Detailed analysis of the drug structure and targeting mechanism of erlotinib

Erlotinib is a small molecule targeted anticancer drug mainly used to treat non-small cell lung cancer (NSCLC) and pancreatic cancer. It belongs to the tyrosine kinase inhibitor (TKI) class of drugs and specifically acts on the epidermal growth factor receptor (EGFR) signaling pathway. The molecular structure of erlotinib consists of a quinazoline core skeleton, which can simulate the shape of ATP and bind to the EGFR tyrosine kinase domain, thereby inhibiting its activity.

At the molecular level, erlotinib competes with the ATP binding site of EGFR to block its autophosphorylation process. Activation of EGFR usually triggers multiple downstream signaling pathways, such as the RAS-RAF-MEK-ERK and PI3K-AKT pathways, which regulate cell proliferation, differentiation, and apoptosis. By inhibiting these pathways, erlotinib effectively inhibits the proliferation of tumor cells and promotes their apoptosis, thus playing an anti-cancer effect.

Erlotinib is particularly suitable for patients with non-small cell lung cancer carrying EGFR mutations, especially the common exon 19 deletion and exon 21 L858R point mutation. These mutations enhance the kinase activity of EGFR and make tumor cells more sensitive to erlotinib. Compared with traditional chemotherapy, erlotinib has the advantages of strong selectivity and fewer side effects, and is one of the first-line treatment options for EGFR mutant NSCLC.
Although erlotinib has significant initial efficacy, patients often develop acquired resistance after long-term use, the most common of which is the T790M mutation. This mutation changes the ATP binding site of EGFR and reduces the binding ability of erlotinib. To overcome this problem, third-generation EGFR-TKI drugs such as Osimertinib were subsequently developed to treat erlotinib-resistant patients.
Reference: https://en.wikipedia.org/wiki/Erlotinib