Data updated: May 26, 2026
ARIMIDEX (anastrozole)
Aromatase Inhibitors
Trial Activity: Stable 42 active trials
Oncology
Approved 1995-12-27
Arimidex is an aromatase inhibitor indicated for the adjuvant treatment of postmenopausal women with hormone receptor-positive (HR+) early breast cancer. It is also indicated for the first-line treatment of postmenopausal women with HR-positive or HR-unknown locally advanced or metastatic breast cancer. Additionally, it is used to treat advanced breast cancer in postmenopausal women whose disease has progressed following tamoxifen therapy. It is important to note that patients with ER-negative disease or those who failed to respond to initial tamoxifen therapy rarely show a response to Arimidex.
How ARIMIDEX Works
Anastrozole is a selective non-steroidal aromatase inhibitor. In postmenopausal women, estrogen is primarily produced through the conversion of adrenal androgens (androstenedione and testosterone) into estrone and estradiol by the aromatase enzyme in peripheral tissues. Anastrozole inhibits this enzyme, thereby suppressing estrogen biosynthesis and reducing the hormonal stimulus for breast cancer growth. It significantly lowers serum estradiol concentrations without affecting the production of adrenal corticosteroids or aldosterone.
Development Insights
Eli Lilly and Company conducting 9 trials (9%)
131 indications explored (Broad Platform)
→ breast cancer (38 trials)
→ breast neoplasms (11 trials)
→ metastatic breast cancer (8 trials)
7
Indications
--
Phase 3 Trials
2
Priority Reviews
30
Years on Market
Details
- Status
- Prescription
- First Approved
- 1995-12-27
- Routes
- ORAL
- Dosage Forms
- TABLET
ARIMIDEX Approval History
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Original
New Indication
New Form
Label Update
24 FDA actions from 1995 to 2024 · 5 indication expansions
May 2006 SUPPL
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Sep 2001 SUPPL
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Aug 1998 SUPPL
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Feb 1998 SUPPL
Label
Sep 1997 SUPPL
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Oct 1996 SUPPL
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Dec 1995 ORIGINAL
New Drug
What ARIMIDEX Treats
1 indicationsARIMIDEX is approved for 1 conditions since its original approval in 1995. These indications span multiple therapeutic areas including oncology, immunology, and more.
- Breast Cancer
Source: FDA Label
ARIMIDEX Competitive Set
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Direct competitors
3
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Indication competitors
10
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What's emerging in ARIMIDEX's indications
See all emerging drugs →Phase 3 candidates targeting molecules with no FDA-approved drug, in indications ARIMIDEX treats. First-in-class if their pivotal trials read out positive.
Drugs Similar to ARIMIDEX
3 of 20FDA-approved drugs for similar conditions. Compare mechanisms and indications to understand treatment alternatives.
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Clinical Trial Registry
105 trials| Trial | Sponsor ID | Phase | Status | Title |
|---|---|---|---|---|
| NCT07391774 | NCI-2026-00634 NCI-2026-00634, EA1242 | Ph 3 | not yet recruiting | Testing Whether Hormone Therapy With Ribociclib is as Effective as Chemotherapy Followed by Hormone Therapy With Ribociclib for the Treatment of High Anatomic Stage Breast Cancer With Low Recurrence Risk, The RxFINE-Low Trial |
| NCT05586802 KLIN-HEALTH | PZ00P3_202151 | Ph 3 | recruiting | Sex Steroids Balance for Metabolic and Reproductive Health in Klinefelter Syndrome |
| NCT06671912 LoTam | A012301 NCI-2024-06672 | Ph 3 | suspended | Testing Low Dose Tamoxifen for Invasive Breast Cancer, the (LoTam) Trial |
| NCT05774951 CAMBRIA-1 | D8531C00002 2022-501024-20-00 | Ph 3 | recruiting | A Study of Camizestrant in ER+/HER2- Early Breast Cancer After at Least 2 Years of Standard Adjuvant Endocrine Therapy |
| NCT03179904 results posted | MC1633 W81XWH-16-1-0269, W81XWH-16-1-0268 | Ph 2 | active not recruiting | TVB-2640 and Trastuzumab With Paclitaxel or Endocrine Therapy for Treatment of HER2 Positive Metastatic Breast Cancer |
| NCT02942355 | IRB00081369 00017766, LCI-BRE-H2N-ANPA-001 | Ph 2 | active not recruiting | Trial of Anastrozole and Palbociclib in Metastatic HER2-Negative Breast Cancer |
| NCT01272037 results posted | NCI-2011-02623 NCI-2011-02623, S12-03603 | Ph 3 | active not recruiting | Tamoxifen Citrate, Letrozole, Anastrozole, or Exemestane With or Without Chemotherapy in Treating Patients With Invasive RxPONDER Breast Cancer |
| NCT05501704 | 22-225 | Ph 2 | recruiting | ETHAN - ET for Male BC |
| NCT07174336 | 27726 J6M-MC-JSGD, 2025-522791-92-00 | Ph 3 | recruiting | A Study of Tersolisib (LY4064809/STX-478) With Other Anti-Cancer Treatments in Participants With Advanced Breast Cancer With a Genetic Change (PIK3CA) |
| NCT06492616 ELEGANT | STML-ELA-0422 2024-515445-42-00 | Ph 3 | recruiting | A Study of Elacestrant Versus Standard Endocrine Therapy in Women and Men With ER+,HER2-, Early Breast Cancer With High Risk of Recurrence |
| NCT05768139 PIKALO-1 | 27691 2023-504807-94-00, 2023-000442-41 | Ph 1, Ph 2 | recruiting | First-in-Human Study of Tersolisib (STX-478) as Monotherapy and in Combination With Other Antineoplastic Agents in Participants With Advanced Solid Tumors |
| NCT04964934 SERENA-6 | D8534C00001 2023-503990-39-00, 2021-000546-17 | Ph 3 | active not recruiting | Phase III Study to Assess AZD9833+ CDK4/6 Inhibitor in HR+/HER2-MBC With Detectable ESR1m Before Progression (SERENA-6) |
| NCT06179303 | RG1122019 NCI-2022-06409, FHIRB0020029 | Ph 2 | recruiting | Functional Imaging in Prediction of Response to Abemaciclib for Advanced Hormone Receptor-Positive, HER2-Negative Breast Cancer |
| NCT01553903 OXYTAM | 11 SEIN 09 | Ph 4 | completed | Feasibility Study for the Determination of Oxysterols in Patients With Breast Cancer Receiving Hormonal Therapy With Tamoxifen or Not |
| NCT06380751 EvoPAR-BR01 | D9722C00001 | Ph 3 | recruiting | Saruparib (AZD5305) Plus Camizestrant Compared With CDK4/6 Inhibitor Plus Endocrine Therapy or Plus Camizestrant in HR-Positive, HER2-Negative (IHC 0, 1+, 2+/ ISH Non-amplified), BRCA1, BRCA2, or PALB2m Advanced Breast Cancer |
| NCT05837455 | 202305007 | Ph 2 | recruiting | NeoTAILOR: ABiomarker-directed Approach to Guide Neoadjuvant Therapy for Patients With Stage II/III ER-positive, HER2-negative Breast Cancer |
| NCT05467891 RaPhLRR | HCRN BRE20-468 | Ph 2 | recruiting | Ribociclib And Endocrine Treatment of Physician's Choice for Locoregional Recurrent, Resected Hormone Receptor Positive HER2 Negative Breast Cancer |
| NCT06072781 RAMP 301 | VS-6766-301 GOG-3097, ENGOT-ov81 | Ph 3 | recruiting | A Study of Avutometinib (VS-6766) + Defactinib (VS-6063) in Recurrent Low-Grade Serous Ovarian Cancer |
| NCT05514054 EMBER-4 | 18459 J2J-MC-JZLH, 2022-501007-28 | Ph 3 | active not recruiting | A Study of Imlunestrant Versus Standard Endocrine Therapy in Participants With Early Breast Cancer |
| NCT05161195 | CLEE011A2412B 2024-514891-41-00 | Ph 4 | active not recruiting | Roll-over Study to Allow Continued Access to Ribociclib |
| NCT00893061 MNEMOSYNE | MNEMOSYNE-0712 2008-003620-32 | Ph 3 | completed | Letrozole, Anastrozole, Exemestane, or Tamoxifen Citrate in Treating Postmenopausal Women With Breast Cancer |
| NCT06016738 OPERA-01 | OP-1250-301 OPERA-01 | Ph 3 | recruiting | OP-1250 (Palazestrant) vs. Standard of Care for the Treatment of ER+/HER2- Advanced Breast Cancer |
| NCT05524584 | 1459 UCI 19-145 | Ph 2 | recruiting | Anastrazole, Fulvestrant & Abemaciclib for HR+HER2- Metastatic Breast Cancer |
| NCT04059484 AMEERA-3 results posted | ACT16105 U1111-1217-2774, 2018-004593-98 | Ph 2 | terminated | Phase 2 Study of Amcenestrant (SAR439859) Versus Physician's Choice in Locally Advanced or Metastatic ER-positive Breast Cancer |
| NCT05896566 PREcoopERA | IBCSG 67-22 | Ph 2 | completed | A Window-of-Opportunity Trial of Giredestrant +/- Triptorelin vs. Anastrozole + Triptorelin in Premenopausal Patients With ER-positive/HER2-negative Early Breast Cancer |
| NCT02947685 PATINA results posted | AFT-38 | Ph 3 | active not recruiting | Randomized, Open Label, Clinical Study of the Targeted Therapy, Palbociclib, to Treat Metastatic Breast Cancer |
| NCT01674140 e3 results posted | S1207 S1207, U10CA032102 | Ph 3 | active not recruiting | S1207 Hormone Therapy With or Without Everolimus in Treating Patients With Breast Cancer |
| NCT02763566 MONARCH plus results posted | 15530 I3Y-CR-JPBQ | Ph 3 | active not recruiting | A Study of Abemaciclib (LY2835219) in Participants With Breast Cancer |
| NCT02246621 MONARCH 3 results posted | 15417 I3Y-MC-JPBM, 2014-001502-18 | Ph 3 | active not recruiting | A Study of Nonsteroidal Aromatase Inhibitors Plus Abemaciclib (LY2835219) in Postmenopausal Women With Breast Cancer |
| NCT02057133 | 15252 I3Y-MC-JPBH | Ph 1 | active not recruiting | A Study of LY2835219 (Abemaciclib) in Combination With Therapies for Breast Cancer That Has Spread |
| NCT02779751 | 16177 I3Y-MC-JPCE, 2015-005156-94 | Ph 1 | active not recruiting | A Study of Abemaciclib (LY2835219) in Participants With Non-Small Cell Lung Cancer or Breast Cancer |
| NCT01953588 | A011106 NCI-2013-01340, U10CA031946 | Ph 3 | active not recruiting | Fulvestrant and/or Anastrozole in Treating Postmenopausal Patients With Stage II-III Breast Cancer Undergoing Surgery |
| NCT06001762 | 23-355 | Ph 2 | active not recruiting | TRADE: Dose Escalation Tolerability of Abemaciclib in HR+ HER2- Early Stage Breast Cancer |
| NCT04556773 DB-08 | D967JC00002 2023-505690-33-00, 2020-002797-27 | Ph 1 | active not recruiting | A Phase 1b Study of T-DXd Combinations in HER2-low Advanced or Metastatic Breast Cancer |
| NCT01723774 results posted | 201301106 | Ph 2 | active not recruiting | PD 0332991 and Anastrozole for Stage 2 or 3 Estrogen Receptor Positive and HER2 Negative Breast Cancer |
| NCT04553770 | 20-001275 NCI-2020-06086 | Ph 2 | recruiting | Trastuzumab Deruxtecan Alone or in Combination With Anastrozole for the Treatment of Early Stage HER2 Low, Hormone Receptor Positive Breast Cancer |
| NCT03822468 AMALEE results posted | CLEE011A2207 2018-004234-15 | Ph 2 | completed | Study of 2 Ribociclib Doses in Combination With Aromatase Inhibitors in Women With HR+, HER2- Advanced Breast Cancer |
| NCT04711252 SERENA-4 | D8532C00001 2020-002276-12 | Ph 3 | active not recruiting | A Comparative Study of AZD9833 Plus Palbociclib Versus Anastrozole Plus Palbociclib in Patients With ER-Positive HER2 Negative Breast Cancer Who Have Not Received Any Systemic Treatment for Advanced Disease |
| NCT06086704 | 2023-1114 Protocol Version 7/30/2024, SMPH/RADIOLOGY/RADIOLOGY | Ph 2 | recruiting | Study of 18F-FFNP Breast PET/MRI |
| NCT05549505 results posted | ARV-471-BC-201 C4891025 | Ph 2 | completed | A Trial Using ARV-471 or Anastrozole in Post-Menopausal Women With Breast Cancer Prior to Surgery |
| NCT04469764 | 20-000769 NCI-2020-04544 | Ph 2 | recruiting | Abemaciclib for the Treatment of Recurrent Ovarian or Endometrial Cancer |
| NCT02476786 | 201611010 | Ph 2 | recruiting | Endocrine Treatment Alone for Elderly Patients With Estrogen Receptor Positive Operable Breast Cancer and Low Recurrence Score |
| NCT06253702 | 2023-0548 1R01HL150361-01, EDUC/KINESIOLOGY | Ph 4 | completed | Brain Blood Flow Responses to Stress: Sex Differences |
| NCT03304080 | GCO 17-0919 | Ph 1, Ph 2 | active not recruiting | Anastrozole, Palbociclib, Trastuzumab and Pertuzumab in HR-positive, HER2-positive Metastatic Breast |
| NCT03099174 results posted | 1280.18 2016-003142-85 | Ph 1 | completed | This Study in Patients With Different Types of Cancer (Solid Tumours) Aims to Find a Safe Dose of Xentuzumab in Combination With Abemaciclib With or Without Hormonal Therapies. The Study Also Tests How Effective These Medicines Are in Patients With Lung and Breast Cancer |
| NCT05952557 CAMBRIA-2 | D8535C00001 2023-504031-41-00 | Ph 3 | recruiting | An Adjuvant Endocrine-based Therapy Study of Camizestrant (AZD9833) in ER+/HER2- Early Breast Cancer (CAMBRIA-2) |
| NCT03554044 | 17753 NCI-2018-00652 | Ph 1 | completed | T-VEC With Chemotherapy or Endocrine Therapy in Treating Participants With HER2- Negative Breast Cancer |
| NCT06957379 | HB1901-005 | Ph 2 | active not recruiting | Sirolimus for Injection (Albumin-bound) in Combination With Endocrine Therapy for HR+/HER2- Advanced/Metastatic Breast Cancer Patients Who Have Failed Standard Therapy |
| NCT03219476 results posted | PRO30178 | Ph 2 | completed | Neoadjuvant Endocrine Therapy in Hormone Receptor-Positive, Human Epidermal Growth Factor Receptor 2 (HER2)-Negative Node-Negative Breast Cancer |
| NCT06223698 SWE-Switch | 280050 | Ph 3 | not yet recruiting | Optimizing Extended Adjuvant Endocrine Therapy in Patients With Breast Cancer |
Showing 50 of 105 trials
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Pro Key Completed Trials
Completed studies with published results, ranked by significance
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Trial Timeline
Full development history with FDA approval milestones
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Understanding FDA Approval Types
| Count | Type | What it means |
|---|---|---|
| - | ORIG | Original approval - drug first enters market |
| - | SUPPL - Efficacy | New indication (new disease/condition approved) |
| - | SUPPL - Labeling | Label text changes (warnings, dosing updates) |
| - | SUPPL - Manufacturing | Production changes (new facility) |
| - | SUPPL - Chemistry | Formulation changes (new dosage strength) |
Green lines in the timeline show ORIG and Efficacy approvals - the clinically meaningful milestones.
ARIMIDEX FDA Label Details
Indications & Usage
FDA Label (PDF)ARIMIDEX is indicated for the treatment of Breast Cancer.
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Data Sources
Data sourced from official FDA and NIH databases. Click links to verify on original sources.
How We Calculate These Metrics
Trial Activity Stage
Measures the current development activity pattern based on trial phases, status, and trends. Important: This measures R&D activity, not commercial lifecycle.
Trial statuses: "Active" means recruiting or ongoing. "Completed" means reached planned endpoint. "Terminated" means stopped early—often due to safety, efficacy, or business reasons.
- Growth: High proportion of early-phase trials (Phase 1/2), active development
- Expansion: Significant Phase 3 activity, approaching or pursuing approvals
- Mature: Substantial Phase 4 post-marketing studies
- Stable: Mixed phase distribution, steady development
- Declining: Low active trial ratio, reduced R&D investment