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Clin Cancer Res. 2009 May 1;15(9):3172-6. doi: 10.1158/1078-0432.CCR-08-2985. Epub 2009 Apr 14.

An open-label, multicenter, phase I/II study of single-agent AT-101 in men with castrate-resistant prostate cancer.

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University of Wisconsin Paul P. Carbone Comprehensive Cancer Center, Madison, Wisconsin, USA.



AT-101 binds and inhibits the antiapoptotic function of Bcl-2, Bcl-xL, Mcl-1, and Bcl-w and is a potent stimulator of proapoptotic proteins. In this multi-institution phase I/II trial, we evaluated the safety and efficacy of single-agent AT-101, in men with chemotherapy naïve, castrate-resistant prostate cancer (CRPC).


Patients with progressive CRPC were to be treated with escalating doses of AT-101 on a continuous daily basis until the maximally tolerated dose was achieved. At the recommended phase 2 dose, an additional 21 patients were planned to assess for preliminary evidence of efficacy.


Twenty-three patients were enrolled. The phase I starting dose was 30 mg/day on a continuous basis; however, ongoing trials with AT-101 showed increased gastrointestinal toxicity with this daily schedule when given for repetitive cycles. As a result, the phase II starting dose was chosen to be 30 mg/day for 21 of 28 days. The most frequent observed adverse events (any grade) were diarrhea (43.5%), fatigue (34.8%), nausea (21.7%), anorexia (21.7%), and small intestinal obstruction (21.7%). Due to the high incidence of grade 3 small intestinal obstruction (n = 5; 21.7%), a reduction in dose to 20 mg/day for 21 of 28 days was mandated for all patients. Two patients had a confirmed > or =50% posttherapy prostate-specific antigen decline. No objective responses (Response Evaluation Criteria in Solid Tumors) were observed.


AT-101 administered at 20 mg/day for 21 of 28 days was well-tolerated. Evidence of single-agent clinical activity was observed with prostate-specific antigen declines in some patients. Further investigation of AT-101 in prostate cancer is warranted and trials combining AT-101 with androgen deprivation, as well as with docetaxel chemotherapy are ongoing.

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