Inclusion Criteria:

- Histologically confirmed aggressive B-cell non-Hodgkin's lymphoma of 1 of the
following subtypes:

- Mantle cell lymphoma

- Diffuse large cell lymphoma

- (Ineligible for or unwilling to undergo stem cell transplantation)

- Relapsed or refractory disease:

- Any number of prior therapies allowed for relapsed disease, including peripheral
blood stem cell or bone marrow transplantation

- No more than 2 prior regimens, excluding monotherapy with monoclonal antibody or
radiotherapy, for refractory disease

- Measurable disease, defined as >= 1 lesion >= 1.5 cm in the longest diameter

- No transformed lymphoma, defined as the transformation of a low-grade lymphoma,
including follicular lymphoma or small lymphocytic lymphoma, to a high-grade lymphoma
(e.g., diffuse large cell lymphoma)

- ECOG performance status 0-2

- Absolute neutrophil count >= 1,000/mm^3 OR >= 500/mm^3 if extensive bone marrow
involvement (> 50%) or hypersplenism with palpable splenomegaly

- Platelet count >= 75,000/mm^3 OR >= 50,000/mm^3 if extensive bone marrow involvement
(> 50%) or hypersplenism with palpable splenomegaly

- Bilirubin normal

- Alkaline phosphatase =< 2 times upper limit of normal (ULN)

- AST =< 2 times ULN

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception

- No significant cardiac disease, including New York Heart Association class III-IV
congestive heart failure

- No history of serious ventricular arrhythmia

- QTc < 500 msec

- No evidence of cardiac hypertrophy on ECG

- No known HIV positivity

- No other uncontrolled serious medical condition or active infection (e.g., chronic
obstructive pulmonary disease, diabetes)

- Recovered from prior therapy

- No prior doxorubicin hydrochloride >= 450 mg/m^2 or mitoxantrone >= 112 mg/m^2
(Patients who received both mitoxantrone and doxorubicin hydrochloride should have a
"doxorubicin equivalent dose" < 450 mg/m^2

- No prior therapy with a histone deacetylase inhibitor

- No concurrent dexamethasone or prednisone except for refractory nausea/vomiting

- No concurrent drugs associated with QTc prolongation (e.g., dolasetron mesylate)

- Concurrent hydrochlorothiazide, furosemide, or other diuretics allowed provided
patient is receiving potassium chloride supplementation (No supplementation needed if
switched to a potassium-conserving diuretic)

- No CNS lymphoma

- Creatinine normal

- Cardiac function >= 50% by MUGA