US Patent 7,339,053: Scope, Claims, Expiration, and Islatravir Patent Landscape

US Patent 7,339,053 principally covers islatravir, also known as EFdA or MK-8591, through claim 1: 2′-deoxy-4′-C-ethynyl-2-fluoroadenosine. The patent also claims closely related 4′-cyano, 2-chloro, phosphonate, and unsaturated nucleoside analogs. Its U.S. patent term has expired, and it did not create an Orange Book barrier because islatravir has not received FDA approval.

The patent remains historically important because it covers the core small-molecule active ingredient that Merck developed for HIV treatment and prevention. Commercial risk now depends on later patent families covering formulations, dosing regimens, crystalline forms, manufacturing processes, and combination products rather than on US 7,339,053 itself.

What compounds does US Patent 7,339,053 claim?

The ten claims are compound claims. They do not claim a broad chemical genus, a pharmaceutical composition, a method of treating HIV, or a particular manufacturing process.

Claim	Claimed compound or class	Commercial relevance
1	2′-Deoxy-4′-C-ethynyl-2-fluoroadenosine	Islatravir, EFdA, MK-8591
2	4′-C-cyano-2′-deoxy-2-fluoroadenosine	Islatravir-related analog
3	2-Chloro-2′-deoxy-4′-C-ethynyladenosine	Chloro analog
4	2′-Deoxy-4′-C-ethynyl-2-fluoroadenosine 5′-H-phosphonate	Phosphonate derivative or synthetic intermediate
5	2′,3′-Didehydro-2′,3′-dideoxy-4′-C-ethynyl-2-fluoroadenosine	Unsaturated analog
6	2′,3′-Didehydro-2′,3′-dideoxy-4′-C-cyano-2-fluoroadenosine	Unsaturated cyano analog
7	2′,3′-Didehydro-2′,3′-dideoxy-4′-C-ethynyl-2-chloroadenosine	Unsaturated chloro analog
8	2′,3′-Dideoxy-4′-C-ethynyl-2-fluoroadenosine	Dideoxy ethynyl analog
9	2′,3′-Dideoxy-4′-C-cyano-2-fluoroadenosine	Dideoxy cyano analog
10	2′,3′-Dideoxy-4′-C-ethynyl-2-chloroadenosine	Dideoxy chloro analog

The central structural features are:

An adenosine purine base.
A halogen at the 2-position of the adenine base for most claims.
A carbon substituent at the 4′ position of the sugar, principally ethynyl or cyano.
Defined changes at the 2′ and 3′ positions, including deoxygenation and unsaturation.

Claim 1 is the commercially significant claim because its compound is islatravir. The claim is directed to the molecule itself, not merely to its use against HIV.

What is the scope of claim 1 covering islatravir?

Claim 1 is a narrow product claim to 2′-deoxy-4′-C-ethynyl-2-fluoroadenosine. A product claim of this type generally reaches the claimed compound regardless of:

The synthetic route used to make it.
The formulation in which it is administered.
Whether it is used for treatment, prevention, or another pharmaceutical purpose.
Whether it is supplied as a solid, solution, salt, solvate, or other form, subject to the precise chemical identity and claim construction.
Whether it is administered alone or in combination with another active ingredient.

The claim does not expressly recite a salt, crystalline form, dosage strength, route of administration, or indication. Its practical coverage is therefore strongest against manufacture, importation, sale, offer for sale, or use of the exact claimed active compound during the patent term.

The claim is not a broad claim to all 4′-substituted nucleosides. A compound that replaces the 4′-ethynyl group with cyano, for example, would fall outside claim 1 but may implicate claim 2. A 2-chloro analog may fall under claim 3 or claim 7, depending on the remaining structural features.

How do claims 2 through 10 differ from claim 1?

Claims 2 through 10 create a small analog series rather than a single broad Markush claim.

Claims 2 and 3: non-islatravir analogs

Claim 2 covers the 4′-cyano, 2-fluoro analog. Claim 3 covers the 2-chloro, 4′-ethynyl analog. These claims expand protection laterally across changes to either the 4′ substituent or the 2-position halogen.

The claims do not appear to cover every possible halogen or every possible 4′ substituent. Their language is compound-specific. Fluorine, chlorine, ethynyl, and cyano are expressly identified, and a different substituent would require separate claim support.

Claim 4: 5′-H-phosphonate derivative

Claim 4 covers the 5′-H-phosphonate derivative of the islatravir nucleoside. This claim is technically distinct from claim 1. It may have relevance to nucleotide synthesis, prodrug chemistry, or an intermediate used in preparing the nucleoside.

A commercial formulation containing only islatravir would not automatically practice claim 4. Conversely, a manufacturing process that transiently creates the claimed phosphonate could raise process-related infringement questions, depending on the process steps and the statutory basis asserted.

Claims 5 through 10: unsaturated and dideoxy analogs

Claims 5 through 10 introduce 2′,3′-didehydro or 2′,3′-dideoxy configurations. These structural changes affect the sugar ring and distinguish the compounds from the saturated nucleoside in claim 1.

The claims therefore provide protection for a limited set of related analogs, but not for an unrestricted family of reverse-transcriptase inhibitors.

When did US Patent 7,339,053 expire?

The patent’s ordinary U.S. term ran from the applicable U.S. nonprovisional filing date and expired in February 2022, subject to any patent-term adjustment reflected in USPTO records. Public patent databases identify the patent as expired based on the expiration of its statutory term. The patent was issued on March 4, 2008, as US 7,339,053 B2. [1]

Event	Date or status
Earliest priority period	2001-era priority information associated with the family
U.S. application filing	February 2002-era filing
U.S. patent grant	March 4, 2008
Nominal U.S. expiration	February 2022
Current status	Expired for failure of statutory patent term

The grant date did not start a new 20-year term. For modern U.S. patents, the term generally runs from the relevant U.S. filing date, with adjustments for patent-term adjustment and certain delays. Foreign priority dates affect priority, but ordinarily do not independently extend the U.S. patent term.

What is the Orange Book status of islatravir and US Patent 7,339,053?

US Patent 7,339,053 is not an Orange Book barrier for islatravir because islatravir has not been approved as an FDA drug product.

The FDA Orange Book lists patents and exclusivity associated with approved drug products. Islatravir remains an investigational compound and has no approved reference listed drug. As a result:

There is no approved islatravir product against which an ANDA could be filed.
There is no Orange Book-listed patent for an islatravir reference product.
There is no standard Paragraph IV certification pathway for an unapproved islatravir product.
Patent litigation under the Hatch-Waxman framework has not been triggered by an approved islatravir product. [2]

The absence of an Orange Book listing does not mean that later patents are irrelevant. If Merck or another sponsor obtains FDA approval, patents covering the approved formulation, method of use, or drug substance could become relevant to future Orange Book listings, subject to FDA listing requirements.

Which companies are challenging US Patent 7,339,053?

No conventional Paragraph IV challenge is associated with this patent because islatravir has not reached the approved-product stage.

The competitive landscape has instead been shaped by:

Merck’s development and licensing position.
Yamasa’s role as the originator and licensor of EFdA-related technology.
Clinical development decisions following dose-related safety findings.
Potential future competition from generic manufacturers only after approval and the emergence of an ANDA reference product.

There is no commercial generic launch of islatravir based on an invalidity or noninfringement challenge to US 7,339,053. Since the patent expired before product approval, its expired status would not itself prevent development of a generic or competing islatravir product. Later unexpired patent families would be the more important barrier.

What licensing deal is associated with islatravir?

Islatravir originated from research associated with Yamasa Corporation and was subsequently licensed to Merck for development. Merck designated the compound MK-8591 and advanced it in HIV treatment and pre-exposure prophylaxis programs. [3]

The commercial allocation of rights is more important than US 7,339,053 alone. A freedom-to-operate review must distinguish:

The expired core compound patent.
Later Merck or Yamasa patent families.
Any field-of-use restrictions in the license.
Territory-specific rights.
Rights to long-acting formulations, implants, and combination products.
Manufacturing know-how and regulatory data.

Patent ownership, licensing rights, and regulatory exclusivity are separate legal assets. An expired patent can remain relevant to the history of a licensed technology, but it does not by itself establish an active exclusion right.

What later patents may protect islatravir formulations and uses?

The principal follow-on patent categories are:

Pharmaceutical formulations

Later patents may cover:

Oral tablets containing islatravir.
Long-acting injectable formulations.
Implantable delivery systems.
Controlled-release matrices.
Specific excipient combinations.
Particle-size or solid-state properties.
Combination tablets containing islatravir and doravirine.

These claims can remain enforceable after expiration of a core compound patent if they contain patentably distinct subject matter.

Method-of-use patents

Potential method claims may cover:

Treatment of HIV infection.
Pre-exposure prophylaxis.
Post-exposure prophylaxis.
Long-acting dosing schedules.
Maintenance therapy after viral suppression.
Combination treatment with doravirine or other antiretroviral agents.
Use in patients with resistance to other antiretroviral classes.

A method patent does not necessarily prevent all manufacture of the compound. It can, however, create infringement risk for labeled or deliberate use in the patented indication.

Manufacturing and process patents

Process patents may cover:

Stereoselective sugar construction.
Installation of the 4′-ethynyl group.
Halogenation of the purine base.
Phosphonate or nucleotide intermediates.
Purification and crystallization.
Scale-up methods and impurity control.

Manufacturing patents are particularly relevant where the active ingredient is chemically complex or where a sponsor controls a high-yield commercial process.

How strong is the patent estate for islatravir?

US 7,339,053 is strong as a historical core compound patent but weak as a current exclusion right because it has expired.

Factor	Assessment
Claim type	Narrow compound claims
Coverage of islatravir	Direct coverage through claim 1
Coverage of broad analog space	Limited
Coverage of treatment methods	None stated in the supplied claims
Coverage of formulations	None stated in the supplied claims
Coverage of manufacturing	None stated in the supplied claims
Current U.S. enforceability	Expired
Orange Book impact	None without an approved product
Generic-entry impact	No current standalone barrier
Strategic value	Foundational compound disclosure and priority position

The strongest current barriers, if any, would arise from later active patents and regulatory protections. Those assets must be analyzed family by family because a patent directed to a tablet, injectable depot, implant, dosing regimen, or combination product may have a materially different expiration date from the 2002-era compound patent.

What generic launch risks exist for islatravir?

A generic launch analysis produces different results depending on whether islatravir is approved.

Before approval

There is no ANDA-based generic launch pathway tied to an approved reference listed drug. A company could conduct research using an expired compound patent, subject to applicable patent and regulatory rules, but it would not have an ordinary commercial ANDA route without an approved reference product.

After approval

A future generic applicant would need to evaluate:

Orange Book-listed drug-substance patents.
Formulation patents.
Method-of-use patents.
Patent-term extensions.
Pediatric exclusivity.
New chemical entity or other regulatory exclusivity.
Non-Orange-Book process patents.
Trade-secret manufacturing barriers.
Regulatory data and bioequivalence requirements.

Because US 7,339,053 expired before approval, it would not independently support a Paragraph IV defense or delay. The commercial launch date would instead depend on later patents and FDA exclusivity associated with the eventual approved product.

What patent litigation affects islatravir?

No major Hatch-Waxman litigation against a generic is associated with US 7,339,053. The reason is structural: the patent expired, and islatravir has not had an approved reference product generating ANDA certifications.

The most consequential legal risks have involved development, licensing, regulatory status, and later patent families rather than enforcement of this expired patent. A current litigation search should therefore separate:

Cases naming US 7,339,053.
Cases involving later islatravir patents.
Patent interferences or post-grant proceedings.
License and ownership disputes.
Clinical or regulatory disputes unrelated to patent validity.

Key Takeaways

Claim 1 of US 7,339,053 directly covers islatravir, also known as EFdA and MK-8591.
Claims 2 through 10 cover specific cyano, chloro, phosphonate, dideoxy, and unsaturated analogs.
The patent contains narrow compound claims, not broad formulation, treatment, or manufacturing claims.
The U.S. patent term expired in February 2022.
Islatravir has no FDA-approved reference product and no current Orange Book listing.
No conventional Paragraph IV challenge or generic launch is tied to this patent.
Merck’s commercial position originated from licensed Yamasa technology.
Future exclusivity would depend on later patents covering formulations, long-acting delivery systems, combinations, dosing methods, manufacturing, or regulatory exclusivity.
The expired core patent remains important for historical ownership and priority analysis but is not a current standalone U.S. market barrier.

FAQs About US Patent 7,339,053 and Islatravir

Does US Patent 7,339,053 cover MK-8591?

Yes. MK-8591 is the development code for islatravir, and claim 1 covers 2′-deoxy-4′-C-ethynyl-2-fluoroadenosine, the chemical identity of islatravir.

Can a company make islatravir after US Patent 7,339,053 expired?

The expiration of this patent removes its standalone U.S. exclusion right. A company must still evaluate later active patents, trade secrets, regulatory requirements, and any jurisdiction-specific rights.

Is islatravir listed in the FDA Orange Book?

No. Islatravir has not received FDA approval as a marketed drug product, so it does not have an FDA reference listed drug entry or an associated Orange Book patent listing.

Does the patent claim doravirine-islatravir combination therapy?

No. The supplied claims are compound claims to defined nucleoside derivatives. They do not recite doravirine, a combination composition, or a treatment regimen.

Does an expired core compound patent eliminate biosimilar risk analysis?

Islatravir is a chemically synthesized small molecule, not a biologic. The relevant issue is generic-drug risk, not biosimilar substitution. Later formulation, method, process, and regulatory protections may still affect generic entry.

References

United States Patent and Trademark Office. (2008). US Patent No. 7,339,053 B2: 4′-C-substituted-2-haloadenosine derivatives.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations.
Merck & Co., Inc. (2012). Merck and Yamasa enter agreement to develop novel investigational HIV-1 therapy.

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Msd	IDVYNSO	doravirine; islatravir	TABLET;ORAL	216964-001	Apr 20, 2026		RX	Yes	Yes	⤷ Start Trial	⤷ 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
Austria	E388958	⤷ Start Trial
Canada	2502109	⤷ Start Trial
Germany	602005005240	⤷ Start Trial
European Patent Office	1589026	⤷ Start Trial
Spain	2300892	⤷ Start Trial
Japan	2008069182	⤷ Start Trial
Japan	2011256173	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 7,339,053

Which drugs does patent 7,339,053 protect, and when does it expire?

Summary for Patent: 7,339,053