ARIMIDEX Drug Patent Profile

Which patents cover Arimidex, and what generic alternatives are available?

Arimidex is a drug marketed by Ani Pharms and is included in one NDA.

The generic ingredient in ARIMIDEX is anastrozole. There are twenty-four drug master file entries for this compound. Twenty-four suppliers are listed for this compound. Additional details are available on the anastrozole profile page.

DrugPatentWatch^® Litigation and Generic Entry Outlook for Arimidex

A generic version of ARIMIDEX was approved as anastrozole by ACCORD HLTHCARE on June 28^th, 2010.

Summary for ARIMIDEX

US Patents:	0
Applicants:	1
NDAs:	1
Finished Product Suppliers / Packagers:	1
Raw Ingredient (Bulk) Api Vendors:	86
Clinical Trials:	152
Patent Applications:	5,009
Drug Prices:	Drug price information for ARIMIDEX
What excipients (inactive ingredients) are in ARIMIDEX?	ARIMIDEX excipients list
DailyMed Link:	ARIMIDEX at DailyMed

See drug prices for ARIMIDEX

Recent Clinical Trials for ARIMIDEX

Identify potential brand extensions & 505(b)(2) entrants

Sponsor	Phase
University of Washington	Phase 2
Breast Cancer Research Foundation	Phase 2
Verastem, Inc.	Phase 3

See all ARIMIDEX clinical trials

Pharmacology for ARIMIDEX

Drug Class	Aromatase Inhibitor
Mechanism of Action	Aromatase Inhibitors

US Patents and Regulatory Information for ARIMIDEX

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Exclusivity Expiration
Ani Pharms	ARIMIDEX	anastrozole	TABLET;ORAL	020541-001	Dec 27, 1995	AB	RX	Yes	Yes

Expired US Patents for ARIMIDEX

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	Patent No.	Patent Expiration
Ani Pharms	ARIMIDEX	anastrozole	TABLET;ORAL	020541-001	Dec 27, 1995
Ani Pharms	ARIMIDEX	anastrozole	TABLET;ORAL	020541-001	Dec 27, 1995

International Patents for ARIMIDEX

See the table below for patents covering ARIMIDEX around the world.

Country	Patent Number	Title	Estimated Expiration
Israel	86499
Hong Kong	1000206
New Zealand	225037	SUBSTITUTED HETEROCYCLIC DERIVATIVES AND PHARMACEUTICAL COMPOSITIONS
Denmark	330488
South Africa	8803691
Portugal	87720	PROCESSO PARA A PREPARACAO DE COMPOSTOS HETEROCICLICOS SUBSTITUIDOS POR ARALQUILO E DE COMPOSICOES FARMACEUTICAS QUE OS CONTEM
Austria	113277

Supplementary Protection Certificates for ARIMIDEX

Patent Number	Supplementary Protection Certificate	SPC Country	SPC Expiration	SPC Description
0296749	97C0023	France		PRODUCT NAME: ANASTROZOLE, EVENTUELLEMENT SOUS LA FORME D UN SEL D ADDITION ACCEPTABLE EN MEDECINE PHARMACEUTIQUE; NAT REG. NO/DATE: NL 21126 19961227; FIRST REG.: 12619/0106 19950811
0296749	97C0032	Belgium		PRODUCT NAME: ANASTROZOLUM; NAT. REGISTRATION NO/DATE: 624 IS 94 F 3 19961216; FIRST REGISTRATION: GB 12619/0106 19950811
0296749	C970012	Netherlands		PRODUCT NAME: ANASSTROZOLUM, DESGEWENST IN DE VORM VAN EEN FARMACEUTISCH AANVAARDBAAR ZUURADDITIEZOUT; NAT. REGISTRATION NO/DATE: RVG 19123 19960905; FIRST REGISTRATION: GB 12619/0106 19950811
0296749	09C0055	France		PRODUCT NAME: ANASTROZOLE, EVENTUELLEMENT SOUS LA FORME D’UN SEL D’ADDITION ACCEPTABLE EN MEDECINE PHARMACEUTIQUE; REGISTRATION NO/DATE IN FRANCE: NL 21126 DU 19961227; REGISTRATION NO/DATE AT EEC: 12619/0106 DU 19950811
0296749	SPC/GB96/004	United Kingdom		PRODUCT NAME: ANASTROZOLE OPTIONALLY IN THE FORM OF A PHARMACEUTICALLY ACCEPTABLE ACID ADDITION SALT; REGISTRATION NO/DATE: UK 12619/0106 19950811

ARIMIDEX Market Dynamics and Financial Trajectory

Last updated: February 19, 2026

This report analyzes the market dynamics and financial trajectory of Arimidex (anastrozole), focusing on its patent status, competitive landscape, and sales performance.

What is Arimidex and its Primary Indications?

Arimidex is a non-steroidal aromatase inhibitor developed by AstraZeneca. Its primary indication is the treatment of hormone receptor-positive breast cancer in postmenopausal women. It functions by reducing the amount of estrogen produced by the body, which can slow or stop the growth of hormone-sensitive breast cancers.

The active pharmaceutical ingredient is anastrozole. Arimidex is available in tablet form, typically 1 mg.

What is the Patent Status of Arimidex?

Arimidex has been subject to patent expirations, leading to generic competition.

• Original Patents: Key patents protecting Arimidex have expired in major markets, including the United States and Europe. For example, the primary U.S. patent expired in 2007. [1]
• Exclusivity Periods: While patent protection has lapsed, various exclusivity periods, such as market exclusivity for new indications or pediatric exclusivity, may have provided temporary market protection. However, these have also largely concluded.
• Generic Entry: The expiration of patents allowed the entry of generic versions of anastrozole. This has significantly impacted the pricing and market share of branded Arimidex.

How Has Generic Competition Affected Arimidex Sales?

The introduction of generic anastrozole has led to a substantial decline in the market share and revenue of branded Arimidex.

• Price Erosion: Generic versions are typically priced significantly lower than the originator brand, driving down overall market value for the drug class.
• Market Share Shift: Prescriptions have increasingly shifted from branded Arimidex to lower-cost generic alternatives.
• AstraZeneca's Revenue Impact: AstraZeneca has experienced declining revenues for Arimidex as a result of generic competition. In 2010, for instance, Arimidex global sales were reported at $1.34 billion, a decrease of 12% compared to the previous year, primarily attributed to generic erosion in the U.S. [2] By 2014, AstraZeneca's disclosed sales for Arimidex were significantly lower, reflecting the ongoing impact of generics. [3]

What is the Current Competitive Landscape for Anastrozole?

The market for anastrozole is characterized by the presence of multiple generic manufacturers.

• Key Generic Players: Major pharmaceutical companies and generic manufacturers produce and market generic anastrozole. Examples include Teva Pharmaceuticals, Mylan (now Viatris), Accord Healthcare, and various others globally.
• Product Differentiation: Differentiation in the generic market is primarily based on price, availability, and distribution networks rather than product innovation.
• Therapeutic Equivalence: Generic anastrozole products are approved by regulatory agencies (e.g., FDA in the U.S.) based on demonstrating bioequivalence and therapeutic equivalence to branded Arimidex.

What are the Sales Trends for Branded Arimidex?

Sales of branded Arimidex have shown a consistent downward trend post-patent expiration and generic entry.

• Historical Peak Sales: Arimidex achieved peak annual sales prior to widespread genericization. Precise figures for peak global sales are difficult to pinpoint without access to AstraZeneca's historical detailed segment reporting but were in the range of over $1 billion annually during its exclusivity period.
• Post-Generic Decline:
  • 2010: Global sales were $1.34 billion, down 12% year-over-year. [2]
  • 2011: Global sales declined further. [4]
  • 2014: AstraZeneca reported $342 million in sales for Arimidex. [3]
  • 2020: Global sales for Arimidex (including generics and branded in markets where it still holds a share) were significantly lower than its peak, with branded Arimidex contributing a smaller fraction. Specific branded Arimidex sales figures for recent years are not prominently disclosed by AstraZeneca due to its mature and genericized status.
• Geographic Variations: Sales trends have varied by region, with earlier generic entry in some markets leading to faster revenue declines compared to others where branded Arimidex might have retained a niche market share for a longer period.

What are the Market Size and Growth Projections for Anastrozole (Including Generics)?

Estimating the exact market size for branded Arimidex is challenging due to its generic nature. However, the broader anastrozole market (including generics) is substantial, driven by the prevalence of hormone receptor-positive breast cancer.

• Global Market Value: The global market for aromatase inhibitors, including anastrozole, is estimated to be several billion dollars annually. While specific forecasts for anastrozole alone are variable, its widespread use in breast cancer treatment underpins a significant market.
• Growth Drivers:
  • Increasing incidence of breast cancer globally.
  • Aging populations, which are at higher risk for breast cancer.
  • Improved diagnostic rates leading to earlier detection.
  • Established treatment protocols recommending aromatase inhibitors as first-line therapy for postmenopausal women with hormone-positive breast cancer.
• Market Restraints:
  • Price pressure from generic competition.
  • Development of new breast cancer therapies, though aromatase inhibitors remain a cornerstone of treatment.
  • Potential side effects that may limit patient adherence or necessitate alternative treatments.
• Projected Growth: The anastrozole market is expected to experience moderate growth, driven by the factors mentioned above. Growth rates are typically in the low to mid-single digits annually for mature drug classes like anastrozole, largely influenced by volume rather than significant price increases. [5]

What is the Future Outlook for Arimidex (Branded)?

The future outlook for branded Arimidex is characterized by its continued position as a mature, genericized product.

• Limited Growth Potential: Branded Arimidex is unlikely to see significant growth. Its primary role is now in markets where physician or patient preference for the original brand persists, or in regions with slower generic adoption.
• Strategic Importance: For AstraZeneca, Arimidex has transitioned from a blockbuster drug to a legacy product. Its contribution to overall revenue is minimal compared to newer pipeline assets. The company's focus has shifted to new oncology treatments.
• Market Saturation: The anastrozole market is largely saturated with generic alternatives, making it difficult for the branded product to regain significant market share.
• Continued Use: Anastrozole, as a molecule, will continue to be a widely prescribed treatment for breast cancer, with the vast majority of prescriptions filled by generic versions due to cost-effectiveness.

Key Takeaways

• Arimidex (anastrozole) patents have expired, leading to widespread generic competition.
• Generic entry has caused significant price erosion and a decline in branded Arimidex sales, from over $1 billion annually to hundreds of millions.
• The anastrozole market is highly competitive, with numerous generic manufacturers.
• The overall anastrozole market (including generics) is substantial and projected for moderate growth, driven by breast cancer incidence and aging populations.
• The future for branded Arimidex is as a mature, legacy product with limited growth prospects, while the anastrozole molecule remains a critical treatment option, predominantly supplied by generic alternatives.

Frequently Asked Questions

1. What is the mechanism of action for anastrozole? Anastrozole is a selective, non-steroidal aromatase inhibitor that reduces circulating estrogen levels by blocking the conversion of androgens to estrogens in peripheral tissues.

2. Are there any new indications for Arimidex being explored? While anastrozole has been extensively studied, significant new indications for branded Arimidex are unlikely given its mature lifecycle and the availability of generic alternatives. Research may continue on related molecules or in combination therapies.

3. What are the common side effects associated with anastrozole therapy? Common side effects include hot flashes, joint pain (arthralgia), headache, fatigue, and mood changes. More serious potential side effects include bone loss (osteoporosis) and cardiovascular events.

4. How does the efficacy of generic anastrozole compare to branded Arimidex? Generic anastrozole products are required to be bioequivalent and therapeutically equivalent to branded Arimidex, meaning they are expected to have the same efficacy and safety profile.

5. What is AstraZeneca's current portfolio strategy regarding oncology drugs? AstraZeneca's oncology strategy has largely shifted towards developing and launching novel therapies with new mechanisms of action, including targeted therapies and immunotherapies, rather than focusing on mature, genericized brands like Arimidex.

Citations

[1] U.S. Food & Drug Administration. (n.d.). Orange Book: Approved Drug Products with Therapeutic Equivalence Evaluations. Retrieved from [FDA Orange Book Database] (Note: Specific patent expiration dates are searchable within the database and vary by specific patent. General expiration for core patents occurred around 2007.)

[2] AstraZeneca. (2011). AstraZeneca Annual Report and Form 20-F 2010. [Link to AstraZeneca Investor Relations/Annual Reports]

[3] AstraZeneca. (2015). AstraZeneca Annual Report and Form 20-F 2014. [Link to AstraZeneca Investor Relations/Annual Reports]

[4] AstraZeneca. (2012). AstraZeneca Annual Report and Form 20-F 2011. [Link to AstraZeneca Investor Relations/Annual Reports]

[5] Global Market Insights. (2023). Aromatase Inhibitors Market Size, Share & COVID-19 Impact Analysis, By Product (Anastrozole, Letrozole, Exemestane), By Application (Breast Cancer, Others), By Distribution Channel (Hospital Pharmacies, Retail Pharmacies, Online Pharmacies), By Region, and Forecasts, 2023 – 2032. (Note: Specific market data requires subscription access to such reports.)