Dr. William Williams reports

BRIACELL SHOWCASES DATA DEMONSTRATING UNMATCHED PROGRESSION-FREE SURVIVAL (PFS) AND CLINICAL EFFICACY IN ANTIBODY-DRUG CONJUGATE (ADC) RESISTANT AND CENTRAL NERVOUS SYSTEM (CNS) METASTATIC BREAST CANCER AT THE 2024 AACR

Briacell Therapeutics Corp. is presenting positive clinical data from its lead product candidate, Bria-IMT, in two posters of its three-poster sessions during the 2024 American Association for Cancer Research (AACR) annual meeting held from April 5 to April 10 at San Diego Convention Center, San Diego, Calif.

"We are extremely impressed by the unprecedented survival and clinical benefit data for Bria-IMT in patients who have failed ADCs [anti-body drug conjugates]," stated Chaitali S. Nangia, MD, lead author, partner at Hoag Medical Group. "ADCs are the latest treatments for very-difficult-to-treat advanced metastatic breast cancer. However, some patients experience resistance with rapid disease progression. To our knowledge, there are no effective treatment options in this patient population for whom the progression-free survival prognosis is only a few weeks. Finding an alternative, well-tolerated treatment option that is effective is a matter of life and death for these patients."

"Our clinical data further validates Bria-IMT's novel mechanism of action to generate potent immune responses in breast cancer patients who failed ADCs, leading to clinically relevant survival and treatment benefit in these patients," commented Dr. Giuseppe Del Priore, Briacell's chief medical officer. "We look forward to building upon the body of evidence with additional clinical data in the coming months from the ongoing pivotal registration trial."

"We are excited about the safety and efficacy data to date with Bria-IMT and expect that Bria-IMT will generate positive effects on survival and clinical benefit in the phase 3 study in advanced breast cancer patients whose medical needs remain unmet," commented Dr. William V. Williams, Briacell's president and chief executive officer.

The posters are summarized herein and linked at the company's website.

Poster 1:

• Title: Efficacy of Bria-IMT regimen in inducing CNS [central nervous system] metastasis regression.
• Abstract presentation No.: CT204.
• Superior clinical benefit of Bria-IMT regimen -- alone or combined with an immune check point inhibitor (CPI) in advanced breast cancer patients with CNS metastatic disease:
  • Clinical efficacy: 71 per cent (five/seven) intracranial objective response rate (iORR), defined as the percentage of patients who achieve a complete response (complete disappearance) or partial response (volume reduction of 30 per cent or more) in intracranial tumours, achieved in patients with central nervous system metastases treated with the Bria-IMT regimen, either alone or in combination with an immune checkpoint inhibitor (that is, PD-1 inhibitor pembrolizumab or retifanlimab). These patients failed multiple prior treatments, including two antibody-drug conjugates in one case. Clinical benefit is observed across all subsets of breast cancer.
  • Safety profile: Absence of both interstitial lung disease (ILD), a common serious adverse event with ADCs, and no Bria-IMT-related treatment discontinuations underscore Bria-IMT's excellent tolerability and favourable safety profile.

In summary, Bria-IMT's tumour reductions observed in all breast cancer subtypes in patients with intracranial disease underlines its potential clinical effectiveness in managing CNS metastatic disease in advanced breast cancer. Briacell will continue to monitor the data in this subgroup of patients, including a preplanned subgroup analysis in the current pivotal phase 3 study in advanced metastatic breast cancer. Treatment of patients with CNS metastatic disease represents a potential additional indication for market approval of Bria-IMT.

Poster 2:

• Title: Efficacy and safety of SV-BR-1-GM after progression on ADC in metastatic breast cancer patients.
• Abstract presentation No.: CT206.
• Notable progression-free survival benefit of Bria-IMT in ADC-resistant advanced metastatic breast cancer.
• Phase 2 clinical data of the Bria-IMT regimen in 23 advanced metastatic breast cancer patients who failed multiple prior treatments, including ADCs and CPIs (median of six prior treatments) are presented:
  • Progression-free survival benefit: Median progression free survival (PFS), defined as the length of time during which a patient's cancer does not get worse, in heavily pretreated patients of 3.5 months is comparable with that seen in similar studies in patients with a history of fewer prior treatments (median of 4). Similarly, median PFS of 4.2 months in patients receiving the Bria-IMT pivotal phase 3 formulation is approximately twice the PFS figures reported for treatment of physician's choice (TPC) in other similar studies. These PFS results suggest superior clinical efficacy considering the larger number of prior treatments in Bria-IMT patients versus those of the other studies.
  • Clinical efficacy: PFS is similar or better than that of the last regimen in 48 per cent (11/23) of the patients, suggesting Bria-IMT effectiveness in delivering clinical and survival benefits in these patients. Additionally, a clinical benefit rate (CBR), defined as percentage of patients whose disease shrinks or remains stable over a certain time, of 56 per cent, is observed in evaluable patients, further highlighting clinical benefit.
  • Subset-specific clinical benefits: Study data to date suggests clinical benefit for multiple breast cancer subtypes, including HR+/HER2- (the most common breast cancer subtype, testing positive for estrogen and/or progesterone receptors, and negative for human epidermal growth factor receptor 2 (HER2)) with a CBR following treatment of 63 per cent (five of eight patients), HER2+ subtype (a positive test for HER2) with a 100 per cent CBR (two of two patients), and HR-/HER2 low subtype (a negative test for estrogen and/or progesterone receptor, and a negative test for HER2) showing a CBR of 66 per cent (two of three patients).
  • Safety profile: There are no incidents of interstitial lung disease -- a well-documented serious adverse event associated with ADCs -- in either ADC-naive or ADC-treated patients, and no treatment-related discontinuations of Bria-IMT.

In summary, the data to date show that Bria-IMT provides prolonged progression-free survival and clinical benefits in heavily pretreated, ADC-resistant breast cancer patients compared with those in other similar studies. Briacell will be monitoring ADC-resistant patients in its continuing pivotal phase 3 study of Bria-IMT and CPI in advanced metastatic breast cancer.

About Briacell Therapeutics Corp.

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

We seek Safe Harbor.