Discovery of MAP855, an Efficacious and Selective MEK1/2 Inhibitor with an ATP-Competitive Mode of Action.

Mutations in MEK1/2 have been described as a resistance mechanism to BRAF/MEK inhibitor treatment. We report the discovery of a novel ATP-competitive MEK1/2 inhibitor with efficacy in wildtype (WT) and mutant MEK12 models. Starting from a HTS hit, we obtained selective, cellularly active compounds that showed equipotent inhibition of WT MEK1/2 and a panel of MEK1/2 mutant cell lines. Using a structure-based approach, the optimization addressed the liabilities by systematic analysis of molecular matched pairs (MMPs) and ligand conformation. Addition of only three heavy atoms to early tool compound 6 removed Cyp3A4 liabilities and increased the cellular potency by 100-fold, while reducing log P by 5 units. Profiling of MAP855, compound 30, in pharmacokinetic-pharmacodynamic and efficacy studies in BRAF-mutant models showed comparable efficacy to clinical MEK1/2 inhibitors. Compound 30 is a novel highly potent and selective MEK1/2 kinase inhibitor with equipotent inhibition of WT and mutant MEK1/2, whose drug-like properties allow further investigation in the mutant MEK setting upon BRAF/MEK therapy.

The Discovery of LML134, a Histamine H3 Receptor Inverse Agonist for the Clinical Treatment of Excessive Sleep Disorders.

Histamine H3 receptor (H3R) inverse agonists that have been in clinical trials for the treatment of excessive sleep disorders, have been plagued with insomnia as a mechanism-based side effect. We focused on the identification of compounds that achieve high receptor occupancy within a short time, followed by rapid disengagement from the receptor, a target profile that could provide therapeutic benefits without the undesired side effect of insomnia. This article describes the optimization work that led to the discovery of 1-(1-methyl-6-oxo-1,6-dihydropyridazin-3-yl)piperidin-4-yl 4-cyclobutylpiperazine-1-carboxylate (18 b, LML134).

From ergolines to indoles: improved inhibitors of the human H3 receptor for the treatment of narcolepsy.

Ergolines were recently identified as a novel class of H3 receptor (H3R) inverse agonists. Although their optimization led to drug candidates with encouraging properties for the treatment of narcolepsy, brain penetration remained low. To overcome this issue, ergoline 1 ((6aR,9R,10aR)-4-(2-(dimethylamino)ethyl)-N-phenyl-9-(pyrrolidine-1-carbonyl)-6,6a,8,9,10,10a-hexahydroindolo[4,3-fg]quinoline-7(4H)-carboxamide)) was transformed into a series of indole derivatives with high H3R affinity. These new molecules were profiled by simultaneous determination of their brain receptor occupancy (RO) levels and pharmacodynamic (PD) effects in mice. These efforts culminated in the discovery of 15 m ((R)-1-isopropyl-5-(1-(2-(2-methylpyrrolidin-1-yl)ethyl)-1H-indol-4-yl)pyridin-2(1H)-one), which has an ideal profile showing a strong correlation of PD effects with RO, and no measurable safety liabilities. Its desirably short duration of action was confirmed by electroencephalography (EEG) measurements in rats.

3-alkoxy-pyrrolo[1,2-b]pyrazolines as selective androgen receptor modulators with ideal physicochemical properties for transdermal administration.

We describe the synthesis and characterization of 3-alkoxy-pyrrolo[1,2-b]pyrazolines as novel selective androgen receptor (AR) modulators that possess excellent physicochemical properties for transdermal administration. Compound 26 bound to human AR with an IC50 of 0.7 nM with great selectivity over other nuclear hormone receptors and potently activated AR in a C2C12 muscle cell reporter gene assay with an EC50 of 0.5 nM. It showed high aqueous solubility of 1.3 g/L at pH 7.4, and an in silico model as well as a customized parallel artificial membrane permeability assay indicated good skin permeation. Indeed, when measuring skin permeation through excised human skin, an excellent flux of 2 µg/(cm(2)·h) was determined without any permeation enhancers. In a 2 week Hershberger model using castrated rats, the compound showed dose-dependent effects fully restoring skeletal muscle weight at 0.3 mg/kg/day after subcutaneous administration with high selectivity over prostate stimulation.

Ergoline-derived inverse agonists of the human h3 receptor for the treatment of narcolepsy.

Ergoline derivative (6aR,9R)-4-(2-(dimethylamino)ethyl)-N-phenyl-9-(pyrrolidine-1-carbonyl)-6,6a,8,9-tetrahydroindolo[4,3-fg]quinoline-7(4H)-carboxamide (1), a CXCR3 antagonist, also inhibits human histamine H3 receptors (H3R) and represents a structurally novel H3R inverse agonist chemotype. It displays favorable pharmacokinetic and in vitro safety profiles, and served as a lead compound in a program to explore ergoline derivatives as potential drug candidates for the treatment of narcolepsy. A key objective of this work was to enhance the safety and efficacy profiles of 1, while minimizing its duration of action to mitigate the episodes of insomnia documented with previously reported clinical candidates during the night following administration. Modifications to the ergoline core at positions 1, 6 and 8 were systematically investigated, and derivative 23 (1-((4aR,8R,9aR)-8-(hydroxymethyl)-1-(2-((R)-2-methylpyrrolidin-1-yl)ethyl)-4,4a,7,8,9,9a-hexahydroindolo[1,14-fg]quinolin-6(1H)-yl)ethanone) was identified as a promising lead compound. Derivative 23 has a desirable pharmacokinetic profile and demonstrated efficacy by enhancing brain concentrations of tele-methylhistamine, a major histamine metabolite. This validates the potential of the ergoline scaffold to serve as a template for the development of H3R inverse agonists.

The promise of genomics to identify novel therapeutic targets.

The cataloguing of the human genome has provided an unprecedented prospectus for target identification and drug discovery. A current analysis indicates that slightly more than 3000 unique protein encoding loci are potentially amenable to pharmacological intervention (the 'druggable genome', which can be queried at http://function.gnf.org/druggable). However, the assessment of genome sequence data has not resulted in the anticipated acceleration of novel therapeutic developments. The basis for this shortfall lies in the significant attrition rates endemic to preclinical/clinical development, as well as the often underestimated complexity of gene function in higher order biological systems. To address the latter issue, a number of strategies have emerged to facilitate genomics-driven target identification and validation, including cellular profiling of gene function, in silico modelling of gene networks, and systematic analyses of protein complexes. The expectation is that the integration of these and other systems-based technologies may enable the conversion of potential genomic targets into functionally validated molecules, and result in practicable gene-based drug discovery pipelines.

Novel dual action AT1 and ETA receptor antagonists reduce blood pressure in experimental hypertension.

Angiotensin II and endothelin-1 activate their respective AT(1) and ET(A) receptors on vascular smooth muscle cells, producing vasoconstriction, and both peptides are implicated in the pathogenesis of essential hypertension. Angiotensin II potentiates the production of endothelin, and conversely endothelin augments the synthesis of angiotensin II. Both AT(1) and ET(A) receptor antagonists lower blood pressure in hypertensive patients; thus, a combination AT(1)/ET(A) receptor antagonist may have greater efficacy and broader utility compared with each drug alone. By rational drug design a biphenyl ET(A) receptor blocker was modified to acquire AT(1) receptor antagonism. These compounds (C and D) decreased Sar-Ile-Angiotensin II binding to AT(1) receptors and endothelin-1 binding to ET(A) receptors, and compound C inhibited angiotensin II- and endothelin-1-mediated Ca(2+) transients. In rats compounds C and D reduced blood pressure elevations caused by intravenous infusion of angiotensin II or big endothelin-1. Compound C decreased blood pressure in Na(+)-depleted spontaneously hypertensive rats and in rats with mineralocorticoid hypertension. Compound D was more efficacious than AT(1) receptor antagonists at reducing blood pressure in spontaneously hypertensive rats, and its superiority was likely due to its partial blockade of ET(A) receptors. Therefore compounds C and D are novel agents for treating a broad spectrum of patients with essential hypertension and other cardiovascular diseases.

Potent quinoxaline-based inhibitors of PDGF receptor tyrosine kinase activity. Part 2: the synthesis and biological activities of RPR127963 an orally bioavailable inhibitor.

RPR127963 demonstrates an excellent pharmacokinetic profile in several species and was found to be efficacious in the prevention of restenosis in a Yucatan mini-pig model upon oral administration of 1-5 mg/kg. The in vitro selectivity profile and SAR of the highly optimized PDGF-R tyrosine kinase inhibitor are highlighted.

Stent-induced restenosis in the swine coronary artery is inhibited by a platelet-derived growth factor receptor tyrosine kinase inhibitor, TKI963.

Activities of vascular smooth muscle cells (SMCs) such as proliferation, migration, and matrix production contribute to restenosis following clinical interventions of angioplasty and stent placement. Because activation of platelet-derived growth factor (PDGF)-receptor tyrosine kinase (PDGFr-TK) influences these processes and promotes restenosis, TKI963, an inhibitor of the PDGFr-TK was discovered, and its efficacy was evaluated in blocking stent-induced restenosis as analyzed by intravascular ultrasound (IVUS). TKI963, a low-molecular-weight compound, inhibited the cell-free PDGFbetar-TK with a K(i) value of 56 +/- 14 nM. TKI963 also inhibited PDGF-dependent events in human aortic SMCs (e.g., in situ PDGFr autophosphorylation, mitogenesis, chemotaxis, and collagen production with median inhibitory concentration values of approximately 300 nM) without affecting the activity of a series of membrane receptor tyrosine kinases and intracellular serine/threonine kinases. In vivo, stent-induced restenosis in the swine coronary artery was reduced by oral administration of TKI963 (1.25, 2.5, and 5 mg/kg BID, for 28 days). Late lumen cross-sectional area (CSA) loss, plaque CSA growth, and plaque volume in the stent determined by IVUS were dose-relatedly decreased (33-62% at 1.25 mg/kg BID to 66-92% at 5 mg/kg BID, depending on the parameter) compared with controls. TKI963 treatment of