Inclusion Criteria:

- Patients must be able to understand and voluntarily sign an informed consent form

- Able to adhere to the study visit schedule and other protocol requirements

- Life expectancy of greater than 6 months

- Must have one of the following diagnoses:

- Pathologically confirmed Chronic myelomonocytic (CMML) or myelodyspalstic
syndrome (MDS) with high risk features at the time of referral for trial as
defined by:

- Intermediate (INT)-2 or high International Prognostic Scoring System (IPSS)
score

- Secondary MDS (Defined as MDS developing in a patient with an antecedent
hematologic disorder or any patient with prior chemotherapy or radiation
exposure)

- INT-1 MDS with excess blasts (>= 5% blasts in bone marrow [BM]) or red
blood cell (RBC) transfusion-dependency

- MDS progressing to oligoblastic acute myelogenous leukemia (AML) with
21-30% BM blasts

- CMML with >= 5% marrow blasts, or RBC or platelet transfusion-dependency,
abnormal karyotype, or proliferative features (white blood cell count
>=13,000/µL , splenomegaly on physical examination, or extramedullary
disease)

- All patients are required to have failed to respond or relapsed after an
initial response to hypomethylating agents 5-azacitidine or decitabine or
have refused to receive hypomethylating therapy; failure to respond is
defined as failing to achieve a complete remission (CR), partial remission
(PR) or HI after at least 4 cycles of hypomethylating therapy; these
patients could have received other therapies or not, but must have received
hypomethylating therapy or have refused to receive hypomethylating therapy

- Pathologically confirmed AML patients who have received one or two courses of
induction chemotherapy or hypomethylating agent therapy AND no plans for further
chemotherapy therapy, but remain with residual disease of < 5% blasts in BM, by
morphology, cytogenetics, fluorescent in situ hybridization (FISH), polymerase
chain reaction (PCR) or flow cytometry

- Patients must not have received any other treatment for their disease, including
hematopoietic growth factors, within three weeks of beginning the trial, and should
have recovered from all toxicities of prior therapy (to grade 0 or 1)

- Eastern Cooperative Oncology Group (ECOG) performance status of =< 2 at study entry
ECOG, or Karnofsky >= 60%

- Calculated creatinine clearance by Modification of Diet in Renal Disease (MDRD)
(CrCL) > 50 ml/min/1.73 squared meter

- Total bilirubin =< 2.0 mg/dL unless due to Gilbert's syndrome, hemolysis, or
ineffective hematopoiesis

- Aspartate aminotransferase (AST) (serum glutamic oxaloacetic transaminase [SGOT]) and
alanine aminotransferase (ALT) (serum glutamate pyruvate transaminase [SGPT]) =< 3 x
upper limit of normal (ULN)

- Females of childbearing potential must have a negative serum or urine pregnancy test
within 72 hours prior to start of ipilimumab

- Patients must have no clinical evidence of central nervous system (CNS) or pulmonary
leukostasis, disseminated intravascular coagulation, or CNS leukemia

- Patients must have no serious or uncontrolled medical conditions

Exclusion Criteria:

- Any serious medical condition, uncontrolled intercurrent illness including, but not
limited to, ongoing or active infection, symptomatic congestive heart failure,
unstable angina pectoris, cardiac arrhythmia, laboratory abnormality, or psychiatric
illness/social situations that would limit compliance with study requirements or
prevent the subject from signing the informed consent form

- Pregnant or breast feeding females (lactating females must agree not to breast feed
while taking ipilimumab)

- Any condition, including the presence of laboratory abnormalities, which places the
subject at unacceptable risk if he/she were to participate in the study or confounds
the ability to interpret data from the study

- Use of any other experimental drug or therapy within 21 days of baseline

- Known hypersensitivity to ipilimumab or history of allergic reactions attributed to
compounds of similar chemical or biologic composition to ipilimumab

- Prior use of ipilimumab, other cytotoxic T-lymphocyte-associated protein 4 (CTLA-4)
blocking therapies, anti-programmed cell death 1 (PD 1) antibody, cluster of
differentiation (CD) 137 agonist or other immune activating therapy such as anti-CD
40 antibody within the last 3 months of enrollment in the study; if any of these of
these agents were used more than 3 months earlier to enrollment in study, the patient
should have recovered from all toxicity and at least 3 months had passed since last
use to allow for clearance and observation of any other side effects from the
previous therapy

- Concurrent use of other anti-cancer agents or treatments, including other
investigational agents

- Autoimmune disease: patients with a history of inflammatory bowel disease, including
ulcerative colitis and Crohn's disease, are excluded from this study, as are patients
with a history of symptomatic disease (e.g., rheumatoid arthritis, systemic
progressive sclerosis [scleroderma], systemic lupus erythematosus, autoimmune
vasculitis [e.g., Wegener's Granulomatosis]); central nervous system (CNS) or motor
neuropathy considered of autoimmune origin (e.g. Guillain-Barre Syndrome and
Myasthenia Gravis, multiple sclerosis)

- Patients with known immune impairment who may be unable to respond to anti-CTLA-4
antibody

- Patients with known other cancers, including brain metastases

- Patients who have had chemotherapy or radiotherapy within 4 weeks (6 weeks for
nitrosoureas or mitomycin C) prior to entering the study or those who have not
recovered from adverse events due to agents administered more than 4 weeks earlier

- Patients with chronic human immunodeficiency virus (HIV), hepatitis B or hepatitis C
infections should be excluded because of potential effects on immune function and/ or
possible drug interactions

- Pregnant women are excluded from this study; breastfeeding should be discontinued if
the mother is treated with ipilimumab