Inclusion Criteria:

          -  Histologically documented malignant salivary gland cancers with or without metastases,
             not amenable to curative treatment; or there is documentation of patient refusal of
             curative treatment.

          -  Previous mutational testing with no evidence of a p53 mutation.

          -  ECOG performance status of ≤ 1.

          -  Presence of measurable disease by CT scan per RECIST v1.1 with > 20% increase in tumor
             burden in the preceding 12 months.

          -  Life expectancy of ≥12 weeks.

          -  Signed and dated informed consent document indicating that the patient (or legally
             acceptable representative) has been informed of all pertinent aspects of the trial
             prior to enrollment.

          -  Willingness and ability to comply with scheduled visits, treatment plans, laboratory
             tests, and other study procedures.

          -  Adequate organ and marrow function obtained ≤ 2 weeks prior to enrollment.

        Exclusion Criteria:

          -  Prior treatment with MDM2 inhibitors.

          -  Patients are not eligible if they have received any systemic anti-cancer therapy
             (including chemotherapy and/or hormone therapy) for salivary gland cancer within 4
             weeks of the start of study therapy.

          -  Patients are not eligible if they have received any of the following within 4 weeks of
             the start of study therapy: live vaccines, antiretroviral drugs

          -  Progressive disease with platinum-based chemotherapy within the last 6 months.

          -  Patients with active brain metastases are excluded because of unknown penetration into
             the CNS. A confirmatory scan for asymptomatic patients is not required. Patients with
             a history of treated central nervous system (CNS) metastases are eligible provided
             they meet all of the following criteria: disease outside the CNS is present, no
             clinical evidence of progression since completion of CNS-directed therapy, minimum 4
             weeks between completion of radiotherapy and enrollment and recovery from significant
             (Grade ≥ 3) acute toxicity.

          -  A serious uncontrolled medical disorder or active infection that would impair their
             ability to receive study treatment.

          -  Patients (male and female) having procreative potential who are not willing or not
             able to use 2 adequate methods of contraception or practicing abstinence during the
             study and for 90 days following their last dose of treatment