RATIONALE: Drugs used in chemotherapy use different ways to stop tumor cells from dividing so they stop growing or die.

PURPOSE: Phase I trial to study the effectiveness of tocladesine in treating patients who have recurrent or progressive metastatic colorectal cancer.

OBJECTIVES:

• Determine the maximum tolerated dose of tocladesine in patients with recurrent or progressive metastatic colorectal cancer.
• Determine the qualitative and quantitative toxicity of this drug in these patients.
• Assess any therapeutic activity in patients treated with this drug.

OUTLINE: This is a dose-escalation, multicenter study.

Patients receive tocladesine IV continuously on days 1-5 and 8-12. Treatment repeats every 21 days for up to 10 courses in the absence of disease progression or unacceptable toxicity.

Cohorts of 3-6 patients receive escalating doses of tocladesine until the maximum tolerated dose (MTD) is determined. The MTD is defined as the dose preceding that at which 2 of 6 patients experience dose-limiting toxicity. Once the MTD is determined, up to 14 additional patients are treated at this dose level.

PROJECTED ACCRUAL: A total of 3-38 patients will be accrued for this study.

DISEASE CHARACTERISTICS:

• Diagnosis of metastatic carcinoma of the colon or rectum

  • Recurrent or progressive after failing prior fluorouracil and irinotecan chemotherapy, sequentially or in combination, unless unable to tolerate irinotecan

• Measurable disease

PATIENT CHARACTERISTICS:

Age:

• 18 to 75

Performance status:

• ECOG 0-2

Life expectancy:

• Not specified

Hematopoietic:

• Granulocyte count at least 1,500/mm^3
• Platelet count at least 100,000/mm^3
• Hemoglobin at least 10 g/dL

Hepatic:

• Bilirubin no greater than 1.5 times upper limit of normal (ULN)
• AST and ALT no greater than 5 times ULN
• PT/aPTT no greater than 1.2 times ULN

Renal:

• Creatinine no greater than 1.5 mg/dL
• Creatinine clearance at least 50 mL/min
• No impaired renal function

Cardiovascular:

• No impaired cardiac function

Other:

• No active infection
• No other malignancy within the past 5 years except basal cell or squamous cell skin cancer
• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY:

Biologic therapy:

• Not specified

Chemotherapy:

• See Disease Characteristics
• At least 4 weeks since prior chemotherapy

Endocrine therapy:

• Not specified

Radiotherapy:

• At least 4 weeks since prior radiotherapy

Surgery:

• Not specified

Other:

• No other concurrent anticancer drugs
• No concurrent chronic non-steroidal anti-inflammatory agents
• No concurrent chronic therapeutic anticoagulation