IMURAN Drug Patent Profile

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

Imuran is a drug marketed by Casper Pharma Llc and Legacy Pharma and is included in two NDAs.

The generic ingredient in IMURAN is azathioprine. There are sixteen drug master file entries for this compound. Seventeen suppliers are listed for this compound. Additional details are available on the azathioprine profile page.

DrugPatentWatch^® Litigation and Generic Entry Outlook for Imuran

A generic version of IMURAN was approved as azathioprine by AMNEAL on February 16^th, 1996.

Summary for IMURAN

US Patents:	0
Applicants:	2
NDAs:	2

US Patents and Regulatory Information for IMURAN

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Exclusivity Expiration
Casper Pharma Llc	IMURAN	azathioprine sodium	INJECTABLE;INJECTION	017391-001	Approved Prior to Jan 1, 1982		DISCN	Yes	No
Legacy Pharma	IMURAN	azathioprine	TABLET;ORAL	016324-002	Approved Prior to Jan 1, 1982		DISCN	Yes	No
Legacy Pharma	IMURAN	azathioprine	TABLET;ORAL	016324-001	Approved Prior to Jan 1, 1982	AB	RX	Yes	Yes

IMURAN (azathioprine) investment scenario and fundamentals analysis for 2026 investors

Last updated: July 23, 2026

IMURAN is a legacy small-molecule immunosuppressant (azathioprine) with a mature global market, limited near-term patent-driven upside in the US, and a competitive pricing structure driven by long-standing generic availability in most geographies. For investors, the central question is not “can new patent exclusivity create major revenue tailwinds,” but whether any specific route can be monetized: switching to higher-value distribution models, capturing share in underpenetrated markets, or leveraging formulation/line-extension IP where it still exists (usually outside the US).

Azathioprine’s investment fundamentals are dominated by (1) declining elasticity and price compression once generics are established, (2) clinical standard-of-care embeddedness in transplant and autoimmune indications, and (3) sensitivity to payer behavior, drug shortages, and supply-chain stability. In the absence of a strong, still-active primary patent wall in major markets, revenue durability typically depends on execution rather than product-level monopoly dynamics.

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What is Imuran azathioprine and where does it make money in 2026?

Drug identity

• Brand: IMURAN
• Active ingredient: azathioprine
• Class: antimetabolite immunosuppressant (purine analog prodrug; converted to 6-thioguanine nucleotides)

Core indication buckets where azathioprine is used

• Solid organ transplantation immunosuppression (typically in combination regimens)
• Autoimmune disease immunosuppression (classically inflammatory bowel disease and other immune-mediated disorders, depending on guideline and country reimbursement norms)

Commercial drivers that matter for an investment case

• Usage is guideline-anchored, so demand is less speculative than in trend-driven markets, but it is still subject to switching to alternatives (mycophenolate, methotrexate, biologics depending on indication and payer).
• Formulary access is the main determinant of volume in mature markets. Once generics dominate reimbursement, brand differentiation rarely supports premium pricing.
• Safety management workflows (TPMT testing patterns, monitoring programs) can influence prescribing and adherence, affecting real-world persistence.

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What is the patent and exclusivity status of IMURAN (azathioprine) in the US?

High-level view Azathioprine is an old molecule with broad generic penetration. For US investment underwriting, the actionable point is that brand IMURAN has no meaningful remaining small-molecule composition-of-matter exclusivity. Any residual patent value would most likely come from:

• specific formulations,
• manufacturing methods,
• packaging or label-related exclusivity,
• or method-of-use patents in narrow settings.

Orange Book relevance (what drives licensing or generic entry risk) The US regulatory-lifecycle logic is:

• If azathioprine products are fully generic and widely substituted, then FDA Orange Book-listed exclusivities/patents are not a barrier to most competitors.
• If a specific strength or dosage form still has “active” Orange Book patents, that is where a brand owner can block Paragraph IV filers. For azathioprine, this barrier is generally weak because of long generics history.

Investment implication

• Treat IMURAN like a mature commodity-to-low-differentiation asset in the US unless a specific, current Orange Book barrier exists for a particular formulation/strength you are underwriting.

(Per operating constraints, no Orange Book table is provided because no reliable, drug-product-specific Orange Book snapshot for IMURAN can be produced here.)

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When does IMURAN lose exclusivity and what does that mean for generic launch risk?

For a molecule this old, “exclusivity loss” has typically already occurred in major markets. The investor question shifts from “timeline” to:

• incremental competitive threat (price erosion rate, settlement dynamics, and supply capacity), and
• whether you can maintain share once lower-cost SKUs widen.

Generic entry risk framework for mature immunosuppressants

• The key risks are not patent invalidation events, but payer-driven switching windows and supply disruptions that create short-lived brand demand.
• If the company owns manufacturing slots or contract packaging, it can blunt near-term volume loss even after patent expiry.

Investment implication

• Model revenues on share + net price rather than monopoly duration.

(Per operating constraints, no specific “date-based” exclusivity timeline is included due to missing product-specific patent and exclusivity records.)

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How many patents cover azathioprine products like IMURAN and what types tend to matter?

In mature small-molecule brands, the remaining IP wall (where it exists) usually clusters into:

• formulation patents (excipients, coatings, dissolution behavior),
• manufacturing/process patents (granulation, impurity control, polymorph/solid-state handling where relevant),
• label/method-of-use patents (narrow protocols, monitoring schedules),
• and sometimes regulatory exclusivities that are not patent-based (rare for older drugs).

Investment implication

• If the patent estate does not map to a defensible, current Orange Book listing for the marketed dosage form, then licensing leverage is low and litigation optionality is limited.

(Per operating constraints, no patent-count or numbered patent estate is provided without a verifiable dataset.)

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What patent litigation affects IMURAN and how does it impact market entry?

For legacy azathioprine brands, litigation that matters is usually:

• between brand owners and generic manufacturers during late-stage Orange Book challenges, or
• around manufacturing/process patents if any were still asserted.

Investment implication

• In a mature market, litigation is more useful as a signal of remaining patent “teeth” than as a cash-flow driver itself. Without evidence of active, current disputes covering the exact marketed product/strength, the litigation tail is usually not material.

(Per operating constraints, no case list is provided because no current, product-specific litigation docket can be stated accurately.)

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How does IMURAN compare with common azathioprine competitors and alternative immunosuppressants?

Within azathioprine

• Branded IMURAN competes against generic azathioprine tablets (multiple manufacturers, aggressive price competition, pharmacy substitution, and payer preference lists).

Against alternative immunosuppressants (competitive substitution risk)

• In transplantation, alternatives can include mycophenolate-based regimens and other immunosuppressive strategies depending on clinical protocols.
• In autoimmune disease, alternatives include methotrexate and biologics depending on severity and guideline pathways.

Investment implication

• Even if patent barriers are weak, share can be defended through:
  • supply reliability,
  • low wholesale acquisition cost positioning,
  • contracted formulary placement,
  • and consistent patient support programs that reduce treatment disruption risk.

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What is the FDA regulatory status and commercial pathway for IMURAN azathioprine?

US regulatory status logic

• Azathioprine is available as approved generics under ANDA pathways historically.
• Brand IMURAN is already established as an NDA/approved branded reference product, but the economic value depends on whether brand pricing can persist after generic substitution.

Investment implication

• For underwriting, treat US regulatory status as a baseline requirement, not an upside lever. The upside lever is whether any differentiation still exists (label nuance, distribution contracts, or remaining regulatory exclusivity tied to a specific product update).

(Per operating constraints, no pathway-specific dataset is provided because it would require a reliable, product-level FDA review and labeling history not available in the prompt.)

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What formulations are protected for IMURAN, and do dosage strengths create separate IP pockets?

Why dosage strength matters

• In generics, each strength can have separate FDA listings and sometimes separate patent coverage. That can change entry timing if a specific strength is still encumbered by active patents.

Typical legacy scenario

• Most azathioprine strengths are interchangeable at the payer level and treated as a “class substitute,” reducing the economic significance of formulation micro-IP unless it is tied to a specific strength/form factor with unique coverage.

Investment implication

• The only formulation IP worth underwriting is what blocks entry on the exact marketed presentations. Without a current Orange Book mapping, the practical conclusion for IMURAN remains a mature, substituted asset.

(Per operating constraints, no formulation-by-strength patent table is included.)

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How do licensing and commercialization deals typically work for mature brands like IMURAN?

Common deal structures

• Co-promotion or distribution agreements in markets where brand recognition still supports prescriber confidence.
• Licensing of manufacturing rights to reduce COGS and ensure supply continuity.
• Contracting for brand differentiation through patient support and monitoring program integration.

Investment implication

• Licensing upside is constrained when:
  • competitors already have broad access,
  • there is no patent wall for exclusivity,
  • and price competition anchors margins.

For IMURAN, deals usually target cost and access, not monopoly profit pools.

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What are the revenue exposure and margin drivers for azathioprine brands?

Revenue exposure

• Volume is exposed to generic substitution and formulary decisions.
• Price is exposed to reference pricing, pharmacy reimbursement dynamics, and wholesaler behavior.

Margin drivers

• Cost of goods through manufacturing yield and impurity control.
• Distribution and rebate structures (especially if the drug participates in payer-negotiated arrangements).
• Supply-chain continuity affecting lost sales due to shortages.

Investment implication

• Underwrite IMURAN-like assets on operational excellence: supply stability, procurement economics, and payer contracting.

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Where can IMURAN still outperform as an investment?

Most plausible upside routes

1. Geographic share capture in markets where branded procurement still exists or generics penetration is less aggressive.
2. Lifecycle management: stable, continuous supply and product continuity that reduces discontinuations.
3. Specialty purchasing programs in transplant centers and specialty GI practices where switching friction is non-zero.

Most plausible downside routes

1. Additional generic entrants causing further net price declines.
2. Guideline substitution toward alternative immunosuppressants in priority indications.
3. Supply disruptions leading to temporary loss of patient continuity and longer-term erosion when patients move to alternatives.

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Key Takeaways

• IMURAN (azathioprine) is best analyzed as a mature, substituted immunosuppressant where pricing and access execution drive returns more than patent exclusivity.
• For 2026 investors, the principal risks are generic-led net price compression and therapeutic substitution by alternatives; the principal opportunities are share gains via formulary access and supply stability.
• Patent-driven “step-function” upside is unlikely for the core azathioprine molecule in major markets; any residual IP value would need product-specific, currently active coverage to be monetizable.

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FAQs

1) What drives net pricing for azathioprine brands after generic substitution?
Payer reimbursement benchmarks, pharmacy substitution rules, contract rebates, and wholesaler buying patterns.

2) Do TPMT and monitoring practices affect market share for azathioprine?
They can influence prescribing persistence and switching friction, which affects real-world retention even after generics enter.

3) Can a branded azathioprine product still win formularies in the US?
Yes, but economics usually require either favorable contracting or non-price differentiation such as supply reliability and patient support that reduces disruption.

4) What indications carry the highest competitive switching risk away from azathioprine?
Indications where alternative immunosuppressants or biologics have stronger efficacy-safety profiles for specific patient subgroups and where guidelines promote substitution.

5) What operational risks most affect investment returns for IMURAN-like products?
Manufacturing yield variability, impurity control, and supply interruptions that can cause longer-term loss of patient continuity.

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References (APA)

No sources were cited because no drug-product-specific FDA/Orange Book, patent, or litigation record can be verified from the provided prompt.