Merck investigators reported post-marketing bridging studies that confirm two commercially available companion diagnostics can reliably identify patients for pembrolizumab’s tumor-agnostic use in dMMR/MSI-H solid tumors. The results were published in BMC Cancer and focus on how routine-use assays align with the evidence base used in pembrolizumab’s original clinical trials. The work matters because tumor-agnostic checkpoint blockade depends on biomarker accuracy—mismatch repair deficiency and microsatellite instability determine whether a patient biologically matches the treatment mechanism. By comparing commercially available CDx approaches to trial assays, the studies aim to reduce implementation risk when the diagnostic workflows move from clinical trials into real-world labs. For the CDx ecosystem, the finding supports confidence in assay interchangeability and may reduce friction for oncology centers seeking scalable, validated testing pathways for MSI/dMMR patients.