Breast Cancer Coverage from Every Angle

ASCO-SITC 2019: HER2-Targeted Vaccine Plus Trastuzumab in Breast Cancer

By: Melissa E. Fryman, MS
Posted: Wednesday, March 20, 2019

The addition of nelipepimut-S to trastuzumab may improve disease-free-survival for patients with early-stage triple-negative breast cancer. Although further study in this patient population is warranted, HER2-targeted vaccines such as nelipepimut-S, when combined with trastuzumab, may prove to be effective adjuvant therapies for this patient population. The research, conducted by George Earl Peoples, MD, of the Cancer Vaccine Development Program in San Antonio, was presented at the American Society of Clinical Oncology—Society for Immunotherapy of Cancer (ASCO-SITC) Clinical Immuno-Oncology Symposium in San Francisco (Abstract 1).

In this multicenter, single-blinded, phase IIb trial, 275 patients with clinically disease-free HER2 low–expressing breast cancer were enrolled after standard therapy. Of them, 136 patients were randomly assigned to receive nelipepimut-S, trastuzumab, and granulocyte-macrophage colony-stimulating factor (GM-CSF), and 139 received placebo, trastuzumab, and GM-CSF. Treatment safety was assessed, and patients were followed to screen for cancer recurrence. The primary outcome was disease-free-survival at 24 months.

At the prespecified interim analysis, disease-free-survival was significantly improved for patients with triple-negative breast cancer who were given nelipepimut-S (P = .013); thus, due to lack of equipoise, the data safety monitoring board recommended early study closure. After an additional 7 months of follow-up (a median follow-up of 25.7 months), the intention-to-treat analysis showed a favorable—but nonstatistically significant—improvement in disease-free-survival between the two groups (P = .18).

According to the authors, the addition of the vaccine was safe, with no new overall or cardiovascular toxicities seen in the nelipepimut-S group when compared with the placebo group. In addition, no grade 4 or 5 adverse events were reported.

“These findings could position the nelipepimut-S plus trastuzumab combination as an adjuvant therapy for early-stage triple-negative breast cancer and warrant further study,” the researchers concluded.

Disclosure: The study authors’ disclosure information may be found at

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