United States Patent 5,480,656: Scope, Claims, Expiration, and Leuprolide Depot Patent Landscape

U.S. Patent No. 5,480,656 protects a narrowly defined leuprolide microcapsule and manufacturing process. The claims require a specific water-in-oil microencapsulation process, a lactic-acid homopolymer with tightly controlled molecular-weight properties, a defined leuprolide loading range, and sustained zero-order release for at least two months. The patent issued on January 2, 1996, and its conventional U.S. patent term expired on January 2, 2013. It therefore does not presently block a generic manufacturer, although later patents, regulatory exclusivities, manufacturing know-how, and formulation differences may remain relevant.

What drug does U.S. Patent 5,480,656 protect?

U.S. Patent 5,480,656 covers a depot microcapsule containing leuprolide, also known as leuprorelin.

The claimed peptide is:

(pyr)Glu-His-Trp-Ser-Tyr-D-Leu-Leu-Arg-ProNHC2H5

This is leuprolide, a gonadotropin-releasing hormone agonist. In commercial products, the active ingredient is generally supplied as leuprolide acetate.

Leuprolide depot products are administered by injection and are used in hormone-dependent conditions, including prostate cancer, endometriosis, uterine fibroids, and central precocious puberty. Lupron Depot is the principal commercial product historically associated with long-acting leuprolide microsphere technology [2].

What are the key patent facts for U.S. Patent 5,480,656?

Field	Information
U.S. patent number	5,480,656
Title	Microcapsule exhibiting zero order release
Grant date	January 2, 1996
Patent type	Utility patent
Active pharmaceutical ingredient	Leuprolide
Dosage technology	Injectable sustained-release microcapsule
Polymer	Homopolymer of lactic acid
Core process	Water-in-oil emulsion followed by microencapsulation
Required release profile	Zero-order release for at least two months
Earliest claim-specific loading range	35% to 60% w/w leuprolide in the inner aqueous phase
Polymer molecular-weight range	Weight-average molecular weight of 14,100 to 18,200
Polymer dispersion degree	1.5 to 2.5
Claim 3 polymer concentration	2% to 60% by weight in the oil phase
Conventional expiration	January 2, 2013
Current blocking effect	Expired

The patent is a pre-Uruguay Round patent for which the conventional 17-year term from grant applies. The relevant expiration date is therefore January 2, 2013, absent a term adjustment or other recorded modification. The patent is no longer an enforceable U.S. exclusion right based on ordinary expiration [1].

What does claim 1 of U.S. Patent 5,480,656 cover?

Claim 1 is a combination claim. A competing product must satisfy all material limitations to fall within its literal scope.

The claim requires:

A microcapsule containing leuprolide.
Zero-order release for at least two months upon administration.
Production from a water-in-oil emulsion.
An inner aqueous phase free from a drug-retaining substance.
The inner aqueous phase containing 35% to 60% w/w leuprolide.
An oil phase containing a homopolymer of lactic acid.
The polymer having a weight-average molecular weight of 14,100 to 18,200.
A dispersion degree, defined as weight-average molecular weight divided by number-average molecular weight, of 1.5 to 2.5.
Microencapsulation of the emulsion to form the outer wall of the microcapsule.

The claim does not cover every leuprolide depot injection, every biodegradable microsphere, or every formulation using polylactic acid. It is directed to the intersection of active ingredient, release behavior, emulsion process, composition, and polymer specifications.

What does “zero-order release” mean in the claim?

Zero-order release generally means that the drug is released at an approximately constant rate over the relevant period. The claim requires this performance after administration, rather than merely requiring a theoretical polymer composition.

This functional limitation can create an infringement dispute over:

The acceptable deviation from a constant release rate.
The testing method used to measure release.
Whether release must be measured in vitro, in vivo, or both.
The meaning of “for a period of at least two months.”
Whether the claimed result must be present in every batch or only in representative product testing.

Because the patent has expired, these construction issues have historical and freedom-to-operate significance rather than current enforcement significance.

How do claims 2 and 3 narrow the patent scope?

Claim 2: Three-month release

Claim 2 depends on claim 1 and requires zero-order release for at least three months rather than two months.

It therefore covers a narrower subset of the products within claim 1. A product releasing leuprolide for three months may satisfy both claims if all other limitations are present. A two-month product would not satisfy claim 2 solely because it meets claim 1.

The claim is particularly relevant to three-month leuprolide depot products, but duration alone does not establish coverage. The polymer, loading, emulsion, and molecular-weight limitations also must be met.

Claim 3: Polymer concentration in the oil phase

Claim 3 depends on claim 1 and requires a homopolymer concentration of 2% to 60% by weight in the oil phase.

This limitation narrows the claim to formulations within the specified concentration range. It does not independently cover any polymer concentration in that range. The product must first meet every limitation of claim 1.

What formulations are protected by U.S. Patent 5,480,656?

The protected formulation concept has four defining technical components:

Technical feature	Claim requirement	Commercial significance
Drug	Leuprolide peptide	Limits the claim to a specific GnRH agonist
Inner phase	Aqueous phase without a drug-retaining substance	Excludes formulations using certain retention agents
Outer wall	Homopolymer of lactic acid	Focuses on polylactic-acid microspheres
Release profile	Zero-order release for at least two or three months	Targets long-acting depot delivery

The patent does not expressly claim:

Leuprolide acetate as a salt in every formulation.
A particular injection dose, such as 3.75 mg, 11.25 mg, or 30 mg.
A particular particle-size distribution.
A specific syringe, needle, reconstitution system, or administration device.
Every biodegradable polymer, including poly(lactic-co-glycolic acid).
Every three-month leuprolide formulation.
The leuprolide molecule itself.
A broad method of treating prostate cancer or endometriosis.

The absence of a drug-retaining substance in the inner aqueous phase is a meaningful limitation. A formulation using gelatin, albumin, polyvinyl alcohol, or another retention material could raise a noninfringement position if the material falls within the technical meaning of a drug-retaining substance. That issue would depend on the formulation record and claim construction.

How strong is the patent estate for leuprolide depot products?

The patent was technically narrow but commercially important during its term. Its strength came from the combination of formulation and process limitations rather than broad compound coverage.

Strengths

It targeted the long-acting microcapsule architecture used for depot leuprolide delivery.
It specified a relatively narrow polymer molecular-weight window.
It claimed a defined molecular-weight distribution.
It tied the formulation to a clinically relevant two- or three-month release period.
It could have been difficult to design around while preserving the same release characteristics and manufacturing process.

Weaknesses

The patent did not cover leuprolide as a chemical entity.
The claim required multiple limitations to be present simultaneously.
Alternative polymers could avoid the literal homopolymer limitation.
A different emulsion process could avoid the process limitation.
A formulation using a different inner-phase composition could create a noninfringement position.
The patent expired in 2013.

The estate was therefore strongest as a product-specific formulation barrier during the patent term. It was not a durable, molecule-level exclusivity right.

When did U.S. Patent 5,480,656 lose exclusivity?

The patent expired on January 2, 2013, based on the 17-year term from its January 2, 1996, grant date [1].

After expiration:

The claims cannot support a new U.S. patent infringement action for post-expiration conduct.
A generic applicant does not need a Paragraph IV certification against this patent if the patent is expired.
The patent may remain relevant as prior art against later patent applications.
The patent may remain relevant to technical due diligence, historical litigation, and manufacturing comparisons.
The patent cannot independently prevent a competing leuprolide depot launch.

Any later patent family member, continuation, divisional, or separate patent must be evaluated independently. Expiration of U.S. Patent 5,480,656 does not automatically eliminate rights under later patents covering alternative formulations, manufacturing steps, delivery devices, or methods of use.

What is the Orange Book status of U.S. Patent 5,480,656?

The Orange Book lists patents and exclusivity information associated with approved drug products. A patent’s historical association with a product does not preserve enforceability after the patent expires.

For leuprolide depot products, the relevant regulatory analysis must distinguish:

The original listed drug.
Different dosing strengths and administration intervals.
Product-specific formulation patents.
Device or reconstitution patents.
Method-of-use patents.
Expired patents.
Current patents, if any, listed for the specific reference product [3].

U.S. Patent 5,480,656 should be treated as expired for current Orange Book and ANDA strategy. A Paragraph IV challenge directed solely to this patent would have no practical value after expiration. A generic applicant would instead focus on any unexpired patents listed for the relevant reference product and on the regulatory requirements for demonstrating pharmaceutical equivalence and bioequivalence.

Which companies are relevant to the leuprolide depot patent landscape?

Takeda and originator technology

The patent is associated with Takeda-originated microcapsule technology. Takeda developed and patented long-acting peptide delivery systems, including formulations relevant to leuprolide.

TAP Pharmaceuticals and Abbott

Lupron Depot was commercialized in the United States through TAP Pharmaceuticals, historically a joint venture involving Takeda and Abbott Laboratories. Abbott later became part of AbbVie. Commercial rights, product ownership, and patent ownership should not be assumed to be identical for every patent or time period.

AbbVie

AbbVie is the successor to Abbott’s pharmaceutical business and has been associated with Lupron products in the United States. Its commercial position relates to the approved product, brand, manufacturing network, regulatory approvals, and any surviving intellectual property, not merely to the expired ’656 patent [2].

Generic manufacturers

Potential generic competition may come from companies pursuing leuprolide acetate injectable depot products through the ANDA pathway. The principal technical barrier is likely to be reproducible long-acting microsphere manufacture, not the expired ’656 patent itself.

What generic entry risks exist after expiration?

The expiration of U.S. Patent 5,480,656 removes one direct patent barrier but does not guarantee immediate generic substitution.

A generic applicant still must address:

Active ingredient identity and salt form.
Dosage strength.
Microsphere composition.
Particle-size distribution.
Reconstitution behavior.
Injection-site performance.
Release profile.
Drug-device compatibility.
Sterility and container-closure requirements.
Bioequivalence or other FDA-requested comparative data.
Manufacturing process validation.

For complex injectable microspheres, FDA may scrutinize product sameness more closely than for a conventional oral tablet. Small changes in polymer molecular weight, residual solvent, particle morphology, porosity, or drug distribution can alter release kinetics.

Are biosimilars relevant?

Biosimilar risk is generally not the correct framework for leuprolide. Leuprolide is a synthetic peptide drug, not a therapeutic protein typically regulated through the biosimilar pathway under section 351(k) of the Public Health Service Act.

Competitive products would generally be assessed under the small-molecule drug framework, including an ANDA where the product qualifies as a generic equivalent, or through an alternative NDA pathway where the product differs materially from the reference product [4].

What manufacturing and IP barriers remain after patent expiration?

The main post-expiration barriers are technical and regulatory.

Manufacturing barriers

A manufacturer must control:

Water-in-oil emulsion formation.
Droplet and microsphere size.
Polymer molecular-weight distribution.
Drug loading.
Residual solvent.
Encapsulation efficiency.
Burst release.
Long-term release kinetics.
Sterility and aseptic processing.
Reconstitution and injectability.

The expired patent discloses a specific operating window, but reproducing the commercial product may require additional unpublished process controls and scale-up knowledge.

Intellectual-property barriers

Later patents may cover:

Alternative biodegradable polymers.
Poly(lactic-co-glycolic acid) systems.
Specific particle structures.
Improved release profiles.
Reconstitution formulations.
Injection devices.
Manufacturing and drying processes.
New indications or dosing schedules.
Combination products.

A freedom-to-operate review must therefore search the entire U.S. family and later assignee portfolios, not only the claims of U.S. Patent 5,480,656.

What litigation and Paragraph IV issues affect this patent?

No current Paragraph IV risk arises from U.S. Patent 5,480,656 because it expired in 2013. Historical litigation or settlement activity concerning Lupron, leuprolide depot products, or related microsphere patents must be separated from the present legal status of the ’656 patent.

A complete litigation review should examine:

Federal district court cases naming the patent number.
Federal Circuit appeals.
Inter partes or post-grant proceedings, if any.
ANDA notices containing Paragraph IV certifications.
Settlement agreements involving leuprolide depot products.
Patent-listing changes in the Orange Book.
Later patents asserted against generic applicants.

The expired status of the patent means any historical settlement provision tied solely to the ’656 patent would not create a new patent term. Contractual provisions could have separate legal effects, but those would depend on the agreement and parties.

How does U.S. Patent 5,480,656 compare with broader leuprolide patent rights?

Patent category	Typical scope	Status relative to ’656
Compound patent	Leuprolide molecule or analog	Broader chemically, generally expired earlier
Depot formulation patent	Microsphere composition and release profile	Closest technical category
Process patent	Emulsion, encapsulation, drying, or particle control	May create separate manufacturing risk
Device patent	Syringe, reconstitution, or delivery system	Separate product and launch analysis
Method-of-use patent	Treatment of a specific disease or patient group	May affect labeling and induced-infringement analysis
Regulatory exclusivity	FDA market protection	Independent of patent expiration
Trade secrets	Scale-up and process controls	Potentially relevant after patent expiry

The ’656 patent should be classified as a formulation-process patent with a narrow product-performance limitation. It is not a foundational leuprolide compound patent.

Key Takeaways

U.S. Patent 5,480,656 covers a leuprolide microcapsule with zero-order release for at least two months.
Claim 2 narrows the release period to at least three months.
Claim 3 adds a 2% to 60% polymer concentration requirement in the oil phase.
Claim 1 requires a water-in-oil emulsion, an inner aqueous phase without a drug-retaining substance, 35% to 60% w/w leuprolide, and a lactic-acid homopolymer with specified molecular-weight parameters.
The patent issued January 2, 1996, and expired January 2, 2013.
It no longer independently blocks generic leuprolide depot entry in the United States.
Biosimilar analysis is generally not applicable; generic-drug and complex-injectable requirements are more relevant.
Remaining risk may arise from later formulation, manufacturing, device, method-of-use, or regulatory rights.
The principal post-expiration barrier is reproducible microsphere manufacturing and FDA approval, not the expired claims of the ’656 patent.

FAQs

Does U.S. Patent 5,480,656 cover Lupron Depot?

It covers a specific leuprolide microcapsule technology that is technically relevant to Lupron Depot-type products. It does not cover every Lupron product or every leuprolide injection.

Can a generic manufacturer launch after the ’656 patent expired?

Yes, the expired patent alone does not prevent launch. The manufacturer must still address any unexpired patents, FDA requirements, formulation equivalence, manufacturing validation, and product-specific regulatory obligations.

Does the patent cover poly(lactic-co-glycolic acid)?

The claims provided require a homopolymer of lactic acid. Poly(lactic-co-glycolic acid) is a copolymer and would not satisfy that limitation literally, although other patents may cover PLGA-based leuprolide microspheres.

Is leuprolide subject to biosimilar competition?

Leuprolide is generally evaluated as a synthetic peptide drug rather than through the biosimilar pathway used for qualifying biologics. The relevant competitive pathway is usually an ANDA or, depending on product differences, an NDA.

Does expiration of the ’656 patent eliminate all leuprolide depot patent risk?

No. It eliminates the direct blocking effect of that patent. Later patents covering alternative formulations, manufacturing methods, devices, dosing regimens, or methods of use may remain relevant.

References

United States Patent and Trademark Office. (1996). U.S. Patent No. 5,480,656, Microcapsule exhibiting zero order release. U.S. Department of Commerce.
U.S. Food and Drug Administration. (n.d.). Lupron Depot: Leuprolide acetate prescribing information. FDA.
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations. FDA, Center for Drug Evaluation and Research.
U.S. Food and Drug Administration. (n.d.). Abbreviated new drug application and generic drug approval process. FDA, Center for Drug Evaluation and Research.

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
Japan	2-033133	Feb 13, 1990

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	123413	⤷ Start Trial
Australia	645108	⤷ Start Trial
Australia	8179491	⤷ Start Trial
Brazil	9103553	⤷ Start Trial
Canada	2036089	⤷ Start Trial
Canada	2316159	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 5,480,656

Summary for Patent: 5,480,656