Foundation Medicine to develop MSI diagnostic for Merck’s Keytruda

The companion diagnostic will complement Keytruda's 2017 siteless approval for all solid tumors deemed microsatellite instability-high or mismatch repair deficient. (Merck)

Merck is pairing up with Foundation Medicine to develop a pan-cancer companion diagnostic for its Keytruda immunotherapy, to measure microsatellite instability across all solid tumors, as well as tumor mutational burden and other potential treatment response biomarkers.

The tests will use the company’s FoundationOne CDx comprehensive genomic profiling assay, which can examine 324 genetic changes linked to cancer growth and guide treatment.

Keytruda received the first organ site-agnostic cancer approval from the FDA in May 2017, for any solid tumor that can be genetically identified as MSI-high or mismatch repair deficient, following approvals in several other traditional cancer types such as metastatic melanoma, bladder cancer, and non-small cell lung cancer.

The wider approval did not include a simultaneous greenlight for a related diagnostic, as other targeted cancer products have seen. Companion diagnostic partnerships can also help broaden patient access to the drug, as noted in a recent deal between Loxo Oncology and Illumina, which agreed to use next-generation sequencing to identify the genetic mutations targeted by Loxo’s investigational drugs.

“The addition of MSI and TMB companion diagnostics to FoundationOne CDx re-affirms the validity and clinical utility of these critical immuno-oncology biomarkers, can simplify diagnostic testing through the use of one test that provides physicians with necessary information to both rule-in and rule-out potential treatment options based on each patient’s genomic and biomarker status, and can help accelerate patient access to personalized healthcare,” Melanie Nallicheri, Foundation’s chief business officer and head of biopharma, said in a statement.

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Foundation's platform is also FDA-approved as a broad companion diagnostic to screen patients with certain types of non-small cell lung cancer, melanoma, colorectal cancer, ovarian cancer or breast cancer to identify those who may benefit from one of 17 on-label targeted therapies, including 12 first-line therapies.