P11.08 Defining EGFR amplification status for clinical trial inclusion

BACKGROUND

Precision medicine trials targeting the epidermal growth factor receptor (EGFR) in glioblastoma patients require selection for EGFR-amplified tumors. However, there is currently no golden standard in determining the amplification status of EGFR or EGFRvIII expression. Here, we aimed to determine which technique and which cut-offs are suitable to determine EGFR amplification status.

MATERIAL AND METHODS

We compared fluorescent in-situ hybridization (FISH) and RT-qPCR data from patients screened for trial inclusion into the Intellance 2 clinical trial, with data from a panel-based next generation sequencing (NGS) platform (both DNA and RNA).

RESULTS

By using data from >1000 samples, we show which cut-offs are optimal to determine EGFR gene amplification by FISH. Our data also show that gene amplification (as determined by FISH) correlates with EGFR expression levels (as determined by RT-qPCR) with ROC analysis showing an under the curve area of up to 0.902. EGFR expression as assessed by RT-qPCR therefore may function as a surrogate marker for EGFR amplification. Our NGS data shows that EGFR copy numbers can strongly vary between tumors with levels ranging from 2 to more than 100 copies per cell. Levels exceeding 5 gene copies can be used to define EGFR-amplification by NGS; below this level FISH detects very few (if any) EGFR amplified nuclei and none of the samples express EGFRvIII.

CONCLUSION

Our data from central laboratories and diagnostic sequencing facilities, using material from patients eligible for clinical trial inclusion, help defining the optimal cut-off for various techniques to determine EGFR amplification for diagnostic purposes.

PL3.5 Efficacy and safety of selinexor in recurrent glioblastoma

BACKGROUND

New treatment modalities are needed for recurrent glioblastoma (rGBM). Selinexor is a novel, oral selective inhibitor of nuclear export which forces nuclear retention of tumor suppressor proteins including p53 and p27, leading to apoptosis. We previously reported interim results showing tolerability, preliminary efficacy, and blood-brain barrier penetration in a surgical cohort (N=8). We now report updated results following completion of accrual to non-surgical cohorts (N=68).

MATERIALS AND METHODS

This is an open-label, multicenter, phase 2 study of selinexor monotherapy. Patients (pts) not undergoing surgery for measurable rGBM per response assessment neuro-oncology criteria (RANO) were enrolled in one of 3 arms encompassing different dosing schedules of selinexor (50 mg/m2 [~ 85 mg] BIW, 60 mg BIW, and 80 mg QW). Treatment was continuous, although cycles were defined as 28 days and response was assessed every other cycle by MRI. Prior treatment with radiotherapy and temozolomide was required and prior bevacizumab was exclusionary. The primary endpoint was 6-month progression free survival (6mPFS) rate, calculated by the Kaplan-Meier method.

RESULTS

76 pts were enrolled; 24, 14 and 30 pts on doses of ~85 mg BIW, 60 mg BIW, and 80 mg QW, respectively. Median age was 56 years (range 21–78). Median number of prior treatments was 2 (range 1–7)

At the end of the 6 cycles, 30.2% pts on 80 mg QW were free from progression. The 6mPFS rate on 80 mg QW was 18.9%. Best RANO-defined responses (assessed locally) among 26 evaluable pts on 80 mg QW included 1 complete response, 2 partial responses, 7 stable disease, and 16 with progressive disease. Complete and partial responses were durable: the complete and a partial responder remain on selinexor for 393 and 1093 days respectively, as of the cut-off date. Median duration of response was 10.8 months. The most common related adverse events (all grades) in pts on ~85 mg BIW/60 mg BIW/80 mg QW were nausea (42%/64%/63%), leukopenia (38%/7%/43%), fatigue (71%/71%/47%), neutropenia (29%/14%/33%), decreased appetite (46%/71%/27%), and thrombocytopenia (67%/29%/23%).

CONCLUSION

Selinexor demonstrated efficacy, with durable responses and disease stabilization in rGBM. Based on the favorable efficacy and safety profile, selinexor at a dose of 80 mg QW is recommended for further development in rGBM.