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Prostate Vaccine Succeeds in Phase I Trial

June 09, 2009
by Lynn Shapiro, Writer
Antigen Express, a subsidiary of biotech firm Generex, told an American Society of Clinical Oncology meeting last week that its prostate cancer vaccine had proved successful in Phase I clinical trials in 29 men with various stages of prostate cancer.

"While Phase I trials are focused on safety, we took blood from patients and found that we got the immunological response that we wanted," Anitigen's president, Eric von Hofe, PhD, told DOTmed News.

"We also saw a decrease in PSA levels in some patients but as this is a Phase I trial, this evidence is preliminary," Dr. von Hofe said.

Antigen's compound, dubbed AE37, is actually a portion of the HER-2/neu protein that immune cells--specifically CD4 cells--are capable of recognizing, Dr. von Hofe says. He calls CD4 cells the "generals" of the immune system.

"Antigen's technology involves taking a fragment of the Her-2 protein in a critical region that immune cells recognize, and modifying it so that it more potently stimulates CD4 cells to fight cancer," he says.

Speaking about cancer vaccines' long road to success, Dr. von Hofe says that up until about a year ago, the field of cancer immunology was littered with failures. The first vaccine to show promise was one made by Dendrion for prostate cancer, called Provenge. The drug recently met its endpoint in Phase III clinical trials. FDA is now reviewing the drug and approval of the first cancer vaccine could be imminent.

"I'm personally convinced that active immunotherapy in cancer will be a significant weapon in oncologists' arsenal for fighting cancer in five to 10 years," Dr. von Hofe tells DOTmed.

Breast Cancer Trial

Meanwhile, he says Antigen's vaccine is in Phase II trials for breast cancer patients, whose tumors over-express the HER-2/neu protein.

He notes that Genentech's blockbuster drug, Herceptin--which also zeroes in on cancer that is over-expressing HER-2/neu--can be used only in patients expressing the highest level of HER-2, or about 25 percent of breast cancer patients. In comparison, Antigen's vaccine stimulates the immune system to recognize tumor cells in patients with a lower expression of HER-2, so that 75 percent of breast cancer patients would respond to Antigen's vaccine.

"We also believe that there could be a synergistic response if we use Herceptin with an immunological drug like AE37, but we haven't tried that yet," Dr. von Hofe says. "We're focused more on looking at AE37 alone."

He notes that Herception sales in 2008 were $1.8 billion, so the potential market for Antigen's vaccine would be even larger.

Breast/Ovarian Cancer Trial

Meanwhile, the company has started another phase I trial for ovarian or breast cancer patients. In that trial, Antigen is combining AE37 with another peptide that stimulates CD8 cells as well as CD4 cells.

"We're stimulating the CD4 cells--considered the immunological generals--with AE37. But there's another peptide to stimulate the infantry and those are the CD8 cells," Dr. von Hofe explains.

He says the prevalence of both prostate and breast cancer in the U.S. is high. There are 186,000 new cases of prostate cancer and 28,600 men die from the disease every year. As for breast cancer, there are 180,000 new cases each year and 40,000 women die each year.

Antigen and Generex

Dr. von Hofe was assistant professor of pharmacology at the University of Massachusetts when he met Robert Humphreys, who was professor of pharmacology there before founding Antigen Express in 1995. Dr. von Hofe joined Antigen Express in 2003, with a mandate to bring drugs from the bench to the clinic. Antigen was purchased by Generex (which trades on Nasdaq) the same year. Dr. Humphreys has since retired.