Anastrozole (Arimidex)

Raw research findings for this medication. Mostly single studies, not curated or confirmed robust.

About Anastrozole

What it is

Anastrozole is an aromatase inhibitor: it blocks aromatase, the enzyme that makes oestrogen in fat and other tissues, which is the main source of oestrogen after the menopause. It is used for hormone receptor-positive breast cancer in postmenopausal women, after surgery and for advanced disease, and to lower breast cancer risk in some women at high risk. It is sold as Arimidex, among other names.

How genes come into it

Studies have looked at CYP19A1, the gene for aromatase itself, and at ESR1, the oestrogen receptor, for how well anastrozole works and for side effects such as joint pain and bone loss. Genome-wide studies flagged CSMD1 and others. Anastrozole is cleared by CYP3A4 and UGT1A4, also studied for blood levels. The findings come from single or a few studies, and there is no CPIC or DPWG guideline.

What research found

Every published finding on gene variants and Anastrozole. Upload your DNA file to see which of these rows apply to you.

Rated evidence (18 rated variants)

PharmGKB weighs all studies of a variant and rates how strong the evidence is, from 1A (strongest) to 4.

rs1437153: Level 3. Efficacy: Breast Neoplasms. 1.

CSMD1 rs6990851: Level 3. Efficacy: Breast Neoplasms. 1.

DLG2 rs2449598: Level 3. Efficacy: Breast Neoplasms. 1.

CSMD1 rs6981827: Level 3. Efficacy: Breast Neoplasms. 1.

Metabolism (7 findings)

Studies of how quickly the body processes this medication.

rs11648166: Allele G is associated with increased concentrations of anastrozole in women with Breast Neoplasms as compared to allele A.

rs28845026: Allele T is associated with increased concentrations of anastrozole in women with Breast Neoplasms as compared to allele C.

ABCB1 rs2032582: Genotype AA is associated with increased concentrations of anastrozole in women with Breast Neoplasms as compared to genotypes AC + CC.

CYP2C9 CYP2C9 intermediate metabolizer: CYP2C9 intermediate metabolizer and poor metabolizer is associated with decreased concentrations of anastrozole in people with Breast Neoplasms and Neoplasm Metastasis as compared to CYP2C9 normal metabolizer and ultrarapid metabolizer.

Response (12 findings)

Studies of how well it worked in people carrying a variant.

rs1437153: Allele T is associated with decreased response to anastrozole in women with Breast Neoplasms as compared to allele G.

CSMD1 rs6981827: Allele T is associated with decreased response to anastrozole in women with Breast Neoplasms as compared to allele C.

CSMD1 rs6990851: Allele G is associated with increased response to anastrozole in women with Breast Neoplasms as compared to allele A.

CYP19A1 rs4646: Genotype AA is associated with decreased response to anastrozole, letrozole or tamoxifen in women with Breast Neoplasms and Menopause as compared to genotypes AC + CC.

Study findings and evidence levels: PharmGKB (CC BY-SA 4.0). Guidelines: CPIC and DPWG, as bundled in PharmCAT. Most studies were done mainly in people of European ancestry.

Related Drugs

More drugs from the same category

Aromasin (Aromatase Inhibitors)

Femara (Aromatase Inhibitors)

5-FU (Antimetabolites)

Not a prescribing recommendation. This page is educational information about pharmacogenomic research and clinical guidelines - it is not medical or dosing advice, and not a prediction of how any medication will work for you. Never start, stop, or change a medication or dose based on it; talk to your doctor or pharmacist, who can order clinical-grade testing if appropriate.

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Content updated September 2026.

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