# FLT3-TKD (D835 and I836 tyrosine kinase domain mutations)

Source: https://onco.cc/biomarkers/flt3-tkd/  
OnCo record `flt3-tkd` (Biomarker). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

FLT3-TKD mutations are point changes in the kinase's activation loop, found in about 7 percent of acute myeloid leukaemias. Midostaurin and gilteritinib labels cover them; quizartinib's does not.

## Summary

D835 substitutions and I836 deletions in exon 20 activate FLT3 without the duplication seen in ITD; their prognostic weight is neutral in ELN 2022. The LeukoStrat CDx assay detects D835 and I836 alongside ITD, which is why midostaurin (newly diagnosed 'FLT3 mutation-positive' AML) and gilteritinib (relapsed or refractory 'with a FLT3 mutation') cover TKD mutations, while quizartinib is labelled for FLT3-ITD only. TKD mutations, especially D835, also arise as resistance to type II inhibitors such as quizartinib and sorafenib.

## Fields

- Kind: Biomarker
- Last checked: 2026-09-23
- Also known as: FLT3-TKD; FLT3 TKD; FLT3 D835; FLT3 D835Y; FLT3 I836; FLT3 tyrosine kinase domain mutation
- Tags: biomarker; flt3

## Sources

- XOSPATA prescribing information (DailyMed): https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=b5ff59aa-9c0d-49a8-9053-1f179b482383

## Connected records

- biomarkers: [FLT3-ITD (internal tandem duplication)](https://onco.cc/biomarkers/flt3-itd/)
- cancers: [Acute myeloid leukaemia](https://onco.cc/cancers/aml/), [FLT3-mutated acute myeloid leukaemia](https://onco.cc/cancers/aml-flt3/)
- drugs: [Gilteritinib](https://onco.cc/drugs/gilteritinib/), [Midostaurin](https://onco.cc/drugs/midostaurin/), [Quizartinib](https://onco.cc/drugs/quizartinib/)
- terms: [On-target resistance mutations (gatekeeper, solvent-front, compound)](https://onco.cc/terms/gatekeeper-mutation/)
- targets: [FLT3](https://onco.cc/targets/flt3/)

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