Guardant Health and Merck entered a multi‑year partnership to use Guardant’s liquid and tissue biopsy assays to support enrollment in Merck’s global clinical studies and to co‑develop companion diagnostics. The agreement covers use of Guardant’s portfolio to identify patients and streamline biomarker‑driven trial matching across indications. Companies highlighted that integrating liquid biopsy testing with clinical trial workflows can accelerate patient identification for targeted therapies and reduce screening burden on sites. The collaboration may also include regulatory and commercialization pathways for prospective companion diagnostics tied to Merck development programs. The deal underscores growing reliance on circulating tumor DNA assays to de‑risk biomarker‑based trials and to standardize diagnostic approaches across global studies.