AE37 is the Ii-Key hybrid of the MHC class II peptide, AE36 (HER2 aa:776-790). Phase I studies showed AE37 administered with granulocyte macrophage colony-stimulating factor (GM-CSF) to be safe and highly immunogenic. A prospective, randomized, multicenter phase II adjuvant trial was conducted to evaluate the vaccine’s efficacy.
Clinically disease-free node-positive and high-risk node-negative breast cancer patients with tumors expressing any degree of HER2 (immunohistochemistry (IHC) 1-3+) were enrolled. Patients were randomized to AE37+GM-CSF versus GM-CSF alone. Toxicity was monitored. Clinical recurrences were documented and disease-free survival (DFS) analyzed.
The trial enrolled 298 patients; 153 received AE37+GM-CSF and 145 received GM-CSF alone. The groups were well-matched for clinicopathologic characteristics. Toxicities have been minimal. At the time of the primary analysis, the recurrence rate in the vaccinated group was 12.4% versus 13.8% in the control group (relative risk reduction 12%, HR 0.885, 95% CI: 0.472-1.659, P=0.70). The Kaplan-Meier estimated 5-year DFS rate was 80.8% in vaccinated versus 79.5% in control patients. In planned subset analyses of patients with IHC 1+/2+ HER2-expressing tumors, 5-year DFS was 77.2% in vaccinated patients (n=76) vs. 65.7% in control patients (n=78), (P=0.21). In patients with triple negative breast cancer (TNBC, HER2 IHC 1+/2+ and hormone receptor negative) DFS was 77.7% in vaccinated patients (n=25) vs. 49.0% in control patients (n=25), (P=0.12).
The overall intention to treat analysis demonstrates no benefit to vaccination. However, the results confirm that the vaccine is safe and suggest that vaccination may have clinical benefit in patients with low HER2 expressing tumors, specifically TNBC. Further evaluation in a randomized trial enrolling TNBC patients is warranted.
© The Author 2016. Published by Oxford University Press on behalf of the European Society for Medical Oncology. All rights reserved. For permissions, please email: [email protected].
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