Gefinix

250 mg

🧬 Mechanism of Action & Genetic Context

• Target & Binding
  Gefitinib inhibits the epidermal growth factor receptor (EGFR), a receptor tyrosine kinase, by binding to its ATP-binding site. This prevents receptor activation and downstream signaling 

• Genetic Predictors of Response
  Only tumors with activating EGFR mutations (e.g., exon 19 deletions, L858R on exon 21) respond well to gefitinib treatment 

• Resistance Mechanisms
  Resistance often arises due to:

  • Secondary EGFR mutations (e.g., T790M),

  • Activation of alternate pathways like PI3K, AXL, and others 

• Pharmacogenetics
  The enzyme CYP2D6 metabolizes gefitinib. Genetic variants can significantly impact drug levels—poor metabolizers may suffer higher toxicity, while ultrarapid metabolizers might clear the drug too fast, reducing its effectiveness.

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📋 Clinical Use & Administration

• Indication: First-line therapy for metastatic NSCLC in patients whose tumors carry specified EGFR mutations (exon 19 deletions or L858R).

• Dosage: 250 mg tablet once daily, with or without food; continued until disease progresses or side effects become severe.

• Side Effects: Common—rash, diarrhea, mouth sores; serious but rare—interstitial lung disease, liver toxicity.

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🧠 Summary Table