Tempus AI has announced the launch of xM for treatment response monitoring (TRM), a liquid biopsy assay designed to detect molecular response to immune-checkpoint inhibitor (ICI) therapy in patients with advanced solid tumors. The assay represents the newest addition to Tempus' portfolio of sensitive assays for monitoring molecular response and minimal residual disease.
Clinical Need and Market Context
In 2023, an estimated 56.55% of patients with advanced or metastatic cancers were eligible for immune-checkpoint inhibitors, with a corresponding estimated response rate of 20.13%. This significant gap between eligibility and response highlights the critical need for better tools to monitor treatment effectiveness and guide therapeutic decisions.
Technology and Mechanism
The xM for TRM assay quantifies changes in circulating tumor DNA (ctDNA) longitudinally from blood samples, enabling early molecular response assessment in patients with advanced cancers receiving immunocheckpoint inhibitors alone or in combination therapies. The assay leverages a unique multi-parametric algorithm that integrates copy number variations (CNVs) along with somatic and germline variant allele frequencies (VAFs) to provide a comprehensive and robust estimation of circulating tumor fraction.
Clinical Validation and ASCO Presentation
Tempus presented new data on xM for TRM at the 2025 American Society of Clinical Oncology (ASCO) Annual Meeting. The study, titled "A molecular biomarker for longitudinal monitoring of therapeutic efficacy in a real-world cohort of advanced solid tumors treated with immune checkpoint inhibitors," demonstrated that longitudinal non-molecular responders are associated with worse survival compared to molecular responders, highlighting the value of xM molecular response monitoring as a tool to guide ICI treatment decisions.
Clinical Impact and Timing Advantages
According to Dr. Halla Nimeiri, Chief Development Officer at Tempus, "With xM for TRM, clinicians can detect molecular response to ICI prior to six weeks into treatment, enabling them to stay ahead of disease progression and optimize therapeutic strategies." This early detection capability is particularly crucial for patients with advanced disease, where timing is critical for treatment success.
Dr. Nimeiri emphasized the comprehensive nature of Tempus' monitoring portfolio, stating, "Our comprehensive monitoring portfolio is designed to support patients throughout the cancer treatment journey. We're excited to introduce a new assay of molecular response for both physicians and biopharma researchers that can timely track changes of quantitative tumor fraction while patients receive ICI therapies."
Availability and Future Plans
The xM for TRM assay is currently available for research use only, with clinical availability expected later this year. This timeline allows for continued validation and regulatory preparation while making the technology accessible to researchers investigating immunotherapy response mechanisms.
Broader Portfolio Context
The xM for TRM launch follows Tempus' recent publication of validation data for its xF+ comprehensive liquid biopsy assay in the Journal of Molecular Diagnostics. The xF+ assay, originally introduced in 2022, covers 523 genes spanning approximately 1.8 Mb of the human genome and has demonstrated concordance with other Tempus assays for microsatellite instability status and gene coverage.
Dr. Ezra Cohen, Chief Medical Officer of Oncology at Tempus, noted that "When we first introduced xF+ in 2022, it was one of the largest clinically available liquid biopsy panels offered to physicians. We have since continued to refine the assay, and are thrilled to further demonstrate its analytical validity in a peer-reviewed study."
