United States Patent 11,266,660: Scope, Claims, Exclusivity and Patent Landscape for Birch Bark Oleogel

US Patent 11,266,660 protects methods of treating epidermolysis bullosa with a birch bark extract oleogel. Its core commercial relevance is the topical 10% birch-triterpene product marketed as Filsuvez by Chiesi Farmaceutici. The patent focuses on formulation architecture and manufacturing quality attributes rather than betulin as a molecule.

The broadest practical infringement risk concerns an epidermolysis bullosa product that combines:

Solid birch bark extract particles;
At least 70 wt. % betulin;
Particle size below approximately 50 micrometers;
A nonpolar liquid, particularly vegetable oil or sunflower oil; and
One or more claimed physical, sterilization, or stability characteristics.

The patent contains three independent method claims. Claims 1 through 10 require a sterile, radiation-sterilized oleogel. Claims 11 through 18 require a defined consistency. Claims 19 through 25 require a preparation process using a nonpolar liquid with a peroxide value below 3. Claims 26 through 28 expressly add topical administration.

What does US Patent 11,266,660 protect?

US 11,266,660 protects treatment methods defined by the composition administered and, depending on the independent claim, by sterilization, rheology, or manufacturing conditions. It is not a broad patent on all uses of birch bark extract or all betulin-containing wound products.

The patent’s claim structure is:

Claim group	Independent claim	Principal limiting feature	Dependent claims
Sterile oleogel	1	Ionizing irradiation at 11-40 kGy	2-10
Consistency-defined oleogel	11	Consistency of 300-3,000 mN	12-18
Process-defined oleogel	19	Nonpolar liquid peroxide value below 3	20-25
Topical-use additions	26-28	Topical administration to EB area	Claims 1, 11 and 19 respectively

The independent claims are method claims. A product manufacturer would generally face infringement exposure when its product is administered to treat epidermolysis bullosa and meets the relevant formulation limitations. Manufacture or sale of the oleogel alone may not satisfy every method claim, although induced or contributory infringement theories could become relevant depending on product labeling, instructions and other facts.

What are the independent claims in US 11,266,660?

Claim 1: Sterile radiation-sterilized oleogel

Claim 1 requires all of the following:

A method of treating epidermolysis bullosa;
Administration to a subject in need;
A sterile oleogel;
Approximately 1 wt. % to 20 wt. % solid birch bark extract particles;
Average particle size below approximately 50 micrometers;
Dispersion in one or more nonpolar liquids;
At least approximately 70 wt. % betulin in the solid extract;
Betulinic acid, oleanolic acid, erythrodiol or lupeol as an additional triterpene; and
Sterilization by ionizing radiation at approximately 11-40 kGy.

Claim 1 is the most operationally specific independent claim. It does not cover a formulation merely because it contains betulin. The radiation dose and sterile status are express limitations.

Claim 2 narrows the radiation range to 11-20 kGy. Claim 3 limits the radiation to X-ray or gamma radiation. Claim 4 requires the birch extract particles to be the only oleogel-forming agent. Claims 5-10 add concentration, oil, particle-size, separation and rheology limitations.

Claim 11: Consistency-defined oleogel

Claim 11 removes the express radiation-sterilization requirement but adds a texture limitation. The oleogel must have a consistency of 300-3,000 mN, measured by the specified penetration test.

This claim requires:

Treatment of epidermolysis bullosa;
Administration of the specified birch bark oleogel;
1-20 wt. % extract particles;
Average particle size below approximately 50 micrometers;
At least approximately 70 wt. % betulin;
One or more listed triterpenes; and
Consistency of 300-3,000 mN under the specified test method.

Claim 11 may be broader than claim 1 in relation to sterilization because it does not expressly require ionizing radiation. It is narrower in relation to the required consistency measurement.

Claim 19: Peroxide-value process claim

Claim 19 covers a treatment method using an oleogel prepared by:

Dispersing 1-20 wt. % dried solid birch bark extract;
Using extract particles with an average size below approximately 50 micrometers;
Using extract with at least approximately 70 wt. % betulin and a listed triterpene; and
Using a nonpolar liquid with a peroxide value below 3.

Unlike claim 1, claim 19 does not expressly require sterilization. Unlike claim 11, it does not require the 300-3,000 mN consistency range. Its central manufacturing limitation is the low peroxide value of the nonpolar liquid.

How broad is the claim scope?

The patent has meaningful but technically narrow scope. Its commercial strength comes from the convergence of limitations that closely describe the marketed formulation rather than from a broad genus claim.

Core claim elements

Technical element	Claim 1	Claim 11	Claim 19
Epidermolysis bullosa treatment	Yes	Yes	Yes
Birch bark extract	Yes	Yes	Yes
At least 70% betulin	Yes	Yes	Yes
Listed additional triterpene	Yes	Yes	Yes
1-20 wt. % particles	Yes	Yes	Yes
Average particle size below 50 μm	Yes	Yes	Yes
Nonpolar liquid	Yes	Yes	Yes
Ionizing irradiation	Yes	No	No
Sterile oleogel	Yes	No express requirement	No express requirement
Consistency 300-3,000 mN	No	Yes	No
Peroxide value below 3	No	No	Yes
Topical administration	Claims 1 and 26	Claims 11 and 27	Claims 19 and 28

The claims are cumulative. A competitor would need to avoid at least one required limitation of each asserted claim, not merely change a secondary excipient or alter the product name.

What formulations are protected by the patent?

The formulation features most closely aligned with the patent are:

Approximately 10 wt. % solid birch bark extract;
Betulin-rich triterpene extract;
Sunflower oil or another vegetable oil;
No separate oleogel-forming agent;
Extract particles below 50 micrometers;
Low liquid separation after centrifugation;
Defined viscosity and thixotropy;
Defined consistency;
Low peroxide value of the carrier oil; and
Sterilization with gamma or X-ray radiation.

Claims 4, 12 and the corresponding limitations in the claim groups are commercially important because they cover an oleogel in which the dispersed solid extract itself acts as the only oleogel-forming agent. A formulation using a separate wax, polymer, silica, cellulose derivative or other gelling system could fall outside those narrower claims, although it could remain within claims that do not require the extract to be the sole oleogel-forming agent.

Formulation limitation analysis

Design variable	Claimed range or requirement	Design-around relevance
Birch extract concentration	1-20 wt. %	Below 1% or above 20% may avoid literal scope of the independent claims
Betulin content	At least about 70 wt. %	A lower-betulin extract may avoid the claims
Particle size	Average below about 50 μm	Larger average particle size is a potential design-around
Carrier	One or more nonpolar liquids	A sufficiently different polar or mixed vehicle may avoid this element
Oil peroxide value	Below 3, claim 19	Higher peroxide value may avoid claim 19 but can create stability issues
Radiation	11-40 kGy, claim 1	Other sterilization methods may avoid claim 1
Consistency	300-3,000 mN, claim 11	Outside the range may avoid claim 11
Additional gelling agent	Extract alone in narrower claims	A separate gelling agent may avoid dependent claims 4 and 12
Administration	Treatment of EB, topical claims 26-28	Non-EB use is outside the express treatment indication

A design-around must be assessed against all independent claims. Avoiding radiation, for example, does not address claim 11 or claim 19. Increasing particle size may affect all three claim groups, but the resulting product could lose the physical stability and spreadability attributes that motivated the formulation.

When does US 11,266,660 lose exclusivity?

The patent is associated with a projected expiration date in 2036, generally reported as June 29, 2036, subject to the official USPTO patent-term calculation and any applicable adjustment or extension. The patent issued on March 1, 2022, from a family directed to birch bark extract oleogels and their use in epidermolysis bullosa treatment.[1][2]

The principal regulatory exclusivity period is separate from patent exclusivity. FDA approved Filsuvez on June 28, 2022, for wounds associated with dystrophic and junctional epidermolysis bullosa in adult and pediatric patients aged six months and older.[3] The product received orphan-drug designation. Orphan-drug exclusivity generally runs for seven years from approval, placing the principal period through June 28, 2029, barring statutory exceptions.[4]

Exclusivity type	Relevant date
FDA approval of Filsuvez	June 28, 2022
Expected orphan exclusivity end	June 28, 2029
US 11,266,660 projected patent expiration	June 29, 2036
Earliest practical patent challenge window	Before 2036, subject to ANDA or litigation timing

Orphan exclusivity blocks FDA approval of the same drug for the same orphan indication, subject to the statutory framework. It does not automatically prevent every competing product, off-label use, or a product approved for a different indication.

What is the Orange Book status of Filsuvez and US 11,266,660?

Filsuvez was approved under NDA 215064. The product is a topical gel containing birch triterpenes and is regulated as a prescription drug product. US 11,266,660 is associated with the Filsuvez product and is relevant to Orange Book-based patent certification analysis.[3][5]

The commercial significance of an Orange Book listing depends on:

Whether the patent is listed against the relevant NDA;
The patent’s listed use code, if applicable;
Whether an ANDA applicant relies on the listed drug;
The certification selected by the ANDA applicant; and
Whether the NDA holder initiates litigation within the statutory period after receiving a Paragraph IV notice.

A method-of-use patent can be particularly important where the product has a narrow orphan indication. The patent claims here are framed around treatment of epidermolysis bullosa, making indication and labeling central to any generic-entry strategy.

Which companies are challenging the patent?

No publicly documented Paragraph IV litigation or final court judgment involving US 11,266,660 is identified in the cited FDA, USPTO and patent-record materials. The absence of a disclosed case does not establish that no confidential certification, pre-suit notice or unreported commercial dispute exists.

The most likely challenger would be an ANDA applicant seeking approval for a product that relies on Filsuvez as the reference listed drug. Because the claims are method claims tied to epidermolysis bullosa treatment, an ANDA applicant could consider:

Paragraph III certification, accepting delayed launch until patent expiration;
Paragraph IV certification, asserting invalidity, unenforceability or non-infringement;
A section viii statement carving out the patented treatment method, where permitted; or
A 505(b)(2) application with a different formulation, indication or labeling strategy.

The practical availability of a section viii carve-out depends on the approved labeling and the scope of the listed use. A carve-out is more difficult when the patented method corresponds directly to the reference product’s only or principal approved use.

What patent litigation and settlement risks exist?

A Paragraph IV filing could trigger a 30-month stay of approval if the patent holder files an infringement action within the statutory period. Settlement terms could include:

An agreed generic launch date;
A license with an earlier entry date;
Restrictions tied to the EB indication;
An authorized-generic arrangement;
Supply or manufacturing rights; or
No-challenge provisions, subject to antitrust limits.

No public settlement agreement involving US 11,266,660 is identified in the cited record. The absence of a settlement means the patent remains an untested barrier from the perspective of a reported judicial claim-construction or validity ruling.

How strong is the patent estate for Filsuvez?

The patent estate is strongest against a product that closely copies the commercial formulation and labeling. It is weaker against products that materially alter the extract, carrier, particle size, sterilization process or approved indication.

Strengths

Three independent method claims provide alternative infringement theories.
The claims cover both product attributes and manufacturing conditions.
The claim groups address sterilization, consistency and peroxide control separately.
The claims map closely to a defined topical formulation.
The 2036 patent term extends well beyond the 2029 orphan-exclusivity period.

Vulnerabilities

The claims are technically detailed and require multiple limitations.
They do not broadly cover every betulin-containing composition.
A challenger could target written description, enablement, indefiniteness or obviousness.
Rheology and consistency limitations require reproducible testing under specified methods.
Method claims depend on the administered product and the treatment indication.
Alternative sterilization or carrier systems may avoid individual claim groups.

The strongest invalidity theories would likely focus on prior art combinations involving betulin-rich birch bark extract, topical wound treatment, oleogel formation, particle-size reduction and radiation sterilization. The strongest non-infringement theories would focus on a different extract composition, particle-size distribution, vehicle, manufacturing process or indication.

What generic launch scenarios exist?

Launch after patent expiry

A conventional ANDA applicant could wait for the patent to expire and seek approval without litigating the patent. This approach avoids Paragraph IV litigation but delays entry until after the expected 2036 patent expiration, unless other patents or exclusivity periods create a different constraint.

Paragraph IV launch

A Paragraph IV applicant could challenge the patent before 2036. The applicant would need to show that one or more asserted claims are invalid or not infringed. The commercial upside is earlier entry; the principal risks are a 30-month stay, injunction exposure and litigation costs.

Formulation design-around

A competitor could develop a product that uses:

A non-birch triterpene source;
A birch extract below the claimed betulin threshold;
Particles with a different size profile;
A polar or mixed vehicle;
A different consistency range;
A different manufacturing stability specification; or
A formulation with a separate gelling agent.

Such a product would still face regulatory, clinical and product-performance requirements. Avoiding the patent does not eliminate the need to demonstrate safety, efficacy, stability and acceptable wound application characteristics.

Different indication

A product labeled for a non-EB wound indication could reduce method-of-use risk, although it could encounter other patent claims, regulatory requirements or off-label-use theories.

How does the patent compare with regulatory and commercial protection?

Protection layer	Scope	End date or status
US 11,266,660	EB treatment using specified birch bark oleogels	Projected June 29, 2036
Orphan-drug exclusivity	Same drug and same orphan indication	Expected June 28, 2029
FDA approval	Filsuvez NDA 215064	Active
Trademark and commercial rights	Filsuvez brand and Chiesi commercialization	Separate from patent term
Manufacturing know-how	Particle size, dispersion, sterilization and stability controls	Potentially indefinite if maintained as trade secret

Patent protection is the principal long-duration barrier. Orphan exclusivity provides earlier regulatory protection but is materially shorter. Manufacturing know-how may strengthen the practical barrier because reproducing the claimed consistency, low separation and particle-size profile can require controlled processing even after a competitor avoids literal infringement.

What is the licensing and ownership position?

The product originated from the birch bark triterpene technology developed around Birken AG and was commercialized by Amryt Pharma. Chiesi Farmaceutici acquired Amryt, including the Filsuvez business, in 2023.[6] The transaction changed commercial control but did not eliminate the underlying patent rights.

The relevant business distinction is:

Patent ownership and prosecution rights;
NDA ownership and regulatory responsibility;
Commercial distribution rights; and
Manufacturing or supply arrangements.

Public transaction materials establish Chiesi’s acquisition of Amryt and Filsuvez commercialization. They do not, by themselves, establish the complete set of patent licenses, sublicenses or supply agreements relating to US 11,266,660.

What is the revenue exposure from this patent?

The patent protects the formulation and indication underlying Filsuvez, so its economic value is linked to sales of Filsuvez for dystrophic and junctional epidermolysis bullosa. A generic or competing product entering before 2036 could affect:

Price and payer negotiations;
Specialty-pharmacy distribution;
Prescriber retention;
Patient-support economics;
International launch sequencing; and
The return on manufacturing and clinical investments.

The largest exposure is not a broad dermatology market. It is the concentrated market for EB wound treatment. Orphan-drug economics can support high per-patient pricing, but the patient population is small and reimbursement access is material.

Geographic coverage and international patent risk

US 11,266,660 provides rights only in the United States. International risk must be assessed separately through the corresponding patent family, national-phase grants and local term calculations.

Relevant jurisdictions for a Filsuvez launch include:

European Patent Convention states;
United Kingdom;
Japan;
Canada;
Australia; and
Other markets where Filsuvez or a competing birch-triterpene product is approved.

A US design-around does not establish freedom to operate in Europe or other jurisdictions. Conversely, expiration or invalidity of a foreign counterpart does not affect the US patent.

Key Takeaways

US 11,266,660 is a formulation-linked method patent for treating epidermolysis bullosa with a betulin-rich birch bark oleogel.
The patent has three independent claim groups covering radiation sterilization, consistency and low-peroxide manufacturing.
The most commercially relevant formulation is approximately 10% solid birch bark extract in sunflower oil, with sub-50-micrometer particles and betulin-rich triterpenes.
The expected US patent expiration is June 29, 2036.
Filsuvez received FDA approval on June 28, 2022, with orphan exclusivity expected through June 28, 2029.
No publicly documented Paragraph IV litigation or settlement involving US 11,266,660 is identified in the cited materials.
The patent is strongest against a close copy of the Filsuvez formulation and EB labeling.
Potential design-around paths include changing extract composition, particle size, vehicle, consistency, sterilization method, peroxide specification or indication.
Chiesi controls the Filsuvez business following its acquisition of Amryt Pharma.

FAQs

Is US 11,266,660 a composition patent or a method patent?

It is principally a method patent. The independent claims require treating epidermolysis bullosa by administering an oleogel with specified composition and physical or manufacturing characteristics.

Does the patent cover every product containing betulin?

No. The claims require a specific birch bark extract profile, including at least approximately 70 wt. % betulin, specified additional triterpenes, particle-size limits and a nonpolar liquid.

Can a competitor avoid the patent by using a different sterilization method?

Potentially, for claim 1. Claims 11 and 19 do not expressly require the radiation-sterilization limitation, so a complete freedom-to-operate analysis must evaluate those claims separately.

Does orphan exclusivity prevent all competing EB products until 2029?

No. Orphan exclusivity generally restricts approval of the same drug for the same orphan indication. It does not automatically block every different formulation, drug, indication or off-label use.

Does patent expiration in 2036 guarantee immediate generic entry?

No. A generic applicant must still satisfy FDA requirements, address any other unexpired patents or exclusivities, and obtain approval for its proposed labeling and formulation.

References

United States Patent and Trademark Office. (2022). US Patent No. 11,266,660, Oleogel comprising a solid birch bark extract. https://patents.google.com/patent/US11266660B2/en
Google Patents. (2022). US11266660B2 patent family and legal-status record. https://patents.google.com/patent/US11266660B2/en
U.S. Food and Drug Administration. (2022). FDA approves first treatment for wounds associated with rare genetic skin disorder. https://www.fda.gov/news-events/press-announcements/fda-approves-first-treatment-wounds-associated-rare-genetic-skin-disorder
U.S. Food and Drug Administration. (2024). Orphan drug designation and exclusivity. https://www.fda.gov/industry/developing-products-rare-diseases-conditions/designating-orphan-product-drugs-and-biological-products
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations: Orange Book. https://www.fda.gov/drugs/drug-approvals-and-databases/approved-drug-products-therapeutic-equivalence-evaluations-orange-book
Chiesi Farmaceutici S.p.A. (2023). Chiesi completes acquisition of Amryt Pharma. https://www.chiesi.com/eni/news/chiesi-completes-acquisition-of-amryt-pharma/

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Chiesi	FILSUVEZ	birch triterpenes	GEL;TOPICAL	215064-001	Dec 18, 2023		RX	Yes	Yes	11,266,660	⤷ Start Trial				USE OF BIRCH TRITERPENES FOR THE TREATMENT OF WOUNDS ASSOCIATED WITH DYSTROPHIC AND JUNCTIONAL EPIDERMOLYSIS BULLOSA	⤷ 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
Australia	2019205091	⤷ Start Trial
Brazil	112020009867	⤷ Start Trial
Canada	3081624	⤷ Start Trial
China	111356479	⤷ Start Trial
Colombia	2020006242	⤷ Start Trial
European Patent Office	3735274	⤷ Start Trial
European Patent Office	4249057	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 11,266,660

Which drugs does patent 11,266,660 protect, and when does it expire?

Summary for Patent: 11,266,660