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9-Aminocamptothecin (9-AC) was administered as a 72-h i.v. infusion every 2 weeks to a total of 99 adults with high-grade astrocytomas. Fifty-one patients with newly diagnosed glioblastoma multiforme received 9-AC treatment prior to radiation therapy and 48 patients with high-grade astrocytomas were treated at the time of tumor recurrence. Upon entrance into these research protocols, all patients had measurable disease that was evaluated on a monthly basis with volumetric CT or MRI scans. A partial response was defined by > or =50% reduction in the contrast enhancing volume on stable or decreasing doses of glucocorticoids. The study specified that all apparent responders would have central review of their radiologic studies and histopathology. The initial patients treated with 9-AC were also receiving anticonvulsants and were noted to have minimal myelosuppression with this chemotherapy. Thus, 9-AC doses were escalated from the previously reported maximum tolerated dose (MTD) of 850 microg/m2/24 h. We then established new MTDs for patients receiving enzyme-inducing anticonvulsants. We defined these MTDs to be 1,776 microg/m2/24 h for newly diagnosed, previously untreated patients and 1,611 microg/m2/24 h for patients with recurrent disease. Twenty-two patients with newly diagnosed glioblastoma multiforme received 9-AC at doses > or =1,776 microg/m2/24 h. Of these, 18 had evaluable disease on central review, and 0 of 18 (0%) demonstrated a partial or complete response. Twenty-one patients with recurrent high-grade astrocytomas were treated at 1,611 microg/m2/24 h; 20 had evaluable disease and 0 of 20 (0%) had a partial or complete response. Thus, the overall response rate in the 38 evaluable patients treated at the MTD was 0 of 38 (0%). Furthermore, of the 51 evaluable patients who were treated at doses less than the MTD, only one partial response was observed, yielding an overall response rate of 2%. Evidence of drug failure was rapid with tumor progression in one-half of patients after 2 drug cycles. 9-AC lacks evidence of substantial activity in patients with newly diagnosed or recurrent high-grade astrocytomas.