Binding characteristics and analgesic effects of mirogabalin, a novel ligand for the α 2 δ subunit of voltage-gated calcium channels

Mirogabalin ([(1 ,5 ,6 )-6-(aminomethyl)-3-ethylbicyclo[3.2.0]hept-3-en-6-yl]acetic acid), a novel ligand for the α δ subunit of voltage-gated calcium channels, is being developed to treat pain associated with diabetic peripheral neuropathy and postherpetic neuralgia. In the present study, we investigated the in vitro binding characteristics and in vivo analgesic effects of mirogabalin, compared to those of pregabalin, a standard α δ ligand. Mirogabalin showed potent and selective binding affinities for the α δ subunits, while having no effects on 186 off-target proteins. Similar to pregabalin, mirogabalin did not show clear subtype selectivity (α δ-1 vs α δ-2) or species differences (human vs rat). However, in contrast to pregabalin, mirogabalin showed greater binding affinities for human α δ-1, human α δ-2, rat α δ-1, and rat α δ-2 subunits; further, it had a slower dissociation rate for the α δ-1 subunit than the α δ-2 subunit. Additionally, in experimental neuropathic pain models, partial sciatic nerve ligation rats and streptozotocin-induced diabetic rats, mirogabalin showed more potent and longer lasting analgesic effects. In safety pharmacological evaluations, mirogabalin and pregabalin inhibited rota-rod performance and locomotor activity in rats; however, the safety indices of mirogabalin were superior to those of pregabalin. In conclusion, mirogabalin shows potent and selective binding affinities for the human and rat α δ subunits, and slower dissociation rates for the α δ-1 subunit than the α δ-2 subunit. It shows potent and long-lasting analgesic effects in rat models of neuropathic pain, and wider safety margins for side effects of the central nervous system. These properties of mirogabalin can be associated with its unique binding characteristics.