['refractory chronic cough']
['5 mg serlopitant tablets', 'matching placebo tablets']

        Inclusion Criteria:

          -  Female and males between 18 and 80 years of age

          -  Have a diagnosis of treatment refractory chronic cough or unexplained cough for at
             least one year

          -  Chest radiograph or computed tomography (CT) Thorax within the last 5 years not
             demonstrating any abnormality considered to be significantly contributing to the
             chronic cough

          -  At Screening have a score of ≥ 40mm on the Cough Severity VAS

          -  At Baseline (Day 0) have a score of ≥ 40mm on the Cough Severity VAS

          -  All female subjects who are of childbearing potential must practice highly effective
             contraception (i.e., pregnancy prevention method with a failure rate of < 1% per year)
             from the time of the initial screening visit until 4 weeks after last dose of study
             drug. Please refer to the protocol for acceptable methods of contraception

        Exclusion Criteria:

          -  Prior treatment with serlopitant or other NK1-R antagonist

          -  Presence of any medical condition or disability that could interfere with study

          -  History of hypersensitivity to serlopitant or any of its components

          -  Currently pregnant or male partner of pregnant female

          -  Females of childbearing potential who are unable or unwilling to use adequate
             contraception or who are breast feeding

          -  Current smoker or individuals who have given up smoking within the past 12 months

          -  FEV1/FVC < 60%

          -  Body mass index (BMI) <18 kg/m2 or ≥ 40 kg/m2 at Screening

          -  History of upper or lower respiratory tract infection or recent significant change in
             pulmonary status within 4 weeks of the Baseline Visit (Day 0)

          -  History of cystic fibrosis

          -  History of opioid use within 1 week of the Baseline Visit (Day 0)

          -  Requiring concomitant therapy with prohibited medications

          -  Treatment with biologic therapies within 8 weeks or 5 half-lives prior to the Baseline
             Visit (Day 0), whichever is longer

          -  Treatment with strong CYP3A4 inhibitors within 4 weeks prior to the Baseline Visit
             (Day 0)

          -  Treatment with any investigational therapy within 4 weeks (investigational biologic
             therapies within 8 weeks) prior to the Baseline Visit (Day 0)

          -  Serum creatinine, total bilirubin, alanine aminotransferase (ALT) or aspartate
             aminotransferase (AST) > 2x the upper limit of normal (ULN) during screening

          -  Positive test for any drug of abuse

          -  History of malignancy within 5 years prior to the Baseline Visit (Day 0), with the
             exception of completely treated and non-metastatic basal cell carcinoma or squamous
             cell carcinoma of the skin

          -  Any known psychiatric diagnosis meeting DSM-5 criteria 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 randomization.
             Examples of such DSM-5 diagnoses include but are not limited to major depressive
             disorder, bipolar disorder, schizophrenia, psychotic disorder, intellectual
             disability, severe alcohol use disorder.

          -  Known active hepatitis infection

          -  Known history of human immunodeficiency virus (HIV) infection
      