THIOGUANINE Drug Patent Profile

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

Thioguanine is a drug marketed by Waylis Therap and is included in one NDA.

The generic ingredient in THIOGUANINE is thioguanine. One supplier is listed for this compound. Additional details are available on the thioguanine profile page.

DrugPatentWatch^® Litigation and Generic Entry Outlook for Thioguanine

A generic version of THIOGUANINE was approved as thioguanine by WAYLIS THERAP on December 31^st, 1969.

Summary for THIOGUANINE

US Patents:	0
Applicants:	1
NDAs:	1

US Patents and Regulatory Information for THIOGUANINE

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Exclusivity Expiration
Waylis Therap	THIOGUANINE	thioguanine	TABLET;ORAL	012429-001	Approved Prior to Jan 1, 1982		RX	Yes	Yes

Thioguanine Investment and Fundamentals Analysis

Last updated: February 19, 2026

Thioguanine, an antimetabolite purine analog, presents a complex investment profile driven by its established role in specific hematological malignancies, evolving treatment landscapes, and the patent expiry of key formulations. Its efficacy in acute myeloid leukemia (AML) and chronic myeloid leukemia (CML) remains a cornerstone, but competition from newer targeted therapies and the inherent toxicity profile necessitate careful consideration.

What is the Current Status of Thioguanine Approvals and Indications?

Thioguanine, historically known by brand names such as Tabloid and Lanvis, is approved for the treatment of acute myeloid leukemia (AML) and chronic myeloid leukemia (CML). Its mechanism of action involves interfering with DNA and RNA synthesis, thereby inhibiting the proliferation of cancer cells.

• Acute Myeloid Leukemia (AML): Thioguanine is indicated as part of induction and consolidation therapy for AML, often in combination with other chemotherapeutic agents. It targets the rapid proliferation of myeloid blast cells.
• Chronic Myeloid Leukemia (CML): While historically used for CML, its role has diminished with the advent of tyrosine kinase inhibitors (TKIs). However, it may still be considered in specific refractory or intolerant patient populations.

The regulatory landscape for thioguanine is mature, with long-standing approvals from agencies like the U.S. Food and Drug Administration (FDA) and the European Medicines Agency (EMA). Generic versions are widely available.

What is the Patent Landscape for Thioguanine?

The original patents covering the synthesis and initial therapeutic uses of thioguanine have long expired. This means the molecule itself is off-patent, allowing for generic manufacturing and distribution. However, nuances exist in patent protection:

• Composition of Matter Patents: Expired.
• Formulation Patents: Specific formulations or delivery systems developed after the initial patent expiry may have had limited periods of protection. However, these are also largely expired or nearing expiry for established formulations.
• Method of Use Patents: Patents claiming new uses or combination therapies involving thioguanine could have offered protection, but these are less common for a drug of thioguanine's age and would have specific expiry dates.

Key observation: The primary hurdle for new market entrants is not patent infringement of the active pharmaceutical ingredient (API) but rather demonstrating bioequivalence for generic formulations and navigating regulatory approval pathways. The lack of proprietary patent protection on the core molecule limits opportunities for novel IP-driven development.

How Does Thioguanine Compare to Emerging Therapies?

The therapeutic landscape for AML and CML has been significantly reshaped by targeted therapies, particularly tyrosine kinase inhibitors (TKIs) for CML and BCL-2 inhibitors, FLT3 inhibitors, and IDH inhibitors for AML.

Comparison Table: Thioguanine vs. Emerging Therapies

Feature	Thioguanine	Emerging Therapies (e.g., TKIs, BCL-2 Inhibitors)
Mechanism	Antimetabolite (purine analog), inhibits DNA/RNA synthesis	Targeted molecular inhibition (e.g., BCR-ABL kinase, BCL-2 protein, FLT3, IDH1/2)
Indications	AML, historically CML	CML (primary), specific AML subtypes (e.g., FLT3-mutated, IDH-mutated)
Efficacy	Established, but variable response rates	High efficacy in specific molecular subtypes, improved survival rates
Toxicity Profile	Myelosuppression, gastrointestinal, hepatic toxicity	Drug-specific toxicities (e.g., cardiovascular, metabolic, cytopenias)
Development Status	Generic, off-patent API	Patented novel molecules, ongoing clinical trials
Market Share	Declining in CML, persistent in specific AML regimens	Dominant in CML, growing in AML for targeted subsets
Cost	Low (generic)	High (branded, often associated with high R&D costs)

Analysis: Thioguanine’s primary advantage is its low cost, making it a viable option in resource-limited settings or as a component of combination therapy where cost-effectiveness is paramount. However, for patients with specific molecular targets in AML or CML, emerging therapies offer superior efficacy and potentially better tolerability, leading to a shift in treatment paradigms.

What is the Market Size and Growth Potential for Thioguanine?

The global market for thioguanine is relatively small and likely experiencing a decline, particularly in developed markets, due to the reasons outlined above.

• Declining Demand in CML: The dominance of TKIs like imatinib, dasatinib, nilotinib, and bosutinib has significantly reduced the use of older cytotoxic agents for CML.
• Niche Role in AML: While still used, its application in AML is often as part of older chemotherapy regimens or in specific patient populations not amenable to targeted therapies. The development of novel AML treatments is rapidly expanding.
• Generic Competition: The market is highly competitive with multiple generic manufacturers, driving down prices and limiting the profit margins for any single entity.

Market Size Estimation Challenges: Quantifying the precise market size is difficult due to:

• Fragmented Generic Market: Data aggregation across numerous generic suppliers globally is complex.
• Limited Public Reporting: Specific revenue figures for individual generic thioguanine products are not typically disclosed by manufacturers.
• Regional Variability: Demand may be more sustained in regions with lower access to expensive targeted therapies.

Growth Outlook: Negative to flat. The long-term growth potential for thioguanine as a standalone therapy is limited. Opportunities may exist in:

• Emerging Markets: Where cost is a significant factor.
• Combination Therapies: If new research demonstrates synergistic benefits with novel agents, though this is speculative.
• Specific Orphan Indications: If new, small patient populations are identified where thioguanine proves uniquely effective and cost-efficient.

What are the Manufacturing and Supply Chain Considerations?

The manufacturing of thioguanine involves standard chemical synthesis processes for small molecules.

• API Production: The active pharmaceutical ingredient (API) is produced by multiple chemical manufacturers globally, primarily in Asia.
• Formulation and Packaging: Finished dosage forms (tablets) are manufactured and packaged by pharmaceutical companies, many of whom are generic specialists.
• Regulatory Compliance: Manufacturers must adhere to Good Manufacturing Practices (GMP) standards set by regulatory bodies like the FDA and EMA. This includes quality control, impurity profiling, and stability testing.
• Supply Chain Stability: Given the mature nature of the drug and multiple suppliers, the supply chain is generally considered stable. However, localized disruptions (e.g., raw material shortages, geopolitical issues affecting shipping) can occur, as with any pharmaceutical product.

Key Considerations for Investors/Manufacturers:

• Cost of Goods Sold (COGS): High competition in the generic market puts significant pressure on COGS. Efficiency in API synthesis and formulation is crucial.
• Quality Assurance: Maintaining high-quality standards is non-negotiable to avoid regulatory action and ensure patient safety.
• Regulatory Hurdles: Navigating FDA/EMA requirements for generic approval, including bioequivalence studies, is a standard but critical process.

What are the Risks and Opportunities for Thioguanine?

Risks:

• Therapeutic Obsolescence: Replacement by more effective and targeted therapies for AML and CML is the most significant risk.
• Toxicity: The inherent toxicity profile can limit its use, especially in frail patients or when competing with better-tolerated novel agents.
• Pricing Pressure: Intense generic competition leads to low profit margins.
• Evolving Treatment Guidelines: Clinical practice guidelines continue to be updated, often favoring newer agents.
• Limited R&D Pipeline: There is minimal ongoing research and development for novel applications or improved formulations of thioguanine due to its off-patent status and established alternatives.

Opportunities:

• Cost-Effective Treatment Option: In regions with limited healthcare budgets or for specific patient populations where cost is a primary driver.
• Combination Therapy Research: Potential for synergistic effects when combined with newer agents, although this would require significant investment in clinical trials with uncertain outcomes.
• Generic Market Entry (New Entrants): For companies with strong API sourcing and generic formulation capabilities, the established market offers a pathway, albeit with low margins.
• Supply Chain Security: For countries or regions seeking to ensure a reliable supply of essential chemotherapy drugs, domestic or regional manufacturing of thioguanine could be a strategic consideration.

Key Takeaways

Thioguanine is a mature, off-patent antimetabolite with established indications in AML and historically CML. Its market position is characterized by declining demand in developed markets, driven by the superior efficacy and targeted mechanisms of newer therapies. Generic competition exerts intense pricing pressure, resulting in low profit margins. Opportunities are largely confined to cost-sensitive markets, potential niche combination therapy roles, or for generic manufacturers with efficient supply chains. The overall investment outlook is characterized by low growth and high competition, with risks dominated by therapeutic obsolescence.

Frequently Asked Questions

1. Is thioguanine still a first-line treatment for any leukemia? Thioguanine is generally not considered a first-line treatment for CML due to the effectiveness of TKIs. For AML, it may be part of induction regimens, but newer targeted agents and immunotherapies are increasingly prioritized as first-line options for specific AML subtypes.

2. What are the most common side effects of thioguanine? Common side effects include myelosuppression (low blood cell counts leading to increased risk of infection, bleeding, and anemia), nausea, vomiting, diarrhea, and liver toxicity.

3. Can thioguanine be used in pediatric oncology? Yes, thioguanine has been used in pediatric oncology for certain types of leukemia, often as part of multi-agent chemotherapy protocols. Its specific role and efficacy in pediatric populations are subject to ongoing clinical evaluation and treatment guidelines.

4. What is the typical dosage of thioguanine? Dosage is highly individualized based on the patient's condition, other therapies, and tolerance. For AML, typical induction doses might range from 100-200 mg per day for adults, often adjusted based on bone marrow response and toxicity. Precise dosing is determined by an oncologist.

5. Are there any new patents being filed for thioguanine? Given the drug's age and off-patent status, new patents are unlikely to cover the molecule itself or its primary uses. Any patent filings would likely relate to novel delivery mechanisms, specific combination therapies, or manufacturing process improvements, which are less common for such an established agent.

Citations

[1] U.S. Food and Drug Administration. (n.d.). Drug Approval Packages. Retrieved from https://www.fda.gov/drugs/new-drugs-fda-cders-new-molecular-entities-and-new-drug-applications/drug-approval-packages (Note: Specific package information for thioguanine would be sought here, but the link represents the type of source) [2] European Medicines Agency. (n.d.). European Public Assessment Reports (EPARs). Retrieved from https://www.ema.europa.eu/en/medicines/human/assessment-reports (Note: Similar to FDA, specific EPAR for thioguanine would be located via search) [3] National Cancer Institute. (n.d.). Leukemia. Retrieved from https://www.cancer.gov/types/leukemia (General oncology information relevant to indications) [4] National Comprehensive Cancer Network. (n.d.). Clinical Practice Guidelines in Oncology. Retrieved from https://www.nccn.org/guidelines/category/1 (Note: NCCN guidelines are proprietary, but represent the source for treatment standard information)