Bibliographic
We previously developed orthosteric M1 muscarinic agonists (e.g., AF102B, AF267B, and AF292), which act as cognitive enhancers and potential disease modifiers. We now report on a novel compound, AF710B, a highly potent and selective allosteric M1 muscarinic and σ1 receptor agonist. AF710B exhibits an allosteric agonistic profile on M1 muscarinic receptor; very low concentrations of AF710B significantly potentiated the binding and efficacy of carbachol on M1 receptors and their downstream effects (phopho-ERK1/2, phospho-CREB). AF710B (1–30 µg/kg, po) was a potent and safe cognitive enhancer in rats treated with the M1 antagonist trihexyphenidyl (passive avoidance impairment). These effects of AF710B involve σ1 receptor activation. In agreement with its anti-amnesic properties, AF710B (at 30 nM), via activation of M1 and a possible involvement of σ1 receptors, rescued mushroom synapse loss in PS1-KI and APP-KI neuronal cultures, while AF267B (1 µM) was less potent in PS1-KI and ineffective in APP-KI models, respectively. In female 3xTg-AD mice AF710B (10 µg/kg, ip/daily/2 months) – i) mitigated cognitive impairments in Morris water maze; ii) decreased BACE1, GSK3β activity, p25/CDK5, neuroinflammation, soluble and insoluble Aβ40, Aβ42, plaques and tau pathologies. AF710B differs from conventional σ1, M1 muscarinic (orthosteric, allosteric or bi-topic) or σ1/ muscarinic agonists. These results highlight AF710B as a potential treatment for AD (e.g., improving cognitive deficits, synaptic loss, amyloid and tau pathologies, and neuroinflammation) with a superior profile over a plethora of other therapeutic strategies.