FDA Approves OncoMate MSI Dx For Pembrolizumab in MSI-H Tumors

The FDA has approved the OncoMate MSI Dx Analysis System as a companion diagnostic for selecting patients with microsatellite instability–high (MSI-H) solid tumors for treatment with the anti–PD-1 therapy pembrolizumab (Keytruda), according to a news release from Promega Corporation.¹

The approved intended use covers identification of patients with MSI-H advanced solid tumors who are eligible for pembrolizumab in accordance with its labeling. The FDA premarket approval database lists the KEYNOTE-028 study (NCT02054806) of pembrolizumab in advanced solid tumors as the associated clinical trial.²

“Our test connects patients with the therapy most likely to help them, working alongside our pharmaceutical collaborators and the clinicians who use the result,” Alok Sharma, global clinical market director at Promega, stated in the news release.¹

Pembrolizumab Indication

The companion diagnostic applies to pembrolizumab’s indication for adult and pediatric patients with unresectable or metastatic MSI-H or mismatch repair–deficient cancer that has progressed after prior treatment and who have no satisfactory alternative treatment options.¹ The FDA granted full approval for this tumor-agnostic indication of pembrolizumab in March of 2023.

The qualitative multiplex polymerase chain reaction (PCR) test assesses 5 mononucleotide microsatellite loci (BAT-25, BAT-26, NR-21, NR-24, and MONO-27), comparing DNA from formalin-fixed, paraffin-embedded (FFPE) solid tumor tissue with DNA from a matched normal FFPE or whole blood specimen from the same patient.² Tumors with 2 or more unstable markers are classified as MSI-H.^2,3

Prior Regulatory History

The FDA previously cleared OncoMate MSI Dx as the first PCR-based molecular diagnostic to identify patients with colorectal cancer who may benefit from further testing for Lynch syndrome.¹ On November 5, 2025, the agency approved the assay through a premarket approval application as a companion diagnostic for identifying patients with microsatellite stable (MSS; not MSI-H) endometrial carcinoma who may benefit from pembrolizumab plus the multikinase inhibitor lenvatinib (Lenvima).

“This approval reflects our dedication to providing meaningful diagnostic advances, developed to the highest quality and regulatory standards,” Sharma said.¹

REFERENCES

FDA Approves Promega OncoMate® MSI Dx Analysis System as Companion Diagnostic for KEYTRUDA® in MSI-High Solid Tumors. News release. Promega Corporation. November 10, 2026. Accessed November 11, 2026. https://tinyurl.com/y9d5ckh4

Premarket approval: OncoMate MSI Dx Analysis System (P250046). US Food and Drug Administration. Decision date September 15, 2026. Accessed November 11, 2026. https://tinyurl.com/3py9njk3

Summary of safety and effectiveness data: OncoMate MSI Dx Analysis System (P240026). US Food and Drug Administration. November 5, 2025. Accessed November 11, 2026. https://www.accessdata.fda.gov/cdrh_docs/pdf24/P240026B.pdf