Antagon is the first gonadotropin-releasing-hormone (GnRH) antagonist approved for this indication in the U.S.

The new treatment will help women undergoing fertility procedures significantly reduce the number of days of medication necessary to suppress LH surges (which cause ovulation) and therefore maintain eggs in the ovaries. While previously-used agonist products for hormone suppression must be taken for as many as 26 days, phase III clinical studies demonstrated that the antagonist action of Antagon is unique because it achieves the same goal within five days, while minimising unpleasant side effects such as hot flashes and headaches.

Infertility affects approximately 6.1 million couples in the U.S, or approximately 10 percent of the reproductive age population, the American Society for Reproductive Medicine reports.

"Antagon is a long-anticipated addition to infertility specialists' drug armamentarium," said Daniel Shapiro, M.D., a reproductive endocrinologist based in Atlanta. "Its primary advantage is that a patient need only take it four or five days as opposed to three weeks for leuprolide."

Antagon, which will be available by prescription later this year, can be self-administered by the patient via a subcutaneous injection, and clinical tests have shown that it is extremely well-tolerated.

Women seeking medical treatment for infertility often face a complex regimen of medications and procedures. In vitro fertilisation treatment cycles have historically been initiated with the administration of leuprolide acetate to suppress the premature release of leutenizing hormones (LH), which trigger ovulation. This practice inhibits ovulation so that the eggs remain available for retrieval by a fertility specialist. In normal ovulatory cycles, the pituitary gland would release a large pulse of LH to initiate egg ripening and release. Leuprolide must be injected daily for as many as 26 days to prevent this from occurring.

In U.S. Phase III clinical trials, patients needed to take Antagon for an average of just five days, compared to 22 days with leuprolide acetate.

"Antagon has the advantage of directly cutting off LH production, while leuprolide tricks the pituitary gland into turning off," Dr. Shapiro said. "Like a light switched off, Antagon works immediately. Leuprolide requires that the light be turned on and left on until the bulb burns out."