US Patent 9,532,991: Scope, Claims, Expiration, Orange Book Status, and Risperidone Microsphere Patent Landscape
US Patent 9,532,991 protects risperidone or 9-hydroxyrisperidone sustained-release microspheres using a defined blend of two uncapped carboxyl-terminated PLGA polymers. The core commercial risk is concentrated in the polymer blend, molecular-weight, lactide-to-glycolide, viscosity, drug-loading, formulation, manufacturing, and treatment limitations. The patent was issued to Luye Pharma Group and is associated with the U.S. long-acting risperidone product Rykindo.
The patent has four principal claim categories:
- Composition claims for risperidone microspheres.
- Injectable pharmaceutical formulation claims.
- Manufacturing-process claims.
- Method-of-treatment claims for psychosis.
The earliest effective patent-family filing is in 2011, placing the expected U.S. patent-term endpoint in 2031 or 2032, subject to the precise U.S. term calculation and any patent-term adjustment. The patent does not broadly cover every risperidone depot formulation. It targets a technically constrained PLGA platform.
What does US Patent 9,532,991 protect?
The patent protects microspheres containing risperidone, 9-hydroxyrisperidone, or a salt of either compound, encapsulated in a blend of two uncapped PLGA polymers. Both polymers must have carboxyl terminal groups.
The primary claim requires the following combination:
| Element |
Claim 1 requirement |
| Active agent |
Risperidone, 9-hydroxyrisperidone, or a salt |
| First PLGA |
Uncapped, carboxyl-terminated |
| First PLGA molecular weight |
55,000 to 85,000 |
| First PLGA lactide:glycolide ratio |
65:35 to 90:10 |
| Second PLGA |
Uncapped, carboxyl-terminated |
| Second PLGA molecular weight |
15,000 to 35,000 |
| Second PLGA lactide:glycolide ratio |
50:50 to 75:25 |
| First:second PLGA weight ratio |
50:50 to 95:5 |
| Drug loading |
10% to 60% by total microsphere weight |
| Drug location |
Encapsulated in the polymer blend |
The claim is cumulative. A competing product must satisfy every limitation of an asserted claim to infringe literally. A formulation using a capped PLGA, a single PLGA polymer, a materially different polymer ratio, or a drug loading outside the claimed range may avoid literal infringement of claim 1, although other claims or the doctrine of equivalents could remain relevant.
How broad are the independent composition claims?
Claims 1 and 14 are the principal composition claims, but they use different molecular-weight frameworks.
Claim 1: narrower number-average or specified molecular-weight ranges
Claim 1 requires:
- First PLGA molecular weight of 55,000 to 85,000.
- Second PLGA molecular weight of 15,000 to 35,000.
- First polymer lactide:glycolide ratio of 65:35 to 90:10.
- Second polymer lactide:glycolide ratio of 50:50 to 75:25.
- First:second polymer ratio of 50:50 to 95:5.
- Drug loading of 10% to 60%.
The claim also requires both polymers to be uncapped and carboxyl terminated. That limitation is central. The patent is directed to a blend of relatively high-molecular-weight, lactide-rich PLGA and lower-molecular-weight, more glycolide-rich PLGA.
Claim 14: broader alternative molecular-weight ranges
Claim 14 covers a broader formulation space:
| Parameter |
Claim 14 range |
| First PLGA weight-average molecular weight |
50,000 to 145,000 |
| First PLGA intrinsic viscosity |
0.4 to 0.9 dL/g |
| First PLGA lactide:glycolide ratio |
65:35 to 90:10 |
| Second PLGA weight-average molecular weight |
4,000 to 45,000 |
| Second PLGA intrinsic viscosity |
0.1 to 0.35 dL/g |
| Second PLGA lactide:glycolide ratio |
50:50 to 75:25 |
| First:second polymer ratio |
50:50 to 95:5 |
Claim 14 does not expressly include the 10% to 60% drug-loading limitation in its base form. Claim 16 adds that range. This creates a potentially important fallback position if a competing formulation falls outside claim 1's narrower molecular-weight ranges but remains within claim 14.
What formulations are protected by the dependent claims?
The dependent claims narrow the platform toward a preferred commercial formulation.
Preferred PLGA composition
Claim 3 specifies:
- First PLGA lactide:glycolide ratio: 75:25.
- Second PLGA lactide:glycolide ratio: 50:50.
Claims 4 and 5 narrow the polymer ratio to:
- 70:30 to 90:10 under claim 4.
- 80:20 under claim 5.
These limitations are commercially important because an 80:20 blend of 75:25 PLGA and 50:50 PLGA appears to represent the patent's preferred formulation architecture.
Preferred drug loading
The patent claims several drug-loading bands:
| Claim |
Risperidone loading |
| Claim 1 |
10% to 60% |
| Claim 6 |
35% to 55% |
| Claim 7 |
40% to 50% |
| Claim 10 |
45% |
Claim 10 is the most specific composition claim. It requires:
- 45% risperidone by weight.
- First:second PLGA ratio of 80:20.
- First PLGA ratio of 75:25 lactide:glycolide.
- Second PLGA ratio of 50:50 lactide:glycolide.
- First PLGA intrinsic viscosity of 0.45 to 0.55 dL/g.
- Second PLGA intrinsic viscosity of 0.2 to 0.3 dL/g.
A product matching these parameters would present a high direct-infringement risk unless it has a viable invalidity or noninfringement position.
Surface-crystal limitation
Claim 2 requires that no crystals of the active agent precipitate on the microsphere surfaces. This limitation may create evidentiary complexity. Testing would likely require representative batch analysis using microscopy, spectroscopy, surface-extraction studies, or comparable analytical methods. The absence of surface crystals may also be relevant to release performance and initial burst.
Salt forms
Claim 11 covers risperidone and 9-hydroxyrisperidone salts, including hydrochloride, hydrobromide, nitrate, sulfate, phosphate, acetate, propionate, pamoate, succinate, methanesulfonate, benzenesulfonate, and toluenesulfonate salts.
The salt claim is broad as to listed inorganic and organic acid salts. A formulation using a salt outside the listed groups would require separate claim analysis.
Does the patent cover an injectable risperidone formulation?
Yes. Claim 12 covers a pharmaceutical formulation for injection containing the claimed microspheres and a pharmaceutically acceptable dispersion solvent. Claim 13 adds mannitol.
This formulation coverage is significant because it reaches the drug product rather than only the isolated microspheres. A formulation can potentially infringe even where the microspheres are incorporated into a commercial vial or injection kit, provided the claim elements are present.
The claims do not require a particular injection route, dose, injection interval, reconstitution volume, needle gauge, or administration device. Those limitations may be relevant to other patents covering a particular product.
What manufacturing process does US 9,532,991 protect?
Claim 17 covers a microsphere manufacturing process involving:
- Dissolving the active agent and PLGA blend in an organic solvent.
- Adding the mixture to an aqueous solution containing a water-soluble polymer for emulsification.
- Removing the organic solvent.
- Washing and filtering the resulting microspheres.
Claim 18 specifies:
- Dichloromethane as the organic solvent.
- Polyvinyl alcohol as the water-soluble emulsifier.
This is an oil-in-water emulsion and solvent-evaporation process. The claim may be relevant to manufacturers using a comparable process, even if the final product's polymer characteristics are difficult to determine from public labeling.
Process infringement analysis would focus on manufacturing records, batch instructions, solvent systems, emulsification conditions, polymer inputs, and quality-control data. Process claims can be more difficult to enforce against an imported finished product than composition claims, but they may increase discovery and supply-chain exposure.
What method of treatment is claimed?
Claim 19 covers a method of treating psychosis by administering the claimed injectable formulation. It identifies:
- Acute schizophrenia.
- Chronic schizophrenia.
- Psychotic states with significant positive symptoms.
- Psychotic states with significant negative symptoms.
- Affective symptoms related to schizophrenia.
The claim is limited by the formulation requirements of claim 12. It is not a standalone claim to treating psychosis with any risperidone product.
When does US Patent 9,532,991 lose exclusivity?
The patent issued on December 27, 2016. The patent family claims priority to an earlier foreign filing, while the U.S. term generally runs from the earliest effective U.S. nonprovisional or PCT filing date rather than the foreign priority date. The relevant family is associated with a 2011 priority filing and a later PCT or U.S. national-stage filing.
| Event |
Date |
| Earliest family priority |
2011 |
| U.S. patent issuance |
December 27, 2016 |
| Expected nominal U.S. term endpoint |
2031-2032 range |
| Regulatory exclusivity |
Separate from patent term |
| Patent-term adjustment |
Must be confirmed from the USPTO patent record |
The practical endpoint should be taken from the USPTO Patent Center term calculation before relying on a launch date. FDA regulatory exclusivity and patent exclusivity are separate. A new drug application may receive five-year new chemical entity exclusivity, three-year clinical-investigation exclusivity, or other protections, but those periods do not automatically extend this patent.
What is the Orange Book status of US Patent 9,532,991?
US Patent 9,532,991 is associated with the risperidone long-acting injectable product Rykindo, which was approved by the FDA in 2023. Rykindo is a risperidone extended-release injectable suspension developed by Luye Pharma. The product uses a sustained-release microsphere platform and is administered intramuscularly.
The Orange Book analysis should distinguish:
- Whether the patent is listed against Rykindo.
- The patent-use code, if any.
- The listed expiration date.
- Whether the listing is for the composition, formulation, method of use, or a combination.
- Whether an approved generic or 505(b)(2) applicant has submitted a Paragraph IV certification.
FDA Orange Book listings are product-specific. A patent may be enforceable against a product linked to the approved NDA without blocking every risperidone depot product in the market. FDA, rather than the patent document alone, controls the official Orange Book listing data.[1]
Which companies are challenging the patent?
No broadly reported final court judgment invalidating US Patent 9,532,991 appears in the public record associated with the principal Rykindo launch period. Public Paragraph IV activity must be evaluated against the FDA listing and the relevant NDA, not inferred from generic risperidone activity involving older patents.
Potential challengers would include:
- Generic manufacturers developing risperidone microspheres.
- 505(b)(2) applicants using a modified long-acting injectable platform.
- Companies developing alternative PLGA blends.
- Developers using subcutaneous or different depot delivery systems.
A Paragraph IV challenge would likely target one or more of the following:
| Vulnerability theory |
Relevant patent issue |
| Anticipation |
Prior risperidone PLGA microsphere disclosure |
| Obviousness |
Combining known PLGA grades and drug-loading ranges |
| Written description |
Breadth of the molecular-weight and viscosity ranges |
| Enablement |
Ability to reproduce all claimed formulations |
| Indefiniteness |
Meaning of “uncapped,” molecular weight, or surface crystals |
| Noninfringement |
Use of capped PLGA, different ratios, or different process |
The strongest design-around route is likely to change multiple parameters simultaneously rather than move only one value marginally outside a claimed range.
How strong is the patent estate for risperidone microspheres?
US Patent 9,532,991 is technically meaningful because it combines several formulation variables that influence release kinetics:
- Polymer end-group chemistry.
- Lactide:glycolide ratio.
- Molecular weight.
- Intrinsic viscosity.
- Polymer blend ratio.
- Drug loading.
- Surface crystallization.
- Solvent-emulsion processing.
The patent's strength is highest against a product that reproduces the preferred 45% risperidone, 80:20 polymer blend, 75:25 and 50:50 PLGA ratios, and specified viscosity ranges. Its strength is lower against a product using a different depot technology or materially different polymer chemistry.
The claim structure also provides layered protection. If a defendant avoids claim 10, the broader claims may remain relevant. If the final product falls outside claim 1, claim 14 may capture it through broader weight-average molecular-weight and viscosity ranges. If a composition claim fails, claims 17 and 18 may create process exposure.
How does this patent compare with Risperdal Consta and UZEDY patents?
Risperdal Consta
Risperdal Consta, marketed by Janssen, is an intramuscular risperidone microsphere product based on PLGA technology. Its early patent estate included foundational risperidone depot and microsphere patents, many of which are now expired or near the end of their enforceable term.
US Patent 9,532,991 is later and more formulation-specific. It does not function as a basic pioneer patent on risperidone microspheres. Its value lies in the defined polymer blend and formulation process.
Rykindo
Rykindo is the product most directly aligned with the patent's subject matter. The patent's claims correspond to a risperidone microsphere platform using mixed PLGA materials and controlled drug loading. Product-specific patents and regulatory exclusivity should be reviewed together with US 9,532,991.
UZEDY
UZEDY is a separate long-acting risperidone product developed by Teva. It uses a distinct extended-release injectable platform and has its own patent and Orange Book position. UZEDY does not automatically fall within US 9,532,991 merely because it contains risperidone and provides extended release.
The principal comparison is:
| Product |
Sponsor |
Delivery profile |
Relevance of US 9,532,991 |
| Risperdal Consta |
Janssen |
Intramuscular microspheres |
Foundational prior-art and legacy estate |
| Rykindo |
Luye Pharma |
Long-acting risperidone microspheres |
Direct commercial relevance |
| UZEDY |
Teva |
Extended-release injectable risperidone |
Separate platform and patent estate |
What generic launch risks exist?
A generic or follow-on developer faces five principal risks.
Composition risk
The developer must characterize both PLGA inputs, including end groups, molecular weight, viscosity, lactide:glycolide ratio, and blend ratio. Public product labels generally do not disclose enough detail to resolve infringement.
Equivalence risk
A product may be therapeutically equivalent yet use different polymer inputs. FDA approval does not establish freedom to operate. A 505(b)(2) or abbreviated pathway applicant may still face patent litigation.
Manufacturing risk
Use of dichloromethane, polyvinyl alcohol, aqueous emulsification, solvent removal, washing, and filtration may create process-claim exposure.
Regulatory timing risk
A Paragraph IV certification can trigger Hatch-Waxman litigation and a potential 30-month stay. A first-filer may obtain 180-day generic exclusivity, but that exclusivity does not eliminate patent-infringement exposure.
Substitution risk
A competing long-acting risperidone product may avoid this patent through a different depot architecture, such as a non-microsphere formulation, a different polymer system, a different administration route, or a modified-release suspension.
What licensing and commercial issues affect the patent landscape?
Luye Pharma's development and commercialization of Rykindo make the patent commercially relevant to licensing and transaction diligence. A license should address:
- US Patent 9,532,991 and continuation patents.
- Foreign counterparts.
- Orange Book listings.
- Regulatory exclusivity.
- Manufacturing know-how for PLGA grade selection.
- Analytical methods for surface-crystal detection.
- Supply of qualified PLGA polymers.
- Patent prosecution and enforcement control.
- Settlement rights in Paragraph IV litigation.
- Rights to future formulations and alternative injection routes.
Revenue exposure cannot be reliably assigned to this patent alone because companies generally report long-acting risperidone sales at the product or franchise level, not by individual patent. The principal economic exposure is the U.S. Rykindo market and any follow-on product that must either license the technology, design around the claims, or litigate.
Key Takeaways
- US Patent 9,532,991 protects risperidone or 9-hydroxyrisperidone microspheres using two uncapped, carboxyl-terminated PLGA polymers.
- The core formulation uses a higher-molecular-weight, lactide-rich PLGA blended with a lower-molecular-weight, more glycolide-rich PLGA.
- Claim 10 targets a particularly important embodiment: 45% risperidone, an 80:20 polymer ratio, 75:25 and 50:50 PLGA ratios, and specified intrinsic viscosities.
- Claims 12 and 13 extend protection to injectable formulations, including formulations containing mannitol.
- Claims 17 and 18 cover an emulsion-solvent-evaporation process using dichloromethane and polyvinyl alcohol.
- Claim 19 covers treatment of specified psychotic conditions using the claimed formulation.
- The expected patent-term endpoint is in the 2031-2032 range, subject to the official USPTO term calculation.
- Rykindo is the product most directly associated with the patent's commercial scope.
- UZEDY and Risperdal Consta involve separate patent and formulation analyses.
- A strong design-around would likely require changes to polymer end groups, polymer chemistry, molecular-weight distribution, blend ratio, or manufacturing process.
FAQs About US Patent 9,532,991
Can a risperidone microsphere product avoid US 9,532,991 by using one PLGA polymer?
Likely yes for claims requiring a blend of first and second uncapped PLGA polymers, assuming no other claim or equivalent formulation applies. A single-polymer product would not literally satisfy the two-polymer blend limitation.
Does the patent cover oral risperidone tablets?
No. The claims are directed to sustained-release microspheres, injectable formulations containing those microspheres, their manufacture, and treatment using the injectable formulation.
Does using risperidone hydrochloride avoid the patent?
No. Claim 11 expressly covers multiple risperidone and 9-hydroxyrisperidone salts, including hydrochloride and other listed salts.
Is a different lactide:glycolide ratio enough to design around the patent?
Not necessarily. The patent contains multiple overlapping ranges and alternative claim structures. A different ratio may avoid one claim while remaining within another claimed range or creating a doctrine-of-equivalents issue.
Are PLGA suppliers exposed to infringement liability?
A supplier ordinarily faces a different analysis from the finished-dose manufacturer. Liability depends on the supplied material, contractual role, knowledge, inducement evidence, and whether the supplier contributes to a claimed combination or process. A qualified PLGA supply agreement should address specifications, indemnity, technical records, and patent allocation.
References
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U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book. FDA.
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U.S. Patent and Trademark Office. (2016). U.S. Patent No. 9,532,991, risperidone microspheres and preparation method thereof. U.S. Department of Commerce.
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U.S. Food and Drug Administration. (2023). Rykindo risperidone for extended-release injectable suspension prescribing information. FDA.
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U.S. Food and Drug Administration. (2023). Uzedy risperidone extended-release injectable suspension prescribing information. FDA.
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U.S. Food and Drug Administration. (2024). Drugs@FDA: FDA-approved drugs database. FDA.
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U.S. Patent and Trademark Office. (2024). Patent Center and patent term adjustment records. U.S. Department of Commerce.
