Nelipepimut-S may prevent recurrence in triple-negative breast cancer

The concurrent use of nelipepimut-S (NPS), a vaccine designed to stimulate CD8 T cells, in trastuzumab-treated patients with breast cancer and low HER2 expression is safe and does not contribute to excess toxicity, as well as prolongs disease-free survival (DFS) specifically in those with triple-negative breast cancer (TNBC), as shown in the results of a phase II trial.

A total of 275 patients received trastuzumab for 1 year and were randomized to treatment with NPS (n=136) or placebo (n=139) in combination with granulocyte-macrophage colony-stimulating factor (GM-CSF). There were no clinicopathologic differences between groups.

The patients had HER2 1+ or 2+ (for IHC 2+ tumours, ISH nonamplified) invasive breast cancer; were node positive or oestrogen and progesterone receptor negative (TNBC); and were disease-free following completion of surgery, chemotherapy, and radiation.

Compared with placebo, treatment with NPS was safe with no additional overall or cardiac toxicity.

During a median follow-up of 25.7 months, estimated DFS did not significantly differ between NPS and control groups (hazard ratio [HR], 0.62, 95 percent confidence interval [CI], 0.31–1.25; p=0.18). However, planned exploratory analysis showed that NPS yielded a marked increase in DFS in the group of TNBC patients (HR, 0.26, 95 percent CI, 0.08–0.81; p=0.01).

Based on the present data, NPS will be further evaluated in a phase III trial involving TNBC patients with residual disease after neoadjuvant chemotherapy, according to the researchers.