Kelun-Biotech's Trastuzumab Botidotin Shows Superior Efficacy in HER2-Positive Breast Cancer Study

CHENGDU, China, Sept. 14, 2026 /CourierPR/ -- Kelun-Biotech, a biopharmaceutical company based in China, has announced the publication of phase III study results for its novel HER2-targeted antibody-drug conjugate (ADC) trastuzumab botidotin. The study, published in the Journal of Clinical Oncology, compared trastuzumab botidotin to the existing treatment, trastuzumab emtansine (T-DM1), in patients with HER2-positive unresectable or metastatic breast cancer who had previously received trastuzumab and taxane-containing regimens.

The randomized, open-label, multicenter phase III study enrolled 365 patients, with half receiving trastuzumab botidotin and the other half receiving T-DM1. The primary endpoint was progression-free survival (PFS), assessed by a blinded independent central review (BICR), with secondary endpoints including overall survival (OS), objective response rate (ORR), and duration of response (DoR).

As of the data cutoff date of April 26, 2025, with a median follow-up of 14.9 months, the results showed a significant improvement in PFS for patients receiving trastuzumab botidotin. The median PFS was 11.1 months in the trastuzumab botidotin group compared to 4.4 months in the T-DM1 group, with a hazard ratio of 0.39. The study also demonstrated deeper and more durable tumor responses, with an ORR of 76.9% in the trastuzumab botidotin group compared to 53.0% in the T-DM1 group, and a median duration of response of 12.2 months versus 5.7 months.

While overall survival data were not yet mature, there was a trend toward improved OS in the trastuzumab botidotin group, showing a 38% reduction in the risk of death. The safety profile of trastuzumab botidotin was also favorable, with a lower incidence of interstitial lung disease (ILD) and lower rates of hematologic, hepatic, and gastrointestinal toxicities compared to T-DM1. The most common treatment-related adverse events (TRAEs) were ocular events, which were generally recoverable or reversible with standardized management strategies.

These findings mark a significant breakthrough for a domestically developed HER2 ADC, backed by high-level clinical evidence. Trastuzumab botidotin is the first domestically developed HER2 ADC to show positive results in a phase III trial compared head-to-head with T-DM1. The positive results have led to the drug's approval by China's National Medical Products Administration (NMPA) for the treatment of second-line or later HER2-positive breast cancer, providing a new treatment option for patients with HER2-positive advanced breast cancer.

Trastuzumab botidotin is a differentiated HER2 ADC designed to treat advanced HER2+ solid tumors. It conjugates a novel, monomethyl auristatin F (MMAF) derivative (Duo-5) via a stable, enzyme-cleavable linker to a HER2 monoclonal antibody with a drug-to-antibody ratio (DAR) of 2. The drug specifically binds to HER2 on the surface of tumor cells, is internalized by tumor cells, and releases the toxin molecule Duo-5 inside the cell, leading to tumor cell apoptosis. Additionally, trastuzumab botidotin can inhibit the HER2 signaling pathway and has antibody-dependent cell-mediated cytotoxicity (ADCC) activity.

Kelun-Biotech, a subsidiary of Kelun Pharmaceutical, focuses on the research, development, manufacturing, commercialization, and global collaboration of innovative biological drugs and small molecule drugs. The company is committed to addressing unmet medical needs in China and the rest of the world, with a globalized drug development and industrialization platform. Kelun-Biotech has more than 30 ongoing key innovative drug projects, including four approved for marketing, two in the New Drug Application (NDA) stage, and more than 10 in clinical stages. The company has established one of the world's leading proprietary ADC and novel DC platforms, OptiDC™, with multiple ADC and novel DC assets in clinical or preclinical research stages.