Researchers at the Population Council have developed MENT® for delivery in a subdermal implant, which would be the first long-acting, reversible male contraceptive method if approved by regulatory authorities.
Men have no contraceptive options other than the condom, withdrawal, and vasectomy. The need for effective and reversible methods of fertility control for men is widely recognized, but continues to be unmet.
There is a growing interest among men in becoming more involved in family planning, and studies have suggested that women would welcome additional male contraceptive choices. The concept of developing new, effective methods of male contraception has been identified as a priority by international organizations, as the male reproductive system offers a number of potential targets for contraceptives.
Male contraceptive methods under development at the Population Council rely on MENT® acetate (7α-methyl-19-nortestosterone), a one-year implant that is placed under the skin of the upper arm. MENT is created from a synthetic steroid that resembles testosterone but does not convert into dihydro testosterone, and therefore does not stimulate prostate growth. If approved by regulatory authorities, MENT would be the first long-acting reversible male contraceptive.
Through the development of MENT, the Council has pioneered an approach to suppress or inhibit sperm cell development without impairing a man’s sexual drive (libido). This approach reduces sperm count by administering an androgen (a male sex hormone) alone or in combination with synthetic progestins.
A hormonal contraceptive that is effective, safe, acceptable, long acting, and reversible requires an approach that will reduce sperm count without requiring frequent administration (e.g., daily use). Early studies showed promising results in inhibiting sperm production with MENT silastic implants. A one-year dose-finding study in healthy men showed that four implants suppress gonadotropin levels completely, leading to significantly reduced sperm count. Eight of 11 men with four implants had zero sperm count, which lasted in many subjects for several months until the implants were removed. Research is ongoing to produce new prototype implants that would deliver a higher daily dose in order to reduce the number of implants needed to be effective.
MENT has several advantages when used for male contraception and androgen substitution therapy, including:
- It strongly suppresses secretion of gonadotropin in men (a hormone that stimulates the growth and activity of the testes, especially pituitary hormones that stimulate the function of the testes).
- It is approximately ten times more active than testosterone. In contrast to testosterone, MENT does not enlarge the prostate, a drawback that occurs with testosterone therapy.
- Because of its high potency, a low daily dose can be administered, making delivery through an implant system preferable for long-term use.
Early studies also suggest that MENT might be appropriate both as a contraceptive in healthy men and as hormone therapy in those with male-hormone deficiency (hypo-gonadal men). In those with male-hormone deficiency, two MENT implants were also proven effective, as men preferred the implants to the standard therapy involving multiple injections of a testosterone derivative.