New Mismatch Repair Test Identifies Patients for Pembrolizumab

M. Alexander Otto, PA, MMS

August 12, 2022

The US Food and Drug Administration has approved a DNA mismatch repair (MMR) companion test to identify patients suitable for treatment with Merck's pembrolizumab (Keytruda).

The Ventana MMR RxDx Panel from Roche assesses expression of MMR proteins responsible for correcting errors in DNA replication. Deficient repair is thought to be involved in about 14% of solid tumors in the United States, the company said in a press release announcing the approval.

The new approval covers use of the test in two settings:

  • to identify patients with endometrial cancer who have mismatch repair proficient (pMMR) tumors, who can then be treated with pembrolizumab in combination with lenvatinib (Lenvima), and

  • to identify patients with solid tumors that are mismatch repair deficient (dMMR), who can then be treated with pembrolizumab

The Ventana panel is already approved to identify patients with dMMR solid tumors eligible for the anti-PD1 immunotherapy dostarlimab-gxly (Jemperli).

Roche said the new approval makes Ventana "the first and only immunohistochemistry-based assay approved to identify" dMMR solid tumor patients for treatment with either dostarlimab or pembrolizumab and also the first to identify pMMR endometrial cancer patients for pembrolizumab/lenvatinib combination therapy.

M. Alexander Otto is a physician assistant with a master's degree in medical science and a journalism degree from Newhouse. He is an award-winning medical journalist who worked for several major news outlets before joining Medscape and is also an MIT Knight Science Journalism fellow. Email:

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