Early study results show new drug shows promise in metastatic breast cancer

Treatment with HER3-DXd (patritumab deruxtecan) has been associated with the induction of encouraging responses in patients with HER3-expressing metastatic breast cancer or triple-negative metastatic breast cancer.

Data presented at the 2022 Annual Meeting of the American Society of Clinical Oncology demonstrated that the new drug, an antibody-drug conjugate directed against HER3, elicited an objective response rate (percentage of patients whose disease responds partially or completely on treatment) by 30.1% at a median follow-up of 31.9 months. It should be noted that treatment with HER3-DXd resulted in only partial responses.

The median duration of response (or the time a disease responds to treatment without getting worse) in this cohort was 7.2 months. Median progression-free survival (time a patient lives without disease progression) was 7.4 months and median overall survival (time a patient is alive regardless of disease progression) was 14 ,6 months.

In patients with HER3-elevated metastatic triple-negative breast cancer, the objective response rate was 22.6%. Again, all treatment responses were partial. The median duration of treatment response in this group was 5.9 months, with a median progression-free survival of 5.5 months and a median overall survival of 14.6 months.

In patients with HER3-high, HER2-positive metastatic breast cancer, the objective response rate was 42.9%. All responses were partial. The median duration of response was 8.3 months, with a median progression-free survival of 11 months and a median overall survival of 19.5 months.

“There remains a significant unmet need for the treatment of patients with metastatic breast cancer and new treatment strategies need to be explored continuously,” said study lead author Ian E. Krop. , Director of Clinical Research and Associate Director of the Cancer Center for Clinical Research at Yale Cancer Center. in New Haven, Connecticut, said in a press release announcing the results. “The results of this trial show that (HER3-DXd) produces clinically significant and durable antitumor activity in patients and further study is warranted to further evaluate the efficacy and safety of this HER3-directed (conjugated antibody -drug) in patients with HR-positive / HER2-negative, HER2-positive and (triple-negative breast cancer).

An analysis of 113 patients with HER3-high or HER3-low, HR-positive/HER2-negative metastatic breast cancer, 53 patients with HER3-high triple-negative breast cancer, and 14 patients with HER3-elevated, HER2-positive metastatic breast cancer was performed.

Evaluation of the safety and efficacy of HER3-DXd treatment was the primary objective of the study.

A median of six prior treatment lines had been administered in the advanced setting to patients with HR-positive/HER2-negative disease prior to study enrollment. People with metastatic triple-negative breast cancer received a median of two prior treatments. As for patients with HER2-positive metastatic breast cancer, they received an average of 5.5 prior treatments.

A pooled safety analysis of all 182 patients was conducted. Treatment-related side effects led 9.9% of patients in the study to discontinue treatment.

Serious or worse treatment-related side effects were reported in 120 patients. Some of the side effects included, but were not limited to, decreased appetite, nausea, fatigue, diarrhea, and vomiting.

Twelve patients developed treatment-related interstitial lung disease or pneumonitis, which is inflammation of the lungs.

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