DISEASE CHARACTERISTICS:

• Histologically or cytologically proven advanced cancer (except hematological cancers) for which there is no standard therapy or have failed standard therapies
• Measurable or evaluable disease
• Clinically controlled brain metastases allowed

PATIENT CHARACTERISTICS:

Age:

• 18 and over

Performance status:

• SWOG 0-2

Life expectancy:

• At least 3 months

Hematopoietic:

• Hemoglobin at least 8.0 g/dL
• Absolute neutrophil count at least 1,500/mm^3
• Platelet count at least 100,000/mm^3

Hepatic:

• Bilirubin no greater than 1.5 times upper limit of normal (ULN) (elevated bilirubin due to Gilbert's syndrome allowed if direct bilirubin normal)
• AST less than 2.5 times ULN

Renal:

• Creatinine normal

Cardiovascular:

• No active cardiac disease

Other:

• Not pregnant or nursing
• Fertile patients must use effective contraception
• No concurrent bacterial infection requiring antibiotics
• No serious concurrent medical condition

PRIOR CONCURRENT THERAPY:

Biologic therapy:

• No concurrent immunotherapy

Chemotherapy:

• At least 3 weeks since systemic cytotoxic chemotherapy (including gemcitabine) and recovered
• No other concurrent chemotherapy

Endocrine therapy:

• Prior hormonal therapy allowed
• No concurrent hormonal therapy (excluding contraceptives, appetite stimulants, or replacement steroids)

Radiotherapy:

• At least 3 weeks since radiotherapy to large areas of active bone marrow and recovered
• No concurrent radiotherapy

Surgery:

• Recovered from prior major surgery

Other:

• No concurrent antiviral nucleosides
• At least 1 month since prior investigational agents
• No other concurrent experimental medications