BB-1701 Shows Promising Efficacy in HER2-Expressing Breast Cancer

In a groundbreaking study presented at the 2025 American Society of Clinical Oncology (ASCO) Annual Meeting, the novel antibody-drug conjugate (ADC) BB-1701 displayed significant efficacy and a manageable safety profile in patients with HER2-expressing metastatic breast cancer who had previously been treated with HER2-directed therapies. The study, led by Dr. Xiaoxiang Guan, MD, PhD, from the First Affiliated Hospital of Nanjing Medical University, involved 31 patients who were evaluated for treatment response and safety outcomes.

The phase 2 trial, identified by Clinical Trial Registration CTR20241422, reported an objective response rate (ORR) of 28.6% among efficacious patients, with a notable disease control rate (DCR) of 78.6%. The cohort of patients with HER2-low and hormone receptor-positive breast cancer exhibited even more promising results, achieving an ORR of 35.3% and a DCR of 82.3%. These results indicate a potential for BB-1701 to be a new treatment option for this patient population, as emphasized by Dr. Guan in the data presentation.

The study's design was an open-label, single-arm trial, focusing on patients aged 18 years and older with locally advanced or metastatic HER2-positive or HER2-low breast cancer. All participants had previously demonstrated disease progression following treatment with a HER2-directed ADC containing a topoisomerase I inhibitor. The safety profile was assessed following the Common Terminology Criteria for Adverse Events (CTCAE) version 5.0, with a fixed dose of 1.6 mg/kg of BB-1701 administered intravenously every three weeks.

Among the 31 enrolled patients, the median age was 54 years, and the majority were female, of Asian descent, with 77.4% having an Eastern Cooperative Oncology Group (ECOG) performance status of 1. The study noted that 71% of the patients had undergone four or more lines of prior systemic therapy, highlighting the advanced nature of their disease.

Adverse effects were documented, with the most common treatment-emergent adverse effects (TEAEs) including peripheral neuropathy (38.7%), increased liver enzymes, and decreased blood cell counts. Importantly, there were no grade 5 TEAEs or reports of interstitial lung disease, indicating a favorable safety profile for BB-1701. One patient discontinued treatment due to peripheral neuropathy, and serious TEAEs were reported, yet no fatalities occurred during the trial period.

The significance of these findings lies in the potential shift in treatment paradigms for patients with HER2-expressing breast cancer, particularly for those who have limited options after multiple lines of therapy. The encouraging results from BB-1701 call for further investigation into its efficacy and safety in larger, randomized trials.

In conclusion, BB-1701 presents a hopeful advance in the treatment landscape for metastatic HER2-expressing breast cancer. The findings warrant further clinical exploration, aiming to solidify BB-1701’s role in therapeutic strategies for patients with exhausted treatment pathways. Future studies will be crucial in confirming these preliminary results and possibly leading to new standards of care in this challenging oncological domain.