Clinical trials in male hormonal contraception to date
M. Meriggiola, S. Cerpolini & A. Costantino
Over the last 50 years, different studies have been carried out in the field of male hormonal contraception. Two multicenter efficacy studies supported by WHO in which the prototype testosterone-alone regimen was used, have demonstrated the validity of the principle of male hormonal contraception. Contraceptive protection is dependent on the degree of sperm suppression. Azoospermia is certainly the gold standard for this type of contraceptive since no pregnancies were reported among azoospermic men. However, the pregnancy rate among azoospermic and severely oligospermic (sperm count <1 million/ml) men was 0.8 per 100 person/year (95% CI 0.12.7; 2 pregnancies in 269.5 years of exposure). Therefore, the threshold of 1 million/ml for sperm suppression after hormone administration seems to be an acceptable interim goal for a hormonal male contraceptive. Further clinical studies have shown that testosterone must be combined with a progestin in order to consistently induce profound sperm suppression. Different androgen-progestin regimens have been tested in small pilot trials suggesting that these regimens can effectively suppress sperm counts without inducing major adverse effects. Two efficacy trials testing two different androgen-progestin combinations have recently been performed confirming the high effectiveness of these combinations in terms of sperm suppression and pregnancy rate. Further studies will be needed to confirm the efficacy of these combinations and to select the safest androgen-progestin combination for market entry.
Declaration of interest: The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the research project.
Funding: This work was supported, however funding details are unavailable.