BioNTech (Nasdaq: BNTX) and DualityBio reported that trastuzumab pamirtecan met its primary endpoint in a Phase II cohort of 145 patients with HER2-expressing recurrent endometrial cancer. The drug candidate posted a confirmed objective response rate of approximately 49% in patients with prior checkpoint inhibitor treatment — a result that, if sustained in confirmatory testing, would position the antibody-drug conjugate (ADC) as the first HER2-directed therapy validated across all IHC expression levels in this setting.
The NCT05150691 trial is a global, multi-cohort Phase I/II study evaluating trastuzumab pamirtecan in patients with advanced or metastatic HER2-expressing solid tumors whose disease had progressed following prior systemic therapy.
In the primary analysis, the cohort met its pre-specified endpoint: a confirmed ORR of 49.3% (95% CI: 37.4–61.3) in 73 patients with prior checkpoint inhibitor treatment and centrally confirmed HER2 status. Across all 96 centrally tested patients, the ORR was 47.9%, with a median progression-free survival of 8.1 months. The median duration of response was 10.3 months. Cross-trial comparisons are limited, but these figures contrast with an approximately 15% response rate reported for single-agent chemotherapy in this population, cited in the press release from a 2023 Journal of Clinical Oncology publication.
Grade ≥3 treatment-related adverse events occurred in 46.9% of patients; adjudicated interstitial lung disease or pneumonitis of grade ≥3 was observed in 4.8%, consistent with the known class profile of HER2-directed ADCs.