OXFORD, England, Dec. 9 (UPI) -- British scientists said Monday they discovered unexpectedly that a drug already approved to treat a rare genetic disorder also might work as a male contraceptive.
A birth control pill for men could result from these findings -- which were made in mice -- with fewer side effects than others in development, they said.
"Quite a large proportion of men want to share responsibility for birth control," Aarnoud van der Spoel, a medical biologist at the University of Oxford, told United Press International. "As this compound has been through all the toxicology studies, it would not take as long for this compound to go through development."
Current options for male contraception are limited to condoms, vasectomies and warmth applied to the testicles, none of which presents a comfortable mix of effectiveness or reversibility. The male birth control drugs closest to market in the United States and Europe attempt to stop sperm production by blocking the secretion of testosterone, the male reproductive hormone.
However, "there are a number of side effects of testosterone replacement -- weight gain and mood changes," van der Spoel explained. "Most of the synthetics also cannot be taken orally, and need to be injected or given as implants, with all those drawbacks."
Male contraception potential was not on the research team's agenda when members investigated the drug NB-DNJ, which chemically mimics sugar. The medicine was approved recently in Europe to treat Gaucher's disease, a rare disorder in which the body cannot break down sugary fats normally. Instead, the "glycolipids" build up to abnormal levels in the liver, spleen and at times brain for potentially fatal results. NB-DNJ hampers the biochemicals that add sugar to these fats.
Researcher Mylvaganam Jeyakumar was trying to set up breeding pairs among mice treated with the sugar mimic.
"This was necessary because (Jeyakumar's) normal breeding stock, not drug-treated, did not produce sufficient numbers of offspring. Then he saw that the drug-treated mice did not reproduce at all," researcher Frances Platt recalled.
Hundreds of mice consumed the drug with their chow for up to six months. After three weeks, males were rendered completely infertile at doses 10 times lower than those used for Gaucher's patients, with no effect on sexual behavior or hormone levels. The sperm of mice treated with the drug had a range of defects, including abnormally shaped nuclei and in some cases tails coiled around the sperm head. The drug had no effect on female fertility. Human patients taking the drug have been warned of possible contraceptive effects.
The contraceptive effect was fully reversed four weeks after males were taken off the sugar mimic. Besides male contraception, the only side effect known of the sugar mimic is diarrhea, since the drug inhibits sugar-sensitive proteins in the bowels. Other male contraceptives in development also do not target hormones, but NB-DNJ has less severe side effects.
Although scientists have known sperm have specialized glycolipids, the researchers do not yet understand how NB-DNJ affects sperm formation.
"Of course there is a long way to go to demonstrate that what happens in mice is applicable to men and safe," researcher Henry Moore said. Abnormally large doses of the drug resulted in unexplained weight loss, for instance.
Platt said her team currently is investigating the effects of long-term use of the sugar mimic.
"This represents the type of research finding that has long been hope for, where responsibility for family planning can be shared between the male and the female," said reproductive medicine scientist Christopher De Jonge of the University of Minnesota in Minneapolis.
"The compound does require additional study in terms of its side effects. One to note is diarrhea, and how severe it could get is not clear. Certainly if one is experiencing dysentery, his libido might not be as it is otherwise."
(Reported by Charles Choi, UPI Science News, in New York)