# VENTANA MMR RxDx Panel

Source: https://onco.cc/drugs/ventana-mmr-rxdx/  
OnCo record `ventana-mmr-rxdx` (Treatment). Data CC BY-NC 4.0, attribute "Data from OnCo (onco.cc)"; commercial use needs a licence.

## TL;DR

A four-stain test that shows whether a womb cancer has lost its DNA spell-checker, which makes immunotherapy likely to work.

## Summary

Approved by the FDA in August 2021 together with dostarlimab for mismatch-repair-deficient (dMMR) recurrent or advanced endometrial cancer, the first immunohistochemistry companion diagnostic for mismatch-repair status. MMR immunohistochemistry is cheap, fast and available in every pathology laboratory, and is the recommended first-line test in endometrial and colorectal cancer, where it also serves as universal screening for Lynch syndrome. Where results are equivocal, PCR or NGS-based microsatellite-instability testing is used. Immunotherapy responses in dMMR tumours are among the most durable in oncology, so the stain has outsized consequences for a patient.

## Fields

- Kind: Treatment
- Status: approved
- Last checked: 2026-09-10
- Tags: test
- Brand: VENTANA MMR RxDx
- Modality: Mismatch-repair immunohistochemistry companion diagnostic assay
- Mechanism: Four immunohistochemical stains (MLH1, PMS2, MSH2, MSH6) read together; loss of nuclear staining for any protein classifies the tumour as mismatch-repair deficient.
- Approvals: US 2021: Companion diagnostic for dostarlimab in dMMR endometrial cancer

## Notes

- What a result means: loss of one or more MMR proteins (dMMR) means checkpoint immunotherapy is an option and that inherited Lynch syndrome should be considered; intact staining (pMMR) means other treatments come first.
- Colorectal cancer: the four-protein mismatch repair immunohistochemistry panel is the guideline-recommended first test on every colorectal cancer, both to find Lynch syndrome and to select immunotherapy (Moreira 2012, Sepulveda 2017).

## Sources

- FDA: dostarlimab accelerated approval (dMMR endometrial cancer) (archived copy): https://web.archive.org/web/20260217063458/https://www.fda.gov/drugs/resources-information-approved-drugs/fda-grants-accelerated-approval-dostarlimab-gxly-dmmr-endometrial-cancer

## Connected records

- cancers: [Colorectal cancer](https://onco.cc/cancers/colorectal/), [Endometrial cancer](https://onco.cc/cancers/endometrial/), [Gallbladder cancer](https://onco.cc/cancers/gallbladder/), [Pancreatic ductal adenocarcinoma](https://onco.cc/cancers/pancreatic/), [Triple-negative breast cancer (TNBC)](https://onco.cc/cancers/tnbc/)
- technologies: [Companion diagnostics](https://onco.cc/technologies/companion-diagnostic/), [Histopathology & immunohistochemistry](https://onco.cc/technologies/histopathology-ihc/), [MSI and mismatch-repair testing](https://onco.cc/technologies/msi-mmr-testing/)
- drugs: [Dostarlimab](https://onco.cc/drugs/dostarlimab/), [Pembrolizumab](https://onco.cc/drugs/pembrolizumab/)
- companies: [Roche / Genentech](https://onco.cc/companies/roche-genentech/)
- terms: [Endometrial cancer molecular classes (POLEmut, MMRd, p53abn, NSMP)](https://onco.cc/terms/endometrial-molecular-classes/), [Lynch syndrome](https://onco.cc/terms/lynch-syndrome/), [Microsatellite instability (MSI-H) / mismatch repair deficiency (dMMR)](https://onco.cc/terms/msi/), [Microsatellite-stable (MSS) / mismatch-repair proficient (pMMR)](https://onco.cc/terms/mss-pmmr/)
- key papers: [Comprehensive characterisation of pancreatic ductal adenocarcinoma with microsatellite instability: histology, molecular pathology and clinical implications](https://onco.cc/key-papers/paper-luchini-msi-dmmr-pancreatic-systematic-review-gut-2021/), [Identification of Lynch syndrome among patients with colorectal cancer](https://onco.cc/key-papers/paper-moreira-lynch-syndrome-identification-jama-2012/), [Molecular biomarkers for the evaluation of colorectal cancer: guideline from ASCP, CAP, AMP and ASCO](https://onco.cc/key-papers/paper-sepulveda-molecular-biomarkers-colorectal-guideline-jco-2017/)
- biomarkers: [dMMR (mismatch repair deficiency by IHC)](https://onco.cc/biomarkers/dmmr-ihc/)
- targets: [MLH1](https://onco.cc/targets/mlh1/), [MSH2](https://onco.cc/targets/msh2/), [MSH6](https://onco.cc/targets/msh6/), [PMS2](https://onco.cc/targets/pms2/)

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