ABSTRACT
Orally bioavailable inhibitors of ß-(1,3)-D-glucan synthase have been pursued as new, broad-spectrum fungicidal therapies suitable for treatment in immunocompromised patients. Toward this end, a collaborative medicinal chemistry program was established based on semisynthetic derivatization of the triterpenoid glycoside natural product enfumafungin in order to optimize in vivo antifungal activity and oral absorption properties. In the course of these studies, it was hypothesized that the pharmacokinetic properties of the semisynthetic enfumafungin analog 3 could be improved by tethering the alkyl groups proximal to the basic nitrogen of the C3-aminoether side chain into an azacyclic system, so as to preclude oxidative N-demethylation. The results of this research effort are disclosed herein.
Subject(s)
Antifungal Agents/chemical synthesis , Enzyme Inhibitors/chemical synthesis , Glucosyltransferases/antagonists & inhibitors , Glycosides/chemistry , Triterpenes/chemistry , Administration, Oral , Animals , Antifungal Agents/chemistry , Antifungal Agents/pharmacokinetics , Candida albicans/drug effects , Enzyme Inhibitors/chemistry , Enzyme Inhibitors/pharmacokinetics , Glucosyltransferases/metabolism , Glycosides/chemical synthesis , Glycosides/pharmacokinetics , Half-Life , Mice , Structure-Activity Relationship , Triterpenes/chemical synthesis , Triterpenes/pharmacokineticsABSTRACT
Nav1.8 (also known as PN3) is a tetrodotoxin-resistant (TTx-r) voltage-gated sodium channel (VGSC) that is highly expressed on small diameter sensory neurons and has been implicated in the pathophysiology of inflammatory and neuropathic pain. Recent studies using an Nav1.8 antisense oligonucleotide in an animal model of chronic pain indicated that selective blockade of Nav1.8 was analgesic and could provide effective analgesia with a reduction in the adverse events associated with nonselective VGSC blocking therapeutic agents. Herein, we describe the preparation and characterization of a series of 5-substituted 2-furfuramides, which are potent, voltage-dependent blockers (IC50 < 10 nM) of the human Nav1.8 channel. Selected derivatives, such as 7 and 27, also blocked TTx-r sodium currents in rat dorsal root ganglia (DRG) neurons with comparable potency and displayed >100-fold selectivity versus human sodium (Nav1.2, Nav1.5, Nav1.7) and human ether-a-go-go (hERG) channels. Following systemic administration, compounds 7 and 27 dose-dependently reduced neuropathic and inflammatory pain in experimental rodent models.
Subject(s)
Amides/chemical synthesis , Analgesics/chemical synthesis , Anti-Inflammatory Agents, Non-Steroidal/chemical synthesis , Furans/chemical synthesis , Sodium Channel Blockers/chemical synthesis , Sodium Channels/physiology , Amides/chemistry , Amides/pharmacology , Analgesics/pharmacokinetics , Analgesics/pharmacology , Animals , Anti-Inflammatory Agents, Non-Steroidal/pharmacokinetics , Anti-Inflammatory Agents, Non-Steroidal/pharmacology , Cell Line , Cricetinae , Cricetulus , Furans/chemistry , Furans/pharmacokinetics , Furans/pharmacology , Ganglia, Spinal/cytology , Humans , In Vitro Techniques , Male , Mice , NAV1.8 Voltage-Gated Sodium Channel , Nerve Tissue Proteins/physiology , Neurons/drug effects , Neurons/physiology , Pain/drug therapy , Pain/etiology , Patch-Clamp Techniques , Peripheral Nervous System Diseases/drug therapy , Rats , Rats, Sprague-Dawley , Recombinant Proteins/antagonists & inhibitors , Sodium Channel Blockers/pharmacokinetics , Sodium Channel Blockers/pharmacology , Structure-Activity RelationshipABSTRACT
BACKGROUND: A new benzodiazepine derivative, CNS 7056, has been developed to permit a superior sedative profile to current agents, i.e., more predictable fast onset, short duration of sedative action, and rapid recovery profile. This goal has been achieved by rendering the compound susceptible to metabolism via esterases. The authors now report on the profile of CNS 7056 in vitro and in vivo. METHODS: The affinity of CNS 7056 and its carboxylic acid metabolite, CNS 7054, for benzodiazepine receptors and their selectivity profiles were evaluated using radioligand binding. The activity of CNS 7056 and midazolam at subtypes (alpha1beta2gamma2, alpha2beta2gamma2, alpha3beta2gamma2, alpha5beta2gamma2) of the gamma-aminobutyric acid type A (GABAA) receptor was evaluated using the whole cell patch clamp technique. The activity of CNS 7056 at brain benzodiazepine receptors in vivo was measured in rats using extracellular electrophysiology in the substantia nigra pars reticulata. The sedative profile was measured in rodents using the loss of righting reflex test. RESULTS: CNS 7056 bound to brain benzodiazepine sites with high affinity. The carboxylic acid metabolite, CNS 7054, showed around 300 times lower affinity. CNS 7056 and CNS 7054 (10 mum) showed no affinity for a range of other receptors. CNS 7056 enhanced GABA currents in cells stably transfected with subtypes of the GABAA receptor. CNS 7056, like midazolam and other classic benzodiazepines, did not show clear selectivity between subtypes of the GABAA receptor. CNS 7056 (intravenous) caused a dose-dependent inhibition of substantia nigra pars reticulata neuronal firing and recovery to baseline firing rates was reached rapidly. CNS 7056 (intravenous) induced loss of the righting reflex in rodents. The duration of loss of righting reflex was short (< 10 min) and was inhibited by pretreatment with flumazenil. CONCLUSIONS: CNS 7065 is a high-affinity and selective ligand for the benzodiazepine site on the GABAA receptor. CNS 7056 does not show selectivity between GABAA receptor subtypes. CNS 7056 is a potent sedative in rodents with a short duration of action. Inhibition of substantia nigra pars reticulata firing and the inhibition of the effects of CNS 7056 by flumazenil show that it acts at the brain benzodiazepine receptor.
Subject(s)
Benzodiazepines/pharmacology , Hypnotics and Sedatives/pharmacology , Animals , Benzodiazepines/pharmacokinetics , Binding, Competitive/drug effects , Cell Line , Cerebral Cortex/drug effects , Cerebral Cortex/metabolism , Electrophysiology , Extracellular Space/drug effects , Extracellular Space/metabolism , Flunitrazepam/pharmacokinetics , Humans , Hypnotics and Sedatives/pharmacokinetics , In Vitro Techniques , Ion Channels/drug effects , Ion Channels/metabolism , Membranes/drug effects , Membranes/metabolism , Mice , Midazolam/pharmacology , Postural Balance/drug effects , Radioligand Assay , Rats , Rats, Sprague-Dawley , Rats, Wistar , Receptors, GABA-A/drug effects , Substantia Nigra/drug effects , Swine , Swine, Miniature , Transfection , gamma-Aminobutyric Acid/physiologyABSTRACT
The synthesis and evaluation of novel ultrashort-acting benzodiazepine (USA BZD) agonists is described. A BZD scaffold was modified by incorporation of amino acids and derivatives. The propionate side chain of glutamic acid tethers an enzymatically labile functionality where the metabolite carboxylic acid displays markedly reduced BZD receptor affinity. The USA BZDs were characterized by full agonism profiles. Copyright2000 Elsevier Science Ltd.
Subject(s)
Benzodiazepines/chemical synthesis , Benzodiazepines/pharmacology , GABA-A Receptor Agonists , Animals , Benzodiazepines/pharmacokinetics , Chromatography, High Pressure Liquid , Humans , Postural Balance/drug effects , Rats , Receptors, GABA-A/metabolism , Structure-Activity RelationshipABSTRACT
The ultrashort-acting benzodiazepine (USA BZD) agonists reported previously have been structurally modified to improve aqueous solubility. Lactam-to-amidine modifications, replacement of the C5-haloaryl ring, and annulation of heterocycles are presented. These analogues retain BZD receptor potency and full agonism profiles.
