Technische Universität München

The Entrepreneurial University

Aromatase inhibitors, selective estrogen receptor modulators (SERMs), agents modifying myostatin function and other anti-estrogenic substances are the major classes which are distinguished by the 2008 Prohibited List.

Aromatase inhibitors are drugs blocking the “enzyme” aromatase which converts androgens (e. g. testosterone) into estrogens by a process called aromatization.  Thereby aromatase inhibitors lower estrogen levels in the blood or in tumour “tissues” by preventing the formation of estradiol. Forbidden aromatase inhibitors are, but not limited to, anastrozole, letrozole, aminoglutethimide, exemestane, formestane and testolactone.

Selective estrogen receptor modulators (SERMs) are compounds that bind with estrogen receptors and exhibit estrogen action in some tissues and anti-estrogen action in other tissues. They are a structurally quite diverse group of compounds which act as either an agonist or antagonist depending on the tissue type and hormonal milieu. For example, the prototypical SERM tamoxifen acts as an antagonist in breast and conversely as an agonist in uterus. The concentration of steroid receptor co-activator is higher in uterus than in breast, therefore SERMs such as tamoxifen are more agonistic in uterus than in breast. In contrast, raloxifene behaves as an antagonist in both tissues. Forbidden SERMs are, but not limited to, raloxifene, tamoxifen and toremifene.

Myostatin or growth differentiation factor 8 is a “protein” of the skeletal muscle cells regulating the size of muscles by blocking extensive growth. Agents modifying the myostatin function, especially inhibiting the myostatin gene, are growth-regulating by apparently accelerating the development of muscle stem cells. In this context the agents are forbidden, but not limited to myostatin inhibitors.

Aromatase inhibitors inhibit the transformation of the male sexual hormone testosterone to the female hormone estrogen.