Phase I clinical trials with three formulations of anti-human chorionic gonadotropin vaccine

Comparative phase I clinical trials were carried out in 5 centres with three formulations of beta-hCG-based vaccines inducing antibodies against human chorionic gonadotropin. The objectives of these trials were to determine their relative immunogenicity, duration, reversibility and safety. A total of 116 tubal ligated women volunteers were enrolled in the study and 101 subjects were followed-up for one year or more until the antibody titres declined to near zero levels. Every woman receiving the vaccine produced anti-hCG and anti-tetanus antibodies. Clinical examination carried out at intervals of 4-6 weeks revealed no abnormality. No serious side effects or adverse reactions were reported with any of the formulations during primary immunization with three monthly injections of the vaccine. Eleven women, however, demonstrated hypersensitivity to test dose at the time of the booster injection. The reaction was to tetanus toxoid; gonadotropin subunits conjugated to another carrier did not evoke any such reaction. Progesterone in bleeds taken at midluteal phase, as well as complete progesterone and estradiol done in two immunized women, indicated normal ovulatory cycles. Immunization with these formulations had no significant effect on haematological, clinical chemistry and other metabolic parameters. In summary, the results indicate that none of the three beta-hCG-based contraceptive vaccines had any adverse effects clinically, on endocrine status and metabolic parameters. Formulations A and B induced comparatively higher anti-hCG titres than M. Thus, further work can be undertaken to study the efficacy of these vaccines in humans for preventing pregnancy.