Inclusion Criteria

- ELIGIBILITY CRITERIA:

Previously treated mantle cell lymphoma or diffuse large B-cell lymphoma (to include
mediastinal (thymic) large B-cell lymphoma; transformed large B-cell lymphoma; follicular
grade IIIB large B-cell lymphoma; intravascular large B-cell lymphoma).

Confirmed pathological diagnosis at the National Cancer Institute, National Institutes of
Health (NIH).

Recurrent measurable disease (measurable disease in 2 dimensions or leukemic disease which
can be quantified and followed).

Prior anthracycline-based treatment for patients with diffuse large B-cell lymphoma
(DLBCL).

Age greater than 18 years.

Eastern Cooperative Oncology Group (ECOG) performance 2 or better.

Major organ function: absolute neutrophil count (ANC) greater than 1000/mcL, Platelet
greater than 50,000/mcL, Creatinine less than 1.5 mg/dL or creatinine clearance greater
than 60 mL/min; serum glutamic pyruvic transaminase (SGPT) less than 5 x upper limit of
normal; bilirubin less than 2 mg/dL (total) except less than 5 mg/dL in patients with
Gilbert's syndrome as defined by greater than 80% unconjugated. ANC and platelet
requirements must be met independent of transfusion.

Informed consent and willingness to use contraception by both men and women.

Both male and female patients must be willing to use adequate contraception (to include
effective barrier methods of contraception) or to completely abstain from heterosexual
intercourse while on protocol treatment.

EXCLUSION CRITERIA:

Pregnant or nursing because of an unknown potential for teratogenic or abortifacient
effects.

Human immunodeficiency virus (HIV) serology negative. HIV positive patients receiving
combination anti-retroviral therapy are excluded from the study because of possible
pharmacokinetic interactions with flavopiridol. Additionally, the biology of HIV
associated DLBCL's is often quite different from HIV negative disease due to involvement
of Epstein Barr virus (EBV).

Hepatitis B surface antigen negative.

Active central nervous system (CNS) lymphoma. These patients have a poor prognosis and
because they frequently develop progressive neurological dysfunction that would confound
the evaluation of neurological and other adverse events.

History of inflammatory bowel disease unless this has been inactive for a period of 2 or
more years.

Recovery from toxicity of prior therapy to a grade 1 or less.

Systemic cytotoxic or experimental treatments within 4 weeks of treatment.

White blood cell (WBC) greater than 100,000 cells/mcL.