Difelikefalin

Several chemically diverse pruritogens, including bombesin, compound 48/80, norbinaltorphimine, and 5'-GNTI, cause rodents to scratch excessively in a stable, uniform manner and consequently provide convenient animal models of itch against which potential antipruritics may be evaluated, structure-activity relationships established, and the nature of spontaneous, repetitive behavior itself analyzed. Decreasing the number of scratching bouts in these apparently simple models has been the requisite first step in the progress of kappa opioid agonists such as nalbuphine, asimadoline, and CR845 toward clinical testing as antipruritics. Nalfurafine is the prime example of a kappa agonist spanning the developmental divide between scratching mice models and commercialization within 10 years. Patients undergoing hemodialysis and suffering from the itching associated with uremic pruritus, and potentially those inflicted with atopic dermatitis, are the beneficiaries.

The opioid pain market is a lucrative one, but is experiencing significant challenges in the U.S. as the country grapples with prescription opioid addiction, overdose and fatalities. The situation has been declared a national Public Health Emergency and the Food and Drug Administration (FDA) has introduced several measures intended to reduce opioid abuse. The development of abuse-deterrent prescription opioids is one such measure, but although abuse-deterrent formulations of opioids reduce drug liking and abuse, concerns have been highlighted by an Institute of Clinical and Economic Review (ICER) report regarding the insufficiency of currently available data to determine the effects of these formulations at the population level. However, the low abuse liability but effective analgesic efficacy reported for drugs such as NKTR-181 and difelikefalin highlight the potential of novel abuse-deterrent opioids.