Oncolytics Biotech (ONCY) Announces Positive Randomized Phase 2 Data from BRACELET-1 Metastatic Breast Cancer Trial

May 25, 2023 6:30 PM EDT

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Oncolytics Biotech® Inc. (NASDAQ: ONCY) today announced positive results from BRACELET-1, a randomized phase 2 trial in HR+/HER2- metastatic breast cancer. The results are published in an abstract accepted for an oral presentation at the upcoming American Society of Clinical Oncology (ASCO) Annual Meeting, taking place from June 2 – 6, 2023 in Chicago, Illinois and online. The abstract is available on the ASCO Annual Meeting website.

BRACELET-1 enrolled 48 patients randomized and well-balanced across three cohorts evaluating: (1) paclitaxel monotherapy; (2) paclitaxel in combination with pelareorep; and (3) paclitaxel plus pelareorep in combination with the anti-PD-L1 checkpoint inhibitor, avelumab (Bavencio®). All participants enrolled in the trial previously progressed on at least one hormone-based therapy with a CDK 4/6 inhibitor.

Compared to the paclitaxel monotherapy cohort, the cohort evaluating the combination of paclitaxel plus pelareorep showed ≥50% improvements on the trial's primary endpoint of overall response rate (ORR) at week 16 (31.3% vs. 20%) as of the ASCO abstract cut-off date (October 2022). This cohort also reported median progression-free survival (mPFS) of 9.6 months vs. 6.4 months as of the cut-off date. Overall survival data from the trial continue to mature. Data from this study validate the results of IND-213, a prior phase 2 trial that showed a statistically significant near doubling of median overall survival in HR+/HER2- metastatic breast cancer patients treated with pelareorep combined with paclitaxel (21.0 months, n = 28) vs. those treated with paclitaxel alone (10.8 months, n = 29).

"BRACELET-1 substantially de-risks our HR+/HER2- breast cancer program by providing a second randomized dataset showing pelareorep plus paclitaxel outperforming paclitaxel alone," said Dr. Matt Coffey, President and Chief Executive Officer. "Importantly, evidence of pelareorep's ability to synergistically enhance paclitaxel's efficacy has now been seen consistently across multiple clinical efficacy endpoints of overall survival, progression-free survival, and ORR. With these data, our program is phase 3-ready, and efforts to expeditiously advance to a two-arm registrational study of pelareorep-paclitaxel combination therapy are well underway. I would like to thank BRACELET-1's participants as well as our collaborators at Pfizer, Merck KGaA, Darmstadt, Germany, and PrECOG, all of whom contributed to an important trial that will inform and accelerate pelareorep's path to approval."

A detailed summary of BRACELET-1's data are shown below. Updated results as of a May cut-off date will be featured in an oral presentation at the ASCO meeting on June 3, 2023.

Response and Progression-free Survival (October 2022 data cut-off):

Paclitaxel (PTX) Monotherapy (n=15)

PTX + Pelareorep (n=16)

PTX + Pelareorep + Avelumab (n=17)

ORR at Week 161

3 (20 %)

5 (31.3 %)

3 (17.6 %)

Disease Control Rate at Week 16 (CR+PR+SD)

7 (46.7 %)

10 (62.5 %)

12 (70.6 %)

mPFS (months)1


(95% CI: 2.0, NR)


(95% CI: 6.5, NR)


(95% CI: 3.8, NR)

6-month PFS Rate


(95% CI: 27.6%, 84.2%)


(95% CI: 59.1%, 99%)


(95% CI: 42%, 89.4%)

1. Three patients who withdrew consent prior to starting therapy and two patints who discontinued treatment after week 1 were considered non-responders and censored for PFS

CI: Confidence interval; CR: Complete response; PR: Partial response; SD: Stable disease; NR: Not reached

Biomarker and Safety

  • A statistically significant increase in T cell fraction, a measure of T cell expansion, was observed in cohort 2 (paclitaxel + pelareorep) but not cohort 3 (paclitaxel + pelareorep + avelumab)
  • Pelareorep displayed an acceptable safety profile consistent with what has been observed in prior clinical trials that have collectively treated over 1,100 patients

Dr. Thomas Heineman, Chief Medical Officer, commented, "BRACELET-1 was a well-conducted study in a randomized setting that included a control arm that performed as expected and a test arm that provides significant evidence of pelareorep's ability to provide additional meaningful clinical benefit in HR+/HER2- breast cancer patients. Mechanistic data from prior clinical trials indicate pelareorep's anti-cancer effects are derived from its ability to reverse immunosuppressive tumor microenvironments and stimulate the expansion of anti-cancer T cells. These prior data align with BRACELET-1's results that show an association between T cell expansion and efficacy."

Andrew de Guttadauro, President of Oncolytics Biotech U.S. and Global Head of Business Development, added, "BRACELET-1's data greatly enhance our pipeline's value proposition, bringing our breast cancer program to pivotal trial-readiness and confirming pelareorep's potential to address large markets by synergistically combining with other anti-cancer agents. Looking ahead, we believe our data in breast cancer, together with the second registration opportunity offered by our pancreatic cancer program, leave us well-positioned as we continue to execute our business development efforts. To ensure we maximize value for shareholders, we remain committed to taking a disciplined and methodical approach as we further discussions with our potential partners in the biopharma community."

Details on the upcoming ASCO oral presentation on BRACELET-1 are shown below.

Title: BRACELET-1 (PrE0113): Inducing an Inflammatory Phenotype in Metastatic HR+/HER2- Breast Cancer with the Oncolytic Reovirus Pelareorep in Combination with Paclitaxel and Avelumab

Abstract Number: 1012

Session Type: Clinical Science Symposium

Session Title: The Dr. Bernard Fisher Memorial Annual Clinical Science Symposium Supported by the Breast Cancer Research Foundation: Harnessing the Breast Cancer Immune Response

Session Date and Time: June 3, 2023 | 1:15 p.m.2:45 p.m. CT

A copy of slides from the ASCO presentation will be available on the Posters & Publications page of Oncolytics' website (LINK) following the conclusion of the meeting.

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