United States Drug Patent 5,225,205: Claim Scope, Expiration, and Peptide Depot Patent Landscape

United States Patent 5,225,205 protects controlled-release microparticles made from lactic/glycolic acid copolymer and poorly soluble salts of natural or synthetic peptides. The broadest issued claims require a specific dry-mixing, precompression, heating, extrusion, and pulverization process, or a composition produced by that process. The patent covers peptide depots, injectable suspensions, and implantable rods, with dependent claims directed to triptorelin and other peptide analogues.

The patent issued on July 6, 1993. Because it is a pre-June 8, 1995 U.S. patent, its ordinary term was 17 years from issue. The patent therefore expired on July 6, 2010, absent an unusual term adjustment or extension. No current blocking right arises from U.S. Patent 5,225,205 itself.[1]

What does United States Patent 5,225,205 protect?

The patent protects a controlled-release delivery platform with four required technical elements:

A biodegradable copolymer of lactic acid and glycolic acid, commonly referred to as PLGA.
A peptide active ingredient in a pharmaceutically acceptable, preferably water-insoluble, salt form.
Fine particle sizes before and after processing.
Thermal extrusion and pulverization that produce substantially uniform peptide dispersion throughout the polymer.

The patent is directed to depot delivery rather than immediate-release peptide formulations. Its commercial value would have depended on achieving sustained peptide release while avoiding conventional solvent-based microsphere manufacturing.

What are the broadest independent claims?

Claim	Claim type	Principal limitations	Practical scope
1	Product-by-process composition	PLGA microparticles and peptide salt microparticles; dry mixing; 0.1%-15% peptide; 85%-99.9% polymer; peptide particles below about 10 microns; polymer particles below about 200 microns; precompression, preheating, extrusion at about 80-100°C, pulverization below about 200 microns	Broad platform claim, but heavily tied to the manufacturing method
4	Controlled-release composition	PLGA at 85%-99.9%; peptide salt at 0.1%-15%; substantially uniform dispersion; dry mixing, compression, heating, extrusion, and pulverization	Broad composition claim, with process-defined structure
2	Injectable suspension	Claim 1 composition combined with a suitable carrier	Injectable product format
3	Narrow process/composition claim	Claim 1 plus specified salts, particle sizes, heating and low-temperature pulverization	Narrower manufacturing claim

Claims 1 and 4 are the commercial center of the patent. Claim 1 expressly recites a composition "obtained by a method," while claim 4 describes a composition in terms of both its composition and the process used to form the dispersion. The scope is therefore materially narrower than a claim covering any PLGA formulation containing any peptide.

How do the patent claims divide between formulation and manufacturing protection?

The patent has two overlapping protection layers.

Formulation limitations

The formulation claims require:

PLGA or a lactic/glycolic acid copolymer;
85%-99.9% polymer by weight;
0.1%-15% peptide active substance;
a natural or synthetic peptide containing 3-45 amino acids;
a pharmaceutically acceptable salt;
in several dependent claims, a water-insoluble salt;
microparticles below approximately 200 microns after pulverization.

Claim 5 narrows the copolymer to L-lactic/glycolic acid or D,L-lactic/glycolic acid having 45-90 mole percent lactic acid and 55-10 mole percent glycolic acid.

Claim 7 limits the peptide to a water-insoluble salt. Claims 8-12 identify peptide classes and specific analogues. The claim set therefore does not cover all peptide-loaded PLGA products. It requires the claimed polymer composition, peptide loading, salt form, and particle characteristics.

Manufacturing limitations

The required process includes:

dry mixing rather than solution mixing;
peptide microparticles below approximately 10 microns;
polymer microparticles below approximately 200 microns;
compression or precompression;
heating to approximately 80°C or extrusion between approximately 80°C and 100°C;
extrusion of the precompressed mixture;
pulverization, in some claims at low temperature;
collection of particles below approximately 200 microns.

These steps create potential design-around routes. A competing product using solvent evaporation, spray drying, phase separation, hot-melt processing outside the claimed temperature range, or a different particle-size profile may avoid literal infringement, subject to the doctrine of equivalents.

Which peptide products are specifically covered?

Triptorelin pamoate

Claims 10 and 11 identify the peptide sequence:

(Pyro)Glu-His-Trp-Ser-Tyr-D-Trp-Leu-Arg-Pro-Gly-NH2

This is triptorelin, a gonadotropin-releasing hormone agonist. Claim 11 narrows the formulation to triptorelin pamoate. Claims 15 and 16 add pharmacodynamic release requirements:

release for at least 25 days at a dose sufficient to reduce serum testosterone to castration levels; or
release for at least 40 days at that dose.

These claims are narrower than claims 1 and 4 because they require a specific peptide, a specific pamoate salt, and a defined in-vivo therapeutic duration.

Other peptide classes

Claim 8 identifies:

LH-RH and analogues or homologues;
somatostatin;
GH-RH;
calcitonin.

Claim 9 covers water-insoluble salts of somatostatin, LH-RH, and related analogues. Claim 17 identifies another cyclic peptide sequence, while claims 18-20 require approximately 7-15 days of release and cover injectable suspensions and implantable rods.

The patent therefore combines a general platform with species-level claims for particular peptide salts and release profiles.

What formulations are protected by United States Patent 5,225,205?

The most commercially relevant protected formats are:

Format	Relevant claims	Key requirements
Microparticle composition	1, 4-12, 17-18	PLGA, peptide salt, defined loading, particle size and processing
Injectable suspension	2, 13, 19	Microparticles added to a pharmaceutically acceptable carrier or solution
Implantable rod	14, 20	Claimed microparticle composition formed into an implantable rod
Long-acting triptorelin depot	10, 11, 15, 16	Triptorelin pamoate with 25- or 40-day release and testosterone suppression
Shorter-duration peptide depot	17, 18	Specified peptide salt with approximately 7-15 days of release

The claims do not require a particular syringe, needle, reconstitution volume, administration route beyond the claimed injectable format, or commercial dose strength unless those features are necessary to satisfy the release and therapeutic-performance limitations.

When did United States Patent 5,225,205 lose exclusivity?

The patent issued July 6, 1993. Under the pre-1995 patent-term rule, the ordinary term was 17 years from issuance, producing an expiration date of July 6, 2010.[1] The patent is therefore expired in the United States.

Milestone	Date or status
U.S. patent number	5,225,205
Issue date	July 6, 1993
Ordinary statutory term	17 years from issue
Expected expiration	July 6, 2010
Current status	Expired
Current U.S. blocking effect	None from this patent

The expiration applies to all claims, including the triptorelin pamoate claims. A later product-specific patent, formulation patent, process patent, or regulatory exclusivity period would have to be analyzed separately.

What is the Orange Book status of United States Patent 5,225,205?

U.S. Patent 5,225,205 is not, by itself, an active Orange Book exclusivity right. Orange Book patent listings are linked to specific approved drug products and are submitted by new drug application holders under FDA procedures. A patent’s existence does not establish that it was listed against a particular NDA.[2]

For products containing triptorelin, the patent is relevant historically because claims 10, 11, 15, and 16 expressly target triptorelin pamoate depot formulations. It does not create a current Orange Book barrier after its 2010 expiration.

Paragraph IV challenge implications

A Paragraph IV certification is used to challenge an unexpired patent listed for an approved drug. An expired patent generally cannot support a current Paragraph IV stay or block generic approval through the Hatch-Waxman mechanism.[3]

Any historical Paragraph IV dispute involving a triptorelin or peptide depot product would have depended on:

whether the patent was listed against the relevant NDA;
whether the challenged product fell within the asserted claims;
whether later-listed patents covered the same product;
whether the applicant pursued a Paragraph IV certification, section viii statement, or another pathway.

The text of Patent 5,225,205 does not establish any historical listing, certification, settlement, or litigation outcome.

How strong was the patent estate?

The patent was technically broad at the platform level but commercially narrower than its title and claim count might suggest.

Strengths

Claims 1 and 4 cover both composition and manufacturing features.
The claims encompass several peptide classes.
The claims address injectable suspensions and implantable rods.
The patent includes species claims for triptorelin pamoate.
The release-performance claims in claims 15 and 16 could have been difficult to challenge solely through compositional testing if the products met the therapeutic limitations.

Weaknesses

The core claims require numerous quantitative limitations.
The claims are tied to dry mixing and extrusion.
The temperature window of approximately 80-100°C creates a clear process boundary.
The peptide must be in a salt form, with several claims requiring a water-insoluble salt.
The copolymer and peptide particle-size limitations provide potential noninfringement positions.
Product-by-process language can create disputes over whether the process limits the scope of the composition claim.
Claim 15 and claim 16 require in-vivo release and testosterone-suppression results, increasing proof complexity.
The patent expired in 2010, eliminating present enforcement value.

The estate was strongest against a product that copied the described dry powder extrusion process and used a named peptide salt in the claimed loading and particle-size ranges. It was weaker against modern PLGA formulations using different manufacturing routes or polymer architectures.

How does this patent compare with competing peptide depot patents?

Platform	Representative products	Core technology	Relationship to U.S. 5,225,205
Triptorelin pamoate depot	Decapeptyl, Trelstar	Long-acting GnRH agonist depot	Directly relevant to claims 10, 11, 15 and 16
Leuprolide depot	Lupron Depot, Eligard	PLGA microspheres or in-situ polymer depot, depending on product	Competes therapeutically but may use different peptide salt and manufacturing claims
Octreotide depot	Sandostatin LAR	PLGA microsphere peptide delivery	Same broad delivery field, different peptide and product-specific patent estate
Exenatide extended release	Bydureon	PLGA microspheres	Demonstrates later commercial use of PLGA peptide depots, but not necessarily the claimed salt or process
Other injectable depots	Various peptide and nonpeptide products	Microspheres, implants, in-situ gels, or polymer matrices	Potential design-around and competitive alternatives

A competitor’s use of PLGA alone would not necessarily infringe. The relevant analysis would compare the complete formulation and manufacturing process against the limitations of claims 1 and 4, then assess dependent claims for the specific peptide, salt, particle size, release duration, and dosage form.

What is the biosimilar risk for this patent?

There is no biosimilar risk associated with Patent 5,225,205. The patent covers synthetic and natural peptides delivered in polymer microparticles. It does not claim a monoclonal antibody, recombinant protein, or other biologic product subject to the FDA biosimilar pathway under section 351(k) of the Public Health Service Act.[4]

Potential competition would arise through generic-drug, hybrid, or product-specific regulatory pathways, depending on the reference product and formulation complexity. The key barrier would be pharmaceutical equivalence, bioequivalence, depot-release characterization, manufacturing reproducibility, and any later unexpired patents.

What manufacturing and geographic barriers remain?

The U.S. patent no longer creates a manufacturing barrier. A manufacturer may use the disclosed dry-mixing and extrusion approach in the United States without infringing the expired patent.

Commercial barriers remain in other areas:

reproducible peptide micronization;
uniform peptide dispersion in PLGA;
control of residual solvent and polymer degradation;
sterilization without peptide degradation;
suspension stability after reconstitution;
scale-up of extrusion and cryogenic pulverization;
demonstration of equivalent release kinetics;
regulatory approval for a complex injectable product.

Foreign rights must be assessed jurisdiction by jurisdiction. U.S. expiration does not establish expiration in Europe, Japan, China, Canada, or other countries. A patent family member may have expired earlier or later depending on filing dates, national-phase prosecution, maintenance fees, supplementary protection certificates, and local term rules. The U.S. patent itself provides no current geographic exclusivity.

What litigation and settlement issues affect the patent?

The patent’s expiration makes new U.S. infringement litigation based solely on its claims commercially immaterial. Historical disputes remain relevant only for due diligence, damages analysis, validity assessments, or freedom-to-operate records.

The claim set presents several likely litigation issues:

Whether "obtained by a method" in claim 1 limits the composition to products made by the stated process.
Whether claim 4 requires proof of the recited processing history or only the resulting uniform dispersion.
Whether approximate particle-size and temperature terms permit reasonable measurement tolerances.
Whether a salt is sufficiently water insoluble to satisfy claims 7-9.
Whether a product meets the release and testosterone-suppression limitations in claims 15 and 16.
Whether alternative polymer ratios fall within claim 5.
Whether nonliteral equivalents can apply to solvent-based or lower-temperature processes.

No current settlement or litigation right can be derived from the patent text. Any historical settlement would require separate court-docket and assignment-record review.

What generic launch risks exist today?

Patent-specific launch risk from U.S. Patent 5,225,205 is zero because the patent expired in 2010. A launch of a triptorelin, peptide PLGA depot, injectable suspension, or implantable rod could still face:

later formulation patents;
manufacturing-process patents;
device patents;
method-of-use patents;
regulatory exclusivity;
product-specific patent listings;
clinical and bioequivalence requirements;
trade-secret restrictions involving scale-up or release testing.

The principal present risk is therefore not this patent but the later patent estate surrounding the particular reference product and dosage form.

Key Takeaways

U.S. Patent 5,225,205 covers PLGA microparticles containing salts of natural or synthetic peptides.
The core claims require specific particle sizes, peptide loading, dry mixing, compression, heating, extrusion, and pulverization.
Claims 10 and 11 specifically target triptorelin pamoate.
Claims 15 and 16 cover at least 25-day and 40-day testosterone-suppressing release profiles.
Claims 2, 13, and 19 cover injectable suspensions; claims 14 and 20 cover implantable rods.
The patent issued July 6, 1993 and ordinarily expired July 6, 2010.
It is not a current U.S. Orange Book barrier.
It creates no current biosimilar risk.
A modern competing product may avoid the historical claims through a different salt, polymer, particle-size range, or manufacturing process.
Current freedom-to-operate analysis must focus on later product, formulation, process, device, and method-of-use patents.

FAQs

Does U.S. Patent 5,225,205 cover all PLGA peptide microspheres?

No. The claims require specific peptide loading, particle sizes, salt forms, processing steps, and, for dependent claims, particular peptides and release outcomes.

Does the patent cover triptorelin pamoate?

Yes. Claim 11 expressly covers a pamoate salt of triptorelin in the claimed PLGA microparticle composition.

Can a company launch a PLGA peptide depot after the patent expired?

Yes, from the standpoint of this patent alone. The company must still evaluate later patents, regulatory requirements, manufacturing patents, and product-specific Orange Book listings.

Is claim 4 broader than claim 1?

Claim 4 is broader in some respects because it omits claim 1’s express 80-100°C temperature range and certain detailed starting-particle limitations. It remains limited by the recited PLGA composition, peptide loading, substantially uniform dispersion, and specified processing history.

Are peptide depots protected by biosimilar law?

Not automatically. Synthetic peptide depots are generally evaluated under drug regulatory pathways rather than treated as biologic biosimilars. The applicable pathway depends on the reference product and FDA classification.

References

U.S. Patent and Trademark Office. (1993). United States Patent No. 5,225,205, Pharmaceutical compositions containing peptides.
U.S. Food and Drug Administration. (2025). Approved drug products with therapeutic equivalence evaluations, 45th edition.
U.S. Food and Drug Administration. (n.d.). Abbreviated new drug application submissions: Patent certifications and exclusivity.
U.S. Food and Drug Administration. (n.d.). Biosimilar and interchangeable biosimilar products.

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
Switzerland	2829/89	Jul 28, 1989

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	397197	⤷ Start Trial
Austria	397198	⤷ Start Trial
Austria	A154590	⤷ Start Trial
Austria	A223591	⤷ Start Trial
Australia	5910390	⤷ Start Trial
Australia	619996	⤷ Start Trial
Belgium	1003093	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 5,225,205

Summary for Patent: 5,225,205