title: The clobazam metabolite N-desmethyl clobazam is an α2 preferring benzodiazepine with an improved therapeutic window for antihyperalgesia.
abstract: Data from genetically modified mice suggest that benzodiazepine (BDZ)-site agonists with improved selectivity for α2-subtype GABAA receptors (α2GABAAR) are potentially useful for the treatment of neuropathic pain. Subtype-selective compounds available for preclinical tests in rodents support this concept but have not been approved for human use, hindering proof-of-concept studies in patients. We recently proposed that N-desmethyl clobazam (NDMC), the main metabolite of the licensed BDZ clobazam (CBZ), is responsible for most of the antihyperalgesia observed in mice after CBZ administration. In order to assess a potentially favorable pharmacological profile of NDMC, we analyzed differences in the GABAAR subtype specificity of CBZ, NDMC and diazepam (DZP) in recombinant receptors. DZP and CBZ potentiated sedating α1GABAARs and antihyperalgesic α2GABAARs with similar efficacies, whereas NDMC preferred α2GABAARs over α1GABAARs across a wide concentration range. In vivo, DZP and NDMC reduced neuropathic pain at doses between 3 and 30 mg/kg. At these doses, DZP had strong locomotor sedating effects while NDMC caused no or only weak sedation. Sedative effects of NDMC became apparent when the action of NDMC was restricted to α1GABAARs. However, when GABAAR point-mutated mice were studied that allow the analysis of antihyperalgesia and sedation in isolation, we found that, compared to DZP, NDMC had a significantly improved therapeutic window, consistent with its more favorable α2/α1 in vitro activity ratio. Given that NDMC should share the safety profile of its parent compound CBZ, it should be well-suited for proof-of-concept studies in human volunteers or patients.
authors.affiliation: Institute of Pharmacology and Toxicology, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland.
authors.forename: William T
authors.initials: WT
authors.lastname: Ralvenius
authors.affiliation: Institute of Pharmacology and Toxicology, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland.
authors.forename: Mario A
authors.initials: MA
authors.lastname: Acuña
authors.affiliation: Institute of Pharmacology and Toxicology, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland.
authors.forename: Dietmar
authors.initials: D
authors.lastname: Benke
authors.affiliation: Division of Clinical Pharmacology and Toxicology, Multidisciplinary Pain Center, Department of Anesthesiology, Pharmacology and Intensive Care, Geneva University Hospitals, University of Geneva, 4 rue Gabrielle-Perret-Gentil, CH-1211 Geneva, Switzerland.
authors.forename: Alain
authors.initials: A
authors.lastname: Matthey
authors.affiliation: Division of Clinical Pharmacology and Toxicology, Multidisciplinary Pain Center, Department of Anesthesiology, Pharmacology and Intensive Care, Geneva University Hospitals, University of Geneva, 4 rue Gabrielle-Perret-Gentil, CH-1211 Geneva, Switzerland.
authors.forename: Youssef
authors.initials: Y
authors.lastname: Daali
authors.affiliation: Laboratory of Genetic Neuropharmacology, McLean Hospital, 115 Mill Street, Belmont, MA 02478, USA; Department of Psychiatry, Harvard Medical School, 401 Park Drive, Boston, MA 02215, USA.
authors.forename: Uwe
authors.initials: U
authors.lastname: Rudolph
authors.affiliation: Division of Clinical Pharmacology and Toxicology, Multidisciplinary Pain Center, Department of Anesthesiology, Pharmacology and Intensive Care, Geneva University Hospitals, University of Geneva, 4 rue Gabrielle-Perret-Gentil, CH-1211 Geneva, Switzerland.
authors.forename: Jules
authors.initials: J
authors.lastname: Desmeules
authors.affiliation: Institute of Pharmacology and Toxicology, University of Zurich, Winterthurerstrasse 190, CH-8057 Zurich, Switzerland; Institute of Pharmaceutical Sciences, Swiss Federal Institute of Technology (ETH) Zurich, Vladimir-Prelog-Weg 10, CH-8093 Zürich, Switzerland; Drug Discovery Network Zurich (DDNZ), CH-8057 Zurich, Switzerland. Electronic address: zeilhofer@pharma.uzh.ch.
authors.forename: Hanns Ulrich
authors.initials: HU
authors.lastname: Zeilhofer
authors.affiliation: Division of Clinical Pharmacology and Toxicology, Multidisciplinary Pain Center, Department of Anesthesiology, Pharmacology and Intensive Care, Geneva University Hospitals, University of Geneva, 4 rue Gabrielle-Perret-Gentil, CH-1211 Geneva, Switzerland.
authors.forename: Marie
authors.initials: M
authors.lastname: Besson
mesh_terms: D018712:Analgesics, Non-Narcotic / Q000378:metabolism* / Q000627:therapeutic use; D000818:Animals; D001569:Benzodiazepines / Q000378:metabolism* / Q000627:therapeutic use; D000078306:Clobazam; D004305:Dose-Response Relationship, Drug; D005260:Female; D057809:HEK293 Cells; D006801:Humans; D006930:Hyperalgesia / Q000188:drug therapy / Q000378:metabolism*; D008297:Male; D051379:Mice; D057507:Mice, 129 Strain; D008810:Mice, Inbred C57BL; D011485:Protein Binding / Q000502:physiology; D011963:Receptors, GABA-A / Q000378:metabolism*
chemical_list: D018712:Analgesics, Non-Narcotic; D011963:Receptors, GABA-A; D001569:Benzodiazepines; D000078306:Clobazam; C024581:N-desmethylclobazam
keywords: Analgesia; Benzodiazepine; GABA(A) receptor subtype; Mouse models; Neuropathic pain; Proof-of-concept