The results, which were published online in Nature Medicine, were the basis for the FDA approval of dupilumab (Dupixent) for adults with PN in September 2022, the first treatment approved for treating PN in the United States.
“These positive studies support the involvement of type 2 cytokines in driving PN disease pathogenesis and the targeting of the [interleukin]-4/IL-13 axis as a novel therapeutic paradigm for patients with PN,” wrote the researchers, who were led by principal investigator Gil Yosipovitch, MD, professor of dermatology at the University of Miami, Fla. Dupilumab, an IL-4 receptor alpha antagonist, blocks the shared receptor component (IL-4R alpha) for IL-4 and IL-13.
For the two phase 3 trials, which were called LIBERTY-PN PRIME and PRIME2 and were sponsored by Sanofi and Regeneron Pharmaceuticals, researchers randomized adults with PN with 20 or more nodules and severe itch uncontrolled with topical therapies 1:1 to 300 mg dupilumab or placebo subcutaneously every 2 weeks for 24 weeks. The primary endpoint was pruritus improvement, which was measured by the proportion of patients with a 4-point or greater reduction in Worst Itch Numeric Rating Scale (WI-NRS) from baseline at week 24 (PRIME) or week 12 (PRIME2). Key secondary endpoints included a reduction in the number of nodules to 5 or fewer at week 24.
PRIME and PRIME2 enrolled 151 and 160 patients, respectively. In PRIME, 60% of patients in the dupilumab arm achieved a 4-point or greater reduction in the WI-NRS at week 24, compared with 18.4% of patients in the placebo arm (P < .001). In PRIME2, 37.2% of patients in the dupilumab arm achieved a 4-point or greater reduction in the WI-NRS at week 12, compared with 22% of patients in the placebo arm (P = .022).
The researchers also reported that, from an initial baseline of 20 to greater than 100 nodules, 32.0% of dupilumab-treated patients in PRIME and 25.6% in PRIME2 showed a reduction to 5 nodules or fewer, which corresponded to a response of “clear” or “almost clear” skin at week 12, compared with 11.8% and 12.2% of placebo-treated patients, respectively. This treatment effect on skin lesions continued to improve after week 12, with 48% of dupilumab-treated patients in PRIME and 44.9% in PRIME2 having five nodules or fewer at week 24, compared with 18.4% and 15.9% of placebo-treated patients, respectively. Safety was consistent with the known dupilumab safety profile.
“Validation is the first success of this paper,” said Adam Friedman, MD, professor and chair of dermatology at George Washington University, Washington, who was asked to comment on the study. “While both the safety and efficacy of dupilumab in these two phase 3 programs is the meat of the matter, nuanced highlights for me include the rigid nature of the exclusion criteria to ensure a study population that truly has PN as a stand-alone disease, rather than a secondary finding as we once believed to be the entire story. I think it’s important for us to recognize that it’s not one or the other, rather there is both ‘primary’ prurigo nodularis, and then there is secondary prurigo nodularis associated with something else [a wide range of underlying medical conditions], just like we divide primary and secondary hyperhidrosis.”
Dr. Yosipovitch reported having competing interests with several pharmaceutical companies, including Regeneron and Sanofi. Dr. Friedman disclosed that he is a consultant to and a speaker for Regeneron.