A Phase I study published in Clinical Cancer Research demonstrates that Personalis’ NeXT Personal MRD assay—an individualized whole‑genome sequencing ctDNA test—accurately predicts immunotherapy responses across metastatic solid tumors. Investigators from Val d’Hebron Institute of Oncology analyzed ~1,455 longitudinal plasma samples from retrospective and prospective cohorts and found that a ~30% ctDNA decline before cycle two correlated with improved progression‑free and overall survival. Complete ctDNA clearance conferred dramatically longer PFS, and sustained MRD negativity at 180 days associated with 100% overall survival in the studied cohort. The work reinforces tumor‑informed ctDNA as a pharmacodynamic biomarker for early response assessment and may influence trial designs and early stopping rules for immune checkpoint inhibitor regimens.