Dr. William Williams reports

BRIACELL PRESENTATIONS HIGHLIGHT POSITIVE CLINICAL DATA FOR BRIA-IMT™ AT ASCO 2026

Briacell Therapeutics Corp. has released positive clinical data from three clinical data poster presentations and three publication-only abstracts at the 2026 ASCO annual meeting, taking place May 29 to June 2, 2026, at McCormick Place, Chicago, Ill. The presentations will include two poster presentations featuring data from Briacell's continuing pivotal phase 3 study of Bria-IMT plus an immune checkpoint inhibitor, Bria-ABC, and one poster highlighting further analyses of phase 2 data.

• Final phase 2 Bria-IMT median overall survival (OS) is 16.6 months (with phase 3 formulation);
• Positive quality of life (QOL) data from the continuing phase 3 study in heavily pretreated metastatic breast cancer (MBC) patients;
• Biomarker analyses from the continuing phase 3 study confirm predictors of anti-cancer response seen in phase 2.

"These data from the continuing pivotal phase 3 Bria-ABC study highlight Bria-IMT's potential to preserve quality of life, limit toxicity and potentially support self-administration -- benefits that would be clinically meaningful for patients," stated Adam M. Brufsky, MD, PhD, FACP, professor of medicine at the University of Pittsburgh School of Medicine and medical director of the Magee-Women's Cancer Program.

"The phase 2 study of the combination of a whole-cell vaccine with anti-PD-1 demonstrated a tolerable safety profile and the emergence of a long-term survivor cohort inclusive of the heavily pretreated nature of these patients," stated Saranya Chumsri, MD, principal investigator in the phase 3 study of Bria-IMT+CPI, and professor of oncology at Mayo Clinic Florida. "I'm proud to do this work that brings new attention to metastatic breast cancer patients who have few or no remaining treatment options."

"Our positive clinical data across six presentations or abstracts at the ASCO 2026 annual meeting highlight the progress we are making in our clinical programs," noted William V. Williams, MD, Briacell's president and chief executive officer. "These data reflect our commitment to advancing innovative therapeutic options for patients with cancer patients who need better treatments."

The details of the presentations and publish-only abstracts are listed below.

Abstract title:  Survival with Bria-IMT + CPI in advanced metastatic breast cancer at 12 and 24 months

Session type/title:  poster session -- breast cancer -- metastatic

Poster board:   222

Date and time:  June 1, 2026, 1:30 p.m. to 4:30 p.m. CT

Clinical data:  Thirty-two phase 2 Bria-IMT patients were randomized to receive immune checkpoint inhibitor (CPI) in the first cycle or delayed to the second cycle. Two Bria-IMT formulations were also evaluated. Patients had median age of 61 (range 41 to 80) and had received median six prior therapies (range two to 13). Median overall survival (OS) was 13.3 versus 7.4 months for starting CPI in cycle 1 versus cycle 2. In patients who developed an immune response as measured by delayed-type hypersensitivity (DTH) positive vs. negative, OS was 11.9 vs. 4.7 months, with 48-per-cent 12-month survival vs. 0.0-per-cent 12-month survival. Patients with circulating tumour cells (CTCs) five at baseline had median OS of 16.6 vs. 5.5 months. Median OS was 16.6 months for the formulation selected for the phase 3 study with 52 per cent of patients surviving at 12 months. The 12-month survival rate was 44 per cent and the 24-month rate was 26 per cent. There were no treatment-related discontinuations and no unexpected safety signals.

Conclusions:  In heavily pretreated MBC patients, Bria-IMT demonstrated a tolerable safety profile and the emergence of a long-term survivor cohort. Durable survival rates were observed beyond 12 and 24 months. Differential survival favored the phase 3 formulation, DTH positivity, lower baseline circulating tumour cell (CTC) levels and early CPI sequencing. These findings support prospective validation of DTH and CTC as predictive biomarkers for effectiveness of the Bria-IMT regimen and the continued use of the phase 3 formulation in the continuing phase 3 study Bria-ABC.

Abstract title:  Quality of life and treatment tolerability of Bria-IMT + CPI in metastatic breast cancer

Session type/title:  poster session -- breast cancer -- metastatic

Poster board:  221

Date and time:  June 1, 2026, 1:30 p.m. to 4:30 p.m. CT

Summary:  Heavily pretreated MBC patients in the pivotal Bria-ABC demonstrated stable global health and key functional domains. Measurements included quality of life (QOL) and time without symptoms or toxicity (TWiST). Blinded data indicated that QOL was largely preserved in a heavily pretreated population with prior antibody-drug conjugate (ADC), checkpoint inhibitor (CPI) and cyclin-dependent kinase 4/6 (CDK4/6) inhibitor exposure. Clinical data demonstrates meaningful benefits without significant toxicity. Continuing follow-up will further characterize durability of patient-reported outcomes and clinical correlation. Data further supports decentralized care and potential home self-administration of the Bria-IMT+CPI regimen.

Abstract title:  Monitoring blood-based biomarkers as early predictors of progression-free survival in a randomized Bria-ABC phase 3 trial for advanced metastatic breast cancer: a continuing analysis

Session type/title:  poster session -- developmental therapeutics -- immunotherapy

Poster board:  442

Date and time:  May 30, 2026, 1:30 p.m. to 4:30 p.m. CT

Summary:  In a continuing analysis of heavily treated MBC patients, the company observed that in the entire blinded population, 65 per cent of patients had stability/drop in cancer-associated macrophage-like cells (CAMLs) and this significantly correlated with better progression-free survival (PFS). Treatment arm specific comparisons will not be unblinded until completion of the designated milestone (144 mortalities).

Publication-only abstract title:  cell-based second-generation immunotherapy BC1 in metastatic breast cancer

Summary:  Dose escalation from 20M to 60M and combination with CPI showed tolerable intradermal BC1, Bria-OTS and potential clinical benefit in refractory MBC patients. One patient received 17 cycles with 12 months of disease control. Expansion cohorts will assess HLA match, DTH, dose optimization and combination activity. Based on very early preliminary data, BC1, Bria-OTS first generation, is a potential new option for late-stage cancer patients with minimal toxicity and potential home administration as a single agent. Clinical trial information: NCT06471673.

Publication-only abstract title:  liquid biopsy to stratify metastatic breast cancer progression risk using multianalyte cell subtyping prior to systemic therapy

Summary:  Circulating tumour cells were uncommon in metastatic breast cancer patients but correlated with very poor clinical outcomes. In parallel analysis, CAMLs were common with CAML size correlating with increasingly poorer outcomes. By combining CTC and CAML subtypes, MBC patients were more accurately stratified by risk of progression and death. Additional multivariate studies correlating treatment class and tumour response rates are continuing.

Publication-only abstract title:  monitoring PD-L1 expression in circulating cancer-associated cells for prediction of clinical outcomes in metastatic breast cancer patients treated with immune checkpoint inhibitors

Summary:  In this study of MBC patients treated with programmed death-ligand 1 (PD-L1) immune checkpoint inhibitors (ICIs), tissue combined positive score (for PD-L1) did not correlate with PD-L1 expression in CTCs or tumour-macrophage fusion cells. Further, neither combined positive score (CPS) nor baseline PD-L1 in CTC/ tumour-macrophage fusion cells (TMFCs) predicted clinical outcomes in ICI therapies. However, PD-L1 in CTC/TMFCs approximately 40 days postinduction of ICI did predict better response rates. While this study suggests predictive value of monitoring PD-L1 in blood during ICI therapies, further studies are required to refine and validate these findings.

About Briacell Therapeutics Corp.

Briacell is a clinical-stage biotechnology company that develops novel immunotherapies to transform cancer care.

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