Making of a vaccine preventing pregnancy without impairment of ovulation and derangement of menstrual regularity and bleeding profiles

Abstract

The story of making a vaccine against human chorionic gonadotropin (hCG) for control of fertility is briefly reviewed. The choice of hCG was made on the consideration that it is not involved in the cascade of hormones leading to ovulation; hence, antibodies against hCG would neither disturb ovulation nor normal production of sex hormones by the female. It would not react with any other tissue of the body because no organ of a healthy noncancerous female expresses hCG. International Committee for Contraception Research played a historic role in testing its immunogenicity, safety and reversibility in women in Finland, Sweden, Chile and Brazil. The Population Council also conducted valuable long-term studies (5 years) in New York in 63 rhesus monkeys, which demonstrated the lack of pathological consequences of antibodies cross-reactive with species luteinizing hormone. The first-ever efficacy trials on a birth control vaccine established high efficacy (one pregnancy in 1224 cycles) of anti-hCG antibodies at and above 50 ng/mL titers. Fertility was regained in the immediate next cycle, at titers falling below 35 ng/mL. A recombinant vaccine, hCGβ-LTB, has been made, which is highly immunogenic in mice. It is due to undergo toxicology studies prior to resumption of clinical trials. An additional utility of this vaccine is likely in advanced-stage terminal cancers expressing hCG/subunits.