Personalis Highlights Clinical Impact of Ultrasensitive ctDNA Monitoring and New Therapy Resistance Tracking at AACR 2026

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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.

neoadjuvant medical

"Neoadjuvant" describes treatments or interventions that are given before the main or primary procedure, such as surgery or a major decision. It’s like preparing the ground before planting seeds, aiming to improve the final outcome. For investors, understanding neoadjuvant approaches can provide insight into how companies enhance results or effectiveness in their processes or products.

dMMR/MSI-H medical

A dMMR/MSI‑H tumor lacks a working DNA “spell‑checker” (deficient mismatch repair, dMMR), which leads to lots of small, repeated DNA errors called high microsatellite instability (MSI‑H). Investors care because this biological signature predicts which cancers are more likely to respond to certain immunotherapies and can influence clinical trial design, regulatory approvals, market size for targeted drugs, and companion diagnostic testing demand.

pathological complete response medical

Pathological complete response is when tissue examined under a microscope after cancer treatment and surgery shows no remaining invasive tumor cells. Investors care because it is a strong signal that a therapy is working, often used as a key endpoint in clinical trials and a predictor of better long‑term outcomes; like finding an empty crime scene after a cleanup, it can boost confidence in a drug’s market potential and regulatory prospects.

negative predictive value medical

Negative predictive value is a measure of how reliable a negative result is in confirming that a person or situation is truly free of a problem or condition. For investors, it indicates the likelihood that a negative signal or indicator truly means there is no risk or issue present, helping them assess how much trust to place in avoiding potential problems based on current information.

minimal residual disease medical

Minimal residual disease (MRD) is the tiny number of cancer cells that remain in the body after treatment, often too few to show up on standard scans but detectable with very sensitive tests. For investors, MRD is important because it predicts the risk of relapse and can determine whether a therapy is seen as effective, influences regulatory and reimbursement decisions, and affects the size and timing of a drug’s market opportunity—like spotting the last weeds that can make a garden regrow if not removed.

ESR1 medical

ESR1 is a gene that makes the estrogen receptor alpha protein, a cellular “lock” that the hormone estrogen (the “key”) fits into to tell cells how to grow, divide and behave. Mutations or changes in ESR1 can change how cancers—especially breast and other hormone-driven tumors—respond to hormone-blocking drugs, so investors track ESR1-linked tests, drugs and trial results because they directly affect treatment choices, market size and regulatory chances in oncology and women’s health.

non-small cell lung cancer medical

A broad category of lung tumors that grow from the cells lining the airways and make up the majority of lung cancer cases; it includes several subtypes that behave and respond to treatment differently, like different models of the same car family. It matters to investors because its large patient population and variety of treatment options — surgery, traditional chemo, targeted drugs and immunotherapies — create major markets where clinical trial results, drug approvals or changing treatment guidelines can quickly affect a company’s revenue and stock value.

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04/21/2026 - 06:00 AM

Podium presentation on NeXT Personal® monitoring neoadjuvant therapy in colorectal cancer;

Real-world data from 10,000 patients reinforce industry-leading sensitivity;

Data presented for a new NeXT Personal feature for monitoring resistance mutations

FREMONT, Calif.--(BUSINESS WIRE)-- Personalis, Inc. (Nasdaq: PSNL), a leader in advanced genomics for precision oncology, today announced the successful presentation of clinical data at the American Association for Cancer Research (AACR) Annual Meeting. The data, spanning one oral podium presentation and three posters, underscore the use of the NeXT Personal ultrasensitive ctDNA assay in monitoring treatment response, identifying early recurrence, and tracking the emergence of therapy resistance.

Neoadjuvant Monitoring in Colorectal Cancer. A highlight was the oral podium presentation of the NEOPRISM-CRC trial, delivered by Dr. Jiang from the University College London, which utilized NeXT Personal to monitor patients with high-risk stage II-III dMMR/MSI-H colorectal cancer (CRC) receiving neoadjuvant pembrolizumab. In addition to 100% sensitivity for disease at baseline, the study identified three distinct groups of patient response to neoadjuvant treatment: super molecular responders, dynamic molecular responders, and poor molecular responders. Notably, 100% of "super molecular responders"—those who cleared ctDNA by the second cycle of treatment—also achieved pathological complete response (pCR). Conversely, of “poor molecular responders”—patients with relatively stable ctDNA levels during neoadjuvant treatment—100% did not achieve pCR. These findings could provide clinicians with a critical window to adjust treatment strategies prior to surgery. Post-surgery, the test achieved a 100% negative predictive value (NPV) and 100% specificity for disease relapse.

"The data presented at AACR confirm ultrasensitive ctDNA detection with NeXT Personal as a promising therapy monitoring tool in neoadjuvant colorectal cancer treatment,” said Dr. Richard Chen, President and Chief Medical Officer at Personalis. "By measuring molecular response with high resolution, we are providing the tools needed to explore ctDNA-guided management of colorectal cancer patients receiving neoadjuvant therapy."

Ultrasensitivity in Real-World Data. In a large-scale analysis of nearly 25,000 plasma samples from 10,000 real-world patients, NeXT Personal demonstrated consistent ultrasensitive performance with a median limit of detection of 1.92 PPM. The study also revealed that 39% of all positive MRD detections occurred in the ultrasensitive range below 100 PPM, with 14.6% below 10 PPM—detections that could be missed with less sensitive assays. This study also highlights the robust ultrasensitive performance of the NeXT Personal assay in real-world testing conditions across more than 14 cancer types, stage I-IV disease, and a variety of challenging sample types.

Innovation in Therapy Resistance Tracking. Personalis also debuted analytical validation and real-world data for a new opt-in feature of its NeXT Personal MRD test: Real-Time Variant Tracker™. This feature allows for the simultaneous monitoring of MRD and the longitudinal tracking of specific resistance-associated mutations, such as ESR1. With a specificity of >99.9%, resistance and other clinical mutations were identified in 38% of MRD-positive patients across the real-world cohort, offering a new tool for tracking treatment resistance as it emerges.

Monitoring Immunotherapy Response in NSCLC. The DARWIN 2 study results in metastatic non-small cell lung cancer (NSCLC) demonstrated NeXT Personal’s ability to stratify risk in patients receiving immunotherapy. Patients who achieved a durable molecular complete response (dmCR) remained 100% progression-free at three years, whereas patients who failed to achieve molecular clearance were five times more likely to experience disease progression.

Together, these studies illustrate Personalis’ commitment to improving cancer management through ultrasensitive MRD testing throughout the patient journey.

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 and can generally be identified by terms such as “believe,” “expect,” “if,” “may,” “will” or similar expressions. These statements include those relating to: the use, clinical impact or real-world clinical performance of NeXT Personal, the ability of NeXT Personal or the Real-Time Variant Tracker feature to inform cancer monitoring or patient management, predict or track therapy response, detect resistance or other clinical mutations, predict relapse, or predict or impact patient outcomes. 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 or utility of the NeXT Personal test and the Real-Time Variant Tracker option, including the NeXT Personal MRD assay remaining unique in its ability to detect traces of cancer in the ultrasensitive range and its ability to monitor mutations; 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, which 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; the partnering and/or collaboration arrangements that Personalis has entered into or may enter into in the future may not be successful, or may terminate, which could adversely impact Personalis’ business or affect its ability to develop and commercialize its services and products; 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, 2025, filed with the Securities and Exchange Commission on February 26, 2026. 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.

Not affiliated with or endorsed by AACR.