Steven D. Young

L-743, 726 (DMP-266): a novel, highly potent nonnucleoside inhibitor of the human immunodeficiency virus type 1 reverse transcriptase.

The clinical benefit of the human immunodeficiency virus type 1 (HIV-1) nonnucleoside reverse transcriptase (RT) inhibitors (NNRTIs) is limited by the rapid selection of inhibitor-resistant viral variants. However, it may be possible to enhance the clinical utility of this inhibitor class by deriving compounds that express both high levels of antiviral activity and an augmented pharmacokinetic profile. Accordingly, we developed a new class of NNRTIs, the 1, 4-dihydro-2H-3, 1-benzoxazin-2-ones. L-743, 726 (DMP-266), a member of this class, was chosen for clinical evaluation because of its in vitro properties. The compound was a potent inhibitor of the wild-type HIV-1 RT (Ki = 2.93 nM) and exhibited a 95% inhibitory concentration of 1.5 nM for the inhibition of HIV-1 replicative spread in cell culture. In addition, L-7743, 7726 was found to be capable of inhibiting, with 95% inhibitory concentrations of < or = 1.5 microM, a panel of NNRTI-resistant mutant viruses, each of which expressed a single RT amino acid substitution. Derivation of virus with notably reduced susceptibility to the inhibitor required prolonged cell culture selection and was mediated by a combination of at least two RT amino acid substitutions. Studies of L-743, 726 in rats, monkeys, and a chimpanzee demonstrated the compounds potential for good oral bioavailability and pharmacokinetics in humans.

Discovery of the dual orexin receptor antagonist [(7R)-4-(5-chloro-1,3-benzoxazol-2-yl)-7-methyl-1,4-diazepan-1-yl][5-methyl-2-(2H-1,2,3-triazol-2-yl)phenyl]methanone (MK-4305) for the treatment of insomnia.

Despite increased understanding of the biological basis for sleep control in the brain, few novel mechanisms for the treatment of insomnia have been identified in recent years. One notable exception is inhibition of the excitatory neuropeptides orexins A and B by design of orexin receptor antagonists. Herein, we describe how efforts to understand the origin of poor oral pharmacokinetics in a leading HTS-derived diazepane orexin receptor antagonist led to the identification of compound 10 with a 7-methyl substitution on the diazepane core. Though 10 displayed good potency, improved pharmacokinetics, and excellent in vivo efficacy, it formed reactive metabolites in microsomal incubations. A mechanistic hypothesis coupled with an in vitro assay to assess bioactivation led to replacement of the fluoroquinazoline ring of 10 with a chlorobenzoxazole to provide 3 (MK-4305), a potent dual orexin receptor antagonist that is currently being tested in phase III clinical trials for the treatment of primary insomnia.

Discovery of [(2R,5R)-5-{[(5-fluoropyridin-2-yl)oxy]methyl}-2-methylpiperidin-1-yl][5-methyl-2-(pyrimidin-2-yl)phenyl]methanone (MK-6096): a dual orexin receptor antagonist with potent sleep-promoting properties.

Insomnia is a common disorder that can be comorbid with other physical and psychological illnesses. Traditional management of insomnia relies on general central nervous system (CNS) suppression using GABA modulators. Many of these agents fail to meet patient needs with respect to sleep onset, maintenance, and next‐day residual effects and have issues related to tolerance, memory disturbances, and balance. Orexin neuropeptides are central regulators of wakefulness, and orexin antagonism has been identified as a novel mechanism for treating insomnia with clinical proof of concept. Herein we describe the discovery of a series of α‐methylpiperidine carboxamide dual orexin 1 and orexin 2 receptor (OX1R/OX2R) antagonists (DORAs). The design of these molecules was inspired by earlier work from this laboratory in understanding preferred conformational properties for potent orexin receptor binding. Minimization of 1,3‐allylic strain interactions was used as a design principle to synthesize 2,5‐disubstituted piperidine carboxamides with axially oriented substituents including DORA 28. DORA 28 (MK‐6096) has exceptional in vivo activity in preclinical sleep models, and has advanced into phase II clinical trials for the treatment of insomnia.

Inhibition of human immunodeficiency virus integrase by bis-catechols.

The human immunodeficiency virus type 1 (HIV-1) integrase protein is required for the productive infection of T-lymphoid cells in culture (R. L. LaFemina, C. L. Schneider, H. L. Robbins, P. L. Callahan, K. LeGrow, E. Roth, W. A. Schleif, and E. A. Emini, J. Virol. 66:7414-7419, 1992). This observation suggests that chemical inhibitors of integrase may prevent the spread of HIV in infected individuals. In our search for such potential chemotherapeutic agents, we observed that beta-conidendrol inhibits both the sequence-dependent and sequence-independent endonucleolytic activities of integrase with comparable potencies in vitro (50% inhibitory concentration, 500 nM). Structurally related compounds tested for their abilities to inhibit integrase generated a limited structure-activity analysis which demonstrated that potency is associated with the bis-catechol structure: two pairs of adjacent hydroxyls on separate benzene rings. beta-Conidendrol did not inhibit several other endonucleases and/or phosphoryltransferases. Although beta-conidendrol was not effective in preventing HIV-1 infection in cell culture, the in vitro data demonstrate that it is possible to identify selective agents targeted against this essential HIV-1 function.

2-Heterocyclic indole-3-sulfones as inhibitors of HIV-1 reverse transcriptase

Abstract A variety of 2-heterocycle substituted 3-phenysulfonyl-5-chloroindoles were investigated as replacements for the 2-carboxamide functionality of the potent HIV-1 reverse transcriptase inhibitor L-737, 126. The 2-carboxamide series of compounds typified by L-737,126 have poor solubility. Replacement of the carboxamide moiety with a variety of heterocycles results in a series of potent enzyme inhibitors with equivalent ex vivo antiviral activity and improved physicochemical properties.

Non-nucleoside inhibitors of HIV-1 reverse transcriptase

Four years ago it became apparent that an allosteric site on HIV-1 reverse transcriptase was responsible for the enzyme inhibitory activity of a number of structurally diverse organic compounds. These molecules bear little resemblance to the endogenous substrate, deoxynucleotide triphosphates, and through kinetic measurements they were found to be noncompetitive inhibitors. When examined in cell culture, these compounds proved to be potent antiviral agents. Improvements made in the potency and pharmacodynamic properties of the early inhibitors quickly allowed evaluation of several compounds in a clinical setting. From these and other studies came a discouraging profile of rapidly emerging viral resistance. Further work in the field may show that a combination of these and other drugs may be of benefit in combatting AIDS.

Discovery of 5′′-Chloro-N-[(5,6-dimethoxypyridin-2-yl)methyl]-2,2′:5′,3′′-terpyridine-3′-carboxamide (MK-1064): A Selective Orexin 2 Receptor Antagonist (2-SORA) for the Treatment of Insomnia

The field of small‐molecule orexin antagonist research has evolved rapidly in the last 15 years from the discovery of the orexin peptides to clinical proof‐of‐concept for the treatment of insomnia. Clinical programs have focused on the development of antagonists that reversibly block the action of endogenous peptides at both the orexin 1 and orexin 2 receptors (OX1R and OX2R), termed dual orexin receptor antagonists (DORAs), affording late‐stage development candidates including Merck’s suvorexant (new drug application filed 2012). Full characterization of the pharmacology associated with antagonism of either OX1R or OX2R alone has been hampered by the dearth of suitable subtype‐selective, orally bioavailable ligands. Herein, we report the development of a selective orexin 2 antagonist (2‐SORA) series to afford a potent, orally bioavailable 2‐SORA ligand. Several challenging medicinal chemistry issues were identified and overcome during the development of these 2,5‐disubstituted nicotinamides, including reversible CYP inhibition, physiochemical properties, P‐glycoprotein efflux and bioactivation. This article highlights structural modifications the team utilized to drive compound design, as well as in vivo characterization of our 2‐SORA clinical candidate, 5′′‐chloro‐N‐[(5,6‐dimethoxypyridin‐2‐yl)methyl]‐2,2′:5′,3′′‐terpyridine‐3′‐carboxamide (MK‐1064), in mouse, rat, dog, and rhesus sleep models.

Discovery of 2,5-diarylnicotinamides as selective orexin-2 receptor antagonists (2-SORAs)

The orexin (or hypocretin) system has been identified as a novel target for the treatment of insomnia due to the wealth of biological and genetic data discovered over the past decade. Recently, clinical proof-of-concept was achieved for the treatment of primary insomnia using dual (OX1R/OX2R) orexin receptor antagonists. However, elucidation of the pharmacology associated with selective orexin-2 receptor antagonists (2-SORAs) has been hampered by the lack of orally bioavailable, highly selective small molecule probes. Herein, the discovery and optimization of a novel series of 2,5-diarylnicotinamides as potent and orally bioavailable orexin-2 receptor selective antagonists is described. A compound from this series demonstrated potent sleep promotion when dosed orally to EEG telemetrized rats.

Synthesis of 5-(1-H or 1-alkyl-5-oxopyrrolidin-3-yl)-8-hydroxy-[1,6]-naphthyridine-7-carboxamide inhibitors of HIV-1 integrase

HIV-1 integrase catalyzes the insertion of viral DNA into the genome of the host cell. Integrase inhibitor N-(4-fluorobenzyl)-8-hydroxy-1,6-naphthyridine-7-carboxamide selectively inhibits the strand transfer process of integration. 4-Substituted pyrrolidinones possessing various groups on the pyrrolidinone nitrogen were introduced at the 5-position of the naphthyridine scaffold. These analogs exhibit excellent activity against viral replication in a cell-based assay. The preparation of these compounds was enabled by a three-step, two-pot reaction sequence from a common butenolide intermediate.

Non-peptide glycoprotein IIb/IIIa inhibitors. 9. Centrally constrained alpha-sulfonamides are useful tools for exploring platelet receptor function

Abstract Two fluorescent, centrally constrained fibrinogen receptor antagonists were prepared to probe ligand receptor interactions.