LY2795050 is a novel selective κ-opioid Receptor (KOR) antagonist (IC50=0.72 nM) and has the potential as a PET tracer to image KOR in vivo. IC50 Value: 0.72 nM (κ-opioid Receptor); 25.8 nM (κ-opioid) [1] Target: κ-opioid Receptor in vitro: LY2795050 displays full antagonist activity and high binding affinity and selectivity for KOR with a ki value of 0.72 nM [1]. in vivo: In the brain, (11)C-LY2795050 displayed fast uptake kinetics (regional activity peak times of <20 min) and an uptake pattern consistent with the distribution of KOR in primates [1]. The LY2795050 ED50 at MOR was 119 μg/kg based on a 1-site model for 11C-carfentanil. The 1-site binding model was also deemed sufficient to describe the specific binding of 11C-LY2795050 at KOR. The ED50 at KOR estimated from the 1-site model was 15.6 μg/kg. Thus, the ED50 ratio for MOR:KOR was 7.6 [2].

Reference:

[1]. Mitch, Charles H.; Quimby, Steven J.; Diaz, Nuria; et al. Discovery of Aminobenzyloxyarylamides as κ Opioid Receptor Selective Antagonists: Application to Preclinical Development of a κ Opioid Receptor Antagonist Receptor Occupancy Tracer. Journal of Medicinal Chemistry (2011), 54(23), 8000-8012.
[2]. Zheng MQ, Nabulsi N, Kim SJ, Synthesis and evaluation of 11C-LY2795050 as a κ-opioid receptor antagonist radiotracer for PET imaging. J Nucl Med. 2013 Mar;54(3):455-63.
[3]. Kim SJ, Zheng MQ, Nabulsi N, Determination of the In Vivo Selectivity of a New κ-Opioid Receptor Antagonist PET Tracer 11C-LY2795050 in the Rhesus Monkey. J Nucl Med. 2013 Aug 5.