GTx's lead clinical development programs evaluate small molecules that selectively bind to and modulate nuclear hormone receptors. Hormone receptors are sites located in tissues to which hormones such as estrogen and testosterone bind. Once a hormone binds with its receptor, a series of cellular events is activated, resulting in estrogenic or androgenic tissue effects. These small molecules may either stimulate or block hormone receptors depending on the type of tissue in which the receptor is found.

A drug that can either block or stimulate the same hormone receptor is called a receptor modulator. If it can block or stimulate a receptor in a tissue-selective manner, it may be able to mimic the beneficial and at the same time minimize the unwanted effects of the natural or synthetic hormones.

Selective Estrogen Receptor Modulators (SERMs)

A selective estrogen receptor modulator, or SERM, is a small molecule that binds to and selectively modulates estrogen receptors. These molecules have the ability to either stimulate or block estrogen's activity in different types of tissue:

In its most advanced clinical programs, GTx is developing a SERM, toremifene, in two separate indications in men: first, in an 80 mg dose for the treatment of multiple side effects of androgen deprivation therapy, and second, in a 20 mg dose for the prevention of prostate cancer in men with the precancerous lesion called high grade prostatic intraepithelial neoplasia (PIN).

Selective Androgen Receptor Modulators (SARMs)

GTx scientists have discovered a new class of drugs, nonsteroidal selective androgen receptor modulators, or SARMs, which, with a convenient oral dosing formula, confer many of the benefits of testerone without the unwanted side effects on prostate and skin. These small molecules selectively modulate the androgen receptor depending on the tissue type. Just as SERMs have redefined the use of estrogen in women’s health, we are looking to SARMs to lead a similar revolution for the therapeutic use of testosterone.

GTx has advanced several SARM compounds, including Ostarine™, from the laboratory into clinical development. Several additional SARMs are being evaluated in preclinical studies for additional indications.