Inclusion Criteria

DISEASE CHARACTERISTICS:

- Histologically confirmed solid tumor that failed to respond or relapsed after prior
therapy or for which no standard therapy exists

- Biopsy-accessible lesion

- No brain metastasis unless clinically stable and off therapy

PATIENT CHARACTERISTICS:

Age:

- 18 and over

Performance status:

- ECOG 0-2

Life expectancy:

- More than 6 weeks

Hematopoietic:

- Absolute neutrophil count greater than 1,500/mm^3

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

- Hemoglobin at least 9.0 g/dL

Hepatic:

- Bilirubin no greater than 2 times upper limit of normal (ULN)

- Transaminases less than 2.5 times ULN

Renal:

- Creatinine less than 2.0 mg/dL

Other:

- Not pregnant or nursing

- Negative pregnancy test

- Fertile patients must use effective contraception during and for at least 30 days
after study

- Able to tolerate oral medication

- HIV negative

- No AIDS

- No serious underlying gastrointestinal disorders (e.g., recurrent vomiting or
inflammatory bowel disease)

- No other serious concurrent illness

PRIOR CONCURRENT THERAPY:

Biologic therapy:

- At least 4 weeks since prior immunotherapy

- Concurrent stable doses of epoetin alfa are allowed during the second and subsequent
courses

- No other concurrent immunotherapy

Chemotherapy:

- At least 4 weeks since prior chemotherapy

- No concurrent chemotherapy

Endocrine therapy:

- At least 4 weeks since prior hormonal therapy

- Concurrent stable doses of steroids for prostate cancer are allowed during the second
and subsequent courses

- No concurrent hormonal therapy

Radiotherapy:

- At least 4 weeks since prior radiotherapy

- No concurrent radiotherapy

Surgery:

- No prior significant gastric resection

Other:

- Recovered from prior therapy

- At least 4 weeks since other prior investigational antitumor drugs

- No other concurrent investigational antitumor drugs

- Concurrent stable doses of bisphosphonates, cyclo-oxygenase-2 inhibitors, and
non-steroidal anti-inflammatory drugs are allowed during the second and subsequent
study courses