Schering AG Germany, a research-based pharmaceutical company, and Organon started a major clinical trial designed to test the reliability and safety of the so-called "Male Pill". The study, which will be conducted in 14 centres throughout Europe is one of the largest trials ever of a hormonal fertility control method for men.

"Research in fertility control has traditionally concentrated on methods for women and with the 'male pill' we aim to increase the choice of methods available to couples", said Professor Günter Stock, member of the Executive Board of Schering AG responsible for Research. He added: "Schering and Organon have decided to join their forces in the development of a male fertility control method. With our joint study we make a big step forward in the development of the first hormonal fertility control for men which has the potential to be marketed worldwide."

The study, a double-blind randomized phase II trial, will be conducted in a total of 350 men in 14 centres throughout Europe. Following encouraging results from earlier pilot studies, the present challenge for both companies is to develop a method that is not only reliable, safe and reversible but also acceptable to users.

The trial medication and modes of administration are based on results from earlier studies showing that sperm concentrations can be suppressed to contraceptive levels by the progestogen etonogestrel. In the trial, the progestogen, developed by Organon, is given in implant form. As this hormone inhibits the body's testosterone production, the test persons are injected with a long-acting testosterone undecanoate developed by Schering, which maintains testosterone levels in the blood within the normal range. This phase II study will evaluate six dose combinations of etonogestrel and testosterone undecanoate.