Abstract 951: Evolution of antibody titers, growth factor levels and in vitro activity in the sera of patients enrolled in the EPICAL trial of afatinib combined with anti-EGF vaccination

Background: We have recently demonstrated that antibodies generated by vaccination (anti-EGFVacAbs) potentiate the effects of EGFR TKIs in epidermal growth factor receptor mutant (EGFR-mut) non-small cell lung cancer (NSCLC) cells growing in vitro and prevent the emergence of resistance to EGFRTKIs (1). Based on these preclinical results we have started the Epical Phase Ib clinical trial(NCT03623750), testing anti-EGF vaccination in combination with EGFR TKI in advanced EGFR-mut NSCLC patients. Methods: The EPICAL trial is a Multicenter, Open-Label, Exploratory Phase Ib Clinical Study in which 23 patients have been enrolled. Anti-EGF VacAbs is a vaccine for intramuscular administration that is designed to be used in conjunction with standard of care treatment which, in this study, is afatinib. Blood samples have been collected at baseline and every three months and sent to a central laboratory. The presence of EGFR mutations has been determined on purified DNA by 5′-nuclease real-time PCR (Taqman®) assay in presence of PNA. All the serum samples have been analyzed by ELISA to determine the levels of EGF, TGFα, HGF and GAS6, together with anti-EGF antibody titers. Sera of patients were added to EGFR-mutant cell lines growing in vitro and Western blot was used to analyze EGFR, AKT andERK activation. Results: Median EGF levels in the sera of enrolled patients was 179.5 pg/mL at baseline and no anti-EGFantibodies were detected. Three months after first immunization, median serum EGF levels decreased to30.8 pg/mL (p=0.0008) while the anti-EGF vaccination titers increased to 1:6000 (p=0.0012). Anti-EGF titers remained high and EGF levels low in the patient9s sera for the duration of the trial. Regarding serum TGFα and HGF levels baseline were 19.4 pg/mL and 861.2 pg/mL, respectively, and after three months dropped to 7.9 pg/mL (p=0.0037) and 341.3 pg/mL (p=0.0259). In EGFR-mutant cell lines in culture, the activation of the EGFR, AKT or ERK was abrogated by the sera of immunized patients. Conclusions: Anti-EGF vaccination induces high anti-EGF antibody titers and effectively reducing the levels of EGF and other growth factors in the blood of advanced NSCLC patients. 1J Thorac Oncol. 2018 Sep;13(9):1324-1337. Citation Format: Silvia Garcia-Roman, Jordi Codony, Miguel Angel Molina-Vila, Nuria Jordana-Ariza, Beatriz Garcia, Monica Garzon, Clara Mayo de las Casas, Maria Jose Catalan, Andres Aguilar, Santiago Viteri, Andres F. Cardona, Delvys Rodriguez, Manuel Cobo, Noemi Reguart, Erik d9Hondt, Rafael Rosell. Evolution of antibody titers, growth factor levels and in vitro activity in the sera of patients enrolled in the EPICAL trial of afatinib combined with anti-EGF vaccination [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 951.