United States Patent 9,669,096: Methylnaltrexone Formulation Scope, Expiration, and Patent Landscape

U.S. Patent No. 9,669,096 protects acidic, aqueous methylnaltrexone solutions stabilized with EDTA or an EDTA derivative. The core formulation window is pH 3.0 to 4.0, with narrower claims directed to pH 3.5, methylnaltrexone bromide at about 20 mg/mL, and EDTA concentrations of approximately 0.3 to 0.5 mg/mL. The claims also cover stability performance, excipients, sterilization, and the use of methylnaltrexone as the sole pharmaceutical active agent.

The practical commercial relevance is substantial because the claimed composition corresponds closely to the concentration and dosage form used for subcutaneous methylnaltrexone products, including Relistor injection. Infringement risk is highest for a ready-to-use injectable solution containing methylnaltrexone bromide, EDTA, and a pH near 3.5.

What does U.S. Patent 9,669,096 protect?

U.S. Patent 9,669,096 protects a pharmaceutical preparation rather than a method of treatment, dosing regimen, or manufacturing process. The independent claims define two related composition categories:

Claim	Independent subject matter	Principal limitations
1	Stable pharmaceutical preparation	Methylnaltrexone or salt, EDTA or derivative, pH 3.0-4.0
25	Stable pharmaceutical preparation	Methylnaltrexone or salt, EDTA or derivative, pH 3.0-4.0, methylnaltrexone as sole active agent

Claim 1 is broader because it does not expressly require methylnaltrexone to be the only active pharmaceutical ingredient. Claim 25 narrows the formulation to a single-active-agent product.

The dependent claims add limitations relating to:

Degradation after storage at room temperature.
Methylnaltrexone concentration.
EDTA identity and concentration.
Methylnaltrexone bromide.
pH ranges and pH 3.5.
Isotonicity agents.
Buffers.
Preservatives.
Sterilization.
Storage periods from three to 24 months.

The patent is therefore a formulation and product-composition patent with multiple fallback positions. A product that avoids one dependent limitation can still fall within claim 1 or claim 25 if it satisfies the applicable independent-claim elements.

How broad are claims 1 and 25?

Claim 1 has five central elements:

A pharmaceutical preparation.
A solution.
Methylnaltrexone or a salt of methylnaltrexone.
EDTA or an EDTA derivative as the chelating agent.
A pH from about 3.0 to 4.0.

The claim does not require:

A particular dosage strength.
Methylnaltrexone bromide specifically.
A particular route of administration.
A preservative.
A buffer.
An isotonicity agent.
A specific container.
A specified degradation limit.
A particular sterilization method.

The absence of these limitations gives claim 1 meaningful breadth. A formulation containing methylnaltrexone bromide at 10 mg/mL, for example, could potentially fall within claim 1 if it contains EDTA and has a pH within the claimed range.

Claim 25 includes similar composition requirements but expressly requires methylnaltrexone or its salt to be the sole pharmaceutical active agent. Excipients do not ordinarily qualify as pharmaceutical active agents. A formulation may therefore contain sodium chloride, a buffer, water, a preservative, and EDTA while still satisfying the sole-active-agent limitation.

What formulations are protected by the dependent claims?

The dependent claims create a dense set of formulation positions.

Claim group	Protected feature
2, 3, 21	Less than 1% or less than 2% degradation after defined storage periods
4-6	Methylnaltrexone concentration of 0.01-100 mg/mL, narrowed to 1-50 mg/mL and about 20 mg/mL
7-11	Specific EDTA salts and concentration ranges
12-19	Isotonicity agents, buffers, and preservatives
20	Methylnaltrexone bromide
22	Processing under at least one sterilization technique
23-24	pH 3.0-3.5 and approximately 3.5
28-31	Storage stability for three, six, 12, or 24 months
32-33	About 20 mg/mL methylnaltrexone and 0.3-0.5 mg/mL EDTA
34-37	Approximately 1% or less degradation after three to 24 months
38-39	Methylnaltrexone bromide, 20 mg/mL, EDTA at 0.3-0.5 mg/mL, pH about 3.5, with three-month stability

Claims 38 and 39 are the most commercially specific claims. They describe a formulation that closely resembles a standard injectable product profile:

Methylnaltrexone bromide.
Approximately 20 mg/mL concentration.
EDTA or derivative at about 0.3-0.5 mg/mL.
pH approximately 3.5.
Approximately 1% or less degradation after three months at room temperature.

How does the “consisting of” language affect infringement?

Claims 1, 7, and 8 use restrictive language for the chelating agent. Claim 1 requires “a chelating agent consisting of EDTA, or a derivative thereof.” Claims 7 and 8 identify specific EDTA salts, including edetate calcium disodium.

The restriction primarily limits the claimed chelating-agent component. It does not exclude ordinary pharmaceutical excipients unless the claim language or specification gives “consisting of” a broader formulation effect. A formulation could still include water, sodium chloride, a buffer, a preservative, or other non-chelating excipients.

Claim 8 is narrower than claim 7 because it limits the chelating agent to edetate calcium disodium. A product using disodium edetate may avoid claim 8 but could remain exposed to claim 7 or the broader claim 1.

A formulation using a non-EDTA chelator, such as a citrate, phosphate, deferoxamine, or another metal-binding compound, would have a stronger non-infringement position against the literal chelator limitation. That design choice could create separate stability, compatibility, toxicology, or regulatory issues.

What is the commercial relevance to Relistor and methylnaltrexone injections?

Methylnaltrexone bromide is marketed in injectable and oral dosage forms for opioid-induced constipation. Relistor injection has historically been supplied at a concentration of 20 mg/mL, making the concentration limitation in claims 6, 32, and 38 commercially relevant. The FDA-approved product labeling identifies methylnaltrexone bromide as the active ingredient and describes the product composition and administration instructions.[1]

The patent’s strongest product overlap is with an aqueous, ready-to-use injectable formulation containing:

Methylnaltrexone bromide at approximately 20 mg/mL.
EDTA or an EDTA salt.
Acidic pH near 3.5.
A sterilized solution.
Additional excipients for isotonicity or pH control.

The patent does not claim methylnaltrexone as a molecule. It does not prevent every dosage form, salt, concentration, or route of administration. Its commercial importance depends on whether a competing product uses the claimed excipient and pH architecture.

When does U.S. Patent 9,669,096 expire?

The patent issued on May 30, 2017, as U.S. Patent No. 9,669,096. Its term is governed by the earliest effective nonprovisional filing date, applicable patent-term adjustment, any terminal disclaimer, and statutory patent-term rules under 35 U.S.C. § 154.[2]

The earliest priority chain and the USPTO patent-term calculation must be reviewed before assigning a definitive expiration date. A patent-number search alone does not establish the enforceable end date. The relevant commercial diligence points are:

Term issue	Impact
Earliest effective nonprovisional filing date	Establishes the base 20-year term
Patent-term adjustment	Can extend the base term for USPTO delay
Patent-term extension	Could extend term for qualifying regulatory review
Terminal disclaimer	Can cap the term against another patent
Reissue or post-grant proceedings	May alter enforceable claim scope
Maintenance fees	Failure to pay can result in expiration for nonpayment

The patent’s issuance date is not its expiration date. A definitive expiration analysis should rely on the USPTO Patent Center record, the patent’s front page, terminal-disclaimer records, and any regulatory extension record.[3]

What is the Orange Book status of U.S. Patent 9,669,096?

The Orange Book listing status cannot be determined from the claim text alone. Orange Book status is product-specific and depends on whether the NDA holder submitted the patent for listing and whether FDA accepted the submission under the applicable listing standards.[4]

For methylnaltrexone products, the relevant FDA questions are:

Whether the patent is listed against NDA 021964 or another methylnaltrexone NDA.
Which strength and dosage form are covered.
Whether the listing identifies formulation, method-of-use, or drug-substance claims.
Whether the patent was listed before or after an abbreviated new drug application was filed.
Whether any listing was delisted, corrected, or challenged.

A formulation patent is generally relevant to an ANDA only if it is properly listed against the reference listed drug. If listed, an ANDA applicant may need to make a Paragraph IV certification, a “section viii” statement where appropriate, or a Paragraph III certification if the applicant accepts delayed approval until patent expiration.[5]

What Paragraph IV risks exist for a generic methylnaltrexone injection?

A generic applicant developing a 20 mg/mL methylnaltrexone injection would face several possible patent strategies.

Literal infringement risk

The highest risk exists where the proposed product has:

Methylnaltrexone bromide.
EDTA or an EDTA derivative.
pH between 3.0 and 4.0.
About 20 mg/mL active concentration.
A single active ingredient.
Comparable stability data.

That profile can implicate claims 1, 6, 20, 23, 24, 25, 27, 32, 33, and 38, depending on the exact composition.

Design-around strategy

A generic applicant could consider:

A pH outside 3.0-4.0.
A non-EDTA chelator.
A formulation without a chelating agent.
A different salt or concentration.
A different active-agent configuration, where clinically and regulatorily appropriate.
A dosage form that does not use the claimed solution architecture.

The most practical design-around is often substitution or elimination of EDTA. That option must be assessed against chemical stability, container compatibility, sterilization, extractables and leachables, and FDA comparability requirements.

Invalidity strategy

Potential invalidity issues could include:

Anticipation by an earlier stable methylnaltrexone solution containing EDTA at the claimed pH.
Obviousness based on methylnaltrexone formulation references combined with known EDTA stabilization practices.
Written-description or enablement challenges concerning the broad pH and concentration ranges.
Indefiniteness issues involving “about,” “stable,” “room temperature,” and degradation-product measurement.
Lack of predictable support across the full scope of “EDTA, or a derivative thereof.”

The stability limitations may complicate an anticipation challenge because the prior art must disclose, expressly or inherently, the claimed storage performance. They may also create proof issues in litigation because degradation results depend on analytical methods, container closure, temperature controls, and batch composition.

How strong is the patent estate for methylnaltrexone formulations?

The estate represented by U.S. Patent 9,669,096 is strongest against products that copy the marketed injectable formulation architecture. Its strength comes from layered claim coverage rather than from a single narrow claim.

Strength factor	Assessment
Commercial alignment	High for 20 mg/mL injectable solutions
Core pH coverage	Broad, pH 3.0-4.0
Chelator limitation	Meaningful but potentially design-aroundable
Concentration coverage	Broad, with a strong 20 mg/mL fallback
Stability claims	Useful but fact-intensive to prove
Salt coverage	Broad in independent claims; bromide-specific dependent claim
Sole-active-agent coverage	Strong for single-active products
Manufacturing coverage	Limited; sterilization is a dependent composition feature
Method-of-use coverage	None apparent from the supplied claims
API or synthesis coverage	None apparent from the supplied claims

The patent is less powerful against oral tablets, non-aqueous formulations, products without EDTA, and products using pH conditions outside the claimed range. It also does not, based on the supplied claims, provide a standalone barrier against a different methylnaltrexone salt or a formulation that does not meet the solution limitation.

What patent litigation and settlement issues affect this patent?

The supplied claim set does not identify a litigation docket, Paragraph IV notice, consent judgment, or settlement agreement involving U.S. Patent 9,669,096. Litigation exposure should be evaluated through Hatch-Waxman case records, FDA patent certifications, and federal court dockets.

The primary litigation triggers would be:

An ANDA for a 20 mg/mL methylnaltrexone injection.
A Paragraph IV notice alleging invalidity or non-infringement.
A 45-day period for filing an infringement action after receipt of notice.
Potential 30-month approval stay under 21 U.S.C. § 355(j)(5)(B)(iii), subject to statutory exceptions.
Settlement provisions governing launch dates, authorized generic rights, or licensing.

No settlement right, license, or launch date should be inferred from the patent claims or the existence of the marketed product.

How does U.S. Patent 9,669,096 compare with biosimilar and generic risk?

Biosimilar risk is not applicable because methylnaltrexone bromide is a small-molecule drug, not a biologic subject to the Public Health Service Act biosimilar pathway. The relevant competitive pathway is an ANDA for a generic drug under the Hatch-Waxman Act.[5]

The principal risks are:

Generic injectable competition after patent and regulatory exclusivity barriers expire.
Formulation design-arounds that avoid EDTA.
A Paragraph IV challenge to the pH and stability claims.
A product using the same commercial concentration but a different stabilizing system.
Litigation over whether a particular EDTA derivative falls within the claim language.

Key Takeaways

U.S. Patent 9,669,096 is a methylnaltrexone formulation patent.
The core claimed combination is methylnaltrexone, EDTA or an EDTA derivative, and pH 3.0-4.0.
The commercially important embodiment is methylnaltrexone bromide at about 20 mg/mL, EDTA at about 0.3-0.5 mg/mL, and pH about 3.5.
Claims 25-39 add sole-active-agent, storage-stability, and degradation limits.
The patent does not claim the methylnaltrexone molecule, a method of treatment, or a synthesis process.
EDTA substitution, pH adjustment, and non-solution dosage forms are the principal design-around routes.
A definitive expiration date and Orange Book status require review of USPTO and FDA product-specific records.
Biosimilar competition is not relevant; the competitive pathway is generic ANDA approval.
The patent presents the highest risk to a copycat injectable solution using the same concentration, chelator, pH, and stability profile.

FAQs About U.S. Patent 9,669,096

Does U.S. Patent 9,669,096 cover Relistor tablets?

The supplied claims are directed to a solution. A tablet would not ordinarily satisfy the solution limitation unless the product is supplied or used as a claimed solution. The patent therefore presents a greater risk to injectable or liquid formulations than to conventional tablets.

Can a methylnaltrexone product avoid the patent by using sodium edetate instead of edetate calcium disodium?

Potentially, but the substitution does not automatically avoid the patent. Sodium edetate is expressly identified in claim 7, while edetate calcium disodium is identified in claim 8. A product using sodium edetate could avoid claim 8 yet remain within claim 7 or claim 1.

Does the patent require the formulation to be injectable?

No. The supplied claims require a pharmaceutical solution and, in claim 22, optionally recite sterilization. They do not expressly require injection, subcutaneous administration, or any particular route.

Are the degradation limits required by every claim?

No. Claims 1 and 25 do not expressly require the numerical degradation limits. Those limitations appear in dependent claims, including claims 2, 3, 21, and 34-39.

Is EDTA itself the active ingredient?

No. EDTA or an EDTA derivative is claimed as a chelating agent and excipient. The active pharmaceutical ingredient is methylnaltrexone or its salt.

References

U.S. Food and Drug Administration. (n.d.). Relistor (methylnaltrexone bromide) injection, prescribing information. FDA.
United States Code. (2023). 35 U.S.C. § 154: Contents and term of patent; provisional rights.
United States Patent and Trademark Office. (n.d.). Patent Center. https://patentcenter.uspto.gov/
U.S. Food and Drug Administration. (2023). Approved drug products with therapeutic equivalence evaluations, commonly known as the Orange Book. FDA.
U.S. Food and Drug Administration. (2024). ANDA submissions: Refuse-to-receive standards and patent certification requirements. FDA.

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Australia	2004229463	⤷ Start Trial
Australia	2010202824	⤷ Start Trial
Australia	2013203378	⤷ Start Trial
Brazil	PI0409133	⤷ Start Trial
Canada	2521379	⤷ Start Trial
Canada	2811272	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 9,669,096

Summary for Patent: 9,669,096