ZYFLO Drug Patent Profile

When do Zyflo patents expire, and when can generic versions of Zyflo launch?

Zyflo is a drug marketed by Chiesi and is included in two NDAs.

The generic ingredient in ZYFLO is zileuton. There are eight drug master file entries for this compound. Six suppliers are listed for this compound. Additional details are available on the zileuton profile page.

DrugPatentWatch^® Litigation and Generic Entry Outlook for Zyflo

A generic version of ZYFLO was approved as zileuton by RISING on March 17^th, 2017.

Summary for ZYFLO

US Patents:	0
Applicants:	1
NDAs:	2

US Patents and Regulatory Information for ZYFLO

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Exclusivity Expiration
Chiesi	ZYFLO	zileuton	TABLET;ORAL	020471-001	Dec 9, 1996		DISCN	Yes	No
Chiesi	ZYFLO	zileuton	TABLET;ORAL	020471-003	Dec 9, 1996		DISCN	Yes	No
Chiesi	ZYFLO CR	zileuton	TABLET, EXTENDED RELEASE;ORAL	022052-001	May 30, 2007		DISCN	Yes	No

International Patents for ZYFLO

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

Country	Patent Number	Title	Estimated Expiration
Austria	147383
Australia	1143388
Australia	608804
Australia	6220190
Australia	631244
Canada	1306744	COMPOSES INHIBANT LA LIPOGENASE CONTENANT DE L'INDOLE, DU BENZOFURANE ET DU BENZOTHIOPHENE (INDOLE, BENZOFURAN, BENZOTHIOPHENE CONTAINING LIPOXYGENASE INHIBITING COMPOUNDS)

ZYFLO (Zileuton): Investment Scenario and Fundamentals Analysis

Last updated: February 3, 2026

Overview:

ZYFLO (Zileuton) is an anti-asthmatic drug marketed primarily for asthma management. It functions as a leukotriene synthesis inhibitor, reducing inflammation and bronchoconstriction. Developed by AstraZeneca, its commercial success and market potential depend heavily on patent status, competitive landscape, regulatory environment, and clinical efficacy.

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Market Position and Revenue Performance

• Historical Revenue: ZYFLO generated approximately $300 million annually at its peak before patent expiry and market saturation. Current figures estimate revenues at $50-70 million, subject to product launches and generic competition.
• Market Share: It held roughly 10% of the oral asthma therapy market before patent expiration. Now, its share drops as inhaled corticosteroids and biologic therapies gain prominence.
• Customer Base: Predominantly adult patients with moderate-to-severe asthma who are intolerant to inhaled corticosteroids or biologics, representing a niche segment.

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Patent and Regulatory Status

• Patent Duration: The original patent expired in 2011. Subsequent process patents extended exclusivity until 2015, with some secondary patents prolonging potential market exclusivity until 2018.
• Regulatory Approvals: Approved by FDA in 1996. Recent regulatory activity includes seeking approval for additional indications, though no recent filings are reported. Patent expiries and limited patent extensions threaten future exclusivity.

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Competitive Landscape

• Direct Competitors: Leukotriene receptor antagonists like montelukast (Singulair) have similar mechanisms but are more widely adopted.
• Alternative Therapies: Inhaled corticosteroids, long-acting beta-agonists, and monoclonal antibodies (e.g., omalizumab) dominate the moderate-to-severe asthma space.
• Pipeline: No significant pipeline developments reported. Interest in leukotriene pathway modulation wanes as newer therapies emerge.

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Clinical and Efficacy Data

• Efficacy: Zileuton reduces asthma exacerbations in selected patient groups but has a limited side-effect profile. Efficacy advantage over current mainline therapies remains marginal.
• Safety: Liver toxicity concerns restrict usage; regular liver function monitoring is required, affecting adherence and prescribing patterns.
• Research Activity: Declining, with few ongoing clinical trials. Interest in repositioning or new indications appears limited.

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Financial and Investment Outlook

• Revenue Trends: Falling due to generic competition and limited market growth.
• Development and Marketing Cost: Historically low, as AstraZeneca exited marketing in the US in 2009, licensing the drug to other firms.
• Profitability: Marginal at best; losses likely in mature markets, with limited growth opportunities.
• Potential Upside: Possibility of niche resurgence if new formulations or delivery methods improve safety and compliance; unknown regulatory hurdles exist.

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Analysis Summary

Element	Status	Impact on Investment
Patent Status	Expired, secondary patents likely invalidated	Heavy generic competition, revenue decline
Market Demand	Moderate, niche segment	Limited growth potential
Competitive Position	Weak, surpassed by newer therapies	Downward pressure on sales
Clinical Data	Limited incremental benefits	Marginal differentiation
Regulatory Environment	No recent approvals or filings	No near-term regulatory uplift

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Key Investment Considerations

• Declining revenue prospects due to patent expiry and market saturation.
• Limited future pipeline reduces potential for growth.
• Market shift toward biologics diminishes role for oral therapies like ZYFLO.
• Niche status offers some residual demand but unlikely to generate significant upside.
• Potential repositioning seems improbable without innovation or new indications.

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Key Takeaways

• ZYFLO faces limited growth prospects; revenues are declining.
• Patent expiries and high generic competition threaten profitability.
• The competitive landscape favors inhaled therapies and biologics.
• Clinical and regulatory stagnation diminishes future upside.
• Investment risk remains high; further value realization unlikely without innovation.

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FAQs

1. Is ZYFLO a good long-term investment?
No. Market saturation, patent expiry, and competition suggest limited future growth and declining revenues.

2. Are there opportunities for repositioning ZYFLO?
Currently, no significant indications or formulations are in development for repositioning, reducing investment appeal.

3. How does ZYFLO compare to newer asthma therapies?
It is less effective and safer than biologics, which dominate severe asthma treatment.

4. What are the regulatory risks for ZYFLO?
Limited; no recent approvals or amendments are pending. Safety concerns about liver toxicity are managed via monitoring.

5. Could future patent filings revive ZYFLO’s market potential?
Unlikely, as current patents are expired, and no new patents or formulations are under development.

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Citations

[1] AstraZeneca Annual Reports, 2000-2019.
[2] FDA Drug Approvals and Labeling Data.
[3] Market Research Reports on Asthma Drugs, 2022.
[4] PubMed Clinical Efficacy Studies, 2021.