Oxa‐azaspiro Derivatives: a Novel Class of Triple Re‐uptake Inhibitors

Abstract

Drugs able to interfere with either the uptake or the metabolism of endogenous monoamines have been used for many years to treat depression. The first drugs of this type, such as the monoamine oxidase (MAO) inhibitors and the tricyclic antidepressants, achieved wide diffusion in the market, but are unfortunately associated with side effects that may influence patient compliance.[1] Over the last few years, compounds acting through the selective blockade of neurotransmitter re-uptake have demonstrated their efficacy as successful antidepressant agents. This blockade can take place in either serotoninergic neurons (SSRI; e.g., paroxetine) or noradrenergic neurons (SNRI; e.g., reboxetine). Moreover, drugs known as "dual uptake" inhibitors, which act on both serotoninergic and noradrenergic transporters (e.g., venlafaxine) or on both noradrenergic and dopaminergic transporters (e.g., bupropion), have also demonstrated good efficacy.[1]More recently, compounds acting as "triple re-uptake" inhibitors (TRUI), [2] such as indatraline and DOV 21,947, have been disclosed. Given the extensive experience of investigators at GlaxoSmithKline (GSK) with selective, dual and triple re-uptake inhibitors, new TRUI scaffolds were rationally planned exploiting a pharmacophore model developed in house More precisely, three specific pharmacophore models for the monoamine transporters, SERT (serotonin transporter), NET (norepinephrine transporter) and DAT (dopamine transporter), were built using structurally rigid and selective derivatives. These compounds were derived both from the GSK proprietary collection and from the public domain (e.g., derivatives described in Reference [3]). The structures were modeled within the Maestro modeling environment.[4] Conformational analyses were carried out for the three structures with BatchMin [5] using the following parameters: 1000 steps/rotatable bond, OPLS_ 2005 FF, implicit water model of solvation, 5000 minimization steps with PRCG. Conformations lying within a 3 kcal mol À1 energy window were kept.A single-ligand pharmacophore was then built over these structures using the Phase [6] module within Maestro, and selecting the most relevant pharmacophoric features. The three pharmacophores were finally merged together to create the triple re-uptake inhibitor pharmacophore. Average coordinates for the common pharmacophoric features were taken to determine their three-dimensional arrangement, as illustrated in Figure 1.The aim of the work described herein was twofold: the first objective was to set up the chemistry to prepare a new series of oxa-spiro derivatives; the second was to validate the capability of the pharmacophore model to predict the rank order of affinity of the new derivatives.It was hypothesized that the introduction of an appropriately located tetrahydrofuran (1) or a tetrahydropyran (2) moiety on the 4-phenyl piperidine scaffold should have satisfied at Figure 1. The triple re-uptake inhibitor pharmacophore. Coding of features: P6 sphere, positive ionizable; A2 sphere, H-bond ac...

Triple Reuptake Inhibitors as Potential Therapeutics for Depression and Other Disorders: Design Paradigm and Developmental Challenges

“…Another class of constrained oxa-azaspiro arylpiperidines was developed by exploiting the in-house pharmacophore model (Figure ) and a hypothesis that an appropriately located tetrahydrofuran (THF)/tetrahydropyran (THP) moiety on the 4-phenylpiperidine scaffold would meet the requirements of the pharmacophore (Figure ). The spiro-THP compound 170 was found to be more potent than the spiro-THF compound 169 . Two more analogues, the oxetane 173 and the fused pyran 174 , which were made to expand the scope, gave inferior triple affinity in agreement with the poor fit of these compounds in the pharmacophore model.…”

“…122 the requirements of the pharmacophore (Figure 31). 124 The spiro-THP compound 170 was found to be more potent than the spiro-THF compound 169. Two more analogues, the oxetane 173 and the fused pyran 174, which were made to expand the scope, gave inferior triple affinity in agreement with the poor fit of these compounds in the pharmacophore model.…”

The solute carrier 6 family of transporters

“…Interestingly, sibutramine, which has been used as an appetite suppressant, might act as ‘a triple uptake inhibitor’ because it is rapidly metabolized to its desmethyl and didesmethyl congeners that display high affinity for all three monoamine transporters (Glick et al ., 2000). More recently, specific triple uptake inhibitors are being developed (Bettati et al ., 2010).…”

Triple Reuptake Inhibitors as Potential Next-Generation Antidepressants: A New Hope?

“…The compound has long in vivo half-life (2.2 h) and exhibited a good brain to plasma ratio of 9.6. However, the compound undergoes extensive metabolism and as a result only overall 9% bioavailability was observed [129].…”