PHASE 2 TRIAL OF SL-701, A NOVEL IMMUNOTHERAPY COMPRISED OF SYNTHETIC SHORT PEPTIDES AGAINST GBM TARGETS IL-13R alpha 2, EphA2, AND SURVIVIN, IN ADULTS WITH SECOND-LINE RECURRENT GBM: INTERIM RESULTS

SL-701 is a novel immunotherapy comprised of synthetic short peptides designed to elicit an immune response against three overexpressed GBM targets: interleukin-13 receptor alpha-2 (IL-13Rα2), EphrinA2 (EphA2), and Survivin. We report preliminary data from an ongoing multicenter, 2-stage Phase 2 clinical trial of SL-701 in HLA-A2 positive adults with first recurrence of GBM. Patients had to have KPS > 60, age > 18, and failed standard RT/TMZ. In Stage 1, SL-701 with adjuvants GM-CSF and imiquimod is administered biweekly for 6 months, then every 28 days thereafter. In Stage 2, SL-701 with the adjuvant poly-ICLC is administered biweekly with bevacizumab (10 mg/kg). Primary objectives: 1) safety and tolerability 2) investigator assessed objective response rate (ORR) using RANO criteria and 3) survival rate at 12 months. As of 5/17/16, 58 patients (46 in Stage 1 and 12 in Stage 2) received SL-701. Accrual for Stage 1 is complete. Stage 2 accrual is ongoing. Median age is 55 years (range: 23–74), median KPS is 90, and 67% are male. Patients received a median of 4 doses. The most frequent grade 3–4 treatment-related adverse events (TRAEs) were fatigue (n = 1; 1.7%) and altered mental status (n = 1, 1.7%). Among 30 evaluable patients in Stage 1, there was 1 partial response (PR) (33+ weeks duration, ongoing) and 15 stable diseases (SD) (median duration: 8 weeks; range: 8–42+ weeks, ongoing). Of the 4 evaluable patients in Stage 2 to date, there has been 1 PR (8+ weeks duration, ongoing) and 3 SD (median duration: 8 weeks; range: 5–8+ weeks, ongoing). SL-701 plus adjuvants GM-CSF/imiquimod or poly-ICLC and bevacizumab is well-tolerated. Patients are being followed for response, SD, PFS, and OS. Updated study data will be presented.