Humans and Health

The Male Contraceptive Pill: Why Has It Taken So Long?

A pile of pill blisters
Leacsaidh MacDonald Marlow

The BBC has just reported on the development of a new prototype for a male contraceptive pill. But why has it taken so long to come about? Leacsaidh MacDonald Marlow discusses…

The function of this pill is based on the location of a cell pathway which can inhibit the movement of sperm, temporarily preventing them from swimming. 

This specific pathway inhibits a cellular signalling protein called soluble adenylyl cyclase, or sAC, a protein which affects the maturation and motility of sperm cells, and therefore targeting this protein allows for the inhibition of sperm motility. 

When sAC is activated in the testes it causes an increase in cAMP, which is important in the cell cycle of the sperm, resulting in their maturation and increased motility, both of which are required for the fertilisation of an egg.

The tests which have thus far been conducted on mice indicate an effective and temporary ‘stunning’ of sperm which lasts for approximately 3 hours, having completely worn off after 24 hours, resulting in no detectable side effects. 

This oral contraceptive is intended to be taken on demand, meaning it does not need to be ingested consistently, only as required, because the effects are strong and temporary. 

But why have we been waiting so long for a widely available oral contraceptive for men?

The most prominent reason is the potential for adverse side effects, which are common in those consistently taking medication containing synthetic hormones. 

Some of the side effects reported in men who trialled a hormonal contraceptive injection were mood disorders and depression, which resulted in the injection not moving past phase one of clinical trials. 

While most polls indicate that one-third of sexually active men in Britain would consider using some form of hormonal contraception, it is clear the general consensus is that the hormonal side effects of any currently available options outweigh the benefits. 

The hope is that this sAC inhibiting prototype pill moving to clinical trials will mark a shift towards widespread availability of male contraceptives

Currently approximately one-third of sexually active women in the UK are taking the birth control pill which contains synthetic forms of oestrogen and progestin (a form of progesterone), a medication which is known to commonly cause nausea, headaches, mood swings, weight gain, high blood pressure and occasionally clots.

Despite this, the combined hormonal pill remains the most commonly used form of contraception worldwide, with the burden of hormonal side effects being a result of contraception falling predominantly on women in relationships. 

So what is the alternative? 

New male contraceptives currently being developed are being designed to not include synthetic hormones, such that hormonal side effects can be bypassed while also preventing unwanted pregnancy. 

Besides vasectomies, these emerging options include the sAC targeting prototype and a physical dam barrier which is intended to stop sperm from entering the penis. 

Ultimately the aim is to block the movement and maturation of the sperm, so the focus of scientists currently working on contraceptive development is the identification of chemicals which can inhibit both of these, ideally in a way which is temporary and reversible. 

The benefit of non-hormonal contraceptive therapies is that they cause fewer physical and psychological changes to peoples’ bodies, and they offer an option to protect against unwanted pregnancy whilst maintaining libido.  

Ultimately, the hope is that this sAC inhibiting prototype pill moving to clinical trials will mark a shift towards widespread availability of male contraceptives, and subsequently increase the proportion of men taking oral contraceptives. 

Leacsaidh MacDonald Marlow

Featured image courtesy of Volodymyr Hryshchenko via Unsplash. Image license found here. No changes were made to this image.  

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