United States Patent 6,251,091: Claim Scope, Expiration, and Needleless Injector Patent Landscape

U.S. Patent No. 6,251,091 protects a prefilled needleless-injector capsule used with a removable filling adaptor. Its core contribution is the use of the adaptor as both a filling passage and a controlled receptacle for excess injectate. The patent also covers adaptor geometry, non-reconnectable attachment mechanisms, sealing structures, compatible material combinations, and associated filling methods.

The patent issued on June 26, 2001. Based on the applicable 20-year term measured from the relevant nonprovisional filing date, the patent term has expired. The claims therefore have no current blocking effect in the United States, although they remain relevant as prior art and as evidence of the technical lineage of prefilled needleless-injector systems.[1][2]

What does U.S. Patent 6,251,091 cover?

The patent covers a combination of three principal components:

A needleless injector capsule.
A movable piston within the capsule chamber.
A removable adaptor used during filling.

The capsule has an injection orifice. The adaptor has a bore that communicates with the capsule chamber through that orifice. During filling, injectate enters the capsule and excess injectate remains in the adaptor bore. The adaptor bore is then closed with a sealing structure.

The independent claim architecture is as follows:

Claim	Category	Main subject matter
1	Apparatus combination	Capsule, piston, removable adaptor, excess injectate in adaptor bore, sealed bore
11	Filling method	Filling capsule and adaptor bore, then sealing adaptor bore
16	Apparatus combination	Capsule and adaptor with stepped bore geometry
23	Apparatus combination	Capsule, adaptor, excess injectate and sealing means

Claims 1 and 23 are closely related. Claim 16 is structurally distinct because it focuses on the adaptor bore having a smaller first portion near the injection orifice and a larger remote portion.

What are the independent claim limitations?

Claim 1: sealed excess-injectate configuration

Claim 1 requires all of the following elements:

A needleless injector capsule.
A capsule chamber.
Injectate located in the chamber.
An injection orifice.
A piston positioned for movement in the chamber.
An adaptor removably connected to the capsule.
An adaptor bore communicating with the capsule chamber through the injection orifice.
Excess injectate partly filling the adaptor bore.
A sealing means closing the bore to the exterior.

The most commercially significant limitations are the adaptor connection, the presence of excess injectate in the adaptor bore, and closure of that bore after filling. A system that uses a filling adaptor but removes it before sealing, or that does not leave excess injectate in the adaptor bore, may fall outside the literal scope of claim 1.

The claim is directed to a physical filled combination, not merely an empty capsule or a filling tool.

Claim 11: filling method

Claim 11 covers a method comprising:

Introducing injectate into the capsule chamber through the injection orifice.
Introducing excess injectate into the adaptor bore.
Closing the adaptor bore to the exterior with a sealing means.

The method does not expressly require a particular drug, formulation, fill volume, piston material, injector actuator, pressure source, or administration site. The claim is therefore technology-focused rather than drug-specific.

A process in which the adaptor is used only as a temporary conduit, with no excess injectate retained in the bore, presents a materially different infringement profile.

Claim 16: stepped adaptor bore

Claim 16 requires a capsule and adaptor in which the bore has:

A first portion with a smaller cross-section adjacent to the injection orifice; and
A second portion with a larger cross-section remote from the orifice.

Unlike claim 1, claim 16 does not expressly require excess injectate in the bore or a sealing means. Its central limitation is the stepped or enlarged bore configuration.

This claim may cover an empty or partially assembled capsule-adaptor combination if the dimensional relationship is present. The claim is potentially broader than claim 1 in relation to filling state, but narrower in relation to adaptor geometry.

Claim 23: sealed filled combination

Claim 23 requires:

A needleless injector capsule.
Injectate in the capsule chamber.
A piston.
An injection or injector orifice.
A removable adaptor.
Excess injectate partly filling the adaptor bore.
A sealing means engaging the adaptor.

The claim resembles claim 1 but is drafted without the same detailed formulation of the adaptor's communication relationship. Its practical scope depends on how the terms "engaging said adaptor," "injector orifice," and "partly filled" are construed.

How do dependent claims narrow the patent scope?

Claims 2 through 10, 12 through 15, and 17 through 22 add specific structural or process limitations.

Claims	Limitation	Technical effect
2, 17	Frangible adaptor connection	Allows controlled breakaway or removal
3, 18	Snap-fit connection preventing reconnection	Supports tamper evidence and one-way assembly
4, 19	Glass capsule or adaptor	Addresses chemical compatibility and sterilization
5, 20	Plastics capsule or adaptor	Supports low-cost molding and impact resistance
6, 21	More than one material	Covers composite construction
7, 22	Internal plastics lining compatible with injectate	Separates drug-contact material from structural material
8, 13	Sealing cap	Covers cap-based closure
9, 14	Plug in adaptor bore	Covers internal plug sealing
10	Adaptor portions sealed after filling	Covers heat sealing, welding or similar closure
12	Dispenser sealingly engages bore wall	Defines a filling-interface configuration
15	Air evacuation before filling	Addresses bubble reduction and fill control

The material claims are functional only to a limited extent. Claim 7 requires an internal plastics lining compatible with the injectate, but it does not identify a specific polymer or drug formulation. A competitor would need to assess both the material composition and the relationship between the lining and the injectate.

What technical problem does the patent address?

The patent addresses filling and sealing problems associated with small needleless-injector capsules.

A capsule used for needleless delivery must contain a controlled liquid volume and must avoid trapped air that could affect dose accuracy, pressure generation, or device performance. The adaptor provides a filling pathway through the injection orifice. Retaining excess injectate in the adaptor bore helps maintain a liquid-filled path and can reduce the risk that air enters the capsule through the orifice.

The claimed arrangement also allows the adaptor to be removed after filling. Frangible and one-way snap-fit connections can reduce reuse risk and help distinguish a filled, prepared capsule from an unfilled or previously handled component.

What formulations and dosage forms are protected?

The patent does not claim a specific active pharmaceutical ingredient, therapeutic indication, concentration, dosage form, or formulation excipient.

The claims can potentially read on a capsule containing:

A small-molecule drug solution.
A vaccine or biologic solution.
A suspension, subject to the physical operation of the injector.
A diagnostic liquid.
A veterinary injectable formulation.
A preservative-containing or preservative-free formulation.

The relevant patent risk is therefore device and packaging risk, not active-ingredient patent risk. A drug manufacturer could face technical overlap even where the drug itself is off patent, if it uses a capsule-adaptor assembly meeting the claim limitations. Because the patent has expired, this issue is now primarily relevant to freedom-to-operate history, prior-art analysis, and design documentation.

When did U.S. Patent 6,251,091 lose exclusivity?

The patent issued on June 26, 2001. U.S. utility patents filed after June 8, 1995 generally receive a term of 20 years from the earliest effective nonprovisional filing date, subject to patent-term adjustment, terminal disclaimers, and other statutory modifications.[2]

The patent is therefore expired based on its ordinary statutory term. A precise term calculation requires the prosecution record, including the effective nonprovisional filing date and any patent-term adjustment. The expiration date should be confirmed through USPTO Patent Center before being used in a litigation or licensing opinion.[3]

Event	Date or status
U.S. patent	6,251,091
Issue date	June 26, 2001
Technology	Needleless injector capsule and filling adaptor
Term basis	20 years from applicable nonprovisional filing date
Current U.S. enforceability	Expired by statutory term
Orange Book status	No expected Orange Book listing as a device-only patent

What is the Orange Book status of U.S. Patent 6,251,091?

U.S. Patent 6,251,091 is a device and filling-system patent rather than a patent claiming a drug substance, drug formulation, or approved method of using a drug. It would not ordinarily qualify as an Orange Book patent.

The FDA Orange Book lists patents submitted by approved applicants for approved drug products, including patents covering drug substances, drug products, and certain methods of use.[4] A standalone needleless-injector capsule patent generally belongs in the device patent landscape, not the Orange Book patent table.

The absence of an Orange Book listing would not eliminate ordinary patent risk while the patent was in force. It means that the patent would not normally support an FDA Paragraph IV certification against an approved drug product.

Were Paragraph IV challenges available?

Paragraph IV certifications apply to patents listed in the Orange Book for an approved reference listed drug.[5] The claims of U.S. Patent 6,251,091 are directed to the capsule, adaptor, sealing arrangement and filling process. They do not claim a particular approved pharmaceutical product.

Accordingly:

The patent was not naturally suited to an ordinary Paragraph IV challenge.
A generic applicant would more likely address it through a conventional freedom-to-operate analysis.
A drug-device combination product could involve separate FDA and patent issues if the injector system were identified in an approved product's patent submission.
Expiration removes any current need for a Paragraph IV certification directed to this patent.

How strong was the patent estate?

Strengths

The patent had several features that could have made it commercially relevant during its term:

It claimed a complete filled capsule-adaptor combination.
It included both apparatus and method claims.
It addressed excess injectate, a specific manufacturing condition.
It covered multiple sealing approaches.
It covered glass, plastics and composite materials.
It included frangible and non-reconnectable adaptor connections.
It claimed a stepped bore independently of the excess-injectate limitation.

The combination of device and process claims could have complicated design-around efforts where the same adaptor was used both to fill and seal the capsule.

Weaknesses

The claims also had material limitations:

They required a removable adaptor connected to the capsule.
Claims 1 and 23 required excess injectate in the adaptor bore.
Claim 16 required a specific two-section bore geometry.
The claims did not cover every needleless injector architecture.
They did not claim the injector actuator, pressure source or nozzle system broadly.
They did not claim the active drug or formulation.
A system using a permanently integrated filling port, a separate sterile transfer system, or a different sealing arrangement could avoid at least some claims.

The patent's strength was therefore concentrated in the prefilled capsule and filling interface, not in needleless injection technology as a whole.

What design-arounds would have reduced infringement risk?

Potential design-around strategies during the patent term would have included:

Eliminating the removable adaptor and using an integral fill port.
Filling the capsule through a rear opening rather than the injection orifice.
Removing the adaptor before final sealing.
Avoiding retention of excess injectate in the adaptor bore.
Using a bore with uniform cross-section rather than the stepped geometry in claim 16.
Using a permanently attached adaptor.
Sealing the capsule independently of the adaptor.
Using a separate transfer vessel and sterile connector.
Designing the adaptor so that it cannot communicate with the capsule chamber after filling.
Changing the connection mechanism and eliminating frangible or one-way snap-fit characteristics.

These strategies would require element-by-element analysis. Avoiding one dependent claim limitation would not avoid claims 1, 11, 16 or 23 if all limitations of another independent claim remained present.

How does the patent compare with the broader needleless-injector landscape?

The relevant competitive landscape has several distinct patent clusters.

Patent cluster	Typical protected subject matter	Relationship to U.S. 6,251,091
Injector actuation	Springs, compressed gas, stored energy and piston drivers	Usually outside the core claims
Nozzle and orifice design	Jet formation, nozzle diameter and pressure control	Separate technical field
Capsule architecture	Ampoules, plungers, burst membranes and discharge tips	Potentially adjacent
Filling and sealing	Sterile filling, port closure and prefilled systems	Closest overlap
Formulation compatibility	Container materials, extractables and stability	Relevant to claims 4-7 and 19-22
Combination products	Injector plus drug cartridge or capsule	Commercially overlapping
Manufacturing methods	Assembly, sterilization, filling and inspection	Potential process overlap

Companies active in needleless or needle-free injection technology have included Bioject, Antares Pharma, PharmaJet and Crossject. Their patent estates have generally focused on injector engines, disposable cartridges, nozzles, pressure delivery and combination-product implementation. Company-level overlap cannot be determined from the claims alone and requires a family-by-family review of published applications, issued claims and continuation practice.

What litigation and settlement issues affected the patent?

The supplied claim text does not establish a particular infringement action, settlement agreement, license, or adjudicated claim construction involving U.S. Patent 6,251,091. The relevant legal records would be the USPTO prosecution file, assignment records, Patent Trial and Appeal Board database, and federal court docket systems.[3][6]

The principal litigation issues that would have mattered during the patent term were:

Whether the accused adaptor was "removably connected."
Whether the bore communicated with the chamber through the injection orifice.
Whether the bore was "partly filled with excess injectate."
Whether a sealing cap, plug or welded adaptor portion satisfied the sealing limitation.
Whether the adaptor connection was frangible or non-reconnectable.
Whether the accused device had the claimed stepped bore.
Whether method claims were performed by the manufacturer, contract filler or end user.
Whether divided infringement affected claim 11 or claim 12.

Because the patent is expired, new infringement litigation based on post-expiration conduct is unavailable. Historical damages, if any, would be limited to the enforceable period and subject to the applicable damages and marking rules.[7]

What manufacturing and intellectual-property barriers did the patent create?

The patent could have affected contract manufacturers that filled needleless injector capsules using:

A filling nozzle inserted into the adaptor bore.
A liquid-filled adaptor passage.
A cap or plug applied after filling.
A frangible or one-way snap-fit capsule connection.
Composite capsule materials with a drug-compatible inner lining.
Air evacuation through the injection orifice.

The manufacturing claims could have reached activities performed before final injector assembly. This distinction matters because a company could infringe a method claim through its filling operation even if the finished injector was sold by another entity.

The patent did not, however, create a broad barrier around sterile filling, piston capsules or needleless injection. The claimed combination required a particular relationship among the capsule orifice, adaptor bore, excess injectate and sealing structure.

What is the current commercial impact?

The direct current exclusivity impact is zero because the patent has expired. Its commercial relevance is historical and technical.

The patent could have affected:

Disposable capsule suppliers.
Needleless injector manufacturers.
Pharmaceutical companies developing prefilled delivery systems.
Contract manufacturing organizations performing final filling.
Combination-product developers.
Companies evaluating acquisitions or licenses involving legacy injector platforms.

Revenue exposure would have depended on the number of products using the claimed adaptor-and-capsule configuration during the enforceable period. The patent does not identify a particular drug or product, so revenue attributable specifically to this patent cannot be calculated from the claims.

What biosimilar and generic entry risks exist?

There is no direct biosimilar risk from this patent because it does not claim a biologic molecule, biologic formulation or biosimilar manufacturing process.

There is also no current generic-entry block because the patent has expired. During its term, the patent could have created a device-related barrier for a generic or follow-on product using the same needleless capsule filling system. That barrier would have existed outside the core Hatch-Waxman substance and formulation patent analysis unless the patent was listed for a specific drug-device product.

Key Takeaways

U.S. Patent 6,251,091 covers a needleless injector capsule combined with a removable filling adaptor.
Claims 1 and 23 focus on retaining excess injectate in the adaptor bore and sealing that bore.
Claim 11 covers the corresponding filling method.
Claim 16 separately protects an adaptor with a smaller bore portion near the injection orifice and a larger remote portion.
Dependent claims cover frangible connections, one-way snap fits, glass, plastics, composite materials, internal linings, caps, plugs and air evacuation.
The patent does not claim a drug, formulation, indication, injector engine or biologic.
It is a device and manufacturing patent, not ordinarily an Orange Book patent.
The patent has expired under the applicable U.S. utility-patent term.
No current generic, biosimilar or Paragraph IV barrier remains from this patent.
Historical freedom-to-operate analysis should focus on the adaptor, excess-injectate condition, sealing step and stepped-bore geometry.

FAQs

Does U.S. Patent 6,251,091 cover all needleless injectors?

No. It covers a specific capsule-adaptor filling arrangement and related method. It does not broadly claim every needleless injector, pressure source, nozzle or actuator.

Can a company still be sued for making the claimed capsule?

No new infringement claim can ordinarily be based on conduct occurring after the patent expired. Historical conduct during the enforceable term may raise separate questions.

Does the patent cover prefilled syringes?

Not generally. The claims require a needleless injector capsule with the specified adaptor and injection-orifice relationship. A conventional prefilled syringe would not satisfy those limitations merely because it is prefilled.

Is a sealed filling adaptor required by every independent claim?

No. Claims 1, 11 and 23 contain sealing or sealing-process limitations. Claim 16 focuses on the adaptor's stepped bore and does not expressly require excess injectate or a sealing means.

Does the patent protect the drug inside the capsule?

No. The claims do not identify or protect a particular active ingredient, formulation, concentration or therapeutic use.

References

United States Patent No. 6,251,091, “Needleless injector capsule and method of filling same,” issued June 26, 2001.
35 U.S.C. § 154, patent term and adjustment provisions.
United States Patent and Trademark Office. (n.d.). Patent Center. https://patentcenter.uspto.gov/
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations: Orange Book. https://www.fda.gov/drugs/drug-approvals-and-databases/orange-book
21 U.S.C. § 355(j)(2)(A)(vii), abbreviated application patent certifications.
United States Patent and Trademark Office. (n.d.). Patent Trial and Appeal Board End-to-End. https://ptab.uspto.gov/
35 U.S.C. §§ 271, 284, and 287, patent infringement, damages and marking.

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
United Kingdom	9525757	Dec 16, 1995

PCT Information
PCT Filed	December 09, 1996	PCT Application Number:	PCT/GB96/03017
PCT Publication Date:	June 26, 1997	PCT Publication Number:	WO97/22375

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	204772	⤷ Start Trial
Australia	1102397	⤷ Start Trial
Australia	4935800	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 6,251,091

Summary for Patent: 6,251,091