Design and Synthesis of a Novel Series of <i>N</i>-Alkyl Isatin Acylhydrazone Derivatives that Act as Selective Cannabinoid Receptor 2 Agonists for the Treatment of Neuropathic Pain

There is growing interest in using cannabinoid receptor 2 (CB2) agonists for the treatment of neuropathic pain. We have synthesized a novel series of N-alkyl isatin acylhydrazone derivatives and have identified and characterized several of them as novel analogues with high functional activity and selectivity at human CB2 receptors using [35S]GTP-γ-S assays. Binding affinities at human CB2 and CB1 were determined for compounds 28, 33, 40, 48, and 58. Structure−activity relationship studies of this novel series led to optimization of our lead compound, compound 33 (MDA19). Compound 33 possessed potent antiallodynic effects in a rat model of neuropathic pain but did not affect rat locomotor activity. More potent and more CB2-receptor−selective compounds, including compounds 37, 40, and 48, were also discovered.