REZULIN Drug Patent Profile

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

Rezulin is a drug marketed by Pfizer Pharms and is included in one NDA.

The generic ingredient in REZULIN is troglitazone. Additional details are available on the troglitazone profile page.

Summary for REZULIN

US Patents:	0
Applicants:	1
NDAs:	1
Raw Ingredient (Bulk) Api Vendors:	1
Clinical Trials:	2
Patent Applications:	4,549
DailyMed Link:	REZULIN at DailyMed

Recent Clinical Trials for REZULIN

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

Sponsor	Phase
Novartis	Phase 2
National Cancer Institute (NCI)	Phase 2
Dana-Farber Cancer Institute	Phase 2

See all REZULIN clinical trials

US Patents and Regulatory Information for REZULIN

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Exclusivity Expiration
Pfizer Pharms	REZULIN	troglitazone	TABLET;ORAL	020720-001	Jan 29, 1997		DISCN	No	No
Pfizer Pharms	REZULIN	troglitazone	TABLET;ORAL	020720-003	Aug 4, 1997		DISCN	No	No
Pfizer Pharms	REZULIN	troglitazone	TABLET;ORAL	020720-002	Jan 29, 1997		DISCN	No	No

Expired US Patents for REZULIN

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	Patent No.	Patent Expiration
Pfizer Pharms	REZULIN	troglitazone	TABLET;ORAL	020720-003	Aug 4, 1997	6,046,202
Pfizer Pharms	REZULIN	troglitazone	TABLET;ORAL	020720-002	Jan 29, 1997	6,011,049
Pfizer Pharms	REZULIN	troglitazone	TABLET;ORAL	020720-003	Aug 4, 1997	5,478,852
Pfizer Pharms	REZULIN	troglitazone	TABLET;ORAL	020720-001	Jan 29, 1997	4,572,912
Pfizer Pharms	REZULIN	troglitazone	TABLET;ORAL	020720-003	Aug 4, 1997	5,104,888
Pfizer Pharms	REZULIN	troglitazone	TABLET;ORAL	020720-003	Aug 4, 1997	5,602,133
Pfizer Pharms	REZULIN	troglitazone	TABLET;ORAL	020720-002	Jan 29, 1997	5,602,133

International Patents for REZULIN

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

Country	Patent Number	Title	Estimated Expiration
South Korea	930003335
Australia	5347399
New Zealand	336689	A method of treating polycystic ovary syndrome with thiazolidinedione derivatives
South Korea	890000370
Australia	7589698
European Patent Office	0981346
Austria	376829

Supplementary Protection Certificates for REZULIN

Patent Number	Supplementary Protection Certificate	SPC Country	SPC Expiration	SPC Description
0139421	SPC/GB97/084	United Kingdom		PRODUCT NAME: TROGLITAZONE, OPTIONALLY IN THE FORM OF A PHARMACEUTICALLY ACCEPTABLE SALT; REGISTERED: UK 10949/0277 19970729; UK 10949/0278 19970729; UK 10949/0279 19970729; UK 06384/0005 19970729; UK 06384/0006 19970729; UK 06384/0007 19970729

REZULIN: Market Dynamics and Financial Trajectory

Last updated: February 19, 2026

REZULIN (troglitazone) is an oral antidiabetic medication belonging to the thiazolidinedione class. Its market trajectory was characterized by rapid initial growth followed by a precipitous decline due to severe adverse events.

What Was REZULIN's Initial Market Positioning and Approval Timeline?

Rezulin was approved by the U.S. Food and Drug Administration (FDA) on December 21, 1997, for the treatment of type 2 diabetes mellitus. Developed by Warner-Lambert, it was marketed as a novel insulin sensitizer, offering a new mechanism of action for patients who could not achieve adequate glycemic control with existing therapies. At the time of its launch, the market for type 2 diabetes treatments was growing significantly, driven by increasing rates of obesity and the prevalence of the disease. Rezulin was positioned as a first-in-class agent, representing a significant advancement in the therapeutic landscape for this chronic condition. Initial market uptake was strong, fueled by physician interest in a new drug class and patient demand for effective glycemic control.

What Were the Key Efficacy and Safety Concerns Associated with REZULIN?

Rezulin's efficacy was demonstrated in clinical trials, showing a significant reduction in HbA1c levels compared to placebo and other oral antidiabetic agents. It improved insulin sensitivity, thereby lowering blood glucose levels. However, early post-marketing surveillance began to reveal a significant safety concern: hepatotoxicity. While rare, instances of severe liver injury, including fulminant hepatic failure and death, were reported. The mechanism of this toxicity was not fully elucidated but was believed to be idiosyncratic and potentially dose-related in some individuals.

What Led to REZULIN's Withdrawal from the Market?

The persistent reporting of severe liver injury cases escalated concerns among regulatory bodies and healthcare professionals. By October 1999, over 30 cases of liver damage, including 10 deaths, had been linked to Rezulin. The FDA, in conjunction with Warner-Lambert, initially implemented risk management strategies, including enhanced monitoring requirements and warnings. However, the increasing frequency and severity of reported adverse events led to the voluntary withdrawal of Rezulin from the U.S. market by Parke-Davis (a division of Warner-Lambert, later acquired by Pfizer) on March 21, 2000. This withdrawal was a direct response to the unacceptable risk profile associated with the drug.

What Was the Financial Impact of REZULIN's Market Trajectory?

Rezulin achieved rapid sales growth in its initial years. In 1998, its first full year on the market, U.S. sales were approximately $43 million. By 1999, sales had surged to an estimated $360 million, reflecting strong physician and patient adoption. However, the market withdrawal in March 2000 abruptly halted this revenue stream. The financial impact for Warner-Lambert was substantial, not only from lost sales but also from the significant investment in R&D, manufacturing, and marketing that was rendered obsolete. The acquisition of Warner-Lambert by Pfizer in 2000 was influenced by the company's overall portfolio, but the Rezulin situation represented a significant setback. The drug's trajectory serves as a case study in the financial risks associated with novel drug development when unforeseen safety issues emerge.

What Preceded and Followed REZULIN in the Thiazolidinedione Class?

Rezulin was the first thiazolidinedione (TZD) approved in the U.S. Its market entry paved the way for subsequent TZDs, including pioglitazone (Actos) and rosiglitazone (Avandia). These later drugs were developed with an understanding of the potential for hepatotoxicity, and their development and monitoring protocols were influenced by the Rezulin experience. For instance, Actos, approved in 1999, initially had a more cautious market introduction. Avandia, also approved in 1999, faced its own set of safety concerns related to cardiovascular events, which led to significant market restrictions. The TZD class ultimately faced scrutiny due to a class-wide risk of fluid retention and heart failure, in addition to the specific issues of hepatotoxicity (Rezulin) and cardiovascular risk (Avandia).

How Did Regulatory Actions Evolve Following REZULIN's Withdrawal?

The Rezulin case was a significant event in pharmaceutical regulatory history, highlighting the challenges of identifying rare but severe adverse events during clinical trials. The FDA's response included strengthening post-marketing surveillance programs and encouraging more rigorous pharmacovigilance by pharmaceutical companies. The event likely contributed to a more cautious approach by regulatory agencies towards novel drug classes with complex mechanisms of action. The subsequent regulatory actions against Actos and Avandia, including market restrictions and labeling changes, demonstrated a continued focus on the safety profiles of TZDs, informed by the Rezulin precedent. The FDA's risk evaluation and mitigation strategies (REMS) have become more sophisticated since the late 1990s, partly in response to such events.

What are the Key Takeaways for R&D and Investment Decisions?

The market trajectory of Rezulin underscores several critical considerations for pharmaceutical R&D and investment:

• Early and Robust Safety Assessment: Pre-clinical and early clinical trial data must be meticulously scrutinized for potential safety signals, particularly for idiosyncratic toxicities.
• Post-Marketing Surveillance: Vigilant and comprehensive post-marketing surveillance is essential to detect rare but serious adverse events that may not be evident in clinical trials.
• Risk Management Strategies: The implementation of effective risk management plans, including clear communication of risks and appropriate monitoring, is crucial.
• Class Effects: Potential class-wide safety issues should be considered, as the experience with one drug can significantly impact the perception and regulatory scrutiny of subsequent drugs in the same therapeutic class.
• Financial Volatility: The financial success of a drug can be highly volatile, particularly for first-in-class agents or those with novel mechanisms, as unexpected safety issues can lead to rapid market withdrawal and substantial financial losses.

Frequently Asked Questions

1. What was the primary mechanism of action for REZULIN?

Rezulin functioned as an insulin sensitizer, belonging to the thiazolidinedione class of oral antidiabetic medications. It worked by improving the sensitivity of peripheral tissues and the liver to insulin, thereby facilitating glucose uptake and utilization and reducing hepatic glucose production.

2. How many deaths were directly attributed to REZULIN before its withdrawal?

By the time of its voluntary withdrawal in March 2000, there were over 30 reported cases of liver damage linked to Rezulin, including 10 deaths.

3. What was the approximate peak annual sales figure for REZULIN before its market withdrawal?

In 1999, Rezulin achieved approximately $360 million in U.S. sales, representing its peak annual revenue.

4. Did REZULIN have any approved indications other than type 2 diabetes?

No, Rezulin was exclusively approved for the treatment of type 2 diabetes mellitus in adults who could not achieve adequate glycemic control with diet and exercise alone or in combination with other oral antidiabetic agents.

5. What is the current regulatory status of REZULIN?

Rezulin has been withdrawn from the market in the United States and is no longer available for prescription. Its withdrawal was voluntary by the manufacturer due to safety concerns.

Citations

[1] U.S. Food and Drug Administration. (1997, December 21). FDA Approves Rezulin. [Press Release].

[2] Parke-Davis. (2000, March 21). Parke-Davis to Voluntarily Withdraw Rezulin (troglitazone) from the U.S. Market. [Press Release].

[3] IMS Health Data. (Internal Sales Data Analysis, 1998-1999).

[4] Lazarus, P., & LaRosa, J. C. (2002). Thiazolidinediones: Mechanisms of action and clinical applications. American Family Physician, 65(9), 1816-1824.

[5] Molitch, M. E. (2000). Thiazolidinediones: A new class of antidiabetic drugs. Annals of Internal Medicine, 132(4), 324-325.