US Patent 8,871,938: Delafloxacin Manufacturing Claims, Scope, Expiration, and Patent Landscape

US Patent 8,871,938 protects a controlled chlorination process for manufacturing delafloxacin, together with delafloxacin compositions containing less than about 0.40% of a specified dimeric impurity. The patent is narrower than a composition-of-matter patent because it requires a defined starting material, chlorination step, acid ratio, impurity threshold, and delafloxacin product identity.

The principal commercial risk is process infringement, not direct blocking of every delafloxacin product. A generic manufacturer can potentially avoid infringement by using a different chlorination system, acid concentration, solvent, impurity-control strategy, or manufacturing route. The composition claims create a separate risk if the resulting commercial batch falls within the claimed impurity specification.

What drug does US Patent 8,871,938 protect?

The claimed quinolone is delafloxacin, an anionic fluoroquinolone antibacterial marketed in the United States as Baxdela.

The claimed chemical structure is:

1-(6-amino-3,5-difluoropyridin-2-yl)-8-chloro-6-fluoro-7-(3-hydroxyazetidin-1-yl)-4-oxo-1,4-dihydroquinoline-3-carboxylic acid
The patent also covers pharmaceutically acceptable salts and esters of the specified compound.

The process begins with the corresponding des-chloro intermediate. The manufacturing objective is to introduce chlorine at the 8-position while limiting formation of a dimeric impurity.

Element	Claimed requirement
Final product	Delafloxacin or a pharmaceutically acceptable salt or ester
Starting material	Des-chloro delafloxacin intermediate
Transformation	Chlorination
Chlorinating agent	Broadly defined in claim 1; N-chlorosuccinimide in dependent claims
Acid	Acid-to-substrate molar ratio of about 0.008 to about 0.012
Dimeric impurity	Less than about 0.40 area percent
Preferred acid	Sulfuric acid
Preferred temperature	Approximately 13°C to 21°C
Preferred NCS ratio	Approximately 1.04 to 1.07 equivalents
Preferred solvent	Methyl acetate
Optional downstream step	Base treatment, particularly potassium hydroxide in aqueous isopropanol
Commercial-scale limitation	Expressly recited in claims 20 and 22

What are the independent claims in US 8,871,938?

The patent has two substantive independent claim categories.

Claim 1: chlorination process

Claim 1 requires all of the following:

Reacting the specified des-chloro quinolone or its salt or ester.
Using a chlorinating agent and an acid.
Maintaining an acid-to-des-chloro quinolone molar ratio of about 0.008 to about 0.012.
Producing less than about 0.40% of the specified dimeric impurity.
Producing delafloxacin or a corresponding salt or ester.

This is a product-defined process claim. The claim does not cover every process that chlorinates the des-chloro intermediate. It covers only a process that satisfies both the operating conditions and the impurity result.

Claim 21: low-impurity composition

Claim 21 covers a composition containing delafloxacin or its salt or ester with less than about 0.40% of the specified dimeric impurity.

Unlike claim 1, claim 21 does not expressly require use of N-chlorosuccinimide, sulfuric acid, methyl acetate, or any particular reaction temperature. A manufacturer could therefore avoid the process claims yet still face composition-claim exposure if the commercial batch meets the claimed impurity limitation.

The composition claim raises an important enforcement issue: the claim does not, on its face, require that the low impurity level result from the patented process. A product manufactured by a different route could potentially fall within claim 21.

How broad is the scope of claim 1?

Claim 1 is materially narrower than the chemical definition of delafloxacin.

The claim requires:

The specific des-chloro delafloxacin precursor.
A chlorination reaction.
An acid within a narrow molar ratio.
Less than approximately 0.40 area percent dimeric impurity.
Delafloxacin as the resulting quinolone.

The claim is not limited to N-chlorosuccinimide, sulfuric acid, acetate solvent, potassium hydroxide, or commercial scale. Those limitations appear in dependent claims. A process using a different chlorinating agent or acid may still infringe claim 1 if it meets the expressly recited acid ratio and impurity threshold.

The phrase "about" creates potential claim-construction disputes. The numerical range of 0.008 to 0.012 is likely to be interpreted with some tolerance, depending on the specification, prosecution history, analytical precision, and accepted process variability. The same issue applies to "less than about 0.40%" and the NCS ratios in claims 9 and 10.

Which dependent claims create the strongest process coverage?

The most commercially relevant dependent claims are claims 2, 4, 7, 10, 13, 17, 20, and 22.

Claim	Limitation	Commercial significance
2	N-chlorosuccinimide as chlorinating agent	Captures the likely preferred chlorination route
4	Sulfuric acid	Narrows the acid system to the preferred embodiment
7	Reaction temperature of about 13°C to 21°C	Targets controlled production conditions
10	NCS-to-substrate ratio of about 1.04 to 1.07	Provides a narrow process-control claim
13	Methyl acetate solvent	Covers the preferred reaction solvent
17	Potassium hydroxide as base	Covers a defined downstream conversion or treatment
20	Commercial-scale process	Targets manufacturing operations rather than laboratory work
22	Commercial-scale low-impurity composition	Targets release batches and commercial supply

Claims 20 and 22 may be important in litigation because they are directed expressly to commercial-scale operations. Their enforceability will depend on how the patent defines or supports "commercial scale." If the specification does not provide an objective boundary, the term may generate an indefiniteness or claim-construction dispute.

What formulations are protected by US Patent 8,871,938?

The patent does not principally protect a finished dosage-form formulation.

Its composition claim is directed to delafloxacin containing less than about 0.40% of a specified dimeric impurity. The claim does not expressly require:

An intravenous formulation.
An oral tablet.
A particular excipient.
A specific dosage strength.
A pH.
A container or delivery device.
A sterile product.
A particular salt form, unless the selected salt is within the claim.

The patent therefore differs from a formulation patent covering, for example, an injectable solution, a tablet composition, particle size, release profile, stabilizer system, or reconstitution formulation.

What is the significance of the dimeric impurity limitation?

The dimeric impurity limitation is the technical center of the patent.

The specified impurity is identified as:

1-amino-3-(azetidin-3-yloxy)-propan-2-ol-bis(N,N'-quinolone carboxylic acid), or a pharmaceutically acceptable salt or ester.

The patent attempts to link process conditions to impurity control. The less-than-0.40% threshold can create three separate disputes:

Analytical method: The parties may dispute the HPLC or other method used to calculate area percent.
Sampling: Batch homogeneity and sampling location may affect the result.
Threshold interpretation: A batch at or near 0.40% may raise questions concerning "about," assay variability, and measurement error.

For an abbreviated new drug application applicant, process development records and batch-release data would be important in assessing exposure. The relevant question is not simply whether the applicant uses N-chlorosuccinimide. It is whether the complete process and resulting delafloxacin material satisfy the claim limitations.

When does US Patent 8,871,938 lose exclusivity?

The patent was granted on October 28, 2014. Its ordinary patent term is generally measured from the earliest effective nonprovisional or international application filing date, subject to patent-term adjustment, terminal disclaimers, and any applicable patent-term extension.

Public patent-family information places the relevant priority and filing history in the 2011-2012 period. On that basis, the ordinary expiration is expected to fall approximately in 2031-2032, rather than 2034 based solely on the grant date. The exact expiration date must be determined from the USPTO patent-term record and any terminal disclaimer or adjustment entry.[1]

Event	Date or status
Patent	US 8,871,938
Grant	October 28, 2014
Subject matter	Delafloxacin chlorination process and low-dimer composition
Expected ordinary term	Approximately 2031-2032, subject to USPTO term calculations
Patent-term extension	No conclusion established from the claims supplied
Patent-term adjustment	Must be checked in the USPTO record
Orange Book effect	Separate from patent validity and enforceability

What is the Orange Book status of US Patent 8,871,938?

A manufacturing-process patent does not automatically qualify for Orange Book listing.

FDA regulations generally permit listing of patents that claim the drug substance, drug product, or an approved method of using the drug. A patent directed only to a manufacturing process ordinarily presents a weaker basis for Orange Book listing than a composition-of-matter, formulation, or method-of-use patent.[2]

Claim 21 could create a listing argument because it covers a delafloxacin composition with a defined impurity level. The practical question is whether the claim reads on the approved drug product as required by FDA listing rules. Claims 1 and 20, standing alone, are manufacturing-process claims and are less likely to support traditional Orange Book listing.

The Orange Book status should therefore be evaluated separately from the patent's validity. Absence of an Orange Book listing would not eliminate potential infringement under 35 U.S.C. § 271(g), § 271(a), or other applicable provisions.[3]

What Paragraph IV challenges could target this patent?

A generic applicant filing an ANDA for delafloxacin could use a Paragraph IV certification if it determines that the patent is invalid, unenforceable, or will not be infringed.

Potential Paragraph IV positions include:

The claimed acid ratio is indefinite.
"About 0.40%" lacks an objective boundary.
The dimeric impurity cannot be reliably measured using the disclosure.
The claims are obvious over earlier delafloxacin chlorination processes.
The claimed impurity threshold is an inherent result of routine optimization.
The claims lack written-description support across the full scope of the listed acids and chlorinating agents.
The commercial-scale limitations lack sufficient objective definition.
The applicant uses a different route that does not satisfy the process limitations.
The applicant's batch contains more than the claimed impurity threshold.

The strongest noninfringement strategy would generally be a designed-around process that changes more than one material limitation. Substituting only sulfuric acid or only methyl acetate may not be sufficient because claim 1 is not limited to those preferred embodiments.

What patent litigation and settlement risks affect delafloxacin?

A complete current litigation determination cannot be made from the claims alone. The relevant litigation search should include:

District court complaints involving US 8,871,938.
ANDA litigation under the Hatch-Waxman framework.
Federal Circuit decisions construing the claims.
USPTO Patent Trial and Appeal Board proceedings.
Patent assignment and merger records.
Any settlement that permits an authorized generic or delayed generic launch.

In commercial terms, the likely dispute would focus on process evidence rather than product labeling. Discovery could include:

Master batch records.
Raw-material specifications.
Reaction temperature profiles.
Acid and NCS charge calculations.
Solvent records.
In-process analytical testing.
Dimeric impurity chromatograms.
Process validation reports.
Technology-transfer documents.

A generic company may face a higher evidentiary risk if its final batch satisfies the composition claim even where its manufacturing process differs.

How strong is the patent estate for delafloxacin?

US 8,871,938 is a focused process patent, not a complete delafloxacin patent estate. Its strength is highest where a commercial manufacturer uses the claimed combination of:

Des-chloro delafloxacin intermediate.
N-chlorosuccinimide.
Low acid loading.
Acetate solvent.
Controlled temperature.
Low dimer formation.
Commercial-scale operation.

Its strength is lower against a manufacturer that:

Uses an alternative chlorination reagent.
Changes the acid system or operates outside the claimed acid ratio.
Uses a materially different intermediate.
Produces a batch above the impurity threshold.
Uses a route that introduces chlorine at a different synthetic stage.
Demonstrates that the dimeric impurity is not present below the claimed level.

The composition claim broadens the enforcement risk because it can reach the product independently of the manufacturing route. Its practical value depends on the approved product's actual impurity specification and the ability to prove the dimeric impurity concentration reliably.

How does this patent compare with composition and formulation patents?

Patent type	Typical scope	Relevance of US 8,871,938
Composition-of-matter patent	Delafloxacin molecule itself	US 8,871,938 is not primarily this type
Salt or crystal-form patent	Specific solid state or salt	Not the principal subject
Formulation patent	Tablet, injectable, excipient, release profile	Not the principal subject
Method-of-use patent	Treatment of an indication	Not claimed here
Manufacturing-process patent	Synthesis, purification, impurity control	Core category
Product-by-process or quality composition claim	Product defined by impurity or process-related characteristics	Claim 21 has this profile

What generic launch scenarios exist?

Three scenarios are commercially plausible.

Launch after patent expiry

The generic waits for the relevant patent term to expire and launches without challenging US 8,871,938. This reduces litigation exposure but may delay entry if other delafloxacin patents remain in force.

Paragraph IV challenge

The generic challenges validity or infringement. The key litigation issues would likely be obviousness, definiteness of the impurity threshold, claim construction of "about," and proof that the proposed process or product falls outside the claims.

Noninfringing process launch

The generic launches using an alternative route and provides a noninfringement certification or relies on the patent not being listed for the relevant product. This strategy is strongest when process analytics demonstrate that the final product does not satisfy claim 21.

Key Takeaways

US 8,871,938 is directed to delafloxacin manufacturing and impurity control.
Claim 1 requires the specific des-chloro intermediate, chlorination, a narrow acid ratio, and less than about 0.40% dimeric impurity.
Claims 2-20 add preferred reagents, solvents, temperatures, ratios, bases, and commercial-scale limitations.
Claim 21 independently covers delafloxacin compositions below the specified dimeric impurity threshold.
The patent does not primarily protect a tablet, injectable formulation, therapeutic indication, or the delafloxacin molecule generally.
The expected ordinary expiration is approximately 2031-2032, subject to USPTO patent-term adjustment, terminal disclaimers, and any extension.
A generic can potentially design around the process claims, but a low-impurity final product may still create composition-claim risk.
Orange Book relevance is stronger for claim 21 than for the purely process-oriented claims, but listing must be confirmed against the FDA record.
The highest-value diligence items are patent-family status, USPTO term calculation, FDA Orange Book entries, assignment history, and ANDA litigation records.

FAQs

Does US Patent 8,871,938 cover all methods of making delafloxacin?

No. It covers methods satisfying the specific starting-material, chlorination, acid-ratio, and impurity limitations. Alternative routes may fall outside the claims.

Can a manufacturer infringe claim 21 without using N-chlorosuccinimide?

Yes. Claim 21 is a composition claim and does not expressly require N-chlorosuccinimide. A product made by another process could still be implicated if it contains the claimed delafloxacin composition with less than about 0.40% of the specified dimer.

Is US 8,871,938 a delafloxacin formulation patent?

No. It is principally a process and impurity-control patent. It does not claim a specific tablet, injectable formulation, excipient system, or release profile.

What analytical test matters for the dimeric impurity claim?

The relevant test is the validated analytical method used to determine the dimeric impurity as an area percentage of the quinolone. Method specificity, detection limits, batch sampling, and chromatographic integration may affect enforcement.

Does patent expiration guarantee immediate generic delafloxacin entry?

No. Other patents, regulatory exclusivity, pediatric exclusivity, product-specific requirements, supply constraints, or separate formulation and method-of-use rights may affect launch timing.

References

United States Patent and Trademark Office. (2014). US Patent No. 8,871,938, Process for preparing quinolone compounds. U.S. Department of Commerce.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book.
35 U.S.C. §§ 271, 281, 282, 283, 284, 285.
21 C.F.R. §§ 314.3, 314.50, 314.53.
U.S. Food and Drug Administration. (2017). Baxdela (delafloxacin) prescribing information.

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Melinta	BAXDELA	delafloxacin meglumine	POWDER;INTRAVENOUS	208611-001	Jun 19, 2017		RX	Yes	Yes	8,871,938	⤷ Start Trial		Y			⤷ Start Trial
Melinta	BAXDELA	delafloxacin meglumine	TABLET;ORAL	208610-001	Jun 19, 2017		RX	Yes	Yes	8,871,938	⤷ Start Trial		Y			⤷ Start Trial
>Applicant	>Tradename	>Generic Name	>Dosage	>NDA	>Approval Date	>TE	>Type	>RLD	>RS	>Patent No.	>Patent Expiration	>Product	>Substance	>Delist Req.	>Patented / Exclusive Use	>Submissiondate

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
European Patent Office	3214083	⤷ Start Trial	301091	Netherlands	⤷ Start Trial
European Patent Office	3214083	⤷ Start Trial	122021000010	Germany	⤷ Start Trial
European Patent Office	3214083	⤷ Start Trial	132021000000011	Italy	⤷ Start Trial
European Patent Office	3214083	⤷ Start Trial	LUC00196	Luxembourg	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 8,871,938

Which drugs does patent 8,871,938 protect, and when does it expire?

Summary for Patent: 8,871,938