Asimadoline (EMD-61753) is a proprietary small molecule therapeutic, originally discovered by Merck KGaA of Darmstadt, Germany. Asimadoline was originally developed to treat peripheral pain such as arthritis. Asimadoline is an orally administered agent that acts as a kappa opioid receptor agonist. It has shown encouraging clinical efficacy for the treatment of IBS in a barostat study in IBS patients and has the potential for treating other gastrointestinal diseases.

Asimadoline hydrochloride (EMD-61753 hydrochloride) is a κ-opioid receptor agonist potentially for the treatment of pruritus. Asimadoline hydrochloride has also been shown to be used in the treatment of irritable bowel syndrome.

CJ-15208 is a potent and selective κ-opioid receptor antagonist from a fungus, Ctenomyces serratus ATCC15502 (IC50 are 47 nM for kappa, 260 nM for mu, and 2,600 nM for delta respectly). In the electrically-stimulated twitch response assay of rabbit vas de