Abstract 4866: Pharmacological mechanisms of osimertinib in advanced non-small lung cancer bearing the deletion exon 19 of EGFR In an original chicken chorioallantoic membrane (CAM) Model
Authors: Barthelemy David , Vigneron Arnaud , Rousset Xavier , Guitton Jerome , Grolleau Emmanuel , Raffin Margaux , Balandier Julie , Lescuyer Gaelle , Geiguer Florence , Couraud Sebastien , Vaillet Jean , Benzerdjeb Nazim , Payen-Gay Lea 
Published: April 2023

Abstract
Introduction: NSCLC accounts for about 80-85% of all lung cancers. Approximately 10-50% of patients with NSCLC harbor EGFR activating mutations, such as in-frame deletions in exon 19 (Ex19del). Currently, for patients with advanced NSCLC, testing for sensitizing mutations in EGFR is mandatory prior to the administration of anti-EGFR inhibitors such as Osimertinib. The CAM xenograft offers a rich environment in nutrients and embryonic growth factors, favorable for aggressive tumor development, with its highly vascularized membrane and natural immunodeficiency at engraftment (at EDD9).
Methods: HCC827 Ex19del cells have been engrafted in ovo, and treated with various doses of osimertinib for seven days (4 treatments). The xenografts were collected and immunohistopathological, transcriptional and genetic analyses were carried out. Based on human transcriptional data, supervised multivariate discrimination between conditions and ontology analysis was performed through GSEA.
Results: The xenograft growth was inversely dependent on the exposure dose of osimertinib, with a reduction in tumor weight of 58% for 10 µM (corresponding to 8.3 µg/Kg, T1/2 =4hr). The histological analysis showed epithelial tumor cells composed of solid sheets. The quantity of tumor cells was significantly lower in the treated group, with an area of tumor necrosis. The immunohistochemistry of tumor cells confirmed the human pulmonary epithelial origin, with TTF1 positive in treated and control groups. As expected, the ontology analysis of transcriptomic findings highlighted a downregulation of the EGFR pathway and its downstream effectors. Furthermore, the transcriptomic responses associated with chemotaxis, immune cell recruitment, and angiogenesis were dampened in the presence of osimertinib. This suggests that therapeutic efficacy was not uniquely guided through cell-autonomous mechanisms, but also takes place at the tissue level. We confirmed this in an independent experiment of in ovo HCC827 engraftment, showing a statically significant reduction of 15% in the number of vessels surrounding the xenograft in the osimertinib-treated condition. This demonstrates the advantage of using the in ovo model to decipher the regulations associated with therapeutics in a complex tissue context.
Conclusions: For the first time, we have observed that osimertinib modulates angiogenesis and chemotaxis, which apparently reduces immune system recruitment and immune checkpoint responses. The ontologic analysis of transcriptomic findings in the CAM model strongly support the clinical observations of the pharmacological tumoral response to targeted therapy. The fact that immune infiltration was reduced in osimertinib-treated tumors may partially explain the lower response to immunotherapy regimens in osimertinib resistance contexts.
Citation Format: David Barthelemy, Arnaud Vigneron, Xavier Rousset, Jerome Guitton, Emmanuel Grolleau, Margaux Raffin, Julie Balandier, Gaelle Lescuyer, Florence Geiguer, Sebastien Couraud, Jean Vaillet, Nazim Benzerdjeb, Lea Payen-Gay. Pharmacological mechanisms of osimertinib in advanced non-small lung cancer bearing the deletion exon 19 of EGFR In an original chicken chorioallantoic membrane (CAM) Model. [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 4866.