Gefitinib is a targeted therapy medication classified as a tyrosine kinase inhibitor. It is primarily used to treat metastatic non-small cell lung cancer (NSCLC) in patients whose tumors harbor specific mutations in the epidermal growth factor receptor (EGFR) gene, notably exon 19 deletions or exon 21 L858R substitutions. These mutations lead to abnormal activation of the EGFR, promoting uncontrolled cancer cell proliferation. Gefitinib works by selectively inhibiting the EGFR tyrosine kinase, thereby blocking downstream signaling pathways that drive tumor growth.

Mechanism of Action

Gefitinib binds to the intracellular tyrosine kinase domain of the EGFR, inhibiting its autophosphorylation. This blockade prevents activation of downstream signaling pathways such as the RAS/RAF/MEK/ERK and PI3K/AKT pathways, which are crucial for cell proliferation and survival. By disrupting these pathways, gefitinib impedes tumor cell growth and induces apoptosis in EGFR-mutated NSCLC cells.

Uses

Gefitinib is indicated for:

• First-line treatment of metastatic NSCLC in patients with EGFR exon 19 deletions or exon 21 L858R mutations, as detected by an FDA-approved test.

• Second-line treatment of metastatic NSCLC in patients who have progressed after platinum-based chemotherapy and have EGFR mutations.

  Adverse Effects

  Common side effects:

  • Skin reactions: acne-like rash, dry skin, itching

  • Gastrointestinal issues: diarrhea, nausea, vomiting, loss of appetite

  • Fatigue and weakness

  • Eye problems: conjunctivitis, irritation

  • Liver enzyme elevation