RATIONALE: Drugs used in chemotherapy use different ways to stop tumor cells from dividing so they stop growing or die.

PURPOSE: Phase II trial to study the effectiveness of piritrexim in treating patients with advanced cancer of the urinary tract that has not responded to previous treatment.

OBJECTIVES: I. Evaluate the antineoplastic activity of piritrexim and its effect on the survival of patients with advanced urothelial carcinoma previously treated with systemic cytotoxic chemotherapy. II. Evaluate the toxicity of piritrexim in these patients.

OUTLINE: Patients receive piritrexim by mouth 3 times daily, 5 days a week, for 3 weeks followed by 1 week of rest. Patients with responding or stable disease continue treatment every 4 weeks until unacceptable toxicity or progression intervenes.

PROJECTED ACCRUAL: A maximum of 40 patients will be entered over 5-6 months if at least 1 response is observed in the first 14 evaluable patients.

DISEASE CHARACTERISTICS: Histologically confirmed transitional cell carcinoma, squamous cell, or adenocarcinoma of the renal pelvis, ureter, bladder, or urethra Progressing regional or metastatic disease after one prior systemic or intra- arterial chemotherapy regimen Bidimensionally measurable disease, e. g.: Pulmonary nodules Palpable lymph nodes Cutaneous or subcutaneous nodules Mediastinal tumor or hepatic metastases if clearly measurable on CT No prior radiotherapy to indicator lesion unless documented progression since completion of radiotherapy

PATIENT CHARACTERISTICS: Age: 18 and over Performance status: ECOG 0 or 1 Hematopoietic: (within 2 weeks prior to entry) WBC at least 4,000/mm3 Platelet count at least 100,000/mm3 Hepatic: (within 2 weeks prior to entry) Bilirubin no greater than 2.0 mg/dL AST no greater than twice normal Renal: (within 2 weeks prior to entry) Creatinine no greater than 1.5 mg/dL OR Creatinine clearance greater than 40 mL/min Other: No active unresolved infection No concurrent parenteral antibiotics At least 7 days since parenteral antibiotics No history of prior malignancy within 5 years except: Curatively treated nonmelanomatous skin cancer In situ cancer of the cervix Not pregnant or nursing Adequate contraception required of fertile patients Physically and medically able to take oral medications

PRIOR CONCURRENT THERAPY: Biologic therapy: One prior systemic biological response modifier therapy allowed At least 3 weeks since biologic response modifier therapy and recovered Chemotherapy: See Disease Characteristics At least 3 weeks since chemotherapy and recovered Endocrine therapy: Not specified Radiotherapy: At least 4 weeks since radiotherapy Surgery: At least 3 weeks since major surgery and recovered