AE37 peptide vaccination in prostate cancer: a 4-year immunological assessment updates on a phase I trial

Cancer Immunol Immunother. 2013 Oct;62(10):1599-608. doi: 10.1007/s00262-013-1461-3. Epub 2013 Aug 10.


In our recent phase I trial, we demonstrated that the AE37 vaccine is safe and induces HER-2/neu-specific immunity in a heterogeneous population of HER-2/neu (+) prostate cancer patients. Herein, we tested whether one AE37 boost can induce long-lasting immunological memory in these patients. Twenty-three patients from the phase I study received one AE37 boost 6-month post-primary vaccinations. Local/systemic toxicities were evaluated following the booster injection. Immunological responses were monitored 1-month (long-term booster; LTB) and 3-year (long-term immunity; LTI) post-booster by delayed-type hypersensitivity, IFN-γ ELISPOT and proliferation assays. Regulatory T cell (Treg) frequencies, plasma transforming growth factor-β (TGF-β) and indoleamine 2,3-deoxygenase (IDO) activity levels were also determined at the same time points. The AE37 booster was safe and well tolerated. Immunological monitoring revealed vaccine-specific long-term immunity in most of the evaluated patients during both LTB and LTI, although individual levels of immunity during LTI were decreased compared with those measured 3 years earlier during LTB. This was paralleled with increased Tregs, TGF-β levels and IDO activity. One AE37 booster generated long-term immunological memory in HER-2/neu (+) prostate cancer patients, which was detectable 3 years later, albeit with a tendency to decline. Boosted patients had favorable clinical outcome in terms of overall and/or metastasis-free survival compared with historical groups with similar clinical characteristics at diagnosis. We suggest that more boosters and/or concomitant disarming of suppressor circuits may be necessary to sustain immunological memory, and therefore, further studies to optimize the AE37 booster schedule are warranted.

Publication types

  • Clinical Trial, Phase I
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Aged
  • Cancer Vaccines / administration & dosage*
  • Cancer Vaccines / adverse effects
  • Cancer Vaccines / immunology*
  • Cell Growth Processes / drug effects
  • Cell Growth Processes / immunology
  • Humans
  • Hypersensitivity, Delayed / chemically induced
  • Hypersensitivity, Delayed / immunology
  • Immunization, Secondary
  • Lymphocyte Activation
  • Male
  • Middle Aged
  • Prostatic Neoplasms / immunology*
  • Prostatic Neoplasms / pathology
  • Prostatic Neoplasms / therapy*
  • Prostatic Neoplasms, Castration-Resistant / immunology
  • Prostatic Neoplasms, Castration-Resistant / therapy
  • Receptor, ErbB-2 / immunology
  • T-Lymphocytes / immunology


  • AE37 vaccine
  • Cancer Vaccines
  • ERBB2 protein, human
  • Receptor, ErbB-2