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BillionToOne appoints Dr. Allen Chen as Vice President of Medical Affairs and Clinical Development, Oncology. Renowned physician executive and clinician-scientist joins BillionToOne to advance oncology medical strategy MENLO PARK, CA, April 2, 2026 - BillionToOne, Inc. (Nasdaq: BLLN), a next-generation molecular diagnostics company focused on making highly accurate testing accessible to all, today announced the appointment of Allen Chen, MD, MBA, FASTRO, FACHE, as Vice President of Medical Affairs and Clinical Development, Oncology. This new appointment reflects BillionToOne's continued commitment to building world-class oncology medical leadership as the company grows its Northstar liquid biopsy portfolio. Dr. Chen brings more than 20 years of experience as a physician-executive, clinician-scientist, and internationally recognized thought leader across academic and community health systems. Dr. Chen joins BillionToOne following a distinguished career across leading academic medical centers, including the University of California Davis, UCLA's David Geffen School of Medicine, the University of Kansas Cancer Center, and the University of California Irvine, where he was appointed tenured Professor and served in senior leadership positions including Chair of Radiation Oncology, Residency and Fellowship Training Director, and Head of the Protocol Activation and Review Committee for Clinical Trials. Dr. Chen holds an MD from Yale School of Medicine, double MBAs from National University of Singapore and UCLA Anderson School of Management, and a Bachelor's Degree from Cornell University. He completed residency training in radiation oncology at the MD Anderson Cancer Center in Houston and the University of California, San Francisco. "Allen is an exceptional physician leader who has spent more than two decades building cancer programs at major academic medical centers and driving impressive clinical transformation at health systems," said Oguzhan Atay, PhD, co-founder and CEO of BillionToOne. "His deep expertise in cancer care, translational research, and clinical trial leadership is precisely what we need as we scale our oncology mission." Throughout his career, Dr. Chen has served as principal investigator for dozens of clinical trials, held leadership roles within national cooperative cancer groups, and contributed to National Cancer Institute task forces focused on clinical trial development for patients with metastatic cancer, treatment-refractory disease, and rare tumors. He has authored more than 300 peer-reviewed publications spanning cancer research, health policy, and healthcare delivery. He is also a strong advocate of AI and has implemented technology solutions focused on digital health and machine learning that transformed care programs at medical centers. "BillionToOne is doing something genuinely impactful by making ultra-sensitive, clinically actionable genomic information accessible to oncologists," said Dr. Chen. "I have spent my career working to close gaps in personalized cancer care delivery, and BillionToOne is truly moving the needle for patients with solid tumors. I am honored to join at this pivotal moment and help oncologists understand and trust the power of these tools. It is such an exciting time in cancer care, and the work happening at BillionToOne is not only groundbreaking but has the potential to change the future." In his new role, Dr. Chen will lead medical affairs strategy as well as clinical and translational research development for BillionToOne's Northstar oncology portfolio. Northstar Select(R) is an ultra-sensitive, 84-gene, single-molecule NGS-based ctDNA panel designed to identify actionable genomic alterations in patients with advanced solid tumors, giving oncologists a comprehensive liquid biopsy tool to guide treatment decisions. Northstar Response(R) is a tissue-free, methylation-based pan-cancer assay that enables physicians to monitor treatment response by measuring changes in circulating tumor-derived signals over time with single-molecule precision, providing a real-time view of a patient's tumor burden and molecular insight into how they are responding to therapy. Dr. Gary Palmer to Retire, Continuing with BillionToOne in a CMO Emeritus Advisory Role BillionToOne also announced that Gary Palmer, MD, is retiring as Chief Medical Officer, Oncology. During his tenure, Dr. Palmer played a central role in establishing BillionToOne's clinical strategy in oncology and shaping the clinical foundation of the Northstar portfolio. He will remain with the company in an emeritus advisory role, continuing to contribute his expertise as BillionToOne grows its oncology business. "Gary has been a foundational voice in everything we have built in oncology, and his fingerprints are on so much of what makes Northstar strong today," said Dr. Atay. "We are grateful for his leadership and his commitment to patients, and we are fortunate that he will remain to advise us as we continue our goal of transforming the standard of care with our oncology products." Forward-Looking Statements This press release contains certain forward-looking statements within the meaning of federal securities laws. These forward-looking statements generally are identified by the words "believe," "project," "expect," "anticipate," "estimate," "intend," "strategy," "future," "opportunity," "plan," "may," "should," "will," "would," "will be," "will continue," "will likely result," and similar expressions. Forward-looking statements are predictions, projections and other statements about future events that are based on current expectations and assumptions and, as a result, are subject to risks and uncertainties. Forward-looking statements in this press release include, but are not limited to, statements regarding the scalability of the company's oncology mission. These statements are based on management's current expectations, forecasts and assumptions, and actual outcomes and results could differ materially from these statements due to a number of factors, some of which are beyond BillionToOne's control. These and additional risks and uncertainties could affect BillionToOne's financial and operating results and cause actual results to differ materially from those indicated by the forward-looking statements made in this press release. These risks and uncertainties include, but are not limited to, the potential growth relating to the company's oncology products as well as those discussed under the captions "Risk Factors" and "Management's Discussion and Analysis of Financial Condition and Results of Operation" and elsewhere in BillionToOne's most recently filed Annual Report on Form 10K and other filings that the company makes with the Securities and Exchange Commission from time to time. The forward-looking statements in this press release are based on information available to BillionToOne as of the date hereof, and BillionToOne disclaims any obligation to update any forward-looking statements provided to reflect any change in its expectations or any change in events, conditions, or circumstances on which any such statement is based, except as required by law. These forward-looking statements should not be relied upon as representing BillionToOne's views as of any date subsequent to the date of this press release. About BillionToOne Headquartered in Menlo Park, California, BillionToOne is a next-generation molecular diagnostics company with a mission to create powerful and accurate tests that are accessible to all. The company's patented Quantitative Counting Templates(TM)(QCT(TM) molecular counting platform is the only multiplex technology that can accurately count DNA molecules at the single-molecule level. For more information, visit www.billiontoone.com. Media Contact

BillionToOne appoints Dr. Allen Chen as Vice President of Medical Affairs and Clinical Development, Oncology. PR Newswire Renowned physician executive and clinician-scientist joins BillionToOne to advance oncology medical strategy MENLO PARK, Calif., April 2, 2026 /PRNewswire/ - BillionToOne, Inc. (Nasdaq: BLLN), a next-generation molecular diagnostics company focused on making highly accurate testing accessible to all, today announced the appointment of Allen Chen, MD, MBA, FASTRO, FACHE, as Vice President of Medical Affairs and Clinical Development, Oncology. This new appointment reflects BillionToOne's continued commitment to building world-class oncology medical leadership as the company grows its Northstar liquid biopsy portfolio. Dr. Chen brings more than 20 years of experience as a physician-executive, clinician-scientist, and internationally recognized thought leader across academic and community health systems. Dr. Chen joins BillionToOne following a distinguished career across leading academic medical centers, including the University of California Davis, UCLA's David Geffen School of Medicine, the University of Kansas Cancer Center, and the University of California Irvine, where he was appointed tenured Professor and served in senior leadership positions including Chair of Radiation Oncology, Residency and Fellowship Training Director, and Head of the Protocol Activation and Review Committee for Clinical Trials. Dr. Chen holds an MD from Yale School of Medicine, double MBAs from National University of Singapore and UCLA Anderson School of Management, and a Bachelor's Degree from Cornell University. He completed residency training in radiation oncology at the MD Anderson Cancer Center in Houston and the University of California, San Francisco. "Allen is an exceptional physician leader who has spent more than two decades building cancer programs at major academic medical centers and driving impressive clinical transformation at health systems," said Oguzhan Atay, PhD, co-founder and CEO of BillionToOne. "His deep expertise in cancer care, translational research, and clinical trial leadership is precisely what we need as we scale our oncology mission." Throughout his career, Dr. Chen has served as principal investigator for dozens of clinical trials, held leadership roles within national cooperative cancer groups, and contributed to National Cancer Institute task forces focused on clinical trial development for patients with metastatic cancer, treatment-refractory disease, and rare tumors. He has authored more than 300 peer-reviewed publications spanning cancer research, health policy, and healthcare delivery. He is also a strong advocate of AI and has implemented technology solutions focused on digital health and machine learning that transformed care programs at medical centers.

BillionToOne, a precision diagnostics company with substantial insider ownership, has raised its profile through strong financial performance and strategic product launches. The company reported significant revenue growth in 2025, transitioning from a net loss to profitability with revenue of $305.11 million. The firm has expanded its market presence through innovative products including Northstar PGx and UNITY Fetal Antigen NIPT. Recent inclusion in the S&P Global BMI Index highlights its growing market influence. Analysts forecast robust annual earnings growth of 39.1%, significantly outpacing the US market average of 16%. However, recent valuation reports suggest the company's share price may be optimistic relative to its fundamentals. Revenue is projected to grow at 20.2% annually.