Study of the Efficacy, Safety, and Tolerability of Serlopitant for the Treatment of Chronic Pruritus of Unknown Origin

Inclusion: * Male or female, age 18 years or older at consent. * The subject must have ongoing chronic pruritus * The subject's pruritus is assessed by the investigator to be of unknown origin at baseline. * 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. * The pruritus must have been unresponsive to prior treatment with emollients. * The subject's pruritus must be present on multiple segments of the body * Willing and able to complete daily eDiary entries within a consistent timeframe for the duration of the study * All females who are of childbearing potential must be willing to practice highly effective contraception and not be pregnant or nursing * Willing to comply with study visits and study related requirements including providing written informed consent. * Adequate cognitive and physical ability, in the investigator's opinion, to comply with study visits and study related requirements including providing written informed consent Exclusion * Prior treatment with any NK1-receptor antagonists * Known dermatologic or systemic condition(s), other than dry skin, that is considered by the investigator to be the primary cause of current pruritus. * Untreated or inadequately treated thyroid, adrenal, or pituitary disease or nodules, or history of thyroid malignancy. * Use of an excluded the…