Oregon Health and Science University and University of North Carolina professors just published research on a potential new male birth control pill. The contraceptive immobilizes sperm and has no observed side effects.

The News Observer first reported on the study, which focuses on a compound called EP055. EP055 essentially stops sperm from swimming without affecting users' hormones.

"There are hormonal drugs in clinical trials that target the production of sperm," The News Observer notes, "but those developed so far usually affect the natural hormones in men, like female contraceptives affect hormones in women."

Male monkeys from the Oregon National Primate Research Center at OHSU were the trial's test subjects. The primates were given high doses of EP055 intravenously and then monitored for sperm mobility and any other adverse side effects.

Thirty hours after an infusion, the monkey's sperm had effectively stalled, and no other physical side effects were observed.

"At 18 days post-infusion, all [monkeys] showed signs of complete recovery," Mary Zelinski, research associate professor at the Oregon National Primate Research Center, and an associate professor of obstetrics and gynecology at the OHSU School of Medicine, said in a statement, "suggesting that the EP055 compound is indeed reversible."

Zelinski and her co-researcher in North Carolina, Michael O'Rand, say more trials will need to be completed before a pill form of the compound is approved for human use. Importantly, the researchers say they still need to test EP055 in mating trials, to definitively "determine its effectiveness against pregnancy."