Inclusion Criteria:

          -  Adults ages 18 years or older.

          -  Participant must have relapsed or refractory acute myeloid leukemia (AML) (excluding
             acute promyelocytic leukemia).

          -  Relapsed patients must have received at least 1 induction chemotherapy regimen or two
             cycles of a hypomethylating agent and achieved a Complete Response (CR), followed by
             relapse of disease.

          -  Refractory patients must have received at least 1 induction chemotherapy regimen or
             two cycles of hypomethylating agent without achieving a CR.

          -  Eastern Cooperative Oncology Group (ECOG) performance status <2.

          -  Participants must have acceptable organ function.

          -  Be able and willing to adhere to the study visit schedule and other protocol
             requirements.

          -  Must be able to swallow capsules and have no evidence of GI tract abnormality that
             would alter the absorption of oral medications.

          -  The effects of Minnelide on the developing human fetus are unknown. For this reason,
             women of child-bearing potential must have a negative serum or urine pregnancy test
             within 24 hours prior to beginning study treatment.

          -  Participants of childbearing potential must practice contraception. Females of
             childbearing potential: Recommendation is for 2 effective contraceptive methods during
             the study. Male participants with female partners who are of childbearing potential:
             Recommendation is for male and partner to use at least 2 effective contraceptive
             methods, as described above, during the study. Should a woman become pregnant or
             suspect she is pregnant while participating in this study, she should inform her
             treating physician immediately.

          -  Because there is an unknown but potential risk for adverse events in nursing infants
             secondary to treatment of the mother with Minnelide, breastfeeding mothers must agree
             to discontinue nursing if the mother is treated with Minnelide.

          -  Provision of signed and dated informed consent document

          -  Patients with prior allogeneic stem cell transplant who experience relapse of AML are
             eligible if they are off of immunosuppressive therapy and without any evidence of
             graft-versus-host disease (GVHD)

        Exclusion Criteria:

          -  Participants may not have received any therapy with any investigational products,
             systemic anti-neoplastic therapy, or radiotherapy within 14 days prior to Cycle 1 Day
             1. Patients actively receiving hydroxyurea are eligible and may continue to receive
             hydroxyurea during protocol treatment.

          -  Candidates for standard and/or potentially curative treatments.

          -  Major surgery within 28 days prior to Cycle 1 Day 1.

          -  New York Heart Association Class III or IV heart failure, myocardial infarction within
             the past 6 months, unstable arrhythmia, or evidence of ischemia on an
             electrocardiogram (EKG)

          -  Active, uncontrolled bacterial, viral, or fungal infections, requiring systemic
             therapy

          -  Known, active HIV, Hepatitis A, B or C infection (prior Hepatitis C infection that has
             been treated and determined to be cured is allowed)

          -  Symptomatic central nervous system (CNS) involvement with leukemia

          -  A concurrent second active and non-stable malignancy with the exception of
             non-melanoma skin cancer or carcinoma in-situ.