BioNTech SE (BNTX), an immunotherapy company, announced results from the primary analysis of a Phase 2 cohort evaluating Trastuzumab Pamirtecan or BNT323/DB-1303 in patients with HER2-expressing advanced endometrial cancer who progressed on or after first-line chemotherapy, with or without prior checkpoint inhibitor treatment.
Trastuzumab pamirtecan (BNT323/DB-1303) is a Topoisomerase-1 inhibitor-based ADC targeting HER2 and is being developed by BioNTech and Duality Biologics' Duality Immune Toxin Antibody Conjugates platform.
Trial Findings
The global, multi-cohort Phase 1/2a clinical trial evaluated the safety and tolerability of Trastuzumab pamirtecan in patients with advanced HER2-expressing solid tumours.
Cohort 2b is a Phase 2 expansion cohort that enrolled 145 patients with advanced/metastatic HER2-expressing endometrial cancer whose disease had progressed after first- and later-line therapy.
The data demonstrated clinically meaningful efficacy, antitumor activity across a range of HER2 expression levels, with patients showing a confirmed objective response rate of 47.9% in all evaluable patients, 49.3% in patients with prior immune checkpoint inhibitor treatment, a median progression-free survival of 8.1 months and the median duration of response was 10.3 months.
Trastuzumab pamirtecan also has demonstrated encouraging antitumor activity across a range of HER2 expression levels, with comparable results whether HER2 testing was conducted locally or centrally.
Meanwhile, the safety profile was manageable, as expected for HER2-targeted ADCs, the firm noted. This includes grade 3 or higher treatment-related adverse events, which were reported in 68 of 145 (46.9%) patients, and adjudicated cases of interstitial lung disease or pneumonitis of grade 3 or higher that occurred in 4.8% of patients.
According to the firm, the majority of events with grades 3 or higher were efficiently manageable with appropriate medical interventions.
What's Ahead
BioNTech and DualityBio plan to file a biologics license application in 2026, subject to FDA feedback.
Trastuzumab pamirtecan received Fast Track and Breakthrough Therapy designations from the FDA for the treatment of endometrial cancer in 2023.
Trastuzumab pamirtecan is also being evaluated in an ongoing Phase 1/2 trial in patients with advanced/metastatic solid tumours, as well as in two global Phase 3 clinical trials.
The Phase 3 studies include Fern-EC-01, an ongoing study in recurrent endometrial cancer with enrollment in progress, and DYNASTY-Breast02 in HR-positive, HER2-low metastatic breast cancer, with data anticipated around 2026 according to company guidance.
BNTX has traded between $79.52 and $124.00 in the last year. The stock closed Friday's trade at $59.50, up 3.83%.
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