This phase I/II trial studies the best dose, possible benefits and/or side effects of oral azacitidine in treating patients with T-cell large granular lymphocytic leukemia that has come back (relapsed) or has not responded to previous treatment (refractory). Chemotherapy drugs, such as azacitidine, work in different ways to stop the growth of cancer cells, either by killing the cells, by stopping them from dividing, or by stopping them from spreading.

PRIMARY OBJECTIVES:

I. To determine the safety and maximum tolerated dose (MTD) of oral azacitidine (CC-486) in patients with symptomatic T-cell large granular lymphocytic leukemia (T-LGLL). (Phase I) II. To determine the overall response rate (complete response [CR] and partial response [PR]) of CC-486 in patients with T-LGLL. (Phase II)

SECONDARY OBJECTIVES:

I. Duration of response to CC-486. II. Progression-free survival. III. Rate of conversion from PR at 4 months to CR at 8 and 12 months. IV. Rate of molecular remission (T-cell receptor [TCR] clearance, STAT3 mutation clearance) at 4, 8, 12 months.

V. Effect of treatment on IL-15 promoter demethylation. VI. Effect of CC-486 on IL-15 promoter demethylation. VII. Safety of CC-486 in T-LGLL patients.

OUTLINE: This is a dose-escalation study.

Patients receive azacitidine orally (PO) on days 1-14. Treatment repeats every 28 days for 4 cycles in the absence of disease progression or unacceptable toxicity. Patients with PR or CR continue treatment for up to 8 additional cycles in the absence of disease progression or unacceptable toxicity.

Inclusion Criteria:

• Age 18 or older

• Diagnosis of T-LGLL defined as: CD3+CD8+ cell population > 650/mm^3 and the presence of a clonal T-cell receptor (within 1 month of diagnosis). This also includes patients with rare T-LGLL variants include CD4+ T-LGLL, and gamma/delta T-LGLL which can be CD4- and CD8, though patients still must have an LGL cell population >500 cells/mm3 and the presence of a clonal T-cell receptor within 1 month of diagnosis or relapse. Note: patients with myelodysplastic syndrome (MDS)-like T-LGLL may be included with principal investigator (PI) approval even if CD3+CD8+ cell population is < 650/mm^3, though +TCR is required. Natural-killer (NK) large granular lymphocytic leukemia (LGL) is also permitted, provided there is a clonal NK-cell population noted with > 500 cells/mm^3

• Failed at least one line of frontline therapy; off treatment for at least 14 days or 5 half-lives, whichever is longer

• Require Treatment for T-LGLL (One or more required)

  • Symptomatic anemia with hemoglobin < 10 g/dL
  • Transfusion-dependent anemia
  • Neutropenia with absolute neutrophil count (ANC) < 500/mm^3
  • Neutropenia with ANC < 1500/mm^3 with recurrent infections

• Platelet count >= 50 x 10^9/L

• Serum creatinine =< 2 x the upper limit of normal (ULN)

• Total bilirubin =< 1.5 x ULN (patients with Gilbert's syndrome with a bilirubin > 1.5 x ULN permitted)

• Aspartate aminotransferase (AST) and alanine aminotransferase (ALT) =< 1.5 x ULN

• Eastern cooperative oncology group (ECOG) performance status =< 2

• Men and women of reproductive potential must agree to follow accepted birth control methods for the duration of the study. Female subject is either post-menopausal or surgically sterilized or willing to use an acceptable method of birth control (i.e., a hormonal contraceptive, intra-uterine device, diaphragm with spermicide, condom with spermicide, or abstinence) for the duration of the study. Male subject agrees to use an acceptable method for contraception for the duration of the study

• Able to sign informed consent

Exclusion Criteria:

• Active Infection requiring ongoing anti-microbial treatment. Patients with human immunodeficiency virus (HIV), positive hepatitis B surface antigen or hepatitis C antibody will be excluded
• Concurrent immune-suppressive therapy (prednisone or equivalent up to 20 mg permitted to treat T-LGL symptoms, but must be weaned within one month of initiation of trial drug). Patients on stable, chronic prednisone =< 10 mg for rheumatologic/autoimmune conditions are exempted from this requirement. They may enroll on the study
• Active, concurrent malignancy unless deemed related to T-LGLL by PI
• Prior use of 5-azacytidine or decitabine
• Positive pregnancy test