Positive Results from BRACELET-1 (PrE0113) trial Evaluating Pelareorep and paclitaxel combo

BRACELET-1 (PrE0113) trial

Preclinical studies demonstrated the oncolytic reovirus Pelareorep's ability to enhance the tumor microenvironment, boosting tumor infiltrating lymphocytes and PD-1/PD-L1 expression, paving the way for immune checkpoint blockade advancements. According to the results presented at ASCO 2023, at the data cutoff (May 2023), around 48 patients were enrolled between June 2020 and June 2022. Three patients who withdrew consent prior to starting therapy and two patients who discontinued treatment after week 1 were considered non-responders and were censored for PFS. Unfortunately, 9 patients (33%) discontinued pelareorep and 6 (35%) discontinued avelumab due to toxicity.

The primary endpoint responses at 16 weeks are discussed in the below table


PTX (n=15)

PTX + PEL (n=16)

PTX+PEL+AVE (n=14)

ORR at 16 week

3 (20%)

5 (31.3%)

2 (14%)

Disease control

(CR + PR + SD)

7 (46.7%)

10 (62.5%)

9 (64%)

Median PFS

6.4 months

9.6 months

5.8 months

6-month PFS rate




1: Only the 45 randomized patients were included in the response analysis

In terms of safety findings, the most common pelareorep-associated toxicities were fever, chills, and flu-like infusion reactions, which were occasionally severe enough to require hospitalization in 5 (15%) patients despite acetaminophen prophylaxis.

KOL insights

“Early data from the Phase II BRACELET-1 study indicates chemotherapy plus the oncolytic reovirus pelareorep has a higher response rate compared to chemotherapy alone for metastatic breast cancer.–Expert Opinion.


The addition of Pelareorep to paclitaxel is worthy of further study, demonstrating a 32% ORR at 16 weeks, followed by an 86% 6-month PFS. Moreover, the addition of avelumab increased the toxicity, which led to no obvious increase in efficacy. Apart from that, throughout the study, flu-like viral infections were common with pelareorep.  Moreover, further biomarker analysis for the study is underway, and while  the overall survival data continues to mature, company has announced a registrational Phase III clinical trial to evalute the efficacy in a larger and substantial patient pool.

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