DISEASE CHARACTERISTICS:

• Histologically confirmed solid tumor that is clinically unresectable

  • No known standard therapy that is potentially curative or definitely capable of extending life expectancy
  • Patients with multiple myeloma may be enrolled to expansion cohort once the recommended phase II dose is established
• Tumor amenable to serial biopsy
• No bone metastases as only site of disease
• No CNS metastases

PATIENT CHARACTERISTICS:

Age:

• 18 and over

Performance status:

• ECOG 0-2

Life expectancy:

• At least 12 weeks

Hematopoietic:

• Absolute neutrophil count at least 1,500/mm^3
• Platelet count at least 100,000/mm^3
• Hemoglobin at least 10.0 g/dL

Hepatic:

• Bilirubin normal
• AST no greater than 2.5 times upper limit of normal (ULN)

Renal:

• Creatinine no greater than 1.5 times ULN

Cardiovascular:

• No New York Heart Association class III or IV heart disease

Gastrointestinal:

• Adequate oral intake
• No malabsorption syndrome
• No disease of terminal small bowel
• No dysphagia or other condition that would interfere with ability to swallow intact capsules

Other:

• No clinical contraindications (e.g., anticoagulant therapy) to biopsy
• No uncontrolled infection
• No seizure disorder
• Not pregnant or nursing
• Negative pregnancy test
• Fertile patients must use effective contraception

PRIOR CONCURRENT THERAPY:

Biologic therapy:

• More than 4 weeks since prior biologic therapy
• More than 4 weeks since prior immunotherapy
• No concurrent immunotherapy

Chemotherapy:

• More than 4 weeks since prior chemotherapy (6 weeks for nitrosoureas or mitomycin) and recovered
• No concurrent chemotherapy

Endocrine therapy:

• No concurrent megestrol

Radiotherapy:

• More than 4 weeks since prior radiotherapy
• No prior radiotherapy to more than 25% of bone marrow
• No concurrent radiotherapy

Surgery:

• See Disease Characteristics
• No prior extensive resection of terminal small bowel
• No prior major resection of the stomach or proximal small bowel

Other:

• No other concurrent ancillary investigational therapy