Triple-targeted therapy of dabrafenib, trametinib, and osimertinib for the treatment of the acquired BRAF V600E mutation after progression on EGFR-tyrosine kinase inhibitors in advanced EGFR-mutated non-small cell lung cancer patients

Background: The B-Raf proto-oncogene, serine/threonine kinase (BRAF) V600E mutation is responsible for approximately 3% of acquired resistance mechanisms to epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) in advanced EGFR-mutant non-small cell lung cancer (NSCLC). This study investigated the efficacy and safety of a triple-targeted therapy combining EGFR/BRAF/mitogen-activated protein kinase kinase (MEK) inhibitors of dabrafenib, trametinib, and osimertinib in NSCLC patients with acquired BRAF V600E mutation after EGFR-TKI treatment.

Methods: A multi-center retrospective review of medical records was performed to analyze EGFR-mutated advanced Chinese NSCLC patients who acquired the BRAF V600E mutation following EGFR-TKI treatment. All patients subsequently received dabrafenib, trametinib, and osimertinib. The clinical characteristics, progression-free survival (PFS), and adverse events (AEs) were documented. The in-vivo drug response of patient-derived organoids (PDOs) was observed. Next-generation sequencing (NGS) was performed upon progression to triple-targeted therapy.

Results: Thirteen patients with BRAF V600E mutations were included. Following triple-targeted therapy, the corresponding objective response rate and disease control rate were 61.5% and 92.3%, respectively. The median PFS was 13.5 months (95% confidence interval: 6.6-20.4). PDOs derived from one patient's tumor sample were established, revealing that the triple-targeted therapy had a significantly lower half-maximal inhibitory concentration (IC₅₀) value compared to other regimens. The tumor growth inhibitory rate was 99.36% for dabrafenib, trametinib, and osimertinib; 99.25% for osimertinib plus vemurafenib; 98.92% for osimertinib, encorafenib, and cetuximab; and 62.83% for pemetrexed plus carboplatin. NGS analysis identified major resistance mechanisms following the triple-targeted therapy, including the EGFR-dependent pathway, EGFR and BRAF V600E-dependent pathway, and an off-target mechanism.

Conclusions: EGFR/BRAF/MEK triple-targeted therapy is an effective and safe approach for treating EGFR-mutated NSCLC patients resistant to EGFR-TKIs with acquired BRAF V600E mutations.