Although a 4-point difference is widely considered to represent clinically meaningful improvement in atopic dermatitis studies, Dr. Menzaghi said psychometric analyses of the difelikefalin trial data indicated that a 3-point or greater improvement in NRS score was associated with clinically meaningful change.
“Our data suggest that a 4-point change may not be generalizable to all conditions,” she said.
Hemodialysis patients with severe baseline itch typically improved to moderate itch on difelikefalin, while those with baseline moderate itch – that is, an NRS of 4-6 – dropped down to mild or no itch while on the drug.
“But that’s just a number. The question is, is that really clinically meaningful?” Dr. Menzaghi noted.
The answer, she continued, is yes. A high correlation was seen between reduction in itch intensity and improvement in quality of life. Scores on the 5-D Itch Scale and Skindex-10 improved two- to threefold more in the difelikefalin 0.5-mcg group than in controls. So did scores on the 12-item Medical Outcomes Study Sleep Scale assessing sleep restlessness, awakening during sleep, and trouble falling asleep.
“We think these results suggest that peripheral kappa opioid receptors play an integral role in the modulation of itch signals and represent a primary target for the development of antipruritic agents,” said Dr. Menzaghi.
Indeed, a phase 3 randomized trial of difelikefalin 0.5 mcg/kg versus placebo in 350 hemodialysis patients with CKD-associated itch is ongoing in the United States, Europe, Australia, and Korea. Also ongoing is a phase 2 U.S. study of oral difelikefalin in patients with CKD-associated pruritus, many of whom are not on hemodialysis. In January, the company announced that enrollment in a phase 3 U.S. study of difelikefalin injection (0.5 mcg/kg) in hemodialysis patients with moderate to severe CKD-associated pruritus had been completed. The trials are funded by Cara Therapeutics.
SOURCE: Menzaghi F. EADV Congress, Abstract FC0.4.7.