Abstract 3774: Unraveling mechanisms of resistance to tepotinib and future treatment options
Authors: Pudelko Linda , Jaehrling Frank , Stroh Christopher , Linde Nina , Sanderson Michael , Musch Doreen , Keil Marina , Esdar Christina , Blaukat Andree , Karachaliou Niki 
Published: September 2020

Abstract
Background Advanced non-small cell lung cancer (NSCLC) patients with MET exon 14 skipping mutations (METex14) or MET amplification (METamp) derive benefit from MET tyrosine kinase inhibitors (TKIs). Tepotinib is an investigational selective MET TKI. Co-occurring MAPK pathway alterations in MET dependent tumors are frequent and may induce primary or acquired resistance to MET TKIs.
Methods METamp (EBC1, NCI-H1993 and MNK-45) and METex14 (Hs746T) cells were obtained from commercial vendors. Tepotinib-resistant (TR) cells (EBC1-TR1, -TR2 and Hs746T-TR) were generated upon continuous exposure of EBC1 and Hs746T cells to tepotinib. The phosphorylation of 49 receptor tyrosine kinases (RTK) and 43 non-RTKs was assessed using Human Phospho-RTK kinase Array Kits (R&D Systems, Minneapolis, MN). Cell viability was evaluated by Resazurin Cell Viability Assay (R&D Systems, Minneapolis, MN) and level of proteins by western blot.
Results First, we assessed the short- and long-term effect of tepotinib on MET downstream signaling. Exposure of EBC1 cells to 0.01 µM of tepotinib for 1h abrogated MET, ERK and AKT phosphorylation, an effect that was sustained even 20h after tepotinib withdrawal. Next, we evaluated the phosphorylation status of other than MET RTKs and non-RTKs on the parental EBC1 and EBC1-TR1 cells. We observed activation of several RTKs, including ERBB (EGFR, ErbB2 and ErbB3), FGFR3, AXL, RET, DDR1, and M-CSFR in both cell lines. EBC1-TR1 cells displayed elevated levels of phosphorylated AXL and EGFR compared to EBC1 parental cells. We also observed increased phosphorylation of ERK1/2, AKT, c-Jun and YES on EBC1-TR1 compared to parental EBC1 cells. Similar results were achieved with EBC1-TR2 and Hs746T-TR cells.
RTK signaling is mediated by the MAPK pathway which is related among others, with the Src-homology 2 domain-containing protein tyrosine phosphatase (SHP2). Therefore, we tested tepotinib in combination with a MEK inhibitor, pimasertib, or a SHP2 inhibitor, RMC-4550, initially in a panel of treatment-naïve MET dependent cells. A moderate or strong synergism was found when tepotinib was combined with either of the two compounds. A stronger decrease of MET phosphorylation was observed upon treatment with a SHP2 inhibitor combined with tepotinib compared to tepotinib alone. Further molecular characterization of the TR cells as well as combinations in vitro and in vivo of tepotinib with drugs that may prolong its effect and overcome resistance, are ongoing.
Conclusions
Our results indicate that co-occurring RAS-MAPK alterations may mediate innate or acquired resistance to tepotinib, despite its prolonged on-target activity. The development of therapeutic strategies co-targeting the MAPK pathway may enhance the initial magnitude and duration of response to tepotinib, delay or overcome acquired resistance and ultimately improve clinical outcomes.
Citation Format: Linda Pudelko, Frank Jaehrling, Christopher Stroh, Nina Linde, Michael Sanderson, Doreen Musch, Marina Keil, Christina Esdar, Andree Blaukat, Niki Karachaliou. Unraveling mechanisms of resistance to tepotinib and future treatment options [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 3774.