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Dupilumab in patients with prurigo nodularis: two randomized, double-blind, placebo-controlled phase 3 trials

Prurigo nodularis (PN) is a chronic infammatory skin disease with intensely pruritic nodules. The LIBERTY-PN PRIME and PRIME2 phase 3 trials enrolled adults with PN with ≥20 nodules and severe itch uncontrolled with topical therapies. Dupilumab, a fully human monoclonal antibody, blocks the shared receptor component for interleukin (IL)-4 and IL-13. Patients were randomized 1:1 to 300 mg dupilumab or placebo subcutaneously every 2 weeks for 24 weeks. The primary endpoint was pruritus improvement, measured by proportion of patients with a ≥4-point reduction in Worst Itch Numeric Rating Scale (WI-NRS) from baseline at week 24 (PRIME) or week 12 (PRIME2). Key secondary endpoints included nodule number reduction to ≤5 at week 24. PRIME and PRIME2 enrolled 151 and 160 patients, respectively. Both trials met all the pre-specifed primary and key secondary endpoints. A ≥4-point WI-NRS reduction at week 24 in the dupilumab and placebo arms was achieved by 60.0% and 18.4% of patients, respectively, in PRIME (95% confdence interval (CI), 27.8–57.7 for the diference, P < 0.001) and at week 12 by 37.2% and 22.0% of patients, respectively, in PRIME2 (95% CI, 2.3–31.2; P = 0.022). Dupilumab demonstrated clinically meaningful and statistically signifcant improvements in itch and skin lesions versus placebo in PN. Safety was consistent with the known dupilumab safety profle.

Prurigo nodularis (PN), a chronic inflammatory skin condition characterized by intensely pruritic papulonodular lesions, substantially impacts quality of life (QoL)1,2. Variable prevalence was reported in several countries3–6 ; in the United States, it affects annually an estimated 18–72 adults per 100,000 population7,8 . PN is driven by an itch–scratch cycle with an intensity and frequency of chronic pruritus among the highest reported in dermatologic and other pruritic diseases9–11, and often is accompanied by skin pain, stinging and burning. The high symptom burden in PN causes sleep impairment and affects mental and emotional health2,12. The disease burden is frequently compounded by associated comorbidities, including infections, malignancies and renal, hepatic and neuropsychiatric disorders13–15; 18.7–46.3% of adult patients have a history of atopy or current atopic comorbidity, such as atopic dermatitis (AD)7,8,11,13,16,17.

PN represents a substantial therapeutic challenge, and inadequate disease control is common in this population2,18–23. Although topical treatments, UV light therapy, immunosuppressive agents and systemic neuromodulators are frequently prescribed, these therapies are limited by insufficient evidence for efficacy and/or associated side effects18,23. Recently, dupilumab was approved as the first systemic therapy indicated in PN24,25. Case reports have shown successful treatment with dupilumab in PN26–28. Dupilumab, a fully human VelocImmune-derived monoclonal antibody29,30, blocks the shared receptor component (IL-4Rα) for interleukin (IL)−4 and IL-13, thus inhibiting signaling of these central drivers of type 2 inflammation. In two parallel phase 3 trials of similar design, LIBERTY-PN PRIME and PRIME2, we assessed the efficacy and safety of dupilumab in adults with PN that was inadequately controlled with topical prescription therapies (Extended Data Fig. 1). Patients were randomized 1:1 to receive subcutaneous dupilumab 300 mg or matching placebo every 2 weeks for 24 weeks. Patients on a stable regimen of low-to-moderate potency topical corticosteroids (TCSs) and topical calcineurin inhibitors (TCIs) before screening were allowed to continue their use throughout the trial. The primary endpoint was the proportion of patients with a ≥4-point reduction in Worst Itch Numeric Rating Scale (WI-NRS) score (range 0 (‘no itch’) to 10 (‘worst imaginable itch’)) at week 24 (PRIME) or week 12 (PRIME2). WI-NRS is validated in PN, with research to date supporting a four-point reduction as clinically meaningful31–33. Key secondary endpoints in both trials included proportion of patients with reduction in skin lesion number to an Investigator Global Assessment for PN-Stage (IGA PN-S) score of 0 or 1 at week 24. IGA PN-S is also validated in PN, with scores ranging from 0 to 4 (0, ‘clear’ (no nodules); 1, ‘almost clear’ (≤5 nodules); 2, ‘mild’ (6–19 nodules); 3, ‘moderate’ (20–99 nodules); 4, ‘severe’ (≥100 nodules))34. Other pre-specified secondary and tertiary endpoints included assessment of QoL, skin pain, sleep and mental health

Results
Patients

In PRIME, 200 patients were screened and 151 were randomized (75 dupilumab and 76 placebo) at 58 study sites in eight countries/ regions. In PRIME2, 221 patients were screened and 160 were randomized (78 dupilumab and 82 placebo) at 55 study sites in 11 countries/ regions (Fig. 1 for CONSORT diagrams and Supplementary Information for lists of investigators). The population sample was representative for the PN real-world sex6,17, age11,16,17,35, racial/ethnic background distribution17 and associated comorbidities1,8,11,13,16,35 (Supplementary Table 1). Assessment scales used to measure disease severity and treatment outcomes (WI-NRS31–33, IGA PN-S34, Dermatology Life Quality Index (DLQI)36,37, Hospital Anxiety and Depression Scale (HADS)38,39, Sleep Numeric Rating Scale (NRS) and Skin Pain NRS) are detailed in Supplementary Table 2. Baseline characteristics were generally balanced between intervention groups in both trials (Table 1). All patients had severe itch at baseline, as demonstrated by a mean (s.d.) WI-NRS score of 8.5 (1.0) in both trials and ≥20 nodules upon entry; 28.7% (PRIME) and 38.4% (PRIME2) of patients had ≥100 nodules (IGA PN-S = 4). Mean (s.d.) DLQI baseline scores were 16.7 (7.2) in PRIME and 18.2 (6.7) in PRIME2, corresponding to ‘very large’ impact of PN on life. All patients in both studies had used topical therapies in the past; 98.7% and 98.1% reported past use of TCS; and 69.5% and 63.1% had previously received systemic therapies (Table 1). The most common associated medical conditions in patients in both trials were hypertension, type 2 diabetes mellitus and hypothyroidism (Supplementary Table 3). Other baseline disease characteristics are summarized in Table 1.

Efficacy analyses

A study-level multiplicity procedure was used to control for the overall type I error rate for testing primary, key secondary and selected other endpoints (Methods and Extended Data Table 1). P values less than 0.05 were considered statistically significant if the endpoint was included in the testing hierarchy

Primary endpoint

The primary endpoint in both trials addressed clinically meaningful itch improvement. A weekly WI-NRS score was calculated as the average of daily non-missing scores within the week window of each trial week. The trials were originally designed similarly, with week 12 as the timing for the primary endpoint. However, results from PRIME2, which preceded PRIME, showed continued improvement of itch after week 12. To represent more precisely the effect of the treatment on itch and to harmonize the assessment of the itch and lesion endpoint evaluations, a protocol amendment was submitted and approved while the PRIME study was ongoing to change the timing for the primary endpoint to week 24.
Significantly more dupilumab-treated patients achieved the primary endpoint of a ≥4-point reduction in WI-NRS compared to placebo-treated patients in both trials: 45/75 (60.0%) versus 14/76 (18.4%) at week 24 in PRIME (95% confidence interval (CI), 27.8–57.7 for the difference; P < 0.001); 29/78 (37.2%) versus 18/82 (22.0%) at week 12 in PRIME2 (95% CI, 2.3–31.2 for the difference; P = 0.022) (Table 2, Fig. 2a and Supplementary Table 4). Patients with missing data (PRIME, week 24: 1 (1.3%) in the dupilumab group and 16 (21.1%) in the placebo group; PRIME2, week 12: 2 (2.6%) and 6 (7.3%), respectively) were considered non-responders due to missing data (see Supplementary Table 5 for a summary of missing data).

Secondary endpoints addressing itch

Proportion of patients achieving a ≥4-point reduction in WI-NRS was also higher in the dupilumab group compared to placebo at week 12 in PRIME: 44% versus 15.8% (95% CI for the difference, 14.5–43.8; non-multiplicity-controlled P < 0.001) and at week 24 in PRIME2 (key secondary endpoint): 57.7% versus 19.5% (95% CI for the difference, 29.1– 56.1; P < 0.001) (Table 2, Fig. 2a and Supplementary Table 5). Compared to placebo, non-multiplicity-controlled significant improvements in least squares (LS) mean percent change in weekly average WI-NRS with dupilumab were observed as early as week 3 in PRIME and week 4 in PRIME2 (Fig. 3a). The proportion of patients achieving a ≥4-point reduction in WI-NRS was significantly higher with dupilumab than with placebo starting at week 4 in PRIME and week 5 in PRIME2 (non-multiplicitycontrolled P versus placebo <0.05) (Extended Data Fig. 2).

Secondary endpoints addressing skin lesions

Significantly more dupilumab-treated patients achieved an IGA PN-S score of 0 or 1 (‘clear’ or ‘almost clear’, ≤5 nodules) in each trial at week 24: PRIME, 48.0% versus 18.4% (95% CI for the difference, 13.4–43.2; P < 0.001); PRIME2, 44.9% versus 15.9% (95% CI for the difference, 16.4–45.2; P < 0.001). At week 12, this endpoint was achieved by 32.0% versus 11.8% of patients in PRIME (95% CI for the difference, 7.8–34.0; non-multiplicity-controlled P = 0.003) and 25.6% versus 12.2% in PRIME2 (95% CI for the difference, 2.6–27.0; P = 0.019) (Fig. 2b, Extended Data Fig. 3 for proportions of patients achieving IGA 0/1 over time and Supplementary Table 5 for a summary of missing data). Significantly more patients achieved the composite endpoint (key secondary endpoint in both trials) of a concomitant ≥4-point reduction in WI-NRS from baseline and an IGA PN-S score of 0 or 1 at week 24 in the dupilumab group (29 (38.7%) and 25 (32.1%) in PRIME and PRIME 2, respectively) compared to seven patients in each placebo group (9.2% and 8.5%, 95% CI, 16.4–42.8 and 13.1–37.9 for the difference, respectively; P < 0.001 for both comparisons), demonstrating efficacy on pruritus and skin lesions within the same patient (Fig. 2c). Supplementary (as-observed and hybrid method) analyses results for primary and key secondary endpoints in both trials were consistent with the primary analysis, confirming the robustness of results (Extended Data Table 2).

Fig. 1 | Consort diagrams of patient disposition. a, PRIME. No patients were lost to follow-up at the time of the cutoff date. * Low-to-medium potency TCS/TCI as background therapy permitted (maintain dose from screening to end of treatment (EOT)).  Patient’s decision (fear of being exposed to Coronavirus Disease 2019 (COVID-19)).  One patient experienced a serious adverse event (SAE) of Hodgkin’s disease; one patient experienced an SAE of duodenal ulcer perforation; and one patient experienced a non-serious event of neurodermatitis. § None was related to safety issues, lack of efficacy or COVID-19.  Poor compliance to protocol. b, PRIME2. No patients were lost to follow-up at the time of the cutoff date. * Low-to-medium potency TCS/TCI as background therapy permitted (maintain dose from screening to EOT).  No discontinuations related to COVID-19.  Patient could not continue the self-administration of investigational medicinal product. § None of the ‘other’ reasons for permanent study intervention discontinuation was related to safety or lack of efficacy. All were reported as the reason for withdrawal by the subject.

Other multiplicity-controlled endpoints

Additional multiplicity-controlled endpoints in both trials included changes from baseline in DLQI, Skin Pain NRS and HADS at week 24 and, in PRIME2 only, change in Sleep NRS at week 24 (Extended Data Table 1 for the testing hierarchy). Dupilumab-treated patients showed significant improvements in QoL compared to placebo-treated patients, as measured by LS mean change (±s.e.) in DLQI score from baseline at week 24: PRIME, −12.0 (1.0) versus −5.8 (1.0); PRIME2, −13.2 (1.2) versus −6.8 (1.2) (95% CI, −8.3 to −4.0 and −8.4 to −4.4 for the difference, respectively; both P < 0.001) (Table 2 and Fig. 3b). Significant improvements in skin pain were also observed, as measured by LS mean change (s.e.) in Skin Pain NRS at week 24: PRIME, −4.3 (0.4) versus −2.2 (0.4); PRIME2, −4.4 (0.5) versus −2.7 (0.5) (95% CI, −3.1 to −1.3 and −2.5 to −0.7 for the difference, respectively; both P < 0.001) (Table 2 and Fig. 3c). Statistical (PRIME) or non-multiplicity-controlled (PRIME2) significant improvements in anxiety and depression, as measured by LS mean change (s.e.) from baseline in total HADS at week 24, were observed in both studies (Table 2 and Fig. 3d). Change from baseline in Sleep NRS at week 24 is shown in Table 2 and over time in Extended Data Fig. 4. Efficacy outcomes were similar between atopic and non-atopic patients as well as those who used TCS/TCI throughout the trial compared to those who did not (Extended Data Tables 3 and 4).

Table 1 | Demographic and clinical characteristics of the patient population at baseline

Note: Higher score indicates worse disease/larger impact, except for Patient Sleep Quality NRS, where higher score indicates better sleep quality. a 31.4% of PRIME patients from the United States and 55.6% of PRIME2 patients from the United States were Black or African American. b Including American Indian, Alaska Native, Native Hawaiian or Pacific Islands, unknown. c PRIME: Argentina, China, France, Japan, Mexico, Russia, South Korea, United States; PRIME2: Canada, Chile, France, Hungary, Italy, Portugal, South Korea, Spain, Taiwan, United Kingdom, United States. d Defined as having a medical history of AD, allergic rhinitis/rhinoconjunctivitis, asthma or food allergy. e Defined as maintaining the same medicine (low-to-medium-potency TCS or TCI) and maintaining the same frequency of treatment (once or twice daily) used from 2 weeks before screening.

Use of rescue medication

Fewer dupilumab-treated patients required rescue medication compared to those given placebo during the 24-week studies (PRIME, 6.7% versus 21.1%; PRIME2, 7.7% versus 24.4%; non-multiplicity-controlled P versus placebo = 0.004 in both trials) (Table 2 and Extended Data Fig. 5). Results for additional efficacy endpoints are summarized in Extended Data Table 5. This manuscript reports on all the multiplicity-controlled and pre-specified supportive endpoints included in the PRIME and PRIME2 trials. Additional pre-specified secondary and tertiary efficacy

Table 2 | Efficacy outcomes

Unless otherwise indicated, efficacy analyses were performed in the full analysis set, which included all patients who underwent randomization. The primary and secondary endpoints were tested with a hierarchical testing procedure in a pre-specified order, and inferential conclusions about successive endpoints required statistical significance of the previous endpoint at a two-sided significance level of 0.05. For endpoints that measured binary responses, P values were derived by a Cochran–Mantel–Haenszel test. The difference versus placebo is the response rate difference derived from the Mantel–Haenszel estimator. For continuous efficacy endpoints, P values and difference versus placebo were derived by an analysis of covariance (ANCOVA) model. For the endpoint of rescue medication, the difference versus placebo is based on the time to first use of rescue medication and was calculated as hazard ratio of dupilumab versus placebo; P values were derived from the Cox proportional hazard model. a Primary endpoint in PRIME, key secondary endpoint in PRIME 2. b Primary endpoint in PRIME 2, secondary endpoint in PRIME. c Key secondary endpoint PRIME and PRIME2. d Key secondary endpoint, United States and United States reference countries only. N/A, not available.