Personalis Announces New Publication Applying Ultrasensitive ctDNA Testing to Monitoring Cancer Immunotherapy Response Across Solid Tumors

Key Terms

ctDNA medical

Circulating tumor DNA (ctDNA) is tiny fragments of genetic material shed by cancer cells into the bloodstream, like breadcrumbs that can reveal a tumor’s presence and genetic makeup without needing a biopsy. For investors, ctDNA matters because tests and technologies that detect and analyze these fragments can speed diagnosis, track treatment response, and signal relapse, creating commercial opportunities in diagnostics, personalized therapies, and monitoring services.

molecular residual disease (MRD) medical

Molecular residual disease (MRD) is the tiny number of cancer cells that remain in a patient after treatment, detected by highly sensitive genetic or molecular tests that can find one cancer cell among thousands or millions of normal cells. MRD matters to investors because it helps predict the chance of relapse and influences whether additional treatment is given; MRD signals are increasingly used as early clinical trial or regulatory endpoints, so positive or negative MRD results can materially affect the market value of diagnostics and therapies—similar to an early warning that shapes future decisions.

immune checkpoint inhibitors medical

Drugs that release the immune system’s natural “brakes,” allowing immune cells to recognize and attack cancer cells; imagine taking the safety off a guard dog so it can chase intruders. They matter to investors because they can become high-value treatments with large sales potential, but their commercial success depends on clinical trial results, regulatory approval, competition and side-effect management, which all affect a company’s valuation.

circulating tumor DNA medical

Fragments of DNA shed by cancer cells into the bloodstream that act like tiny fingerprints of a tumor; they can be detected with a blood test rather than a biopsy. Investors care because circulating tumor DNA (ctDNA) enables faster, lower-cost ways to detect disease, track treatment response, identify emerging resistance and enroll patients in trials—factors that can materially affect the commercial prospects of diagnostics and therapeutics.

overall survival medical

Overall survival is the average or median length of time patients remain alive after starting a treatment or entering a clinical study, measured regardless of cause of death. Investors care because it is a clear, hard measure of a therapy’s real-world benefit — like timing how long a new battery actually runs — and strong improvements in overall survival can drive regulatory approval, market adoption and revenue potential.

overall response rate medical

Overall response rate is the percentage of patients in a clinical study whose measurable disease shrinks or disappears after receiving a treatment. Investors watch it like a product’s “hit rate” because higher response rates can signal a drug’s effectiveness, boost chances of regulatory approval and market demand, and affect a company’s future revenue prospects, similar to how a higher batting average suggests a more reliable player.

immunotherapy medical

Treatment that uses or enhances the body’s immune system to detect and fight disease, most often cancers or chronic infections; think of it as training or arming the body’s own soldiers to find and destroy targets. It matters to investors because successful immunotherapies can lead to high-value drug approvals, recurring revenue from long-term treatments, and changes in competitive dynamics, while failures or safety issues in clinical trials can materially affect company valuations.

stage IV medical

Stage IV is the most advanced classification of cancer, meaning the disease has spread from its original site to distant parts of the body. For investors, stage IV matters because treatments, trial outcomes, and regulatory decisions for advanced disease often drive demand, pricing, and revenue potential for drugs and diagnostics; think of it as a late-stage problem that requires more intensive, higher-value solutions than early-stage cases.

FREMONT, Calif.--(BUSINESS WIRE)-- Personalis, Inc. (Nasdaq: PSNL), a leader in advanced genomics for precision oncology, today announced the publication of a new study in Clinical Cancer Research, a journal of the American Association for Cancer Research (AACR). The paper, titled "Broad Utility of Ultrasensitive Analysis of ctDNA Dynamics across Solid Tumors Treated with Immunotherapy," details results from Dr. Rodrigo Toledo and a leading team at the Vall d’Hebron Institute of Oncology (VHIO) in Barcelona, Spain. The study provides compelling clinical evidence that the company’s ultra-sensitive, tumor-informed molecular residual disease (MRD) assay, NeXT Personal®, can effectively predict patient outcomes across a diverse set of cancers and immunotherapy modalities.

The study analyzed 202 patients with stage IV solid tumors—spanning 24 different cancer types—treated with immune checkpoint inhibitors and other immunotherapies. Utilizing a personalized testing approach that tracks up to ~1,800 tumor-specific variants unique to each patient’s tumor, the NeXT Personal test achieves ultrasensitive detection of small traces of circulating tumor DNA (ctDNA) from a patient’s blood sample.

Key findings published in Clinical Cancer Research include:

• High Sensitivity: The test detected ctDNA in 98% of patients at baseline across all 24 tumor types, demonstrating robust performance even in a diverse set of cancers.
• Early ctDNA Dynamics are Highly Prognostic: Patients who demonstrated decreases in ctDNA levels early in immunotherapy treatment had significantly higher overall survival. Conversely, patients with increasing ctDNA levels early while on immunotherapy had a zero percent overall response rate.
• Durable ctDNA Clearance was a Positive Predictor: Patients who achieved durable molecular clearance (negative ctDNA for at least 180 days) had 100% overall survival (OS) in the study.

"We are excited about these results showing how NeXT Personal can be used to monitor therapy in late-stage metastatic patients," said Rich Chen, M.D., M.S., Chief Medical Officer and Executive Vice President, R&D at Personalis. “This study, together with our previous publications, shows the broad potential impact of ultrasensitive ctDNA testing, both in early and late stage cancers.”

Dr. Rodrigo Toledo, Group Leader of the Biomarkers and Clonal Dynamics Laboratory at VHIO and senior author of the study, noted, "immunotherapy has revolutionized cancer care, but response patterns can be difficult to interpret using imaging alone. Our findings show that ultrasensitive ctDNA dynamics provide a clear, early molecular view of benefit or non-response, offering a powerful tool to guide patient management across a broad spectrum of solid tumors."

About Personalis, Inc.

At Personalis, we are transforming the active management of cancer through breakthrough personalized testing. We aim to drive a new paradigm for cancer management, guiding care throughout the patient journey. Our highly sensitive assays combine tumor-and-normal profiling with proprietary algorithms to deliver advanced insights even as cancer evolves over time. Our products are designed to detect minimal residual disease (MRD) and recurrence at the earliest timepoints, enable selection of targeted therapies based on ultra-comprehensive genomic profiling, and enhance biomarker strategy for drug development. Personalis is based in Fremont, California. To learn more, visit www.personalis.com and connect with us on LinkedIn and X (Twitter).

Forward-Looking Statements

This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. Forward-looking statements include all statements that are not historical facts, including statements relating to: the attributes, advantages, sensitivity, and clinical relevance of the NeXT Personal test and the potential impact or expected benefits of the VHIOstudy. Such forward-looking statements involve known and unknown risks and uncertainties and other factors that may cause actual results to differ materially from any anticipated results or expectations expressed or implied by such statements, including the risks, uncertainties and other factors that relate to Personalis’ ability to demonstrate attributes, advantages or clinical validity of the NeXT Personal test, including the NeXT Personal MRD assay remaining unique in its ability to detect traces of cancer in the ultra-sensitive range; future clinical data differing from the clinical data previously presented or expected results; the rate of adoption and use of the NeXT Personal test; changes in health care policy could increase Personalis’ costs, decrease Personalis’ revenue, and impact sales of and reimbursement for Personalis’ tests; the impact of competition and macroeconomic factors on Personalis’ business; having a limited number of suppliers; and customer concentration. These and other potential risks and uncertainties that could cause actual results to differ materially from the results predicted in these forward-looking statements are described under the captions “Risk Factors” and “Management’s Discussion and Analysis of Financial Condition and Results of Operations” in Personalis’ Annual Report on Form 10-K for the year ended December 31, 2024, filed with the Securities and Exchange Commission (SEC) on February 27, 2025 and subsequent Quarterly Reports on Form 10-Q, including the Quarterly Report on Form 10-Q for the quarter ended September 30, 2025, filed with the SEC on November 4, 2025. All information provided in this release is as of the date of this press release, and any forward-looking statements contained herein are based on assumptions that we believe to be reasonable as of this date. Undue reliance should not be placed on the forward-looking statements in this press release, which are based on information available to us on the date hereof. Personalis undertakes no duty to update this information unless required by law.

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Source: Personalis, Inc.