N-Alkylidenearylcarboxamides as new potent and selective CB(2) cannabinoid receptor agonists with good oral bioavailability.

A novel series of N-alkylidenearylcarboxamides 4, a CB(2) receptor agonist, were synthesized and evaluated for activity against the human CB(2) receptor. In a previous paper, we reported that sulfonamide derivative 1 acted as a potent CB(2) receptor agonist (IC(50)=65 nM, EC(50)=19 nM, E(max)=90%). However, compound 1 also exhibited poor metabolic stability in human liver microsomes. During the structural modification of 1, we found that a novel series of N-alkylidenearylcarboxamide, 4-1, had a moderate affinity for the CB(2) receptor (IC(50)=260 nM, EC(50)=86 nM, E(max)=100%) and good metabolic stability in human liver microsomes. We explored its analogues to discover compounds with a high affinity for the CB(2) receptor and with good oral bioavailability. Among them, compounds 4-9 and 4-27 had high affinities for the human CB(2) receptor (CB(2) IC(50)=13 nM and 1.2 nM) and a high selectivity for CB(2) (CB(1) IC(50)/CB(2) IC(50)=270 and 1600); furthermore, significant plasma levels were observed following oral administration in rats (C(max)=233 ng/mL and 148 ng/mL, respectively, after a dose of 10 mg/kg). Furthermore, compound 4-9 had good oral bioavailability (F=52%, 3mg/kg).