United States Drug Patent 8,741,866: Claim Scope, Patisiran Coverage, Expiration and Patent Landscape

US Patent No. 8,741,866 is an Alnylam patent directed to transthyretin, or TTR, RNA interference. Its central claims cover dsRNA molecules containing a defined antisense sequence, use of those molecules to degrade TTR mRNA, lipid formulations using the ionizable lipid MC3, and treatment of transthyretin amyloidosis, including familial amyloidotic polyneuropathy, or FAP. The patent is closely associated with the active pharmaceutical ingredient and delivery technology used in Onpattro, patisiran.

The most commercially important claims are claims 16, 25, 26 and 27. Claim 27 is the narrowest and most product-specific claim. It requires the precise SEQ ID NO:1009/1010 duplex, an MC3-containing formulation, intravenous treatment of FAP, and a 0.3 mg/kg dose.

What does US Patent 8,741,866 cover?

US 8,741,866 covers methods of suppressing TTR expression with a defined double-stranded RNA. The patent does not broadly claim every TTR-targeting RNAi agent. Its scope is limited by the required sequence relationship, duplex length, therapeutic use, formulation, dose, or combination of those elements.

Claim group	Subject matter	Commercial relevance
Claims 1-15	In vitro or in vivo inhibition of TTR expression	Foundational RNAi activity claims
Claims 5-6	Specific sense and antisense sequence pairs	Sequence-specific coverage
Claims 7, 13-14	Lipid formulations, including MC3	Delivery-system coverage
Claims 16-24	Treatment of TTR amyloidosis	Core therapeutic method claims
Claims 25-26	SEQ ID NO:1009/1010 in an MC3 formulation	Product-linked method claims
Claim 27	FAP, exact duplex, MC3 formulation, 0.3 mg/kg	Narrowest high-value claim
Claims 28-30	Intravenous administration and MC3 formulation	Administration and formulation fallback claims

The independent claims are claims 1, 16 and 27. Claim 1 concerns TTR mRNA degradation in a cell. Claim 16 concerns treatment of a human with TTR amyloidosis. Claim 27 concerns FAP treatment with an exact duplex and a specified formulation and dose.

Which technical elements are required for infringement?

Literal infringement generally requires each limitation of the asserted claim to be present. The principal limitations are:

A double-stranded RNA.
A sense strand and an antisense strand.
An antisense region complementary to TTR mRNA.
A region of complementarity comprising SEQ ID NO:170.
Strand lengths of 19, 20, 21, 22, 23 or 24 nucleotides.
For treatment claims, administration to a human with a specified TTR-mediated disorder.
For narrower claims, the exact SEQ ID NO:1009/1010 duplex.
For formulation claims, an MC3-containing lipid formulation.
For claim 27, intravenous treatment of FAP at 0.3 mg/kg.

The use of "comprising" in claims 1, 4, 16 and related claims generally leaves room for additional elements or sequences, subject to the ordinary rules of claim construction. Claims 5, 6, 25, 26 and 27 use "consists of" for the identified strands. Those claims are materially narrower because the claimed strand sequence must match the specified sequence.

A competing TTR RNAi product with a different antisense sequence may avoid literal infringement of sequence-specific claims. It could still face separate patents covering other TTR sequences, chemical modifications, lipid nanoparticles, conjugates, dosing regimens or manufacturing methods.

What is the scope of claims 1 through 15?

Claims 1 through 4: basic TTR knockdown

Claim 1 requires contacting a cell with a TTR-targeting dsRNA and maintaining the cell long enough to degrade the TTR mRNA transcript. It covers both in vitro and in vivo activity through dependent claims 2 and 3.

Claim 4 requires the region of complementarity to consist of SEQ ID NO:170. The claim does not itself require the complete sense and antisense strands to be the sequences in claims 5, 6 or 7. This creates a broader sequence-format claim than the exact-duplex claims, provided the accused duplex contains the specified complementary region and satisfies the strand-length limitations.

Claims 5 and 6: specific duplexes

Claims 5 and 6 identify two precise sense/antisense pairs:

SEQ ID NO:449 and SEQ ID NO:450.
SEQ ID NO:729 and SEQ ID NO:730.

These claims are more resistant to ambiguity about the target sequence but are narrower than claim 1. Claim 6 serves as the basis for claims 29 and 30, which add lipid formulation and MC3 formulation limitations.

Claims 7 through 14: chemistry, conjugation and delivery

Claim 7 identifies SEQ ID NO:1009/1010 and requires a lipid formulation. Claims 13 and 14 more generally cover lipid formulations and MC3-containing formulations.

Claim 9 covers dsRNA containing at least one modified nucleotide. Claim 10 lists the principal modification categories, including:

2'-O-methyl nucleotides;
2'-deoxy-2'-fluoro nucleotides;
locked nucleotides;
2'-amino and 2'-alkyl modifications;
phosphorothioate groups;
morpholino nucleotides;
phosphoramidates;
non-natural bases; and
terminal cholesterol or dodecanoic acid bisdecylamide conjugates.

Claims 11 and 12 narrow the modification and conjugation scope by requiring at least one 2'-O-methyl modification or a ligand conjugate.

These claims are important because commercial siRNA products generally use chemical modification to improve nuclease stability, reduce innate immune activation and control pharmacokinetics. A product could avoid one modification claim while still falling within another sequence or formulation claim.

Claim 15: performance limitations

Claim 15 recites measured knockdown outcomes in HepG2 or Hep3B cells and dose-response results, including approximately:

95% TTR mRNA inhibition by real-time PCR;
74% inhibition by branched-DNA assay;
an IC50 below 10 pM;
an ED50 of approximately 1 mg/kg;
98.9% knockdown at 0.1 nM; and
99.4% knockdown at 10 nM.

These limitations create potential evidentiary disputes. A patent owner would need to establish that the accused product produces the claimed result under the specified assay or dose conditions. The claim may be less useful against a product whose sequence and formulation are identical but whose measured performance is not demonstrated under the recited conditions.

What diseases and dosing regimens are protected by claims 16 through 24?

Claim 16 covers treatment of TTR amyloidosis, including:

familial amyloidotic polyneuropathy;
familial amyloidotic cardiomyopathy;
leptomeningeal or central nervous system amyloidosis;
senile systemic amyloidosis; and
senile cardiac amyloidosis.

Claims 17 and 18 identify doses ranging from approximately 0.01 mg/kg to 5.0 mg/kg, with a specific dependent claim directed to 1.0 mg/kg.

Claims 21 and 22 add liver disease and liver transplantation. Those limitations may be relevant to clinical subpopulations but do not expand the basic disease scope of claim 16.

Claim 23 recites clinical or translational outcomes, including:

approximately 80% reduction of human liver TTR mRNA at 3 mg/kg;
lack of immunostimulatory activity measured by IFN-alpha and TNF-alpha assays;
approximately 97% reduction in liver TTR mRNA;
approximately 90% reduction in serum TTR protein;
suppression lasting up to 22 days; and
serum TTR suppression through day 14 after 1 mg/kg or 3 mg/kg treatment.

Claim 24 adds MC3 formulation and dose-dependent reduction of TTR mRNA or protein, including approximately 85% to 90% mRNA reduction at 0.3 mg/kg and approximately 50% reduction at 0.1 mg/kg.

These claims combine molecular identity, delivery system, dose and pharmacodynamic performance. They may be difficult to assert unless the relevant product and clinical protocol correspond closely to the claimed limitations.

Does claim 27 cover patisiran?

Claim 27 is strongly aligned with the original patisiran development program. It requires:

treatment of FAP;
administration to a human;
a dsRNA whose sense strand consists of SEQ ID NO:1009;
an antisense strand consisting of SEQ ID NO:1010;
a formulation containing MC3; and
administration at 0.3 mg/kg.

Onpattro is patisiran, an intravenously administered lipid complex containing a TTR-targeting siRNA. The FDA-approved product uses a lipid nanoparticle delivery system that includes the ionizable lipid DLin-MC3-DMA, commonly referred to as MC3. The approved product is indicated for polyneuropathy caused by hereditary transthyretin-mediated amyloidosis in adults. The approved clinical regimen is 0.3 mg/kg intravenously once every three weeks, subject to the product label and body-weight dosing rules. [1]

Claim 27 is therefore commercially important but narrow. It does not cover every patisiran dose or every TTR amyloidosis indication. It requires FAP, the precise duplex, MC3 and the 0.3 mg/kg dose. Claims 16, 19, 20, 25 and 26 provide broader or alternative routes to infringement depending on the accused product and use.

What are the patent expiration and exclusivity dates?

The patent issued on June 10, 2014. Its nominal patent term is based on the earliest relevant nonprovisional filing date in the family and is expected to extend into approximately December 2027, subject to any terminal disclaimer, patent-term adjustment or other USPTO term calculation. The exact enforceable expiration date should be taken from the USPTO Patent Center record and the current Orange Book entry rather than inferred solely from the issue date. [2,3]

Event	Date or status
Patent	US 8,741,866
Assignee	Alnylam Pharmaceuticals, Inc.
Issue date	June 10, 2014
Technology	TTR-targeting dsRNA and MC3 lipid formulation
Expected nominal term	Approximately December 2027
FDA product associated with technology	Onpattro, patisiran
Regulatory pathway	New drug application, not a biosimilar pathway
Key commercial risk	Generic or 505(b)(2) challenge after applicable regulatory and patent protections

Patent expiration is separate from FDA regulatory exclusivity. Onpattro received FDA approval in August 2018. Its approval was supported by orphan-drug designation for hereditary transthyretin-mediated amyloidosis, which provided seven years of orphan-drug exclusivity for the approved indication under the applicable statutory framework. Orphan exclusivity does not prevent approval of a product for a different indication or necessarily block all forms of competition. [1,4]

What is the Orange Book status of US 8,741,866?

The relevant question is whether US 8,741,866 is listed for Onpattro and whether the listing covers the approved product, method of use or both. Orange Book listings can change through FDA updates, patent expiration, delisting, corrections and litigation certifications.

The patent's claims are structurally suitable for Orange Book listing because they include methods of treating TTR amyloidosis and formulation-linked treatment methods. However, an Orange Book listing does not establish infringement or validity. It gives an NDA holder a statutory mechanism to receive notice of an abbreviated new drug application containing a Paragraph IV certification.

The practical review should distinguish:

patents listed against Onpattro;
patents covering the active siRNA sequence;
patents covering MC3 lipid nanoparticles;
patents covering manufacturing processes;
patents covering dosing schedules; and
patents covering alternative TTR RNAi sequences.

A complete freedom-to-operate analysis cannot rely on US 8,741,866 alone. Patisiran-related protection is distributed across sequence, formulation, lipid composition, manufacturing and therapeutic-use families.

Are there Paragraph IV challenges or generic-entry risks?

A generic applicant could challenge an Orange Book-listed patent by certifying that the patent is invalid, unenforceable or not infringed under Paragraph IV of the Hatch-Waxman Act. The applicant would need to address both the active siRNA and the injectable lipid formulation.

The practical generic-entry risks are:

Entry route	Risk profile
505(j) ANDA for identical patisiran	High sequence and formulation overlap; technical equivalence is demanding
505(b)(2) application with a related lipid formulation	Potentially more flexible, but still exposed to method and formulation patents
Alternative TTR siRNA	Lower risk under exact-sequence claims; separate patent families may apply
Non-lipid delivery system	May avoid MC3 claims but face bioavailability and efficacy barriers
Biosimilar application	Not applicable to Onpattro because it is regulated as a small-molecule/new-drug product rather than a biologic

FDA approval of a generic or 505(b)(2) product would also require resolution of patent certifications, litigation stays, regulatory exclusivity and any applicable pediatric or orphan protections. No biosimilar pathway applies because Onpattro is not licensed under the Public Health Service Act as a biological product.

Which companies challenge the commercial position of patisiran?

The principal competitive products are other TTR-lowering medicines rather than conventional generics.

Product	Company	Modality	Administration	Competitive distinction
Onpattro, patisiran	Alnylam	siRNA in lipid nanoparticle	Intravenous	First approved TTR RNAi product; MC3 delivery
Amvuttra, vutrisiran	Alnylam	GalNAc-conjugated siRNA	Subcutaneous	Less frequent administration and no intravenous infusion
Tegsedi, inotersen	Ionis Pharmaceuticals/AstraZeneca	Antisense oligonucleotide	Subcutaneous	TTR antisense mechanism
Wainua, eplontersen	Ionis Pharmaceuticals/AstraZeneca	Ligand-conjugated antisense	Subcutaneous	Designed for less frequent dosing
Tafamidis products	Pfizer and others by market	TTR stabilizer	Oral	Stabilizes TTR rather than reducing TTR production

Vutrisiran is the most direct Alnylam competitor to patisiran. Its sequence and GalNAc delivery system differ from the MC3-liposomal patisiran platform. The different molecular architecture reduces the likelihood of literal infringement of claim 27, but it does not eliminate exposure to separate TTR sequence or use patents.

How strong is the patent estate for patisiran?

US 8,741,866 is strongest in four areas:

Exact or near-exact TTR-targeting sequences.
MC3-containing lipid formulations.
Treatment of hereditary TTR amyloidosis.
Clinical dose and pharmacodynamic combinations tied to the patisiran development program.

Its principal limitations are equally important:

It is a method patent rather than a composition-of-matter claim to every possible TTR RNAi agent.
Several claims require specific sequence identifiers.
Claim 27 requires FAP, MC3 and 0.3 mg/kg.
Performance claims may require assay-specific proof.
A competitor using another TTR sequence or a different delivery system may avoid literal infringement.
Patent expiration is expected well before the end of the commercial life of the broader TTR therapeutic class.

The estate is therefore strong against an identical or highly similar patisiran copy, but less decisive against competing TTR silencers using alternative sequences, conjugates or delivery technologies.

What manufacturing and IP barriers affect generic entry?

The main technical barriers are lipid nanoparticle production, siRNA chemical synthesis, duplex annealing, impurity control, particle-size consistency, encapsulation efficiency and release testing. A generic applicant would need to demonstrate pharmaceutical equivalence and bioequivalence under a complex injectable product framework.

MC3-related patents may create additional exposure even if the applicant uses the same TTR sequence. Conversely, a non-MC3 formulation may avoid some patent claims but create new clinical and regulatory hurdles.

Manufacturing patents can remain commercially relevant after a sequence patent expires if they cover:

lipid nanoparticle assembly;
mixing and encapsulation conditions;
purification;
sterile filtration;
vial composition;
particle-size control; or
stability and storage processes.

Geographically, US 8,741,866 has no direct effect outside the United States. Corresponding national-phase patents may create separate risks in Europe, Japan, China, Canada and other markets. Patent term, prosecution history, claim amendments and enforceability must be reviewed jurisdiction by jurisdiction.

What litigation and settlement issues should investors monitor?

The principal litigation triggers are:

Paragraph IV certification against an Orange Book-listed patent;
declaratory judgment actions concerning non-infringement or invalidity;
disputes over whether the accused duplex contains the claimed sequence;
challenges to MC3 formulation claims;
obviousness and written-description attacks on sequence claims;
enablement challenges involving the breadth of TTR dsRNA claims;
prosecution-history estoppel; and
settlements that restrict launch timing or define authorized generic rights.

A settlement can materially change the effective market-entry date without changing the statutory patent expiration date. Public litigation dockets, FDA Orange Book updates, USPTO Patent Center and company SEC filings are the controlling sources for current litigation and settlement status. [2,3,5]

Key Takeaways

US 8,741,866 covers TTR-targeting dsRNA methods, TTR amyloidosis treatment, MC3 lipid formulations and specified patisiran-related sequences.
Claims 16, 25, 26 and 27 are the principal commercial claims.
Claim 27 is narrow but closely aligned with a patisiran treatment using the exact SEQ ID NO:1009/1010 duplex, MC3 and 0.3 mg/kg for FAP.
The expected patent term extends into approximately December 2027, subject to the official USPTO and Orange Book term records.
The patent is relevant to Onpattro but does not cover every TTR-lowering product.
Vutrisiran, inotersen and eplontersen use materially different molecular or delivery technologies and represent competitive, not necessarily infringing, products.
Generic entry would face sequence, formulation, manufacturing, regulatory and patent-certification barriers.
No biosimilar pathway applies to Onpattro.
A complete market-entry analysis must review the entire Alnylam TTR patent family, Orange Book listings, formulation patents, manufacturing patents and current Paragraph IV litigation.

FAQs About US Patent 8,741,866 and Patisiran

Does US 8,741,866 claim patisiran itself?

It primarily claims methods using specified TTR-targeting dsRNA molecules. It is not a universal composition claim covering every physical sample of patisiran, but several claims are closely tailored to patisiran-related sequences and MC3 formulations.

Does the patent cover vutrisiran?

Not necessarily. Vutrisiran uses a different TTR-targeting siRNA and a GalNAc conjugate rather than the MC3 lipid nanoparticle platform. Separate sequence, conjugate and method-of-use patents must be analyzed.

Can a generic launch occur immediately after the patent expires?

Not automatically. FDA exclusivity, other Orange Book patents, formulation patents, manufacturing patents, litigation stays and regulatory review can affect the actual launch date.

Is MC3 itself patented separately from US 8,741,866?

Yes, MC3 and lipid nanoparticle technology may be covered by separate patents and patent families. The existence of MC3 limitations in US 8,741,866 does not define the entire MC3 patent landscape.

What is the primary invalidity risk for this patent?

Potential challenges may focus on obviousness, written description, enablement, claim construction and whether the claimed sequence, formulation and clinical limitations are adequately supported by the specification. The risk must be assessed claim by claim rather than at the patent level as a whole.

References

U.S. Food and Drug Administration. (2018). Onpattro prescribing information: Patisiran lipid complex injection.
U.S. Patent and Trademark Office. (2014). US Patent No. 8,741,866, Double-stranded ribonucleic acid for inhibiting transthyretin expression.
U.S. Food and Drug Administration. (n.d.). Approved drug products with therapeutic equivalence evaluations, Orange Book.
U.S. Food and Drug Administration. (n.d.). Orphan drug designation and exclusivity.
Alnylam Pharmaceuticals, Inc. (2023). Annual report on Form 10-K.

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Alnylam Pharms Inc	ONPATTRO	patisiran sodium	SOLUTION;INTRAVENOUS	210922-001	Aug 10, 2018		RX	Yes	Yes	8,741,866	⤷ Start Trial				TREATMENT OF POLYNEUROPATHY OF HEREDITARY TRANSTHYRETIN-MEDIATED AMYLOIDOSIS	⤷ 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	2937418	⤷ Start Trial	122018000133	Germany	⤷ Start Trial
European Patent Office	2937418	⤷ Start Trial	300965	Netherlands	⤷ Start Trial
European Patent Office	2937418	⤷ Start Trial	PA2019501	Lithuania	⤷ Start Trial
European Patent Office	2937418	⤷ Start Trial	2019C/501	Belgium	⤷ Start Trial
European Patent Office	2937418	⤷ Start Trial	3/2019	Austria	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 8,741,866

Which drugs does patent 8,741,866 protect, and when does it expire?

Summary for Patent: 8,741,866