency, Pharmacokinetics, and Metabolic Properties to Obtain Atropisomeric Quinolinone (AM-0466) that Affords Robust in Vivo Activity

Because of its strong genetic validation, NaV1.7 has attracted significant interest as a target for the treatment of pain. We have previously reported on a number of structurally distinct bicyclic heteroarylsulfonamides as NaV1.7 inhibitors that demonstrate high levels of selectivity over other NaV isoforms. Herein, we report the discovery and optimization of a series of atropisomeric quinolinone sulfonamide inhibitors [ Bicyclic sulfonamide compounds as sodium channel inhibitors and their preparation . WO 2014201206, 2014 ] of NaV1.7, which demonstrate nanomolar inhibition of NaV1.7 and exhibit high levels of selectivity over other sodium channel isoforms. After optimization of metabolic and pharmacokinetic properties, including PXR activation, CYP2C9 inhibition, and CYP3A4 TDI, several compounds were advanced into in vivo target engagement and efficacy models. When tested in mice, compound 39 (AM-0466) demonstrated robust pharmacodynamic activity in a NaV1.7-dependent model of histamine-induced pruritus (itch) and additionally in a capsaicin-induced nociception model of pain without any confounding effect in open-field activity.