Abstract
A human immunogenicity trial a phase I trial is being conducted under the guidance of Professor Warren Jones Head of the Department of Obstetrics and Gynecology (Flinders Medical Centre Flinders University South Australia). The trial is designed to test the immunosafety and immunogenicity of a 35-amino acid synthetic peptide corresponding to the carboxyterminal region of the B-chain of human chorionic gonadotropin (hCG). This is the 1st time a synthetic peptide the basis of a contraceptive vaccine has been used in a human trial. The World Health Organizations (WHO) Special Programme of Research Development and Training in Human Reproduction would take responsibility for distributing the vaccine to the public health sector in developing countries; Sandoz would have the global private sector rights. Human chorionic gonadotropin a protein hormone which is produced soon after the fertilized egg has begun to divide and which can be detected prior to implantation of the embryo was chosen as a suitable antigen for vaccination because of its role in maintaining progesterone production by the corpus luteum and its presence of the surface of the implanting blastocyst. Antibodies could be expected to neutralize hCG leading to breakdown of the corpus luteum and resulting in menstruation apparently indistinguishable from a normal nonconceptual cycle. As the trial is not an efficacy trial volunteers are female students over age 29 who have previously undergone sterilization. Trials in baboons and marmosets which use a fragment of hCG as the immunogen have demonstrated the potential of the approach. Control animals show a high incidence of pregnancy compared to virtually zero in the vaccinated animals. After about 12 months as immunity diminishes the animals regain the ability to become pregnant. The animal studies have failed to demonstrate any evidence of auto-antibody or immune-complex formation or any other adverse side-effects. The volunteers in the trial have had 2 doses of deep intramuscular injection separated by 6 weeks. After several months they are producing persisting levels of antibody sufficient to neutralize hCG in early pregnancy. A phase II trial most likely will be able to be conducted on the basis of these data.
Published Version
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