Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically or cytologically confirmed solid tumor

- Advanced, metastatic, or recurrent disease

- No curative therapy exists

- Measurable or evaluable disease

PATIENT CHARACTERISTICS:

Age:

- 18 and over

Performance status:

- WHO 0-2

Life expectancy:

- At least 3 months

Hematopoietic:

- Absolute granulocyte count at least 1,500/mm^3

- Platelet count at least 100,000/mm^3

- Hemoglobin at least 9 g/dL

Hepatic:

- Bilirubin no greater than 1.5 mg/dL (unless due to Gilbert's syndrome)

- SGOT OR SGPT no greater than 2 times upper limit of normal (ULN) (5 times ULN if
liver metastases present)

Renal:

- Creatinine no greater than 1.5 mg/dL

- Creatinine clearance at least 60 mL/min

Other:

- No unstable or severe concurrent medical condition that would preclude study
participation

- No sociological or familial condition that would preclude study compliance

- No psychological or addictive disorder that would preclude study compliance

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY:

Biologic therapy:

- Not specified

Chemotherapy:

- At least 4 weeks since prior chemotherapy (6 weeks for nitrosourea or mitomycin) and
recovered

Endocrine therapy:

- Not specified

Radiotherapy:

- At least 4 weeks since prior radiotherapy and recovered

- No prior radiotherapy to more than 40% of bone marrow

Surgery:

- Not specified

Other:

- At least 2 weeks since prior blood transfusions

- At least 4 weeks since prior investigational agent and recovered

- No prior glycinamide ribonucleotide formyltransferase (GARFT) inhibitor

- No concurrent extradietary folate supplements

- No concurrent allopurinol

- No other concurrent anticancer or investigational agents