(E/Z)-CLH304a (GABAB receptor antagonist 1) is a mixture of (E)-CLH304a and (Z)-CLH304a. (E)-CLH304a (CLH304a) is a specific and noncompetitive GABA B receptor negative allosteric modulator (NAM). CLH304a inhibits Baclofen -induced ERK1/2 phosphorylation in HEK293 cells overexpressing GABAB receptors.