EPICAL Trial. A Phase Ib StudyCombining Anti-Epidermal Growth Factor (EGF) Vaccination With Afatinib in EGFR-Mutant Non-Small Cell Lung Cancer

ABSTRACT

Introduction: Stage IIIB-IV non-small cell lung cancer patients with mutations in the EGF receptor gene (EGFR) usually derive clinical benefit from to tyrosine kinase inhibitors (EGFR TKIs) but ultimately relapse. In preclinical studies, we have showed that anti-EGF antibodies generated by vaccination significantly increased the antitumor activity of TKIs in EGFR-mut cell lines, blocking EGFR, Erk1/2, Akt and STAT3 activation and delaying emergence of resistance. Based on these findings, the EPICAL trial was initiated (ClinicalTrials.gov number, NCT03623750). Methods: The EPICAL was a single arm, phase 1b, single arm study to evaluate the safety and efficacy of first line anti-EGF vaccination combined with afatinib. The trial enrolled advanced NSCLC patients with sensitizing EGFR mutations confirmed in a central laboratory. Patients received 40 mg/day of afatinib and five intramuscular anti-EGF vaccinations every 14 days and then every three months until progression. Four medical centers in Spain participated, with a target enrollment of 30 patients. However, the COVID-19 outbreak forced an early termination of the study in March 2020 with only 23 patients included. Serial blood samples were collected and used to evaluate the levels of selected growth factors by ELISA and biological activity by addition of sera to in vitro cultures of EGFR-mut cells followed by Western blotting. Results: Of the 23 patients enrolled in the trial, nine (39%) had exon 19 in-frame deletions, twelve (52%) exon 21 substitutions and two (9%) exon 18 missense mutations. Combination treatment was well tolerated and no SAES related to anti-EGF vaccination were reported. Objective response and disease control rates were 78.3% (95%CI=53.6-92.5) and 95.7% (95%CI=78.1-99.9), respectively. At data cut-off, with a median follow-up of 11.4 months (95%CI=8.1-15.2), the median progression-free survival was 17.4 months (95% CI=13.22-NA) and median survival not reached (95% CI=15.21-NA). Median PFS for patients with exon 19 deletions and exon 21 point mutations were 13.9 months (95%CI=8.7-NR) and 17.4 months (95%CI=13.2-NR), respectively. Three months after initiation of treatment, high titers of anti-EGF antibodies were detected in all patients and serum EGF and TGFα levels were found to be significantly lower compared to baseline levels. Finally, treatment with post-vaccination patient’s sera inhibited EGFR, AKT and ERK1/2 phosphorylation in EGFR-mut cells growing in vitro. Conclusion: The combination of an anti–EGF vaccine with afatinib is well tolerated and induces a sustained immunogenic effect. Vaccination against EGF might enhance the clinical efficacy of EGFR TKIs. Keywords anti-EGF vaccination, EGFR-mutant non-small cell lung cancer, EGFR inhibitors