FDA Approves Promega OncoMate MSI Dx Analysis System as Companion Diagnostic for Merck’s KEYTRUDA in MSI-H Solid Tumors
Promega Corporation has announced that the U.S. Food and Drug Administration (FDA) has approved its OncoMate® MSI Dx Analysis System as a companion diagnostic to identify patients with microsatellite instability-high (MSI-H) solid tumors who may benefit from treatment with KEYTRUDA®, Merck’s anti-PD-1 therapy. Merck is known as MSD outside the United States and Canada.
The FDA approval represents an important development in the application of molecular diagnostics to cancer treatment. By identifying the microsatellite instability status of solid tumor tissue, the OncoMate MSI Dx Analysis System can provide clinicians with information that may help guide treatment decisions and determine whether patients meet the biomarker criteria for specific targeted or immunotherapy-based treatment approaches.
The newly approved companion diagnostic is based on polymerase chain reaction (PCR) technology and is designed to evaluate microsatellite instability in tumor tissue. MSI status is an important molecular biomarker in oncology because it can help characterize certain cancers and identify patients who may benefit from immunotherapy.
The approval also strengthens the collaboration between Promega and Merck, which markets KEYTRUDA. Both companies are working to support personalized medicine by connecting molecular diagnostic testing with appropriate therapeutic options. The expanded regulatory status of the OncoMate system provides another diagnostic pathway for identifying patients with MSI-H solid tumors who may be candidates for KEYTRUDA under its applicable FDA-approved indication.
FDA Approval Strengthens Precision Oncology Testing
Microsatellite instability is a molecular condition associated with changes in the length of repetitive DNA sequences known as microsatellites. These sequences are distributed throughout the genome and can become unstable when the DNA mismatch repair system does not function properly.
The mismatch repair system normally identifies and corrects errors that occur during DNA replication. When this repair mechanism is deficient, errors can accumulate in microsatellite regions, resulting in microsatellite instability. Tumors with high levels of this instability are classified as MSI-H.
MSI-H status is clinically relevant because it can help identify a group of patients whose tumors may respond to immune checkpoint inhibitor therapies. In particular, MSI-H and mismatch repair-deficient cancers can have biological characteristics that make them suitable for treatment with certain immunotherapies.
However, identifying these patients requires reliable molecular testing. A companion diagnostic provides information that helps healthcare professionals determine whether a patient has the biomarker characteristics associated with a particular treatment. In this case, Promega’s OncoMate MSI Dx Analysis System is designed to identify MSI-H solid tumors that may be appropriate for KEYTRUDA treatment.
The FDA approval therefore expands the clinical application of the assay and supports the use of biomarker-based testing in treatment selection. It also highlights the growing importance of diagnostic technologies in modern oncology, where treatment decisions increasingly depend on the molecular characteristics of individual tumors rather than cancer type alone.
PCR-Based Assay Evaluates Microsatellite Instability
The OncoMate MSI Dx Analysis System uses PCR-based molecular testing to assess microsatellite instability in solid tumor tissue. PCR is a widely used laboratory technique that amplifies selected DNA regions, allowing specific genetic sequences to be analyzed.
For MSI testing, the assay evaluates microsatellite regions to determine whether changes in their length are present. The resulting information can help classify a tumor as MSI-H or microsatellite stable, depending on the test findings and applicable interpretation criteria.
The ability to identify MSI status is important for precision oncology because patients with different molecular tumor profiles may respond differently to available treatments. Testing can therefore help clinicians make more informed decisions about treatment options and determine whether a patient may meet the biomarker requirements for a particular therapy.
Promega’s system is designed to provide this information through a standardized molecular diagnostic process. Its use as a companion diagnostic for KEYTRUDA establishes a direct connection between the test result and the treatment-selection process for patients with MSI-H solid tumors.
The company stated that the approval reflects its commitment to developing diagnostic technologies that meet high-quality and regulatory standards while helping patients access therapies that may be appropriate for their disease.
Promega Highlights the Importance of Diagnostic Innovation
Alok Sharma, Global Clinical Market Director at Promega, said the FDA approval demonstrates the company’s continued focus on advancing molecular diagnostics and supporting treatment decisions through clinically meaningful testing.
“This approval reflects our dedication to providing meaningful diagnostic advances, developed to the highest quality and regulatory standards,” Sharma said.
He emphasized that diagnostic testing plays an important role in connecting patients with therapies that may provide clinical benefit. He also highlighted the importance of collaboration among diagnostic developers, pharmaceutical companies and healthcare professionals in bringing precision medicine approaches into clinical practice.
“Our test connects patients with the therapy most likely to help them, working alongside our pharmaceutical collaborators and the clinicians who use the result,” Sharma added.
The comments reflect the broader role of companion diagnostics in the development and use of targeted medicines and immunotherapies. As oncology treatments become increasingly dependent on molecular biomarkers, diagnostic companies and pharmaceutical developers must work together to ensure that appropriate tests are available to identify eligible patients.
For Promega, the expanded FDA approval of OncoMate MSI Dx Analysis System adds to its portfolio of molecular diagnostic applications and reinforces its work in the field of cancer biomarker testing.
Collaboration With Merck Supports Personalized Medicine
The latest approval was supported through a collaboration between Promega and Merck, the pharmaceutical company responsible for marketing KEYTRUDA.
The collaboration reflects the importance of integrating diagnostic development with therapeutic research and commercialization. For a companion diagnostic to support a specific treatment, the test must be designed and evaluated in relation to the relevant biomarker and therapeutic indication.
KEYTRUDA is an anti-programmed death receptor-1 (PD-1) therapy that works by targeting the PD-1 pathway, an immune checkpoint involved in regulating immune responses. By blocking PD-1, the treatment is designed to help restore the immune system’s ability to recognize and attack cancer cells.
In certain MSI-H and mismatch repair-deficient cancers, the biological characteristics of the tumor may make immune checkpoint inhibition an appropriate treatment strategy. Molecular testing can help identify patients whose tumors carry these characteristics.
Through their collaboration, Promega and Merck are working to advance personalized medicine and expand access to diagnostic technologies that support informed therapeutic choices.
The latest FDA decision provides an additional regulatory application for Promega’s MSI testing platform in the United States. It also demonstrates how companion diagnostics can support the appropriate identification of patients for biomarker-directed treatment.
OncoMate Has Multiple Previous Regulatory and Clinical Applications
The newly announced FDA approval builds on the existing regulatory history of the OncoMate MSI Dx Analysis System.
Promega previously received FDA clearance for the assay as the first PCR-based molecular diagnostic designed to identify colorectal cancer patients who may benefit from additional testing for Lynch syndrome.
Lynch syndrome is an inherited condition associated with an increased risk of developing certain cancers, particularly colorectal and endometrial cancers. It is commonly linked to inherited changes in genes involved in the DNA mismatch repair system.
Because mismatch repair deficiency can be associated with microsatellite instability, molecular testing can provide useful information when evaluating patients for potential Lynch syndrome. The OncoMate system’s earlier clearance established its role in identifying colorectal cancer patients who may require further diagnostic assessment.
The assay also has an approved companion diagnostic application for identifying patients with microsatellite stable (MSS) endometrial carcinoma who may benefit from treatment with KEYTRUDA in combination with LENVIMA® (lenvatinib).
LENVIMA is an orally available multiple receptor tyrosine kinase inhibitor discovered by Eisai. Its combination with KEYTRUDA represents a treatment approach for certain patients with advanced endometrial carcinoma.
The MSS endometrial cancer application demonstrates that the OncoMate platform has regulatory use beyond identifying MSI-H tumors. It also supports the identification of a specific patient population for whom KEYTRUDA plus LENVIMA may be an appropriate treatment option under the applicable indication.
These FDA clearances and approvals apply to the United States and its territories.
International Regulatory Progress Expands Access to MSI Testing
In addition to its U.S. regulatory status, Promega’s MSI technology has received regulatory recognition in international markets.
The technology is CE-marked under the In Vitro Diagnostic Regulation (IVDR) in the European Union. The IVDR establishes regulatory requirements for in vitro diagnostic medical devices marketed in the EU, including requirements related to safety, performance and clinical evidence.
Promega’s MSI technology has also received approval from China’s National Medical Products Administration (NMPA) as a companion diagnostic for identifying patients with MSI-H solid tumors who may benefit from KEYTRUDA treatment.
These regulatory developments demonstrate the company’s efforts to expand the availability of MSI testing across major healthcare markets. International access to validated molecular diagnostics is important because patients and healthcare systems increasingly rely on biomarker testing to guide cancer treatment decisions.
Regulatory approvals in different regions can also help support the integration of companion diagnostics into local oncology care pathways, subject to the applicable regional indications and requirements.
KEYTRUDA Indication for MSI-H and Mismatch Repair-Deficient Cancers
KEYTRUDA is indicated for adult and pediatric patients with unresectable or metastatic MSI-H or mismatch repair-deficient cancer who have experienced disease progression following prior treatment and have no satisfactory alternative treatment options.
The indication covers eligible patients whose tumors demonstrate the relevant molecular characteristics, making biomarker testing an important part of treatment evaluation.
As an anti-PD-1 therapy, KEYTRUDA is designed to interfere with the interaction between PD-1 and its associated ligands. This pathway can act as a mechanism through which cancer cells suppress immune activity. Blocking PD-1 can help enable immune cells to recognize and attack cancer cells.
The availability of a companion diagnostic such as the OncoMate MSI Dx Analysis System supports the identification of patients whose tumors meet the MSI-H biomarker criteria associated with the treatment indication.
The FDA approval of the Promega assay as a companion diagnostic therefore represents an important link between molecular testing and therapeutic decision-making. It provides clinicians with an additional diagnostic option for evaluating MSI status in solid tumor tissue when considering KEYTRUDA for eligible patients.
KEYTRUDA is a registered trademark of Merck Sharp & Dohme LLC, a subsidiary of Merck & Co., Inc., based in Rahway, New Jersey.
Supporting the Continued Growth of Biomarker-Driven Oncology
The FDA approval of the OncoMate MSI Dx Analysis System adds to the expanding role of molecular diagnostics in cancer care. As more treatments are developed for patients with specific genetic and molecular characteristics, reliable biomarker testing is becoming increasingly important in determining appropriate therapeutic options.
MSI testing is particularly relevant because it can identify patients with tumors that may respond to immune checkpoint inhibitors. The ability to detect this biomarker through a validated PCR-based assay can support clinical decision-making and help healthcare professionals evaluate treatment eligibility.
Promega’s existing regulatory applications for colorectal cancer, endometrial cancer and MSI-H solid tumors demonstrate the broader potential of its MSI technology across different diagnostic and treatment settings.
The collaboration with Merck further illustrates the importance of partnerships between diagnostic developers and pharmaceutical companies in advancing precision medicine. By aligning diagnostic capabilities with therapeutic indications, these collaborations can help improve the process of identifying patients who may benefit from specific cancer treatments.
Promega stated that the latest approval reflects its commitment to providing diagnostic advances that meet regulatory and quality expectations while supporting clinicians and pharmaceutical partners.
Additional information about Promega’s microsatellite instability technology and the OncoMate MSI Dx Analysis System is available at www.promega.com/MSI.
Overall, the FDA approval represents another milestone for Promega’s molecular diagnostics portfolio and strengthens the role of OncoMate MSI Dx Analysis System in biomarker-guided cancer care. By supporting the identification of patients with MSI-H solid tumors who may be eligible for KEYTRUDA, the assay contributes to the continued development of personalized treatment strategies in oncology.
About Promega Corporation
Promega Corporation is a leader in providing innovative solutions and technical support to the life sciences industry. The company’s portfolio of over 4,000 products supports a range of life science work across areas such as cell biology; DNA, RNA and protein analysis; drug development; human identification and molecular diagnostics. These tools and technologies have grown in their application over the last 45 years and are used today by scientists and technicians in labs for academic and government research, forensics, pharmaceuticals, clinical diagnostics and veterinary, agricultural and environmental testing. Promega is headquartered in Madison, WI, USA with branches in 16 countries and over 50 global distributors.