Vaccines for control of fertility and hormone dependent cancers

Abstract

Two vaccines, namely one inducing antibodies against hCG and the other against GnRH, are now in clinical trials. The hCG vaccine has entered Phase II clinical trials in three centres in India after successfully completing Phase I clinical studies in several centres in India and in four countries abroad. The vaccine was found to be devoid of side-effects; its effect was reversible. The available data on 179 cycles indicate that the vaccine prevents pregnancy at antibody titres above 50 ng/ml. A genetically engineered version of the vaccine has also been approved for trials in human lung cancer patients of the type which make hCG. hCG is observed to be a growth factor for such tumours. The GnRH vaccine is usable in both males and females as the deca-peptide is common to both sexes. Following suitable experimental and toxicology studies, the vaccine is currently in Phase I/Phase II clinical trials in patients of prostate carcinoma. Where antibody GnRH antibodies were induced, the LH, FSH and testosterone levels declined. This was accompanied by a reduction in prostate specific antigen. Clinical improvement was observed in many cases. The vaccine has also entered Phase I clinical studies in postpartum women, with the objective to extend the lactational amenorrhoea and extend inter-child interval.

PIP: Researchers at the National Institute of Immunology (NII) in New Delhi, India have studied 2 vaccines to control fertility: the human chorionic gonadotropin (hCG) vaccine and the gonadotropin releasing hormone (GnRH) vaccine. Animal studies of both vaccines do not indicate any side effects. These 2 vaccines are at the clinical trial stage. Phase II clinical trials of hCG vaccine uses the heterospecies dimer conjugated to tetanus toxoid, diphtheria toxoid, or cholera toxin chain B as carriers. The subjects include hyperfertile women with at least 2 living children. They receive 3 primary immunizations every 6 weeks then a booster immunization as needed. As of May 1991, women with titers of 50ng of hCG bioneutralization capacity/ml had experienced 179 pregnancy-free cycles, and their sexual activity surpasses that prior to receiving the vaccine. 1 study shows that the lung tumors in nude mice which have passive immunization with anti-alpha hCG antibodies necrotize when researchers implant lung tumor cells. Injection of antibodies at the same time of implantation of tumor cells inhibits lung tumor growth. NII researchers plan to conduct a clinical trial with a beta hCG vaccine conjugated with vaccinia in lung cancer patients. The GnRH vaccine has the potential to be effective in both men and women. A study in male rats using diphtheria toxoid as the GnRH vaccine carrier reveals that antibody titers rise, testosterone levels fall, weight of testis decreases, and the prostate disappears. NII has begun clinical trials with postpartum women and, as of April 1992, 20 women were enrolled and immunized at 2 centers in India. Similar research in monkeys does not show evidence of passage of GnRH antibodies through breast milk. GnRH vaccine research in prostate cancer patients demonstrates declining levels of testosterone, luteinizing hormone, and follicle stimulating hormone, shrinkage of the prostate, and clearance of urinary ducts.