A Norwegian company seeking to develop a male birth control (search) pill has signed a licensing agreement with the University of Massachusetts Medical School covering research that could lead to a drug to block sperm's ability to swim and fertilize an egg.

The method that led to the long-term deal announced Monday could expand the decades-long search for a male pill by targeting a protein found only in sperm cells.

Researchers at the University of Massachusetts in Worcester and elsewhere say that approach carries far less risk of side effects than manipulating a man's hormones, the avenue that has attracted the most research aimed at finding alternatives to condoms and vasectomies (search).

"You wouldn't think there would be side effects because there is no other place in the body where these specific proteins are formed," said Dr. Louis De Paolo, associate chief of the National Institute of Child Health and Human Development, an arm of the National Institutes of Health that has funded male contraception research. "They could make very useful targets for regulating fertility."

Terms of the deal with Oslo-based SpermaTech AS (search) aimed at developing a drug based on the UMass-patented contraception approach were not disclosed.

"We are all very excited about this effort, because the contraceptive pills now available are based on hormones, which float around in the body and have significant side effects elsewhere," said Bjorn Steen Skalhegg, who helped found the Norwegian company in 2001.

Risks from hormone therapy include harming the prostate gland (search) and permanently reversing sperm production.

SpermaTech said it is searching for a molecular compound to block the so-called Cs protein, and is meeting with large drug companies to find a development partner.

Such a drug potentially could take the form of a pill, implant, patch or gel, and take as long as a decade to develop, De Paolo said.

"The challenge will be to come up with a compound that blocks the protein in the sperm without blocking other proteins in the body," said Dr. John K. Amory, an assistant professor of medicine at the University of Washington with expertise in male contraceptive development.

In addition to potentially carrying few if any side effects, such a drug would be faster-acting than hormone therapy, which requires two to three months to affect male fertility because sperm cells require 72 days to fully mature, Amory said.