BriaCell Reports Robust Overall Survival and Clinical Benefit Data at ASCO 2025

Three BriaCell posters and one publish-only abstract highlight robust clinical data from Bria-IMT™ and Bria-OTS™ studies in metastatic breast cancer (MBC)Median Overall Survival of 17.3 months in Phase 2 study patients treated with Phase 3 formulation (since 2022) is superior to outcomes reported for comparable patients in the literatureMeaningful Clinical Benefit observed in all MBC subtypes, including HER2+, HR+/HER2-, and triple-negative breast cancer (TNBC)Overall survival and clinical benefit data reported meets or exceeds that of FDA-approved therapies in comparable patientsNo treatment-related discontinuations PHILADELPHIA and VANCOUVER, British Columbia, June 02, 2025 (GLOBE NEWSWIRE) -- BriaCell Therapeutics Corp. (Nasdaq: BCTX, BCTXW, BCTXZ), (TSX:BCT) (“BriaCell” or the “Company”), a clinical-stage biotechnology company developing novel immunotherapies to transform cancer care, today presents clinical data in three clinical poster presentations and one publish-only abstract at the 2025 American Society of Clinical Oncology (ASCO) Annual Meeting. BriaCell has featured robust survival and clinical benefit data from its Bria-IMT Phase 2 clinical study, clinical progress data from its ongoing pivotal Bria-IMT Phase 3 study (ClinicalTrials.gov identifier: NCT06072612), and Phase 1/2 study of Bria-OTS (ClinicalTrials.gov identifier: NCT06471673) in metastatic breast cancer. “Prolonging survival and providing meaningful clinical benefit for patients whose disease has demonstrated resistance to multiple treatment options remains a critical unmet need in breast cancer. These Bria-IMT regimen results are promising for individuals with metastatic breast cancer,” said Sara A.

Hurvitz, MD, FACP, Senior Vice President, Director of the Clinical Research Division, and Smith Family Endowed Chair in Women’s Health at Fred Hutch Cancer Center, as well as Professor and Head of the Division of Hematology and Oncology at the University of Washington, Seattle, WA, and co-author of one of the clinical posters. “The low incidence of all grade and grade 3/4 adverse events is particularly notable.” “We are thrilled with our Phase 2 overall survival and clinical benefit data which meets and exceeds those of FDA approved drugs — even in very heavily pre-treated patients in our study,” noted Dr. William V. Williams, BriaCell’s President & CEO. “We look forward to further confirming these impressive results in our ongoing pivotal Phase 3 study with the ultimate goal of bringing novel treatments to cancer patients in need.” The details of the poster presentation sessions and publish-only abstract are listed below.

Poster Title: Update on phase III pivotal trial of Bria-IMT + CPI vs physician’s choice in advanced metastatic breast cancer (BRIA-ABC) Session Date and Time: June 2, 2025 9:00 AM-12:00 PM CDT Abstract Number for Publication: TPS1138 Poster Board Number: 108a Session Type and Title: Poster Session – Breast Cancer—Metastatic “Trial in Progress” poster presents early enrollment data and the overall design of the Phase 3 pivotal trial along with updated clinical outcomes from the Phase 2 Bria-IMT study. Poster Title: Bria-IMT + checkpoint inhibitor: Phase I/II survival results compared to benchmark trials in metastatic breast cancer Session Date and Time: June 2, 2025 9:00 AM-12:00 PM CDT Abstract Number for Publication: 1096 Poster Board Number: 75 Session Type and Title: Poster Session – Breast Cancer—Metastatic In the Phase 2 study of Bria-IMT combined with an immune checkpoint inhibitor (CPI) in 54 heavily pre-treated metastatic breast cancer (MBC) patients (median of six prior systemic therapies; range 2–13), Bria-IMT demonstrated promising efficacy and safety. Notably, 44% of patients had failed a prior antibody-drug conjugate, and 20% had failed a prior CPI. Among these patients, the overall clinical benefit rate (CBR; defined as CR, PR, or SD) was 55%, with CBRs of 100% in HER2+, 55% in HR+/HER2-, and 45% in triple-negative breast cancer (TNBC) subgroups, indicating antitumor activity across MBC subtypes. Additionally, patients treated with the selected Phase 3 formulation (without IFNγ; N=37) experienced significantly improved overall survival (13.9 vs.

6.93 months; P=0.01) compared to those receiving the alternate formulation, highlighting the potential of Bria-IMT for advancing in clinical development. Table 1. Median overall survival (OS) in BriaCell Phase 2 Study patients who were treated with Phase 3 formulation (without IFNγ) compared with comparable patients in the literatureN = 54Breast Cancer TypesMedian Prior Lines of TherapyMedian (months)Phase 3 formulation (without IFNγ)61% HR+ 33% TNBC 6% HER2+ 617.3* 13.9Cortes et al.157% HR+ 18-19% TNBC 18-20% HER2+ 49.1-9.3Kazmi et al.251-52% HR+ 25-29% TNBC 9-24% HER2+ 27.2-9.8 * Patients treated since 2022 1. Cortes J, et al. Annals of Oncology 2018 2.

Kazmi S, et al. Breast Cancer Res Treat. 2020 Table 2. Median overall survival (OS), and clinical benefit rate (CBR) in TNBC patients treated with Bria-IMT Phase 3 formulation compared with pivotal Phase 3 ASCENT1 study results (Trodelvy® (SG) vs. Treatment of Physicians Choice (TPC) in triple-negative breast cancer (TNBC)) Trial (Cohort) Age (Median, Range) Prior Therapies (Median) Prior ADC/CPI (%)CNS MetsOS (Median, Months)CBR (%) TNBC Bria- IMT (Phase 3 Formulation) 62 (44-80) 6 (2-13) 20/19411.4 45 % ASCENT (SG)54 (27-82)4 (2-17)27/None ListedNone Listed11.840% ASCENT (TPC)53 (27-81)4 (2-14)27/None ListedNone Listed6.98% 1Bardia, A., et al Journal of Clinical Oncology, 42(15), 1738–1744.

As shown in table 2, both OS and CBR values were in line or higher than those reported in the treatment arm of the ASCENT study for TNBC patients treated with Phase 3 formulation of Bria-IMT regimen but were almost 2 times higher than those shown in the TPC comparator arm. Table 3: Median overall survival (OS), and clinical benefit rate (CBR) in HR+/HER2- patients treated with the Bria-IMT (Phase 3 formulation) compared with pivotal Phase 3 TROPiCS-022 study results (SG or Chemo in Hormone Receptor +/HER2- MBC) Trial (Cohort) Age (Median, Range) Prior Therapies (Median) Prior ADC/CPI (%)CNS MetsOS (Median, Months)CBR (%) HR+/HER2- Bria-IMT (Phase 3 Formulation) 62 (44-80) 6 (2-13) 17/2117.3 60 % TROPiCS (SG)57 (49-65)3None ListedNone Listed14.434% TROPiCS (Chemo)55 (48-63)3None ListedNone Listed11.222% 2Rugo, H. S., et al. The Lancet, 402(10411), 1423–1433. As shown in table 3, both OS and CBR values for patients treated with Phase 3 formulation of the Bria-IMT regimen were higher than those reported in both arms of the TROPICS study.Favorable tolerability profile: Bria-IMT was well-tolerated with no treatment-related discontinuations.

22% of patients are still in active survival follow up with one patient remaining on study now for over 18 months. The efficacy data and favorable safety profile of the Phase 3 formulation support the continued evaluation of Bria-IMT in BriaCell’s ongoing pivotal Phase 3 trial (NCT06072612), which compares Bria-IMT to the treatment of physician’s choice. The ongoing patient subset analysis in this trial aims to identify the patients who may derive the greatest benefit from Bria-IMT treatment. Poster Title: Trial in progress: A study of Bria-OTS™ cellular immunotherapy in metastatic recurrent breast cancer Session Date and Time: June 2, 2025 9:00 AM-12:00 PM CDT Abstract Number for Publication: TPS1136 Poster Board Number: 107a Session Type and Title: Poster Session – Breast Cancer—Metastatic In a dose-escalation Phase 1/2 study, heavily pre-treated MBC patients received Bria-OTS monotherapy (single agent Bria-OTS cells only). The Phase 1 segment enrolled and treated 3 patients with the first patient achieving a confirmed resolution of a breast cancer lung metastasis and remaining on study with single agent Bria-OTS.

Following successful completion of safety evaluations, BriaCell has initiated the combination cohort dosing the first patient with Bria-OTS plus checkpoint inhibitor (CPI). Publish-Only Abstract Title: Impact of HLA Matching on Clinical Outcomes in a Phase 2 Trial of Bria-IMT Plus Anti PD1 in Advanced Breast Cancer Following the presentations, copies of the presentations will be posted on https://briacell.com/scientific-publications/. About BriaCell Therapeutics Corp. BriaCell is a clinical-stage biotechnology company that develops novel immunotherapies to transform cancer care. More information is available at https://briacell.com/.

Safe Harbor This press release contains “forward-looking statements” that are subject to substantial risks and uncertainties. All statements, other than statements of historical fact, contained in this press release are forward-looking statements. Forward-looking statements contained in this press release may be identified by the use of words such as “anticipate,” “believe,” “contemplate,” “could,” “estimate,” “expect,” “intend,” “seek,” “may,” “might,” “plan,” “potential,” “predict,” “project,” “target,” “aim,” “should,” “will,” “would,” or the negative of these words or other similar expressions, although not all forward-looking statements contain these words. Forward-looking statements, including those about BriaCell’s Bria-IMT regimen presenting promising results for individuals with metastatic breast cancer, including with respect to its efficacy and safety; BriaCell further confirming such results in their ongoing pivotal Phase 3 study with the ultimate goal of bringing novel treatments to cancer patients in need; and Bria-IMT’s potential for advancement in clinical development, are based on BriaCell’s current expectations and are subject to inherent uncertainties, risks, and assumptions that are difficult to predict. Further, certain forward-looking statements are based on assumptions as to future events that may not prove to be accurate.

These and other risks and uncertainties are described more fully under the heading “Risks and Uncertainties” in the Company's most recent Management’s Discussion and Analysis, under the heading "Risk Factors" in the Company's most recent Annual Information Form, and under “Risks and Uncertainties” in the Company's other filings with the Canadian securities regulatory authorities and the U.S. Securities and Exchange Commission, all of which are available under the Company's profiles on SEDAR+ at www.sedarplus.ca and on EDGAR at www.sec.gov. Forward-looking statements contained in this announcement are made as of this date, and BriaCell Therapeutics Corp. undertakes no duty to update such information except as required under applicable law. Neither the Toronto Stock Exchange nor its Regulation Services Provider (as that term is defined in the policies of the Toronto Stock Exchange) accepts responsibility for the adequacy or accuracy of this release.

Contact Information Company Contact: William V. Williams, MD President & CEO 1-888-485-6340 [email protected] Investor Relations Contact: [email protected]