Vaccine antibodies against a synthetic epidermal growth factor variant enhance the antitumor effects of inhibitors targeting the MAPK/ERK and PI3K/Akt pathways.

BACKGROUND: The EGFR pathway is involved in intrinsic and acquired resistance to a wide variety of targeted therapies in cancer. Vaccination represents an alternative to the administration of anti-EGFR monoclonal antibodies, such as cetuximab or panitumumab. Here, we tested if anti-EGF antibodies generated by vaccination (anti-EGF VacAbs) could potentiate the activity of drugs targeting the ERK/MAPK and PI3K/Akt pathways. METHODS: Non-small cell lung cancer (NSCLC), colorectal cancer (CRC) and melanoma cell lines harboring KRAS, NRAS, BRAF and PIK3CA mutations were used. Anti-EGF VacAbs were obtained by immunizing rabbits with a fusion protein containing a synthetic, highly mutated variant of human EGF. Cell viability was determined by MTT, total and phosphorylated proteins by Western blotting, cell cycle distribution and cell death by flow cytometry and emergence of resistance by microscopic examination in low density cultures. RESULTS: Anti-EGF VacAbs potentiated the antiproliferative effects of MEK, KRAS G12C, BRAF, PI3K and Akt inhibitors in KRAS, NRAS, BRAF and PIK3CA mutant cells and delayed the appearance of resistant clones in vitro. The effects of anti-EGF VacAbs were comparable or superior to those of panitumumab and cetuximab. The combination of anti-EGF VacAbs with the targeted inhibitors effectively suppressed EGFR downstream pathways and sera from patients immunized with an anti-EGF vaccine also blocked activation of EGFR effectors. CONCLUSIONS: Anti-EGF VacAbs enhance the antiproliferative effects of drugs targeting the ERK/MAPK and PIK3CA/Akt pathways. Our data provide a rationale for clinical trials testing anti-EGF vaccination combined with inhibitors selected according to the patient's genetic profile.

Anti-epidermal growth factor vaccine antibodies increase the antitumor activity of kinase inhibitors in ALK and RET rearranged lung cancer cells.

Advanced NSCLC patients harboring EML4-ALK and CCDC6-RET rearrangements derive benefit from treatment with ALK and RET TKIs but not immune checkpoint inhibitors. New immunotherapeutic approaches, such as immunization against growth factors, can be of particular interest for combination treatment in these patients. Here, we investigated the effects of anti-EGF antibodies generated by vaccination (anti-EGF VacAbs), TKIs and combinations in EML4-ALK and CCDC6-RET NSCLC cell lines. We found that EGF and tumor growth factor alpha (TGFα) significantly decreased the antiproliferative activity of the RET inhibitor BLU-667 in CCDC6-RET cells and brigatinib, alectinib and crizotinib in EML4-ALK translocated cells. The addition of anti-EGF VacAbs reversed the effects of EGF and TGFα, potentiated the antitumor effects of the kinase inhibitors and delayed the appearance in vitro of resistant clones. Western blotting demonstrated that the combination of anti-EGF VacAbs with ALK or RET TKIs effectively suppressed EGFR downstream pathways in EML4-ALK translocated and CCDC6-RET cells, respectively. In conclusion, anti-EGF VacAbs significantly increased the antitumor activity of TKIs in ALK and RET-positive cell lines. Clinical trials of an EGF vaccine in combination with ALK and RET TKIs are warranted.

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.

INTRODUCTION: Mutations in EGFR correlate with impaired response to immune checkpoint inhibitors and the development of novel immunotherapeutic approaches for EGFR mutant NSCLC is of particular interest. Immunization against epidermal growth factor (EGF) has shown efficacy in a phase III trial including unselected NSCLC patients, but little was known about the mechanisms involved in the effects of the anti-EGF antibodies generated by vaccination (anti-EGF VacAbs) or their activity in tumor cells with EGFR mutations. METHODS: The EGFR-mutant, NSCLC cell lines H1975, and PC9, together with several gefitinib and osimertinib-resistant cells derived from PC9, were treated with anti-EGF VacAbs and/or EGFR tyrosine kinase inhibitors (TKIs). Cell viability was analyzed by proliferation assays, cell cycle by fluorescence-activated cell sorting analysis, and levels of RNA and proteins by quantitative retro-transcription polymerase chain reaction and Western blotting. RESULTS: Anti-EGF VacAbs generated in rabbits suppressed EGF-induced cell proliferation and cycle progression and inhibited downstream EGFR signaling in EGFR-mutant cells. Sera from patients immunized with an EGF vaccine were also able to block activation of EGFR effectors. In combination, the anti-EGF VacAbs significantly enhanced the antitumor activity of all TKIs tested, suppressed Erk1/2 phosphorylation, blocked the activation of signal transducer and activator of transcription 3 (STAT3) and downregulated the expression of AXL receptor tyrosine kinase (AXL). Finally, anti-EGF VacAbs significantly delayed the emergence in vitro of EGFR TKI resistant clones. CONCLUSIONS: EGFR-mutant patients can derive benefit from immunization against EGF, particularly if combined with EGFR TKIs. A phase I trial of an EGF vaccine in combination with afatinib has been initiated.

Pathway Targeted Immunotherapy: Rationale and Evidence of Durable Clinical Responses with a Novel, EGF-directed Agent for Advanced NSCLC.

Abnormalities in the epidermal growth factor (EGF) and EGFR pathway promote progression of NSCLC. Immunization with EGF vaccine induces specific, neutralizing anti-EGF antibodies that prevent binding of the ligand to its receptor. This concept of pathway targeted immunotherapy (PTI) was validated in vitro by dose-related suppression of EGFR, Akt, and Erk1/2 phosphorylation in cell lines with different mutations. A randomized phase II trial showed improved overall survival (OS) in subgroups with advanced NSCLC showing a clear immunologic response. By per-protocol analysis of the ensuing phase IIb trial, patients receiving EGF PTI survived 3 months longer than controls (12.43 versus 9.43 months; hazard ratio = 0.77 [95% confidence interval, 0.61-0.98]). These data were confirmed in a larger trial showing an OS benefit over control of >3 months. The variable most strongly correlated with efficacy was circulating EGF at enrolment. Patients with serum EGF levels >250 pg/mL benefited most from treatment with EGF PTI. Of 188 patients tested, 94 were above this biomarker threshold. The OS benefit from active versus control treatment was 6.7 months. More than 15% of patients had responses for >5 years. Long-term survivors are seen in all EGF PTI trials. Treatment is well-tolerated, induces high anti-EGF antibody titers, reduces levels of circulating serum EGF, achieves durable responses, and significantly prolongs OS. A threshold of 250 pg/mL has been set to enrich the study population in the ongoing pivotal trial. This biomarker-guided study in an enriched population of patients with both squamous and nonsquamous stage IV NSCLC aims to replicate the favorable efficacy/tolerability balance of earlier studies.