Vaccination Equivalent to Surgical Castration

Applied Genetics News, April, 1999

In an ongoing phase I/II clinical trial in patients with advanced prostate cancer, a gonadotropin releasing hormone (GnRH ) vaccine made by Apthon Corp. (444 Brickell Ave., Miami, FL; Tel: 305/374- 7338, Fax: 305/374-7615, Website: www.aphton.com) reduced testosterone to levels comparable to surgical castration.

According to the company, this constitutes "proof of concept" that the vaccine, or "pharmaccine," as Aphton calls it, may have therapeutic benefit in the treatment of prostate cancer. In addition to a drop in testosterone, the cancer progression marker, prostate specific antigen (PSA) was markedly reduced in the treated patients. The patented GnRH pharmaccine consists of synthetic peptides constructed to simulate GnRH bound chemically to a carrier and suspended in a proprietary delivery vehicle. The pharmaccine is administered by intramuscular injection. The pharmaccine induces antibodies to GnRH, which bind the hormone and remove it from circulation. After immunity has been established by an initial series of injections, follow-up injections are given at regular intervals to maintain immunity. The immunological neutralization of GnRH prevents the pituitary from releasing gonadotropins, LH and FSH, which stimulate the production of testosterone. Most prostate tumors are testosterone dependent; removal of testosterone prevents both early stage prostate cancer and metastases. New cases of prostate cancer are expected to exceed 370,000 in the U.S. and Europe annually, adding to the 2.3 million existing cases existing in 1998. Early stage prostate cancer is now treated in some cases with GnRH superagonists (see preceeding story), which have the undesirable effect of creating a surge of testosterone before shutting down production of the steroid. Aphton's GnRH pharmaccine will be marketed world-wide in collaboration with SmithKline Beecham.