Study of the Efficacy, Safety and Tolerability of Serlopitant for the Treatment of Pruritus (Itch) With Prurigo Nodularis

Inclusion Criteria (Subjects must meet the following criteria to be randomized into the study:

1. Male or female, age 18 years or older at consent.

2. Prurigo nodularis (PN), with at least ten nodules on at least two different body surface areas.

3. Idiopathic PN, or an identified pruritic condition associated with the PN with persistent pruritus despite at least 6 weeks of optimized and stable treatment of the underlying condition.

4. The worst pruritus is identified as within the areas of the PN lesions, with a Worst-Itch Numeric Rating Scale (WI-NRS) score in the 24-hour period prior to the Screening visit, and average weekly WI-NRS score in each of the 2 weeks prior to Baseline visit indicating an appropriate pruritus level for the study.

5. Female subjects of childbearing potential must be willing to practice highly effective contraception until 5 weeks after last dose of study drug.

6. Willing and able to complete daily eDiary entries within a consistent timeframe for the duration of the study.

7. Willing and able to comply with study visits and study related requirements including providing written informed consent.

Exclusion Criteria (Subjects who meet any of the following criteria are not eligible for participation in the study):

1. Prior treatment with serlopitant.

2. Active pruritic skin disease, other than PN, within 6 months (with the exception of acute dermatoses such as contact dermatitis, sunburn, viral exanthem, which have been resolved for longer than 4 weeks).

3. Treatment with any of the following therapies within 4 weeks.

4. Other neurokinin-1 receptor antagonists (e.g., aprepitant, fosaprepitant, rolapitant).

5. Systemic or topical immunosuppressive/immunomodulatory therapies.

6. Systemic therapies with recognized anti-pruritic properties.

7. Strong cytochrome-P 3A4 inhibitors.

8. Use of an indoor tanning facility, or natural sun exposure resulting in significant tanning or sunburn.

9. Treatment with topical anti-pruritic therapies within 2 weeks.

10. Treatment with biologic therapies within 8 weeks or 5 half-lives, whichever is longer.

11. Treatment with any investigational therapy within 4 weeks (8 weeks for investigational biologic therapies) or 5 half-lives, whichever is longer.

12. Serum creatinine, total bilirubin, alanine aminotransferase or aspartate aminotransferase > 2.5 times the upper limit of normal during screening.

13. Untreated or inadequately treated thyroid adrenal, or pituitary nodules or disease, or history of thyroid malignancy.

14. Malignancy within 5 years prior to enrollment (exception for non-melanoma cutaneous malignancies).

15. Relevant major psychiatric diagnosis in the past 3 years, such as major depressive disorder, bipolar disorder, schizophrenia, psychotic disorder, intellectual disability, severe alcohol use disorder.

16. Documented history of parasitic infection, including skin parasites such as scabies, within 8 weeks.

17. Any medical condition or disability that could interfere with the assessment of safety or efficacy in this study or compromise the safety of the subject.

18. History of hypersensitivity to serlopitant or any of its components.

19. Currently pregnant or breastfeeding or planning to become pregnant during the study.

20. Planned or anticipated major surgical procedure or other activity that would interfere with the subject's ability to comply with protocol-mandated assessments during participation in the study.