Erlotinib vs Gefitinib
Overview
Erlotinib and gefitinib are both first-generation reversible EGFR TKIs with very similar mechanisms and clinical profiles. Erlotinib has a unique indication in pancreatic cancer; gefitinib was the first EGFR TKI approved. Both have largely been supplanted by osimertinib for first-line EGFR-mutated NSCLC.
Mechanism of Action
Both are ATP-competitive reversible inhibitors of EGFR tyrosine kinase. They have nearly identical mechanisms and overlapping resistance profiles (primarily T790M mutation).
Pharmacokinetics
Erlotinib: ~60% bioavailability (food increases absorption ~33% — historically contraversial dosing with food requirement). Half-life ~36 h. Gefitinib: ~60% bioavailability (no significant food effect), half-life ~48 h.
Clinical Efficacy
Multiple head-to-head trials (IPASS, ENSURE, others) show equivalent efficacy in EGFR-mutated NSCLC. Both reduce HbA1c/tumor response rate ~70–75% in EGFR-mutated patients.
Unique Erlotinib Indications
Erlotinib is FDA-approved for pancreatic cancer (with gemcitabine) — the only EGFR TKI with this indication. This was a modest overall survival benefit (~2 weeks) in EGFR-unselected pancreatic cancer.
Key Takeaways
- Both 1st-gen reversible EGFR TKIs; largely interchangeable for NSCLC
- Erlotinib: unique pancreatic cancer indication
- Both now second-choice behind osimertinib for NSCLC
Verdict
Erlotinib and gefitinib are clinically equivalent for EGFR-mutated NSCLC and can be used interchangeably where osimertinib is unavailable. Erlotinib is uniquely indicated for pancreatic cancer (with gemcitabine) — the only indication where it is preferred over gefitinib.