Study of the Long Term Safety of Serlopitant for the Treatment of Pruritus (Itch)

Inclusion Criteria: * Male or female, age 18 years or older at consent. * Pruritus associated with prurigo nodularis, atopic dermatitis, or psoriasis. * Female subjects of childbearing potential must be willing to practice highly effective contraception until 5 weeks after last dose of study drug. * Willing and able to comply with study visits and study related requirements including providing written informed consent. Exclusion Criteria: * Malignancy within 5 years prior to enrollment (exception for non-melanoma cutaneous malignancies). * Any known major psychiatric diagnosis, such as major depressive disorder, bipolar disorder, schizophrenia, psychotic disorder, intellectual disability, severe alcohol use disorder, which may confound the assessment of serlopitant safety or efficacy, or interfere with the subject's ability to comply with protocol-mandated activities, within 3 years prior to enrollment. * Untreated or inadequately treated thyroid, adrenal, or pituitary nodules or disease, or history of thyroid malignancy; or the prescense of any medical condition or disability, that could interfere with the assessment of safety in this study or compromise the safety of the subject. * Investigational therapy within 4 weeks or 5-half-lives prior to enrollment (whichever is longer) or expected participation in another clinical study involving an investigational product or device during the subject's participation in this study. * Treatment with other neurokinin-1 receptor (NK1-R) antagonists (e.g., aprepitant, fosaprepitant, rolapitant) within 4 weeks. * Treatment with strong cytochrome P450 3A4 inhibitors within 4 weeks. * Currently pregnant or breastfeeding or planning to become pregnant during the study.