Two post-marketing bridging studies presented work validating that commercially available companion diagnostics can reliably identify patients eligible for tumor-agnostic pembrolizumab in dMMR/MSI-H solid tumors. The results, published in BMC Cancer, extend the original clinical trial assay logic—based on mismatch repair protein status and microsatellite instability biology—into real-world CDx performance. The studies focus on how diagnostic tests used in routine practice map onto evidence generated with trial assays, a key requirement once drugs are approved. For pembrolizumab, the biological rationale is mismatch repair deficiency driving microsatellite instability, generating neoantigens that improve checkpoint inhibitor responsiveness. For biotech teams, the update is a practical blueprint for CDx “bridging” strategy—covering both immunohistochemistry and PCR/NGS-style interrogations of MMR/MSI status—and underscores that diagnostic interchangeability is scrutinized even after drug authorization.