PARIS – while achieving across-the-board clinically meaningful improvements in quality of life measures in patients with hemodialysis-associated pruritus in a phase 2 study, Frédérique Menzaghi, PhD, reported at the annual congress of the European Academy of Dermatology and Venereology.
At present there is no approved medication in the United States or Europe for the often intense itching associated with chronic kidney disease. Off-label treatments have limited efficacy.
Dr. Menzaghi is senior vice president for research and development at Cara Therapeutics, which is developing difelikefalin.
More than half – 60% to 70% – of patients on hemodialysis for end-stage renal disease experience chronic pruritus, as do a smaller proportion of individuals with chronic kidney disease (CKD) not requiring dialysis. CKD-associated pruritus is a day-and-night itch that makes life miserable for affected patients. Not only must they endure the predictable complications of skin excoriation, including impetigo, ulcerations, papules, and prurigo nodularis, but they also experience sleep disruption, depressed mood, and a 10%-20% increased mortality risk compared with CKD patients without pruritus.
Difelikefalin is a potent and selective peripheral kappa opioid receptor agonist that doesn’t activate mu or delta opioid receptors. It’s a synthetic drug that mimics endogenous dynorphin. Its key attribute is that it doesn’t cross the blood/brain barrier, so it doesn’t pose a risk for adverse events caused by activation of central opioid receptors. Difelikefalin has two mechanisms of action in CKD-associated pruritus: an antipruritic effect due to inhibition of ion channels responsible for afferent peripheral nerve activity; and an anti-inflammatory effect mediated by activation of kappa opioid receptors expressed by immune system cells, according to Dr. Menzaghi.
She reported on 174 hemodialysis patients with moderate to severe CKD-associated pruritus who were randomized to a double-blind, phase 2, dose-ranging study featuring an intravenous bolus of difelikefalin at 0.5, 1.0, or 1.5 mcg/kg or placebo given immediately after each of the thrice-weekly hemodialysis sessions for 8 weeks.
An oral formulation of difelikefalin is also under investigation for treatment of CKD-associated pruritus. The IV version is being developed for hemodialysis patients because difelikefalin is renally excreted.
“We’re taking advantage of the fact that their kidneys aren’t working. The drug stays in the system until the next dialysis because it can’t be eliminated. It’s quite convenient for these patients,” she explained.
The primary endpoint in the phase 2 study was change from baseline through week 8 in the weekly average of a patient’s daily self-rated 0-10 worst itching intensity numeric rating scale (NRS) scores. All participants had to have a baseline NRS score of at least 4, considered the lower threshold for moderate itch. In fact, the mean baseline score was 6.7-7.1 in the four study arms.
Sixty-four percent of patients on difelikefalin 0.5 mcg/kg – the most effective dose – experienced at least a 3-point reduction, compared with 29% of placebo-treated controls. And a 4-point or greater reduction in NRS from baseline was documented in 51% of patients on difelikefalin at 0.5 mcg/kg, compared with 24% of controls.