Antibody Drug Conjugate Targeting A New Protein, HER3, Shows Promise for Heavily Pre-Treated ER+ and TNBC (Triple Negative) Breast Cancers

Presented at the 2023 American Society of Clinical Oncology Meeting, Phase II Clinical Trial NCT04699630 showed promising results in the treatment of advanced ER+ and TNBC breast cancers using an antibody drug conjugate called HER3-Dxd.

By combining paritumab, which recognizes HER3, with the existing antibody drug conjugate deruxtecan, the HER3 targeting antibody drug conjugate Her3-Dxd was created. This clinical trial tested it's effectiveness in treating advanced ER+/TNBC.

The clinical trial consisted of a small number of people, mostly women, all with advanced ER+ or Triple Negative Breast Cancer, and most with either liver or lung metastasis. The aim of the clinical trial was to evaluate the overall response rate and the clinical benefit rate of the drug.

The Overall Response Rate (ORR) is the percentage of patients who had a partial or complete response to the treatment, meaning their cancer was either eradicated or shrunk.

The Clinical Benefit Rate (CBR) is the percentage of participants who had a complete response or partial response to the drug, OR their cancer remained stable (didn't shrink or grow).

Results:

The study demonstrated a 35% overall response rate (ORR) and a 43% clinical benefeit rate, and the duration of response (how long the response lasted) was six months or more in over 50% of those who responded, showing a very promising overall outcome.

Furthermore, the clinical trial involved cancers with a wide range of HER3 expression, meaning that this new drug could possibly work for all types of metastatic breast cancer, regardless of the level of HER3 expression.

Finally, although there were adverse side effects associated with the drugs, most were manageable and non life threatening.

In conclusion the Phase II Clinical Trial NCT04699630 showed an overall positive outcome regarding the effectiveness/safety of the new HER3-Dxd drug, showing it's promise for treating advanced ER+/Triple Negative breast cancer in the future.

References: Breast Cancer Research Foundation. (2023). ASCO 2023: Updates from Major Breast Cancer Clinical Trials. https://www.bcrf.org/blog/bcrf-asco-2023-clinical-trials-news-updates/

ASCO Publications. (2023). A phase 2 study of HER3-DXd in patients (pts) with metastatic breast cancer (MBC). https://ascopubs.org/doi/10.1200/JCO.2023.41.16_suppl.1004

Cancer Network. (2023). HER3-DXd Yields Positive Efficacy/Safety Profile in Breast Cancer. https://www.cancernetwork.com/view/her3-dxd-yields-positive-efficacy-safety-profile-in-breast-cancer