DISEASE CHARACTERISTICS: Histologically confirmed cholangiocarcinoma, bile duct cancer, or gallbladder cancer with or without evidence of unresectable extrahepatic metastasis Previously untreated disease OR Progressive disease after first line chemotherapy Bidimensionally measurable disease by CT scan, chest x-ray, or MRI of the abdomen No known brain metastases

PATIENT CHARACTERISTICS: Age: 16 and over Performance status: ECOG 0-2 Life expectancy: At least 12 weeks Hematopoietic: Absolute neutrophil count at least 1,500/mm3 Platelet count at least 100,000/mm3 Hemoglobin at least 9.0 g/dL Hepatic: Bilirubin no greater than 2.0 mg/dL Albumin at least 2.8 g/dL SGOT or SGPT no greater than 5 times upper limit of normal (ULN) PT or INR no greater than 1.5 times ULN (if not on Coumadin therapy) Renal: Creatinine no greater than 1.5 mg/dL Cardiovascular: No active congestive heart failure No uncontrolled angina No myocardial infarction within the past 6 months Other: Not pregnant or nursing Negative pregnancy test Fertile patients must use effective contraception before and during study No concurrent serious infection No other life threatening illness No overt psychosis or mental disability that would preclude informed consent No other malignancy within the past 5 years, except: Curatively treated nonmelanomatous skin cancer Carcinoma in situ of the cervix

PRIOR CONCURRENT THERAPY: Biologic therapy: No concurrent biologic therapy Chemotherapy: See Disease Characteristics At least 4 weeks since prior chemotherapy and recovered No prior camptothecin analogues No other concurrent chemotherapy Endocrine therapy: Not specified Radiotherapy: At least 4 weeks since prior radiotherapy and recovered No concurrent radiotherapy Surgery: At least 4 weeks since prior major surgery and recovered No concurrent surgery Other: No other concurrent anticancer therapy At least 4 weeks since prior investigational drugs No other investigational drugs during or within 4 weeks after final dose of study drug No concurrent drugs that induce or inhibit CYP3A enzyme