United States Patent 8,101,743: Scope, Claims, Expiration, and Transthyretin Antisense Patent Landscape

U.S. Patent No. 8,101,743 is an Isis Pharmaceuticals patent directed to 20-nucleotide antisense oligonucleotides targeting transthyretin, or TTR, using a 5-10-5 gapmer architecture. The core claim covers a sequence-defined TTR antisense compound with 2′-O-methoxyethyl or constrained sugar wings, a deoxynucleotide gap, and broad phosphorothioate and cytosine-methylation options. The claimed chemistry is consistent with the architecture used for inotersen, marketed as Tegsedi, although product coverage depends on whether the marketed sequence falls within SEQ ID NO: 74 and the remaining limitations.

The patent’s principal commercial value was composition-of-matter protection for a TTR-targeting antisense sequence. Its nominal U.S. patent term has ended or is near the end of term based on the earliest claimed priority date, subject to the USPTO’s final patent-term-adjustment and terminal-disclaimer records. Later TTR patents, regulatory exclusivities, manufacturing know-how, and sequence-specific patent families may still affect generic entry.

What drug and technology does U.S. Patent 8,101,743 cover?

The patent covers antisense oligonucleotides designed to bind TTR messenger RNA and reduce TTR expression through RNase H-mediated degradation. The claimed compounds use a “gapmer” structure:

Structural element	Claimed configuration
Total length	20 linked nucleosides
Central gap	Deoxynucleosides
5′ wing	Modified-sugar nucleosides
3′ wing	Modified-sugar nucleosides
Preferred architecture	Five modified nucleosides, ten deoxynucleosides, five modified nucleosides
Wing chemistry	2′-O-methoxyethyl or 4′-(CH2)n-O-2′ bridged sugar
Backbone	At least one phosphorothioate linkage; claim 9 requires all linkages to be phosphorothioate
Base modification	Optional or complete 5-methylcytosine substitution
Target	Nucleobase sequence complementary to SEQ ID NO: 4 and at least 95% identical to SEQ ID NO: 74

The patent is directed to a platform and sequence-specific species rather than to a conventional small-molecule active ingredient. The relevant product class is a chemically modified antisense oligonucleotide, not a biologic antibody or peptide.

Inotersen is a 20-nucleotide antisense oligonucleotide approved by the FDA in 2018 for hereditary transthyretin-mediated amyloidosis in adults. Its approved labeling describes a phosphorothioate backbone and 2′-O-methoxyethyl-modified wings, which are technically consistent with the claimed gapmer design.[2]

How does claim 1 define the protected compound?

Claim 1 contains several cumulative limitations. An accused molecule must satisfy all of them.

1. A 20-nucleoside compound

The modified oligonucleotide must consist of exactly 20 linked nucleosides. Molecules containing 19 or 21 nucleosides fall outside the literal length limitation, although a different patent could cover those molecules.

2. Sequence complementarity to SEQ ID NO: 4

The claim requires a nucleobase sequence “100% complementary” to SEQ ID NO: 4 over the entire modified oligonucleotide. This is a full-length complementarity requirement. It excludes partial target binding arrangements unless the relevant sequence is still fully complementary across the 20-nucleotide claimed sequence.

3. At least 95% identity to SEQ ID NO: 74

For a 20-nucleotide sequence, 95% identity generally means at least 19 of 20 positions are identical, depending on the identity convention used in the patent and litigation record. The claim therefore covers the exact SEQ ID NO: 74 sequence and certain one-base variants, subject to the separate requirement of complete complementarity to SEQ ID NO: 4.

This creates an important claim-construction issue. A sequence variant must satisfy both sequence conditions. A one-base substitution may meet the identity limitation but fail the full-complementarity limitation.

4. Gapmer configuration

The deoxynucleotide gap must be located between a 5′ wing and a 3′ wing. The claim does not require five nucleosides in each wing; that narrower architecture appears in claim 6.

5. Modified sugars in both wings

Each nucleoside in each wing must have a modified sugar. The central gap is limited to linked deoxynucleosides, while the wings can use one or more modified-sugar classes identified in the dependent claims.

What do claims 2 through 9 add?

Claim	Added limitation	Practical effect
2	2′-O-methoxyethyl sugar or 4′-(CH2)n-O-2′ bridge, where n is 1 or 2	Covers major modified-sugar chemistries, including MOE-type and bridged sugar structures
3	At least one phosphorothioate linkage	Broad backbone limitation
4	At least one 5-methylcytosine	Covers partial methylation
5	Bicyclic sugar	Covers constrained or bridged sugar systems
6	Five-nucleotide 5′ wing, ten-nucleotide DNA gap, five-nucleotide 3′ wing; all wing sugars are 2′-MOE; all cytosines are 5-methylcytosine; every linkage is phosphorothioate	Narrow, commercially relevant 5-10-5 MOE gapmer species
7	Composition with compound or salt plus pharmaceutically acceptable carrier or diluent	Covers formulated pharmaceutical compositions
8	Sugar mimetic	Extends sugar coverage beyond the expressly recited sugar structures
9	Every internucleoside linkage is phosphorothioate	Narrows claim 3 from one or more phosphorothioates to a fully phosphorothioate backbone

Claim 6 is the most commercially important dependent claim because it describes the classic 5-10-5 MOE gapmer configuration associated with first-generation Ionis antisense products. Claim 9 separately reinforces the full-phosphorothioate backbone.

What formulations are protected by U.S. Patent 8,101,743?

Claim 7 covers a composition containing the claimed oligonucleotide, or a salt of that oligonucleotide, together with a pharmaceutically acceptable carrier or diluent. The claim is broad as to the carrier. It does not require a particular injection vehicle, concentration, buffer, preservative, syringe, vial, or dosing regimen.

The claim can potentially reach:

A pharmaceutical solution containing the claimed antisense oligonucleotide.
A prefilled syringe containing the compound.
A vial formulation containing the compound and diluent.
A salt form of the oligonucleotide in a pharmaceutical carrier.
A formulation used for subcutaneous administration.

Claim 7 does not, on its face, establish protection for a specific formulation technology. A later patent would be needed to protect a particular concentration, stabilizer, buffer system, delivery device, depot formulation, or administration protocol.

What is the scope of the 5-10-5 MOE gapmer claim?

Claim 6 is a narrow but commercially significant composition claim. It requires:

Exactly 20 linked nucleosides.
Five-nucleoside 5′ wing.
Ten linked deoxynucleosides in the gap.
Five-nucleoside 3′ wing.
2′-O-methoxyethyl sugar in every wing nucleoside.
5-methylcytosine at every cytosine position.
Phosphorothioate at every internucleoside linkage.

A product that has the same target sequence but uses a 2′-fluoro, 2′-constrained ethyl, morpholino, peptide nucleic acid, phosphodiester, or mixed backbone may avoid literal infringement of claim 6. It could still implicate claim 1, claim 2, claim 5, claim 8, or other patent families depending on its precise structure.

Claim 6 is therefore narrower than claim 1 but potentially stronger for a product that exactly follows the commercial MOE gapmer design.

What is the relationship between Patent 8,101,743 and inotersen?

Inotersen, sold as Tegsedi by Ionis Pharmaceuticals and commercialized with Akcea Therapeutics, is the principal commercial product associated with the TTR antisense technology covered by this patent family. The FDA approved Tegsedi under NDA 211172 in October 2018 for hereditary transthyretin-mediated amyloidosis in adults.[2]

Product	Active modality	Target	FDA status
Tegsedi	Inotersen antisense oligonucleotide	TTR mRNA	FDA approved
Vutrisiran	siRNA	TTR mRNA	FDA approved
Patisiran	siRNA lipid nanoparticle	TTR mRNA	FDA approved
Eplontersen	Ligand-conjugated antisense oligonucleotide	TTR mRNA	FDA approved in the United States in 2023

Inotersen and the TTR small-interfering RNA products share a biological target but use different delivery and gene-silencing mechanisms. Patent overlap is therefore more likely at the target, sequence, formulation, manufacturing, or therapeutic-use level than at the literal compound level.

When does U.S. Patent 8,101,743 lose exclusivity?

The nominal patent term is calculated from the earliest effective nonprovisional filing date, subject to patent-term adjustment, patent-term extension, and any terminal disclaimer. U.S. Patent 8,101,743 is an early-2000s patent and its ordinary 20-year term is associated with an expiration period in the 2023-2024 range.

The exact enforceable endpoint must be determined from the USPTO patent-term record, not from the issued claims alone. FDA regulatory exclusivity is separate from patent term. For inotersen, the product was approved in 2018, and the five-year New Chemical Entity exclusivity period would have expired in 2023. Because inotersen is an oligonucleotide, it does not present the biosimilar pathway issues that apply to protein biologics.

Patent term versus regulatory exclusivity

Protection type	Relevance to TTR antisense products
Composition patent	Protects the defined oligonucleotide structure and sequence
Formulation patent	Protects a particular pharmaceutical composition
Method-of-use patent	Protects treatment of a defined disease or patient group
Manufacturing patent	Protects synthesis, purification, conjugation, or process controls
FDA NCE exclusivity	Blocks certain abbreviated applications for five years from approval
Orphan-drug exclusivity	May block approval of the same drug for the same orphan indication for seven years
Patent-term extension	Potentially extends a qualifying patent based on regulatory review

The patent’s expiration does not automatically create generic competition. An applicant must still establish pharmaceutical equivalence, analytical comparability, manufacturing control, and clinical or regulatory acceptability for the applicable FDA pathway.

What is the Orange Book status of inotersen and this patent?

Tegsedi is approved under an NDA and may be evaluated through FDA’s Approved Drug Products with Therapeutic Equivalence Evaluations, commonly called the Orange Book, for listed patent information. The Orange Book is primarily relevant to small-molecule drug products and does not create a separate biosimilar framework for antisense oligonucleotides.[3]

A patent’s presence or absence in the Orange Book does not determine its validity. It affects the statutory notice and certification framework for an ANDA applicant. Patents that are not listed may still create infringement risk under 35 U.S.C. § 271(e)(2), depending on the application and asserted patent.

For an oligonucleotide product, the most relevant regulatory alternatives may include:

An ANDA, if FDA determines that the applicant’s product can meet the generic-drug requirements.
A 505(b)(2) application, if the product differs in formulation, route, dosage, or other clinically relevant attributes.
A full NDA, if the product is not sufficiently similar to the reference product.
A biosimilar application is generally not the natural pathway because inotersen is not a protein biologic.

Which companies are challenging the patent estate?

No broadly established public record identifies a litigated Paragraph IV challenge specifically directed to U.S. Patent 8,101,743. The known competitive challenge to TTR antisense products has primarily come from alternative modalities and products rather than from a disclosed generic infringement case.

The principal competitors are:

Company	Product	Modality	Competitive position
Alnylam Pharmaceuticals	Patisiran, Onpattro	Lipid nanoparticle siRNA	Established TTR silencing product
Alnylam Pharmaceuticals	Vutrisiran, Amvuttra	GalNAc-siRNA	Subcutaneous TTR silencing competitor
AstraZeneca	Vutrisiran commercialization collaboration	GalNAc-siRNA	Commercial partner for Amvuttra
Ionis Pharmaceuticals	Inotersen, Tegsedi	Antisense oligonucleotide	First-generation TTR antisense product
Ionis Pharmaceuticals and AstraZeneca	Eplontersen, Wainua	Ligand-conjugated antisense	Newer antisense TTR product

The main competitive threat to inotersen is product substitution by longer-interval or more convenient TTR-lowering therapies. Vutrisiran and eplontersen have more favorable dosing convenience than weekly inotersen, which can reduce the commercial value of legacy inotersen patents even before complete generic entry.

What method-of-use patents affect TTR antisense products?

U.S. Patent 8,101,743 is principally a compound and composition patent based on the supplied claims. It does not expressly claim:

A weekly dosing regimen.
Treatment of hereditary ATTR polyneuropathy.
Treatment of ATTR cardiomyopathy.
Reduction of serum TTR concentration.
A particular patient genotype.
Use in combination with a TTR stabilizer.
A specific loading or maintenance schedule.

Those concepts may be covered by separate method-of-use patents or regulatory exclusivities. For inotersen, the FDA-approved indication is hereditary transthyretin-mediated amyloidosis in adults. The commercial patent analysis must therefore separate the sequence patent from later patents directed to dosing, patient selection, disease subtype, safety management, and administration.

The distinction matters because a generic applicant may avoid an asserted method-of-use patent through a section viii “skinny label” if the patented indication can be carved out, while a composition patent generally presents a more direct barrier.

How strong is the patent estate for inotersen?

The patent estate is strongest where the marketed product matches the claimed sequence and chemistry exactly. It is weaker against structurally redesigned oligonucleotides that maintain TTR activity through a different backbone or sugar system.

Strength factors

Exact 20-nucleotide sequence coverage.
Full-length complementarity requirement tied to a defined target sequence.
95% identity language covering limited sequence variation.
Broad dependent claims covering MOE, bridged sugars, bicyclic sugars, and sugar mimetics.
Separate protection for a pharmaceutical composition.
Commercially validated 5-10-5 phosphorothioate gapmer architecture.

Weakness factors

The patent term is at or near expiration.
Claim 1 requires multiple structural and sequence limitations simultaneously.
Claim 6 is narrow and may be avoided through chemistry or architecture changes.
The patent does not independently claim every TTR therapeutic use.
Antisense products can be designed around through alternative sugar, backbone, conjugation, or sequence choices.
Validity challenges may focus on written description, enablement, anticipation, obviousness, and the scope of sequence identity.

The 95% identity limitation could face written-description and enablement scrutiny if interpreted to cover a broad set of sequence variants without commensurate support. The patent’s specification, sequence listings, prosecution history, and any terminal disclaimer would be central to that analysis.

What generic entry risks exist for inotersen?

A generic or follow-on applicant faces several technical and legal barriers:

Sequence identity. The applicant must determine whether its product uses the same or an equivalent sequence.
Sugar chemistry. MOE, constrained, bridged, and other sugar systems may trigger different claims.
Backbone structure. An all-phosphorothioate backbone is more exposed to claims 6 and 9 than a redesigned mixed backbone.
Analytical comparability. Oligonucleotide impurities, stereochemistry, chain length, metabolites, and aggregate profiles must be controlled.
Pharmacokinetic comparability. Tissue distribution and plasma half-life may differ from small molecules.
Regulatory pathway. FDA may require a 505(b)(2) or NDA rather than an ANDA.
Use patents. A noninfringing compound can still face method-of-use assertions.
Manufacturing patents. Solid-phase synthesis, purification, scale-up, and impurity removal can be separately protected.

A generic launch scenario is most plausible after expiry or invalidation of the core composition claims, provided no later patent blocks the proposed product. A 505(b)(2) applicant could launch earlier only after addressing listed patents, unlisted patent litigation risk, regulatory exclusivity, and any required clinical bridging.

How does Patent 8,101,743 compare with competing TTR patent estates?

Issue	Inotersen / 8,101,743	Patisiran	Vutrisiran	Eplontersen
Modality	Antisense gapmer	siRNA in lipid nanoparticle	GalNAc-siRNA	Ligand-conjugated antisense
Claimed sequence risk	Direct sequence and chemistry coverage	Different RNA duplex and delivery claims	Different siRNA and conjugate claims	Later antisense sequence and conjugate claims
Delivery	Subcutaneous oligonucleotide	Intravenous lipid nanoparticle	Subcutaneous conjugate	Subcutaneous conjugate
Generic pathway	Likely ANDA or 505(b)(2), depending on product	Complex NDA/biologic-like comparability issues	Complex siRNA comparability	Likely 505(b)(2) or NDA
Principal commercial issue	Weekly dosing and legacy product position	Infusion burden	Dosing convenience	Newer antisense platform
Patent exposure	Core composition term largely exhausted or near exhaustion	Multiple formulation, delivery, and use families	Conjugate and use patent families	Newer composition, conjugate, and use families

The competing products do not automatically infringe Patent 8,101,743 because they use different molecular architectures. Their patent estates may nevertheless overlap in disease treatment, TTR suppression, dosing, patient selection, or manufacturing.

What patent litigation affects this patent family?

The supplied claim set alone does not identify a reported infringement action involving Patent 8,101,743. Public litigation analysis should distinguish among:

Cases naming U.S. Patent 8,101,743 directly.
Cases involving continuation or divisional patents in the same TTR family.
Inter partes review or post-grant proceedings.
Patent-listing disputes involving Tegsedi.
Litigation involving competing TTR products but unrelated patents.

The absence of a known public Paragraph IV case directed to this patent does not establish that the patent was unasserted or uncontested. It indicates that the commercial record is more heavily shaped by patent expiration, newer TTR products, and modality competition than by a visible generic court battle.

What manufacturing and intellectual-property barriers remain?

Manufacturing may remain a meaningful barrier after composition-patent expiry. Commercial antisense production requires control over:

Solid-phase synthesis.
Phosphorothioate stereochemistry.
Deprotection and cleavage.
Full-length and n-1 impurity removal.
Residual solvent and metal control.
Duplex or secondary-structure impurities.
Sterile filtration and aseptic fill.
Stability in the final injectable formulation.

These processes may be covered by separate patents, trade secrets, regulatory filing data, or manufacturing know-how. A competitor can avoid the expired composition patent yet face substantial development cost and regulatory risk.

Key Takeaways

U.S. Patent 8,101,743 covers a 20-nucleotide TTR antisense gapmer with defined sequence, complementary-target, and modified-sugar limitations.
Claim 6 is the narrow commercial species: a 5-10-5 gapmer with 2′-MOE wings, a ten-nucleotide DNA gap, 5-methylcytosines, and an all-phosphorothioate backbone.
Claim 7 extends protection to pharmaceutical compositions containing the compound or its salt.
The claims are consistent with the chemistry used for inotersen, or Tegsedi, subject to sequence confirmation against the patent’s sequence listings.
The patent’s nominal U.S. term falls in the 2023-2024 period, subject to USPTO patent-term adjustment and terminal-disclaimer data.
Inotersen does not present a conventional biosimilar risk because it is an antisense oligonucleotide rather than a protein biologic.
Generic entry would still face sequence, chemistry, analytical, manufacturing, regulatory, and potential method-of-use barriers.
Patisiran, vutrisiran, and eplontersen compete through different molecular platforms and do not automatically fall within the literal claims.
The principal residual value is likely in later TTR patent families, regulatory exclusivity, manufacturing know-how, and product differentiation rather than in the original composition claims alone.

FAQs

Does Patent 8,101,743 cover all TTR antisense oligonucleotides?

No. It covers a defined 20-nucleotide sequence or narrowly related sequence, specific gapmer architecture, and modified-sugar limitations. A different TTR sequence or substantially different chemistry may fall outside the claims.

Can a 19-mer or 21-mer avoid this patent?

It may avoid the literal “consisting of 20 linked nucleosides” limitation, but it could still implicate other patents or an infringement theory based on equivalents. The full patent family and prosecution history would control the analysis.

Does a phosphorothioate backbone alone infringe claim 9?

No. Claim 9 requires the other limitations of claim 3 and claim 1, including the 20-nucleotide sequence and gapmer structure. It then requires every internucleoside linkage to be phosphorothioate.

Is inotersen protected by a biosimilar patent framework?

No. Inotersen is an antisense oligonucleotide. A follow-on product would more likely use an ANDA, 505(b)(2), or NDA pathway rather than the conventional biologic biosimilar pathway.

Can an alternative TTR siRNA infringe Patent 8,101,743?

A conventional siRNA product using a different duplex architecture would generally not satisfy the claimed 20-nucleotide antisense gapmer limitations. It could face separate patents directed to TTR silencing, delivery, formulation, or treatment methods.

References

United States Patent and Trademark Office. (2012). U.S. Patent No. 8,101,743, antisense modulation of transthyretin expression.
U.S. Food and Drug Administration. (2018). Tegsedi (inotersen sodium) injection: Prescribing information.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations, commonly known as the Orange Book.
United States Code. (2023). 35 U.S.C. §§ 154, 156, 271(e), and 282.
United States Patent and Trademark Office. (2024). Patent term adjustment and patent term disclaimer records.

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Astrazeneca Ab	WAINUA (AUTOINJECTOR)	eplontersen sodium	SOLUTION;SUBCUTANEOUS	217388-001	Dec 21, 2023		RX	Yes	Yes	⤷ Start Trial	⤷ Start Trial	Y	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

Details for Patent: 8,101,743

Which drugs does patent 8,101,743 protect, and when does it expire?

Summary for Patent: 8,101,743