A phase II trial of the mTOR inhibitor AP23573 as a single agent in advanced endometrial cancer

5516 Background: There are few effective therapies for women with advanced or recurrent endometrial cancer. Targeted therapies such as AP23573, a novel mTOR inhibitor, may result in clinical benefit with fewer side effects. Preliminary results of a trial of single agent AP23573 in patients with progressive endometrial cancer who may have had up to 2 prior regimens of cytotoxic chemotherapy are reported. Methods: The trial is an open-label, Simon 2-stage, single-arm study enrolling patients who have advanced endometrial cancer with documented progression in the 3 months prior to entry. Patients receive 12.5mg AP23573 QDx5 as a 30-min. intravenous infusion every other week for 28-day cycles. The primary efficacy endpoint is Clinical Benefit Response (CBR), defined as a complete or partial response or prolonged stable disease (= 16 weeks) by modified RECIST guidelines. Results: Seven of the first 19 patients achieved CBR, allowing expansion to the second stage. Enrollment is now complete (45 patients). Demographic data are available for 35 (median 66 yrs.; range 46–89) patients who received treatment: 23 adenocarcinomas, 5 carcinosarcomas, 6 papillary serous carcinomas (UPSC) and 1 clear cell carcinoma. Thirty-four patients had prior chemotherapy including doxorubicin, taxanes or platinum agents. Fourteen of the 26 patients with available history had prior pelvic radiotherapy. Nine of 27 (33%) patients evaluable for response had CBRs, including 2 partial responses (PRs). One CBR had UPSC, the remaining patients, including the PRs, had adenocarcinomas. Seven of the patients achieving CBR are still on treatment. Eighteen of the 27 patients discontinued treatment before 4 cycles because of progressive disease (14), consent withdrawal (1) or unrelated adverse events (3). Adverse event data are available for 27 patients. The most common adverse events are fatigue, anemia (33% each), mouth sores and nausea/vomiting (30% each). There have been 16 grade 3/ 4 treatment related adverse events (2 hyperglycemia, 14 separate events similar to those reported in other AP23573 trials). Conclusions: AP23573 shows encouraging single-agent activity in pretreated patients with advanced, progressive endometrial cancer and is well tolerated. No significant financial relationships to disclose.