An anchor-tether ‘hindered’ HCN1 inhibitor is antihyperalgesic in a rat spared nerve injury neuropathic pain model

• Published in: British journal of anaesthesia : BJA Vol. 131; no. 4; pp. 745 - 763
• Main Authors: Tibbs, Gareth R., Uprety, Rajendra, Warren, J. David, Beyer, Nicole P., Joyce, Rebecca L., Ferrer, Matthew A., Mellado, Wilfredo, Wong, Victor S.C., Goldberg, David C., Cohen, Melanie W., Costa, Christopher J., Li, Zhucui, Zhang, Guoan, Dephoure, Noah E., Barman, Dipti N., Sun, Delin, Ingólfsson, Helgi I., Sauve, Anthony A., Willis, Dianna E., Goldstein, Peter A.
• Format: Journal Article
• Language: English
• Published: England Elsevier Ltd 01.10.2023; Elsevier
• Subjects: Animals; antihyperalgesia; Drug Inverse Agonism; Electrophysiological Phenomena; HCN1; Hyperpolarization-Activated Cyclic Nucleotide-Gated Channels - therapeutic use; ion channel; nerve injury; Neuralgia - drug therapy; neuropathic pain; Pain; Quality of Life; rat; Rats; neuropathic pain; rat; ion channel; nerve injury; antihyperalgesia; HCN1
• ISSN: 0007-0912; 1471-6771; 1471-6771
• DOI: 10.1016/j.bja.2023.06.067

Neuropathic pain impairs quality of life, is widely prevalent, and incurs significant costs. Current pharmacological therapies have poor/no efficacy and significant adverse effects; safe and effective alternatives are needed. Hyperpolarisation-activated cyclic nucleotide-regulated (HCN) channels are causally implicated in some forms of peripherally mediated neuropathic pain. Whilst 2,6-substituted phenols, such as 2,6-di-tert-butylphenol (26DTB-P), selectively inhibit HCN1 gating and are antihyperalgesic, the development of therapeutically tolerable, HCN-selective antihyperalgesics based on their inverse agonist activity requires that such drugs spare the cardiac isoforms and do not cross the blood–brain barrier. In silico molecular dynamics simulation, in vitro electrophysiology, and in vivo rat spared nerve injury methods were used to test whether ‘hindered’ variants of 26DTB-P (wherein a hydrophilic ‘anchor’ is attached in the para-position of 26DTB-P via an acyl chain ‘tether’) had the desired properties. Molecular dynamics simulation showed that membrane penetration of hindered 26DTB-Ps is controlled by a tethered diol anchor without elimination of head group rotational freedom. In vitro and in vivo analysis showed that BP4L-18:1:1, a variant wherein a diol anchor is attached to 26DTB-P via an 18-carbon tether, is an HCN1 inverse agonist and an orally available antihyperalgesic. With a CNS multiparameter optimisation score of 2.25, a >100-fold lower drug load in the brain vs blood, and an absence of adverse cardiovascular or CNS effects, BP4L-18:1:1 was shown to be poorly CNS penetrant and cardiac sparing. These findings provide a proof-of-concept demonstration that anchor-tethered drugs are a new chemotype for treatment of disorders involving membrane targets.