Abstract 338: Anti-EGF antibodies significantly improve the activity of BRAF and KRAS inhibitors in preclinical models
Authors: Garcia-Roman Silvia , Molina-Vila Miguel A. , d'Hondt Erik , Rosell Rafael 
Published: June 2022

Abstract
Background: The EGF/EGFR pathway is involved in the emergence of resistance to BRAF and MEK inhibitors and the combination of encorafenib with the anti-EGFR antibody cetuximab has been recently approved in BRAF-positive, advanced colorectal cancer (CRC). Vaccination against EGF represents an alternative to the administration of monoclonal antibodies against EGFR 1-2. In this study, we tested if antibodies generated by vaccination with IN01 (biologic fusion molecule), could improve the antitumor activity of encorafenib and sotorasib in BRAF and KRAS colorectal (CRC) and non-small cell lung cancer (NSCLC) cell lines.
Methods: Cell lines with BRAF V600E (HT29, CRC) and KRAS G12C mutations (H2122 and H23, NSCLC) were used. Anti-EGF VacAbs were obtained by immunizing rabbits with recombinant human EGF. Cell lines were treated with encorafenib or sotorasib in combination with anti-EGF VacAbs and the antitumor effects compared to the combination of encorafenib/cetuximab and sotorasib/panitumumab. Cell viability was determined by MTT, changes of total and phosphorylated proteins by Western blotting and emergence of resistance by direct microscopic examination in low density cultures.
Results: Anti-EGF VacAbs suppressed the EGF-induced proliferation and blocked the EGFR signaling pathways more efficiently than cetuximab and panitumumab in KRAS and BRAF cell lines. In combination, anti-EGF VacAbs significantly enhanced the antitumor activity of encorafenib (in HT29 cells) and sotorasib (in H2122 and H23 cells), further suppressing EGFR, PRAS40 and ERK 1/2 phosphorylation. Also, the antitumor effects of the anti-EGF VacAbs in combination were superior to those of cetuximab and panitumumab. Finally, the addition of anti-EGF VacAbs to the culture medium significantly delayed the emergence of resistant clones to encorafenib (in HT29) and sotorasib (in H23). Again, the effect was more pronounced than the delay observed when adding cetuximab or panitumumab. Resistant clones generated under all combinations are being analyzed by NGS and Western blotting to determine the possible mechanisms of acquired resistance.
Conclusions: Anti-EGF VacAbs potentiate the antitumor effects of encorafenib and sotorasib in cancer cell lines more efficiently than cetuximab and panitumumab. Our data provide a rationale for clinical trials testing the combination of anti-EGF VacAbs with targeted inhibitors in BRAF and KRAS mutant CRC and NSCLC patients. (1)“Anti-Epidermal Growth Factor Vaccine Antibodies Enhance the Efficacy of Tyrosine Kinase Inhibitors and Delay the Emergence of Resistance in EGFR Mutant Lung Cancer Cells” García-Roman S, Molina-Vila MA, et al. J Thorac Oncol. 2018. (2) “Anti-epidermal growth factor vaccine antibodies increase the antitumor activity of kinase inhibitors in ALK and RET rearranged lung cancer cells” García-Roman S, Molina-Vila MA, et al. Transl. Oncol. 2020.
Citation Format: Silvia Garcia-Roman, Miguel A. Molina-Vila, Erik d'Hondt, Rafael Rosell. Anti-EGF antibodies significantly improve the activity of BRAF and KRAS inhibitors in preclinical models [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 338.