Rationale TRV130 (oliceridine; N-[(3-methoxythiophen-2-yl)methyl]-2-[(9R)-9-pyridin-2-yl-6-oxaspiro[4.5]decan-9-yl]ethanamine) is a novel mu opioid receptor (MOR) agonist that preferentially activates G-protein vs. β-arrestin signaling pathways coupled to MORs. Prevailing evidence suggests that TRV130 and other G-protein-biased MOR agonists may produce therapeutic analgesic effects with reduced adverse effects compared to existing MOR agonists. Objectives This study compared effects of acute and repeated TRV130 administration on measures of antinociception, gastrointestinal function, and abuse liability in rodents. We hypothesized that TRV130 would produce robust and sustained antinociception and abuse-related effects during repeated treatment, but that tolerance would develop to GI inhibition. Methods Antinociception was assessed using a warm-water tail-withdrawal procedure in mice. Gastrointestinal function was assessed in mice using an in vivo measure of fecal output and in vitro assays of colonic propulsion and of colon and ileum circular muscle contraction. Abuse liability was assessed in rats using an intracranial self-stimulation (ICSS) procedure. (+)-TRV130 was administered with acute and repeated dosing regimens, and (−)-TRV130 was also examined in the ICSS procedure to assess stereoselectivity. Results Acute (+)-TRV130 treatment produced robust antinociception, complete inhibition of gastrointestinal function, and weak abuse-related effects. Repeated (+)-TRV130 treatment failed to produce tolerance to antinociception or GI inhibition, and abuse-related effects were enhanced by repeated treatment. Effects of acute and repeated (+)-TRV130 in these procedures resemble effects of morphine, with the exception that TRV130 antinociception was more resistant to tolerance. (−)-TRV130 was inactive. Conclusions These results suggest that TRV130 retains undesirable constipating and abuse-related effects during repeated treatment despite its bias for G-protein signaling.

Cannabinoid CB 1 receptors (CB 1 Rs) mediate the presynaptic effects of endocannabinoids in the central nervous system (CNS) and most behavioral effects of exogenous cannabinoids. Cannabinoid receptor-interacting protein 1a (CRIP 1a ) binds to the CB 1 R C-terminus and can attenuate constitutive CB 1 R-mediated inhibition of Ca 21 channel activity. We now demonstrate cellular colocalization of CRIP 1a at neuronal elements in the CNS and show that CRIP 1a inhibits both constitutive and agonist-stimulated CB 1 Rmediated guanine nucleotide-binding regulatory protein (G-protein) activity. Stable overexpression of CRIP 1a in human embryonic kidney (HEK)-293 cells stably expressing CB 1 Rs (CB 1 -HEK), or in N18TG2 cells endogenously expressing CB 1 Rs, decreased CB 1 Rmediated G-protein activation (measured by agonist-stimulated [ activation. These effects were not attributable to differences in CB 1 R expression or endocannabinoid tone because CB 1 R levels did not differ between cell lines varying in CRIP 1a expression, and endocannabinoid levels were undetectable (CB 1 -HEK) or unchanged (N18TG2) by CRIP 1a overexpression. In CB 1 -HEK cells, 4-hour pretreatment with cannabinoid agonists downregulated CB 1 Rs and desensitized agonist-stimulated [ 35 S]GTPgS binding. CRIP 1a overexpression attenuated CB 1 R downregulation without altering CB 1 R desensitization. Finally, in cultured autaptic hippocampal neurons, CRIP 1a overexpression attenuated both depolarizationinduced suppression of excitation and inhibition of excitatory synaptic activity induced by exogenous application of cannabinoid but not by adenosine A1 agonists. These results confirm that CRIP 1a inhibits constitutive CB 1 R activity and demonstrate that CRIP 1a can also inhibit agonist-stimulated CB 1 R signaling and downregulation of CB 1 Rs. Thus, CRIP 1a appears to act as a broad negative regulator of CB 1 R function.