Personalis NeXT Personal® Data Showcasing Ultrasensitive MRD to be Presented at ESMO 2026

Late-breaking oral presentation highlights the role of ultrasensitive ctDNA in drug development; first data from prospective B-STRONGER-1 study in early-stage triple-negative breast cancer

Personalis, Inc. (Nasdaq: PSNL), a leader in advanced genomics for precision oncology, today announced that two oral presentations and two poster presentations featuring its NeXT Personal ultrasensitive circulating tumor DNA (ctDNA) test will be presented at the European Society for Medical Oncology (ESMO) Congress 2026, taking place October 23-27 in Madrid, Spain. Highlights include a late-breaking oral presentation of NeXT Personal data for the C-POST Phase 3 study in cutaneous squamous cell carcinoma, as well as a Rapid Oral presentation from B-STRONGER-1, a prospective, multicenter study evaluating NeXT Personal for detecting molecular residual disease in patients with early-stage triple-negative breast cancer receiving neoadjuvant therapy.

“B-STRONGER-1 builds on our earlier work in triple-negative breast cancer demonstrating the use of ultrasensitive MRD testing for monitoring neoadjuvant therapy response,” said Richard Chen, MD, President and Chief Medical Officer of Personalis. “We are also excited to see NeXT Personal data presented from biopharma in new indications like cutaneous squamous cell carcinoma as we continue to expand evidence around NeXT Personal for a broad range of solid tumors.”

Presentation Schedule

Late-Breaking Oral Presentation

• Title: C-POST phase 3 trial of adjuvant (adj) cemiplimab (cemi) vs placebo (pbo) for high-risk cutaneous squamous cell carcinoma (CSCC): Updated overall survival (OS) and outcomes from circulating tumour DNA (ctDNA) analyses
• Presenter: Danny Rischin, M.D.; Peter MacCallum Cancer Centre
• Abstract: LBA59 | Session: Rapid Oral - Melanoma and Other Skin Tumours
• Time: Sun, 10/25/2026, 10:42 - 10:47 CET
• Location: Granada Auditorium - Hall 4

Rapid Oral Presentation – B-STRONGER-1

• Title: Ultrasensitive monitoring of early ctDNA dynamics during neoadjuvant treatment in early-stage triple-negative breast cancer: Pre-interim results from the B-STRONGER-I study
• Presenter: Carlos Barcenas, M.D.; The University of Texas MD Anderson Cancer Center
• Abstract: 540RO | Session: Rapid Oral - Breast Cancer, Early Stage
• Time: Fri, 10/23/2026, 16:42 - 16:47 CEST
• Location: Alicante Auditorium - Hall 6

Poster Presentations

• Title: Ultrasensitive ctDNA kinetics predict early immunotherapy response and complement radiographic assessment in advanced cancer. (UC San Diego). Abstract # 4280P | Session: Translational Research and Biomarkers | Time: Fri, 10/23/2026, 15:15 - 16:00 CEST | Location: Poster Area - Hall 5
• Title: Circulating tumour DNA (ctDNA), cancer antigen 125 (CA125) and human epididymis protein 4 (HE4) associate with survival outcomes in patients with platinum- resistant ovarian cancer (PROC) treated with ubamatamab (uba). (Yonsei University Health System). Abstract # 1957P | Session: Investigational Immunotherapy | Time: Sat, 10/24/2026, 12:00 - 12:45 CEST | Location: Poster Area - Hall 5

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 clinical performance, clinical utility or clinical impact of NeXT Personal, including its ability to detect molecular residual disease in early-stage triple-negative breast cancer or to provide a clearer assessment of treatment response and residual disease; the results or significance of the studies presented; and the role of ultrasensitive ctDNA testing in drug development and clinical research. 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, including the NeXT Personal MRD assay remaining unique in its ability to detect traces of cancer in the ultrasensitive 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, which could increase Personalis' costs, decrease Personalis' revenue, and impact sales of and reimbursement for Personalis' tests; Personalis' ability to obtain Medicare coverage and reimbursement in additional indications and the timing thereof; 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, and subsequent Quarterly Reports on Form 10-Q and Current Reports on Form 8-K. 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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