Study of Intravenous BCX-1777 in Relapsed or Refractory Aggressive T-Cell Leukemias or Lymphomas

Inclusion Criteria:

* Previously treated, relapsed or refractory aggressive T-cell malignancies (leukemias and lymphomas) histologically proven with measurable disease.
* Capable of only limited self-care, confined to bed or chair more than 50% of waking hours.
* All ages are eligible. Pediatric patients (\<15 years of age) are eligible to be treated at a dose level previously tested in adults.
* Adequate liver and renal function.
* Patients with prior history of stem cell transplant if they meet all other eligibility requirements.
* Negative pregnancy test within 72 hours of study treatment in females of childbearing potential.
* Life expectancy of at least 2 months.

Exclusion:

* Active serious infection not controlled by oral or intravenous antibiotics.
* Treatment with any investigational antileukemic agents or chemotherapy agents in the last 7 days before study entry, unless full recovery from side-effects has occurred or patient has rapidly progressive disease judged to be life-threatening by the investigator.
* Concurrent treatment with other anti-cancer agents.
* Known CNS leukemia or lymphoma requiring intrathecal or craniospinal radiation therapy. Lumbar puncture not required in asymptomatic patients.
* Pregnant and/or lactating women; or fertile men or women not willing to use contraception.