# EGFR T790M

Source: https://onco.cc/biomarkers/egfr-t790m/  
OnCo record `egfr-t790m` (Biomarker). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

T790M is the gatekeeper mutation that lung cancers acquire to escape first- and second-generation EGFR inhibitors. Finding it, in tissue or blood, is the historic gate for osimertinib after an earlier EGFR drug.

## Summary

The c.2369C>T (T790M) substitution in exon 20 enlarges the ATP-binding pocket's affinity for ATP and confers resistance to erlotinib, gefitinib and afatinib; it arose in about half of patients progressing on those drugs. Osimertinib's 2015 accelerated approval (AURA) was for metastatic EGFR T790M-positive NSCLC after an EGFR TKI, detected by the cobas EGFR Mutation Test v2 in tissue or plasma, the first plasma companion diagnostic. That indication remains on the label, though first-line osimertinib has made acquired T790M uncommon. FoundationOne CDx and Guardant360 CDx also list T790M in their EGFR claims.

## Fields

- Kind: Biomarker
- Last checked: 2026-09-23
- Also known as: T790M; EGFR T790M mutation; gatekeeper mutation EGFR; EGFR exon 20 T790M
- Tags: biomarker; egfr; resistance

## Sources

- TAGRISSO prescribing information (DailyMed): https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=5e81b4a7-b971-45e1-9c31-29cea8c87ce7

## Connected records

- biomarkers: [EGFR exon 19 deletion](https://onco.cc/biomarkers/egfr-exon-19-deletion/), [EGFR L858R](https://onco.cc/biomarkers/egfr-l858r/), [MET amplification (gene copy number)](https://onco.cc/biomarkers/met-amplification-readout/)
- cancers: [Non-small-cell lung cancer](https://onco.cc/cancers/nsclc/)
- drugs: [cobas EGFR Mutation Test v2](https://onco.cc/drugs/cobas-egfr-mutation-test/), [Osimertinib](https://onco.cc/drugs/osimertinib/)
- terms: [EGFR C797S](https://onco.cc/terms/c797s/), [EGFR mutation subtypes (exon 19 deletion, L858R, exon 20 insertion, T790M)](https://onco.cc/terms/egfr-mutation-subtypes/), [On-target resistance mutations (gatekeeper, solvent-front, compound)](https://onco.cc/terms/gatekeeper-mutation/)
- targets: [EGFR](https://onco.cc/targets/egfr/)

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JSON: https://onco.cc/api/v1/entities/egfr-t790m.json