Updated results of a phase II trial of AP23573, a novel mTOR inhibitor, in patients (pts) with advanced soft tissue or bone sarcomas

Abstract

9505 Background: AP23573 is an mTOR inhibitor that has shown anti-tumor activity in phase 1 clinical trials, particularly in patients with advanced sarcomas. Given this observation, this phase 2 trial was undertaken to assess further the efficacy and safety of AP23573 across various sarcoma subtypes. Methods: Advanced sarcoma pts, with no restrictions on prior therapies, were enrolled into 4 cohorts based on histologic subtype, in a phase 2 trial with Simon’s 2-stage design. AP23573 (12.5 mg, i.v.) is administered for 5 days every 2 wks. Efficacy is assessed using RECIST guidelines, with clinical benefit response (CBR) defined as complete or partial response (PR) or stable disease (SD) for at least 16 wks duration. For each cohort, treatment was defined as successful if the proportion of patients with CBR was ≥ 25%. Studies of potential predictive markers of response include 18 FDG-PET imaging, analysis of mTOR pathway proteins in tumoral tissue, and measurement of plasma cytokines and angiogenic factors. Results: In total, 216 pts were enrolled as all cohorts met criteria to enter Stage 2 of the trial. Of these pts, 213 were treated (106 M/107 F) (age 17–79 yrs, median 50 yrs). Most frequent related adverse events included mucositis, rash, hyperlipidemia, fatigue, and thrombocytopenia. Preliminary response data for 193 evaluable pts are available: overall 54 (28%) had CBRs, including 5 PRs (3 pts with osteo, 1 with spindle cell of bone, and 1 with MFH). Twenty of 76 pts (26%) imaged with PET had rapid induction of partial metabolic responses following 3 to 5 days of study treatment. Conclusions: Initial assessments from this trial show that single-agent AP23573 is well tolerated and has efficacy in pts with advanced sarcomas that warrants evaluation in phase 3. Analysis of the potential utility of FDG-PET and a broad set of candidate biomarkers continues. Enrollment is complete, and pt treatment and follow-up are ongoing. [Table: see text] [Table: see text]