AE37 shows initial activity in Phase I prostate cancer trial

Research into new “vaccine” immunotherapies for prostate cancer continues to be a hot topic following the approval of Dendreon’s Provenge just 3 weeks ago.

Perez et al. have reported data from an early stage (Phase I) clinical trial of a targeted, hybrid, peptide immunotherapeutic “vaccine” called Ii-Key/HER-2/neu(776-790) or AE37 in patients with hormone-sensitive and castration-resistant prostate cancer.

The primary goals of this trial were:

  • To assess whether AE37 showed any signs of toxicity in patients
  • To monitor patients’ immune responses to this form of treatment.

The study was not designed to show that the drug was clinically effective.

The investigators enrolled 32 patients, all of whom had HER-2/neu+ prostate cancer. Of these 32 patients, 29 (90.6 percent) completed all six cycles of vaccination with AE37.

Results of this initial clinical trial in prostate cancer were as follows:

  • There was no sign of any grade 3 or grade 4 toxicities.
  • 75 percent of patients developed augmented immunity to the AE37 vaccine.
  • 65 percent of patients developed immunity to the unmodified AE36 peptide.
  • AE37 was able to stimulate CD4+ and CD8+ T-cell responses.
  • 80 percent of patients developed a positive delayed-type hypersensitivity (DTH) reaction to AE36.
  • Significant decreases were detected in circulating Treg frequencies, in plasma HER-2/neu levels, and in serum TGFβ levels.
  • Patients with less extensive disease developed better immunological responses after vaccination.

The authors conclude that AE37 vaccine is safe and can induce HER-2/neu-specific cellular immune responses in patients with hormone-sensitive and castration resistant prostate cancer.

AE37 is being developed by Antigen Express, a wholly owned subsidiary of  Generex Biotechnology. In a separate media release, Generex Biotechnology states that, “These results warrant a Phase II clinical study to establish the efficacy of AE37 in prostate cancer patients.” Now they’ll need to come up with the funding to underwrite such a Phase II trial.

The “New” Prostate Cancer InfoLink warns patients that — despite the approval of Provenge — few of these other forms of prostate cancer “vaccine” are likely to be able to demonstrate a significant effect in large Phase III clinical trials. Developing new and effective drugs is hard, even with a model to work from. A very high proportion of cancer therapies that make it into Phase II and Phase III stages of clinical development are still not able to  show sufficient activity to merit approval for clinical use by the U.S. Food and Drug Administration and other regulatory agencies. It would also be several years yet before an immunotherapy like AE37 can make it through all the steps of the clinical development process (including necessary Phase II and Phase III clinical trials, and FDA review of the trial data) that would be necessary before it can be approved for therapeutic use outside of clinical trials.

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