JNJ16259685, a highly potent, selective and systemically active mGlu1 receptor antagonist

We examined the pharmacological profile of (3,4-dihydro-2H-pyrano[2,3]b quinolin-7-yl) (cis-4-methoxycyclohexyl) methanone (JNJ16259685). At recombinant rat and human metabotropic glutamate (mGlu) 1a receptors, JNJ16259685 non-competitively inhibited glutamate-induced Ca2+ mobilization with IC50 values of 3.24+/-1.00 and 1.21+/-0.53 nM, respectively, while showing a much lower potency at the rat and human mGlu5a receptor. JNJ16259685 inhibited [3H]1-(3,4-dihydro-2H-pyrano[2,3-b]quinolin-7-yl)-2-phenyl-1-ethanone ([3H]R214127) binding to membranes prepared from cells expressing rat mGlu1a receptors with a Ki of 0.34+/-0.20 nM. JNJ16259685 showed no agonist, antagonist or positive allosteric activity toward rat mGlu2, -3, -4 or -6 receptors at concentrations up to 10 microM and did not bind to AMPA or NMDA receptors, or to a battery of other neurotransmitter receptors, ion channels and transporters. In primary cerebellar cultures, JNJ16259685 inhibited glutamate-mediated inositol phosphate production with an IC50 of 1.73+/-0.40 nM. Subcutaneously administered JNJ16259685 exhibited high potencies in occupying central mGlu1 receptors in the rat cerebellum and thalamus ( ED50=0.040 and 0.014 mg/kg, respectively). These data show that JNJ16259685 is a selective mGlu1 receptor antagonist with excellent potencies in inhibiting mGlu1 receptor function and binding and in occupying the mGlu1 receptor after systemic administration.