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Erlotinib (Erlotinib) belongs to the first generation of EGFR (epidermal growth factor receptor) tyrosine kinase inhibitors (TKI) and is mainly used to treat EGFR Mutation-positive non-small cell lung cancer (NSCLC) and advanced pancreatic cancer. As a first-generation EGFR-TKI, erlotinib can reversibly bind to the EGFR receptor and block the signal transduction of tumor cells, thereby inhibiting the growth and proliferation of cancer cells.

The main target is EGFR (ErbB1 or HER1), the epidermal growth factor receptor. In many cancer types, EGFR undergoes genetic mutations or overexpression, leading to abnormal activation of signaling pathways and promoting tumor growth. Erlotinib competitively inhibits the ATP binding site of EGFR and blocks its downstream signaling pathways (such as RAS/RAF/MEK/ERK and PI3K/AKT) is activated, thereby inhibiting tumor cell proliferation and promoting cell apoptosis.

Although erlotinib shows good efficacy in EGFR mutated NSCLC patients, many patients will develop acquired resistance as the treatment time is prolonged. The most common resistance mechanism is the T790M mutation. This mutation will enhance the affinity of EGFR and ATP, making it difficult for erlotinib to continue to work, leading to disease progression. To address this problem, second-generation (afatinib) and third-generation (osimertinib) EGFR-TKIs were subsequently developed to overcome drug resistance.

Overall, erlotinib is a first-generation EGFR-TKIMutated lung cancer has played an important role in the treatment, but due to its reversible binding characteristics and high drug resistance rate, it has been gradually replaced by higher-generation targeted drugs. However, in some patients who are not resistant or do not have the T790M mutation, erlotinib remains an effective treatment option, especially in combination with chemotherapy or maintenance therapy.