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 tributyrin in treating patients with refractory stage IV prostate cancer or other solid tumors.

OBJECTIVES: I. Determine the maximum tolerated dose and optimum schedule of tributyrin in patients with prostate cancer or other solid tumors. II. Determine the toxic effects of tributyrin in these patients. III. Determine the pharmacodynamics of tributyrin, including modulation of tumor markers, evaluation of clinical remission (when possible), assessment of F-reticulocytes and/or F cells, and evaluation of hemoglobin F before and after treatment, in these patients. IV. Determine the pharmacokinetics of tributyrin, including maximum plasma concentration, terminal half-life, area under the concentration time curve, volume of distribution, and clearance of butyrate, in these patients. V. Determine the relationship between the pharmacokinetics and toxic or therapeutic pharmacodynamic effects of butyrate in these patients. VI. Calculate a tributyrin dose, using results from pharmacokinetic and pharmacodynamic studies, that achieves sustained butyrate concentrations capable of increasing therapeutic effects with reduced toxicity.

OUTLINE: This is a dose escalation study. Patients receive oral tributyrin every 8 hours for 3 weeks. Treatment continues every 4 weeks for 2 courses in the absence of disease progression or unacceptable toxicity. Patients who achieve stable disease may receive additional courses at the discretion of the protocol chairperson. Cohorts of 3-6 patients receive escalating doses of tributyrin 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.

PROJECTED ACCRUAL: Approximately 24 patients will be accrued for this study within 1 year.

• Prostate Cancer
• Unspecified Adult Solid Tumor, Protocol Specific

• Drug: chemotherapy
• Drug: tributyrin

DISEASE CHARACTERISTICS: Histologically proven prostate cancer or other solid tumor that is refractory to standard treatment or for which no standard therapy exists Patients with prostate cancer must meet the following conditions: Stage D2 disease Disease progression after orchiectomy or treatment with leuprolide or flutamide If no prior orchiectomy, must continue leuprolide or other antiandrogen throughout study No CNS neoplasms or brain metastases

PATIENT CHARACTERISTICS: Age: 18 and over Performance status: ECOG 0-2 Life expectancy: More than 3 months Hematopoietic: WBC at least 3,000/mm3 Platelet count at least 100,000/mm3 Hemoglobin at least 9 g/dL Hepatic: Bilirubin no greater than 1.5 mg/dL AST and ALT no greater than 1.5 times normal Renal: Creatinine no greater than 1.5 mg/dL OR Creatinine clearance greater than 50 mL/min Other: No concurrent medical or psychiatric condition that would preclude study Able to swallow numerous capsules Willing to participate in pharmacokinetic studies 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 (more than 8 weeks since prior carmustine, mitomycin, or other drugs with delayed toxic effects) and recovered No prior suramin Endocrine therapy: See Disease Characteristics At least 4 weeks since prior flutamide No concurrent hydrocortisone or other steroids Radiotherapy: At least 4 weeks since prior radiotherapy and recovered No concurrent palliative radiotherapy Surgery: See Disease Characteristics