The CAT Study: Atamestane Plus Toremifene Versus Letrozole in Advanced Breast Cancer

2014-08-27 03:53:52 | BioPortfolio


The purpose of this study is to determine whether maximal estrogen suppression achieved via the combination of an experimental drug, atamestane, plus an FDA-approved drug, toremifene (Fareston®), is more effective than another approved drug, letrozole (Femara®), in delaying the growth of breast cancer, and whether the side effects of the combined hormonal therapy are different from the side effects of letrozole.


Aromatase is an enzyme expressed in tissues such as muscle and fat in postmenopausal women. These non-ovarian tissues become the dominant sources of estrogen in postmenopausal women. Breast cancer cells are often very dependent on estrogens to continue to grow. Atamestane blocks the formation of estrogens from androgenic precursors in the body via the aromatase enzyme. Toremifene blocks circulating and intracellular estrogens from stimulating estrogen receptors in breast cancer cells. The goal of therapy with atamestane, an aromatase inhibitor, in combination with the estrogen receptor antagonist, toremifene, is to achieve complete suppression of estrogen stimulation of breast cancer cells. This study is designed to determine whether combined hormonal therapy will lengthen the time to disease progression and the rate of objective response, as compared to single agent therapy with the approved aromatase inhibitor letrozole.

Study Design

Allocation: Randomized, Control: Active Control, Endpoint Classification: Safety/Efficacy Study, Intervention Model: Parallel Assignment, Masking: Double Blind (Subject, Caregiver, Investigator, Outcomes Assessor), Primary Purpose: Treatment


Breast Neoplasms


Atamestane, Toremifene, Letrozole, Aromatase inhibition, Estrogen receptor blocker, Hormone therapy, Endocrine therapy, Antiestrogen therapy


Research Site
United States




Intarcia Therapeutics

Results (where available)

View Results


Published on BioPortfolio: 2014-08-27T03:53:52-0400

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Medical and Biotech [MESH] Definitions

A first generation selective estrogen receptor modulator (SERM). Like TAMOXIFEN, it is an estrogen agonist for bone tissue and cholesterol metabolism but is antagonistic on mammary and uterine tissue.

One of the ESTROGEN RECEPTORS that has marked affinity for ESTRADIOL. Its expression and function differs from, and in some ways opposes, ESTROGEN RECEPTOR BETA.

An enzyme that catalyzes the desaturation (aromatization) of the ring A of C19 androgens and converts them to C18 estrogens. In this process, the 19-methyl is removed. This enzyme is membrane-bound, located in the endoplasmic reticulum of estrogen-producing cells of ovaries, placenta, testes, adipose, and brain tissues. Aromatase is encoded by the CYP19 gene, and functions in complex with NADPH-FERRIHEMOPROTEIN REDUCTASE in the cytochrome P-450 system.

One of the ESTROGEN RECEPTORS that has greater affinity for ISOFLAVONES than ESTROGEN RECEPTOR ALPHA does. There is great sequence homology with ER alpha in the DNA-binding domain but not in the ligand binding and hinge domains.

A selective aromatase inhibitor effective in the treatment of estrogen-dependent disease including breast cancer.

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