Biased agonism of the μ-opioid receptor by TRV130 increases analgesia and reduces on-target adverse effects versus morphine: A randomized, double-blind, placebo-controlled, crossover study in healthy volunteers

Opioids provide powerful analgesia but also efficacy-limiting adverse effects, including severe nausea, vomiting, and respiratory depression, by activating mu-opioid receptors. Preclinical models suggest that differential activation of signaling pathways downstream of these receptors dissociates analgesia from adverse effects; however, this has not yet translated to a treatment with an improved therapeutic index. Thirty healthy men received single intravenous injections of the biased ligand TRV130 (1.5, 3, or 4.5 mg), placebo, or morphine (10 mg) in a randomized, double-blind, crossover study. Primary objectives were to measure safety and tolerability (adverse events, vital signs, electrocardiography, clinical laboratory values), and analgesia (cold pain test) versus placebo. Other measures included respiratory drive (minute volume after induced hypercapnia), subjective drug effects, and pharmacokinetics. Compared to morphine, TRV130 (3, 4.5 mg) elicited higher peak analgesia (105, 116 seconds latency vs 75 seconds for morphine, P < .02), with faster onset and similar duration of action. More subjects doubled latency or achieved maximum latency (180 seconds) with TRV130 (3, 4.5 mg). Respiratory drive reduction was greater after morphine than any TRV130 dose (-15.9 for morphine versus -7.3, -7.6, and -9.4 h * L/min, P < .05). More subjects experienced severe nausea after morphine (n = 7) than TRV130 1.5 or 3 mg (n = 0, 1), but not 4.5 mg (n = 9). TRV130 was generally well tolerated, and exposure was dose proportional. Thus, in this study, TRV130 produced greater analgesia than morphine at doses with less reduction in respiratory drive and less severe nausea. This demonstrates early clinical translation of ligand bias as an important new concept in receptor-targeted pharmacotherapy. (C) 2014 International Association for the Study of Pain. Published by Elsevier B.V. All rights reserved.