Abstract 1196: Combination of neuregulin with EGFR activation signatures predict activity of the anti-ErbB3 antibody KTN3379 in SCCHN

Abstract

Abstract ErbB3, the kinase-dead member of the EGFR/ErbB family, has been implicated as an oncogenic driver in a number of solid tumor types, including squamous cell carcinoma of the head and neck (SCCHN). However, clinical trials have demonstrated limited responses with certain single agent anti-ErbB3-directed therapies, suggesting that multiple ErbB inhibition and/or biomarker-directed patient selection may be beneficial. The anti-EGFR antibody cetuximab has demonstrated improved overall survival in SCCHN, but the overall response rate is relatively low. Several preclinical studies have suggested that pan-ErbB inhibition may result in improved clinical benefit and additionally, may overcome cetuximab resistance. Here we show that ErbB3 and its ligand neuregulin (NRG) are widely expressed in SCCHN, and that ErbB2, but not EGFR, drives ErbB3 activation in the presence of NRG. Although NRG is required for ErbB3 activation, it is not sufficient to fully predict activity of the anti-ErbB3 antibody KTN3379 in SCCHN models. Metadata analysis of human SCCHN tumors revealed that NRG expression is significantly associated with expression of EGFR ligands amphiregulin (AREG) (P<0.0001; R2 = 0.33) and transforming growth factor α (TGFα) (P<0.0001; R2 = 0.25) but not other EGFR ligands. We demonstrate using NRG-positive cell lines that KTN3379 antitumor activity correlates with the level of secreted AREG and TGFα. Using a proximity-based assay for EGFR homodimerization as a surrogate assay for ligand (AREG or TGFα)-induced EGFR activation, we show that high EGFR homodimer levels correlate with KTN3379 antitumor activity in NRG-positive SCCHN cell lines and primary tumor models in vitro and in vivo. These preclinical studies provide the molecular rationale for combination treatment with KTN3379 and cetuximab in SCCHN patients. We propose that an enrichment strategy for NRG expression and EGFR activation signature may result in better clinical activity in response to treatment with KTN3379 and cetuximab in SCCHN patients. Citation Format: Gwenda F. Ligon, Jay S. Lillquist, Scott B. Seibel, Jerry Wallweber, Veronique Neumeister, David L. Rimm, Theresa M. LaVallee, Diego Alvarado. Combination of neuregulin with EGFR activation signatures predict activity of the anti-ErbB3 antibody KTN3379 in SCCHN. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1196.