Phase 2 trial of SL-701, a novel immunotherapy comprised of synthetic short peptides against GBM targets IL-13ra2, EPHA2, and survivin, in adults with second-line recurrent GBM

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BACKGROUND: SL-701, a novel immunotherapy comprised of synthetic peptides elicits immune responses against overexpressed GBM targets: interleukin-13 receptor alpha-2 (IL-13Rα2), EphrinA2 (EphA2), and Survivin. Updated data reported from a multicenter, 2-stage Phase 2 clinical trial of SL-701 in HLA-A2+ adults with relapsed GBM. METHODS: Patients enrolled had KPS > 60 and failure of standard RT/TMZ. Stage 1: SL-701 was administered with adjuvants GM-CSF and imiquimod biweekly for 6 months, then q28 days. Stage 2: SL-701 and adjuvant poly-ICLC were administered biweekly with bevacizumab (10 mg/kg). Primary objectives include: safety and tolerability, investigator assessed objective response rate (ORR) using RANO criteria and 12 month-survival rate. RESULTS: As of 16May2017, 74 patients (46 in Stage 1 and 28 in Stage 2) received SL-701. Accrual for Stage 1 and 2 is complete. Patients were 100% bevacizumab naïve, 65% male with a median age of 56 years (range: 24-79). Patients received a median of 8.5 doses. The most frequent grade 3-4 treatmentrelated adverse event was fatigue (n = 2; 2.7%). Among 46 evaluable Stage 1 patients, 1 partial response (PR; duration: 78 weeks) and 15 stable disease (SD; median duration: 16 weeks; range: 1.3 - 99 weeks) were observed. Of 28 evaluable Stage 2 patients, 21% ORR consisting of 2 complete response (CR; duration: 30 and 46 weeks, respectively) and 4 PR (median duration: 31 weeks; range: 12 - 47 weeks) was observed with 19 SD (median duration: 14 weeks; range: 0.1 - 41 weeks) achieved. Median overall survival (mOS) of 11.2 and 11.7 months was observed for Stage 1 and 2 patients, respectively with a 25% survival probability at 14 weeks. SL-701 plus adjuvants with or without bevacizumab have a manageable safety profile with anti-tumor activity, several CRs, and a preliminarily promising survival curve, warranting further study. Updated study data will be presented.




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