Inclusion Criteria:

          -  Have either of the following diagnoses:

               1. Morphologically confirmed acute myeloid leukemia (AML), except acute
                  promyelocytic leukemia (APL), including leukemia secondary to prior therapy or
                  antecedent hematologic disorder (e.g., MDS or myeloproliferative disorders), who
                  have failed to achieve CR or who have relapsed after prior therapy and are not
                  candidates for potentially curative therapy

               2. Intermediate-2 or High-grade risk MDS (including chronic myelomonocytic leukemia
                  (CMML))

          -  Have received at least one prior therapy. Patients who are over age 65 and have not
             received therapy for AML are also eligible, if they are not candidates for induction
             chemotherapy

          -  ECOG performance status of 0 to 2

          -  Predicted life expectancy of ≥ 3 months

          -  Adequate liver, renal and cardiac function

        For Group 1 in Part 2 of the Study ONLY:

        • Positive for RAS mutation at a Clinical Laboratory Improvement Amendments
        (CLIA)-certified laboratory prior to study entry

        Exclusion Criteria:

          -  Concomitant malignancies except carcinoma in situ, basal or squamous cell skin
             carcinoma; low grade prostate cancer treated with prostatectomy more than 10 years
             ago; early stage melanoma treated with complete surgical excision more than 5 years
             ago; carcinoma in situ of cervix treated with cone procedure more than 8 years ago

          -  Gastrointestinal condition which could impair absorption of study medication

          -  Uncontrolled or severe intercurrent medical condition

          -  Patients with rapidly increasing peripheral blood blast counts

          -  Known uncontrolled central nervous system involvement

          -  Any cancer-directed therapy within 28 days or 5 half-lives, whichever is shorter

          -  Any concurrent or prior use of an investigational drug (including MEK inhibitors)
             within previous 28 days or 5 half-lives, whichever is shorter

          -  Received chemotherapy regimens with delayed toxicity within the last four weeks (six
             weeks for prior nitrosourea or mitomycin C). Received chemotherapy regimens given
             continuously or on a weekly basis with limited potential for delayed toxicity within
             the last two weeks.

          -  Ongoing anticoagulant therapy that cannot be held if necessary to permit bone marrow
             sampling.

          -  Major surgery within 4 weeks prior to first dose

          -  Pregnant or breast-feeding women

          -  Any evidence of serious active infections

          -  Any important medical illness or abnormal laboratory finding that would increase the
             risk of participating in this study

          -  A history or current evidence/risk of retinal vein occlusion or central serous
             retinopathy

          -  Concurrent therapy with drugs known to be strong inhibitors of CYP1A2, CYP2D6, and
             CYP3A4, or strong inducers of CYP3A4