A groundbreaking study in developing a male birth control was halted after 20 men jumped ship due to reported side effects.

The World Health Organization study, released last Friday, found that a male contraceptive injection had a success rate of 96 percent – nearly as effective as the female birth control pill.

Researchers injected 320 men between the ages of 18 and 45 with regular shots over the course of 56 weeks. The injections included two hormones – progestogen, which lowers sperm counts, and testosterone, which decreases the effects of the progestogen (progesterone also reduces testosterone).

Despite showing a very high success rate, research ended early after 20 men abandoned the study, most of whom cited side effects like mood changes. Others reported acne, pain or panic at first injections, palpitations, hypertension and erectile dysfunction.

The side effects of female birth control have, of course, been well documented; including moodiness, nausea, weight gain, and depression (as proven in recent monumental research.)

Despite the abrupt end to this most recent study into a male birth control, researchers still consider it a win.

“The study found it is possible to have a hormonal contraception for men that reduces the risk of unplanned pregnancies in the partners of men who use it,” said researcher Mario Philip Reyes Festin from the World Health Organization in a press release.

Study author Richard Anderson told Broadly “it’s a great step forward.”

“A lot of people reported the side effects in quite a mild way and not very many people withdrew from the study,” he said.

Thankfully, this is far from the only encouraging development in the world of male contraception.

In a manner both accidental and ironic, researchers from the University of Wolverhampton have gotten one step closer to developing a reversible contraceptive for men.

Dr. Sarah Jones and professor John Howl were studying peptides (short strings of amino acids) that are able to enter sperm cells and change how they function. They were hoping to determine how this could allow men who are infertile due to low sperm motility to conceive by getting their sperm moving.

As it turns out, it could enable the researchers to design a new treatment that would do the complete opposite.  

“We are basically designing peptides that can alter the physiology of sperm,” said Jones.

“Ironically, sperm are notoriously difficult to penetrate, but with cell-penetrating peptides we are now able to cross an otherwise impermeable barrier to manipulate the intracellular biology of sperm so as to enhance or inhibit motility. We hope to develop something that will be clinically useful and can be taken forward in the future.”

Jones and Howl have been leading research that examines cell-penetrating peptides, and what they’ve discovered is that it’s possible to design them so that when they enter the sperm cell, they can target and change the expression of certain proteins related to the cell’s ability to swim.

In experiments conducted with both bovine and human sperm, they found that the peptides are able to reduce the sperm’s motility within minutes.

“Dr. Jones and I have proven, through extensive research studies, that it is feasible to design cell-penetrating peptides to be biologically active,” said Howl.

“Such molecules, synthesized in our laboratory, represent a new class of agent that we have named bioportides. This state-of-the-art technology enables the control of processes that happen inside cells and which often represent intractable targets for conventional drugs.”

The duo suggest that with further development, this could possibly result in a male contraceptive in the form of a pill, a sub-skin implant or perhaps even a nasal spray that could be taken several hours before sex and last a few days.

h/t IFLScience, Broadly, The Guardian