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Tempus Announces New ctDNA Assay, xF Monitor

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Tumor uninformed treatment response monitoring assay for research use only

CHICAGO–(BUSINESS WIRE)–Tempus, a leader in artificial intelligence and precision medicine, today announced xF Monitor – a new circulating tumor DNA (ctDNA) assay for research use only, which detects and monitors changes in circulating tumor fraction to determine early response to immunotherapy for patients with advanced cancers.

Tempus’ xF Monitor assay measures quantitative molecular changes in ctDNA tumor fraction by utilizing diverse genomic events, dynamically weighting somatic variant allele frequencies and copy number variants, while using germline information to inform these estimates. The algorithm that powers xF Monitor – xF ctDNA tumor fraction – utilizes multiple single input models and weights their importance based on failure modes observed in Tempus’ multimodal database. The Tempus team will debut the xF Monitor assay at the Society for Immunotherapy of Cancer’s 38th Annual Meeting this week.

“We are excited to add the xF Monitor assay to our comprehensive suite of precision medicine offerings here at Tempus,” said Kate Sasser, PhD, Chief Scientific Officer at Tempus. “There has been tremendous progress in the utilization of ctDNA for monitoring patient response to treatment, especially for immunotherapy. We are looking forward to bringing our xF Monitor assay forward as a diagnostic tool to help biopharma develop innovative medicines and physicians to tailor therapies for patients.”

xF Monitor is now available for research use only for both Tempus’ 105-gene liquid assay, xF, and Tempus’ 523-gene liquid assay, xF+.

About Tempus

Tempus is a technology company advancing precision medicine through the practical application of artificial intelligence in healthcare. With one of the world’s largest libraries of multimodal data, and an operating system to make that data accessible and useful, Tempus provides AI-enabled precision medicine solutions to physicians to deliver personalized patient care and in parallel facilitates discovery, development and delivery of optimal therapeutics. The goal is for each patient to benefit from the treatment of others who came before by providing physicians with tools that learn as the company gathers more data. For more information, visit


Erin Carron

Senior Director of Communications