With an ever-growing societal attitude of equality and the push forward towards feminism, there is a desire for the development of a male contraception in order to have both individual and shared responsibility for family planning. Currently, the available options for male contraception are condoms, which have a failure of rate of 3.3%% when used correctly (Moreau C et al, 2007). Sterilisation via vasectomy, a more invasive form of male contraceptive, which has varying rate of reversibility dependent on the duration since the vasectomy, which may act as a deterrent from its use. Subsequently this has left a heavy weighting on female hormonal contraception and a gap in the market for an effective, non-invasive male contraceptive. A male contraceptive would allow for ownership of family planning as well as relieving a partner of the burden and often negative side effects caused by female contraception such as weight gain, headaches and a decreased libido (Wallwiener CW et al, 2010. Cooper DB et al, 2019).
Testosterone replacement therapy (TRT) is currently in use for treatment of males with hypogonadism, caused by a decrease in serum testosterone. Treatment with exogenous testosterone can overcome symptoms of this disorder such as decreased libido and decreased muscle mass. However, a notable side effect of TRT is the suppression of the hypothalamic-pituitary gonadal axis which lowers sperm production. Due to this hormonal feedback mechanism exogenous testosterone has been explored historically as a potential contraceptive technique.
Previous male contraceptives began in the 1970’s with the injectable intramuscular administration of testosterone precursors, such as Testosterone enanthate. These had a high efficacy for suppressing sperm concentration when administered weekly but with side effects including discomfort at injection site, acne and weight gain. Testosterone undecanoate is a long-acting monthly intramuscular injection which reached phase II clinical studies, with a total efficacy rate of 94.8% (Gu Y-Q et al, 2003). However, these trials while effective in the Chinese men, were seen to be less efficient in Caucasian men due to ethnic differences in testosterone response. Patients undergoing TRT may experience a decline in spermatogenesis, but it should not be used as the sole form of contraception. Condoms still have a higher success rate at 96.7% and vasectomies at 99.06% (Zini A et al, 2016).
Phase IIb clinical trials for a male contraceptive began in the USA on 25th of October 2018 and the 22nd of June 2019 in Edinburgh, the primary outcome of these trials is to measure contraceptive efficacy provided by daily use of NES/T (NCT03452111). The project is funded by Eunice Kennedy Shriver National Institute of Child Health and Human Development (NICHD) and lead by the Los Angeles Biomedical Research Institute and the Washington School of Medicine. As previously mentioned, the development of a male contraceptive causes unpleasant side effects such as acne, loss of libido and weight gain. Currently, the trials are investigating a reversible hormonal gel consisting of a synthetic progesterone compound, Segesterone Acetate, combined with Testosterone (NES/T), which aims to lessen and prevent these side effects. The gel is dispensed in specific volume and is then applied to the chest and shoulders daily whereby it is absorbed into the blood stream via the skin.
Progesterone suppresses gonadotropin secretion in the pituitary and causes a reduction in Follicle Stimulating Hormone (FSH) and Luteinising Hormone (LH) which in turn reduces endogenous testosterone and therefore reduce the stimulation of spermatogenesis. The addition of replacement exogenous testosterone in the gel is theorised to counter this decrease in endogenous testosterone, to maintain male sexual characteristics. The secondary outcome of azoospermia, a sperm count of <1 million/mL, is estimated to take up to 20 weeks upon daily use of the NES/T during the suppression phase. Semen is considered to be a low sperm count when <15million/mL. Once the sperm count has declined to a sufficient level so to decrease the likelihood of pregnancy, the gel will be the participants sole method of contraception for 52 weeks. The participants sperm counts are measured regularly to minimise possibility of pregnancy during the trial. Results are expected September 2021.
With a growing interest and willingness among men to have an active role in family planning and a shared ownership of responsibility, male contraception is an area expected to propel in the future. A contraceptive method with an effectiveness comparable to that of female methods such as the contraceptive pill would be well received. Recent studies have shown that 44-83% of men would use a male method of oral contraceptive (Martin CW et al, 2000), with parallel studies showing only 2% of females would not trust their partner to use a male pill (Glasier AF et al, 2000) indicating a potential market for male contraceptive methods.