What question did this study set out to answer?

This study aims to assess the safety and efficacy of neoadjuvant patritumab deruxtecan combined with pembrolizumab for early-stage triple-negative and HR-low+/HER2− breast cancer.

February 19, 2026Clinical Cancer Research

Abstract PS5-12-21: Herthena-breast03: a phase 2, randomized, open-label study evaluating neoadjuvant patritumab deruxtecan (HER3-DXd) + pembrolizumab before or after pembrolizumab + chemotherapy for early-stage TNBC or HR-low+/HER2− breast cancer

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This study aims to assess the safety and efficacy of neoadjuvant patritumab deruxtecan combined with pembrolizumab for early-stage triple-negative and HR-low+/HER2− breast cancer.
Randomized, open-label design with two phases
Participants include adults with locally advanced, untreated triple-negative or HR-low+/HER2− breast cancer
Part 1 focuses on dose-finding for patritumab deruxtecan
Part 2 randomly assigns participants to three treatment arms
Primary endpoints include safety and rate of pathological complete response
HER3-DXd showed antitumor activity and manageable safety in early studies
Dose-limiting toxicity evaluation is ongoing in Part 1
Enrollment targets approximately 342 participants in Part 2

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Implication

Phase 2 trial evaluates neoadjuvant therapy outcomes in early-stage HER2− breast cancer, suggesting safety and efficacy improvements.

Cite This Study

O'Shaughnessy et al. (2026) studied this question.

synapsesocial.com/papers/6996a887ecb39a600b3ef540 https://doi.org/10.1158/1557-3265.sabcs25-ps5-12-21

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Abstract PS5-12-21: Herthena-breast03: a phase 2, randomized, open-label study evaluating neoadjuvant patritumab deruxtecan (HER3-DXd) + pembrolizumab before or after pembrolizumab + chemotherapy for early-stage TNBC or HR-low+/HER2− breast cancer

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Discussion

Implication

Cite This Study

Abstract PS5-12-21: Herthena-breast03: a phase 2, randomized, open-label study evaluating neoadjuvant patritumab deruxtecan (HER3-DXd) + pembrolizumab before or after pembrolizumab + chemotherapy for early-stage TNBC or HR-low+/HER2− breast cancer

Key Points

Discussion

Implication

Cite This Study

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