Clinical and Immunologic Responses of HLA-A3  Breast Cancer Patients Vaccinated with the HER2/ neu-Derived Peptide Vaccine, E75, in a Phase I/II Clinical Trial Ritesh Patil, MD, Guy T Clifton, MD, Jarrod P Holmes, MD, Asna Amin, MD, Mark G Carmichael, MD, Jeremy D Gates, MD, Linda H Benavides, MD, Matthew T Hueman, MD, Sathibalan Ponniah, PhD, George E Peoples, MD, FACS BACKGROUND: We have treated disease-free breast cancer patients with an HER2/neu-derived peptide, E75, as an adjuvant vaccine. E75 was originally described as HLA-A2-restricted and has been previously tested in this population. Based on computer modeling, E75 is predicted to bind to HLA-A3, and preclin- ical data support this. We conducted a clinical trial of E75 in HLA-A3 + , A2 - (A3) patients. STUDY DESIGN: Disease-free breast cancer patients were enrolled after standard therapy in phase I/II trials. A3 patients were enrolled in parallel with A2 patients and vaccinated with E75 and granulocyte-macrophage colony- stimulating factor immunoadjuvant. A2 - , A3 - patients were followed as controls. Toxicities were graded. Immunologic responses were assessed by delayed-type hypersensitivity reactions and E75-specific interferon-  enzyme-linked immunosorbent spot assay. Clinical recurrences were documented. RESULTS: Thirteen A3 patients completed the vaccine schedule. Clinicopathologic features were similar between A3, A2, and control patients, except for more HER2/neu-overexpressing tumors in the A2 group and more estrogen-receptor/progesterone-receptor-negative tumors in A2 and A3 groups. Toxicity profiles and postvaccination delayed-type hypersensitivity were similar in A3 and A2 patients. Enzyme-linked immunosorbent spot assay results varied, but A3 patients’ median spots increased pre- to postvaccination (p = 0.2). Recurrences were lower in the A3 group (7.7%) at 30-month median follow-up compared with published recurrence in A2- vaccinated (8.3%) and control groups (14.8%) at 26-month median follow-up. CONCLUSIONS: HLA restriction limits potential use of peptide-based cancer vaccines. This trial demonstrates that HLA-A3 patients respond similarly to E75 vaccination as HLA-A2 patients, suggesting the potential use of the E75 vaccine in up to 76% of the population. (J Am Coll Surg 2010;210: 140–147. Published by Elsevier Inc. on behalf of the American College of Surgeons) Tumor-associated antigens (TAA) are a promising area of active research for cancer immunotherapy. Cancer vaccine re- search has centered on priming the body’s immune system so that it will recognize and specifically attack cancer cells ex- pressing TAAs. There have been multiple approaches used to prime the immune system to these antigens. We have used single-peptide vaccines given with immunoadjuvant (granulocyte-macrophage colony-stimulating factor [GM- CSF]) in the adjuvant setting to patients who are surgically disease free and after completion of standard chemo/radiation therapy. Advantages of this method include a lack of substan- tial toxicity in addition to simplicity; low cost of production; stability in storage; and ability to generate a strong, specific immune response that is easily monitored. The disadvantage of this method is that single peptides are often HLA-restricted and could have limited applicability. HER2/neu, a proto-oncogene expressed in many epithe- lial malignancies, is one of the most extensively investigated Disclosure Information: Dr Peoples holds patent rights to the E75 vaccine. This study was supported by the United States Military Cancer Institute, Department of Surgery, Uniformed Services University of the Health Sci- ences, and the Department of Clinical Investigation, Walter Reed Army Med- ical Center, Bethesda, MD. This article represents the personal viewpoint of the authors and cannot be construed as a statement of official Department of the Army, Department of the Navy, or Department of Defense policy. Received August 26, 2009; Revised October 20, 2009; Accepted October 21, 2009. From the Joyce Murtha Breast Care Center, Windber Medical Center, Windber, PA (Patil); Department of Surgery, Brooke Army Medical Center, Fort Sam Houston, TX (Clifton, Gates, Benavides, Peoples); Department of Hematology and Medical Oncology, Naval Medical Center, San Diego, CA (Holmes); and the Cancer Vaccine Development Program, United States Military Cancer Institute, Department of Surgery, Uniformed Services University of the Health Sciences, Bethesda, MD (Amin, Carmichael, Hueman, Ponniah, Peoples). Correspondence address: COL George E Peoples, MD, FACS, Department of Sur- gery, General Surgery Service, Brooke Army Medical Center, 3851 Roger Brooke Dr, Fort Sam Houston, TX 78234. email: george.peoples@amedd.army.mil 140 Published by Elsevier Inc. on behalf of the American College of Surgeons ISSN 1072-7515/10/$36.00 doi:10.1016/j.jamcollsurg.2009.10.022