US Drug Patent 4,689,320: Claim Scope, Expiration, Litigation Risk and Antisense Herpes Patent Landscape

US Patent 4,689,320 covers antiviral pharmaceutical compositions and treatment methods using DNA oligonucleotides designed to hybridize with viral messenger RNA. Its strongest claims target antisense DNA sequences directed to herpes simplex virus, particularly the immediate-early ICP4 gene. The patent issued on August 25, 1987, and its ordinary pre-URAA term expired on August 25, 2004. It therefore has no current US enforceability or generic-entry blocking power.

What does US Patent 4,689,320 protect?

US 4,689,320 protects compositions and treatment methods using an oligodeoxynucleotide or polydeoxynucleotide that:

Has a sequence identical to a portion of viral DNA.
Is capable of hybridizing with viral messenger RNA.
Is administered in an effective antiviral amount.
Is combined with a pharmaceutically acceptable carrier or diluent.

The claims use an antisense mechanism. The DNA oligonucleotide is designed to bind complementary viral mRNA and interfere with viral gene expression.

The patent is broader in its independent claims than the dependent claims suggest. Claims 1 and 13 generally address herpes virus messenger RNA, while claim 22 extends the method to adenovirus, vaccinia virus, influenza virus, rhinovirus and poliovirus.

Core patent data

Item	Data
Patent	US 4,689,320
Title	Antiviral compositions and methods
Issue date	August 25, 1987
Original patent term	17 years from grant under pre-URAA law
Ordinary expiration	August 25, 2004
Technology	Antisense oligodeoxynucleotides
Principal use	Viral mRNA hybridization and inhibition
Main viral targets	Herpes virus, HSV, HSV-1, ICP4
Dosage-form coverage	Injectable, topical and ophthalmic
Current enforceability	Expired
Orange Book status	No current Orange Book blocking effect identified
Biosimilar relevance	None; this is an oligonucleotide drug patent, not a biologic patent

The patent record should be treated as the controlling source for bibliographic information and prosecution history.[1]

How broad are the composition claims?

Claim 1: broad antisense antiviral composition

Claim 1 is the principal composition claim. It requires:

An effective antiviral amount;
An oligodeoxynucleotide or polydeoxynucleotide;
A sequence identical to a portion of DNA;
Hybridizability to viral messenger RNA; and
A pharmaceutically acceptable carrier.

The claim does not require a particular viral gene, sequence length, backbone chemistry, administration route or dosage form. On its face, it reaches a genus of DNA oligonucleotide compositions directed to herpes-virus mRNA.

The phrase “consisting essentially of” narrows the permissible additional ingredients. The composition can contain excipients and components that do not materially alter the basic antiviral function of the antisense oligonucleotide. An added active ingredient or delivery component that materially changes the claimed mechanism could create a claim-construction dispute.

Claim 1 does not expressly require:

A phosphorothioate backbone;
A particular sugar modification;
A particular oligonucleotide length;
Cellular uptake;
RNase H activation;
A defined viral load reduction;
A particular route of administration; or
A specific formulation excipient.

Claims 2 through 6: virus and gene limitations

Claims 2 and 3 narrow the virus to herpes simplex virus and HSV-1.

Claim 4 requires hybridization with immediate-early herpes messenger RNA. Claim 5 requires a non-structural gene target, and claim 6 specifies ICP4.

ICP4 is an important limitation because it converts a broad functional target into a defined herpes viral gene. A product directed to a late structural gene would not literally satisfy claim 6, although it could remain within claim 1 if the other limitations were met.

Claims 7 and 8: defined 20-mer sequences

Claims 7 and 8 identify two specific oligonucleotides:

3'-CGC.AGC.CTC.TTG.TTC.GTC.GC-5'
3'-GCA.CCC.GGG.ACC.TTT.ACC.GC-5'

Each sequence is approximately 20 nucleotides long. The 3'-to-5' presentation is consistent with an antisense orientation relative to the viral mRNA target.

These claims are narrower and easier to evaluate than the genus claims. A product that uses a materially different sequence would not literally infringe claims 7 or 8, although it could potentially implicate broader claims if it satisfies their functional and structural requirements.

The punctuation in the supplied sequence text appears to be formatting used to group nucleotides. It should not be read as requiring chemical linkers, phosphodiester breaks or nonstandard nucleotides unless the specification or prosecution history gives those marks a technical meaning.

What formulations and administration routes are covered?

Claims 9 through 11 cover the composition in three dosage forms:

Injectable solution;
Topical preparation; and
Eye-drop solution.

The claims do not establish a detailed formulation platform. They do not specify:

Concentration;
pH;
Osmolality;
Preservatives;
Surfactants;
Lipid or nanoparticle carriers;
Viscosity;
Container closure;
Stability period; or
Sterility specifications.

The patent therefore protects the antisense active ingredient in the identified dosage-form categories, rather than a modern formulation architecture.

Claim 12 covers a mixture of the claimed oligonucleotides. The mixture must remain within the composition requirements of claim 1. A mixture containing unrelated oligonucleotides would raise questions about whether the composition still “consists essentially of” the claimed antiviral antisense components.

What do the treatment-method claims cover?

Claims 13 through 22

Claim 13 covers treating herpes virus infections by applying the claimed composition to a subject. Claims 14 through 16 specify:

Topical administration;
Ocular administration; and
Injection.

Claim 17 provides a dose range of 1 to 20,000 micrograms per kilogram per day. This is a very wide range. It covers 1 µg/kg/day through 20 mg/kg/day, subject to the requirement that the dose be an effective antiviral amount.

Claims 18 and 19 limit the method to herpes simplex virus and HSV-1. Claim 20 requires minus-strand DNA. Claim 21 specifies the first sequence listed above.

Claim 22 is the broadest virus-specific method claim. It covers treatment of infection caused by:

Adenovirus;
Vaccinia virus;
Influenza virus;
Rhinovirus; or
Poliovirus.

The claim does not limit the treatment to herpes virus. It also does not specify a viral gene, sequence or administration route.

Functional limitations and proof of infringement

The claims require that the oligonucleotide be capable of hybridizing to viral mRNA. That limitation creates a technical proof issue. An infringement analysis would generally examine:

The accused oligonucleotide sequence;
The relevant viral genome and transcript;
Complementarity and hybridization conditions;
The claimed viral target;
The pharmaceutical composition;
The administration method; and
Whether the oligonucleotide is present in an effective antiviral amount.

A sequence that binds cellular RNA, viral DNA or an unrelated viral transcript would not automatically satisfy the claim. The claimed target is viral messenger RNA.

When did US Patent 4,689,320 lose exclusivity?

US 4,689,320 expired on August 25, 2004, based on the 17-year term applicable to patents filed before the Uruguay Round Agreements Act transition rules.[2]

Event	Date
Patent issued	August 25, 1987
Ordinary 17-year expiration	August 25, 2004
Post-expiration status	Public domain
Current Paragraph IV relevance	None for this patent
Current injunction risk	None based solely on US 4,689,320

No current patent-term extension or regulatory exclusivity is associated with this patent in the available record. Even if the invention later supported a regulated product, expiration of the patent would not itself create a new period of patent protection.

What is the Orange Book status of US 4,689,320?

US 4,689,320 has no current Orange Book significance.

The Orange Book lists patents submitted for approved small-molecule drug products, including certain formulation, composition and method-of-use patents. A patent does not receive Orange Book protection merely because it describes a pharmaceutical composition. It must be associated with an approved drug product and submitted under FDA listing requirements.[3]

No FDA-approved herpes antisense product appears to have been marketed under this patent. The patent therefore did not create a current Orange Book obstacle for acyclovir, valacyclovir, famciclovir, penciclovir, docosanol or other conventional herpes treatments.

Paragraph IV challenges

A Paragraph IV certification applies when an abbreviated new drug application applicant asserts that a listed patent is invalid, unenforceable or will not be infringed. Because US 4,689,320 expired in 2004 and is not a current listed barrier, it does not present an operative Paragraph IV challenge path.

Any historical ANDA strategy involving this patent would have become moot upon expiration unless other unexpired patents remained relevant to the same product.

Which companies are challenging or relying on this patent?

No active US litigation or commercial challenge to US 4,689,320 is identified as a current market issue. The patent expired before antisense oligonucleotide products became a major commercial category.

The relevant commercial companies in the broader antisense field have included:

Isis Pharmaceuticals, now Ionis Pharmaceuticals;
Gilead Sciences, through its acquisition of certain antiviral assets;
Novartis, in connection with ophthalmic antiviral development;
Bayer and other historical antiviral developers; and
Generic manufacturers of conventional nucleoside antivirals.

Those companies’ products and later patent estates generally involve different active ingredients, delivery systems, chemical backbones or viral targets. Commercial use of a later-generation antisense oligonucleotide would need to be analyzed against later patents rather than against the expired claims of US 4,689,320.

How strong was the patent estate for antisense herpes treatment?

Strengths of the issued claims

The patent had several features that were commercially useful during its term:

Composition and method claims were both included.
The claims covered multiple administration routes.
The claims reached broad functional targeting of viral mRNA.
Specific claims identified HSV-1 and ICP4.
The method claims included a broad dose range.
Claim 22 extended beyond herpes to several other viruses.

The combination of composition and method claims could have supported enforcement against a product marketed as an antisense antiviral, particularly one using the specified sequences or targeting ICP4.

Weaknesses and validity pressure points

The claims also presented potential validity and enforcement vulnerabilities:

The broad genus language covers many possible viral sequences and targets.
The specification would need to support and enable the full scope of the claimed virus groups.
Claim 22 reaches five virus families with different biology and transcript structures.
“Effective antiviral amount” is functional and may require experimental proof.
“Capable of hybridizing” depends on sequence, conditions and target accessibility.
The claims do not clearly define chemical modifications or backbone variants.
The scope of “sequence identical to a portion of DNA” could exclude modified or nonidentical analogues.
The claim text contains apparent drafting or transcription errors, including “which has a hybridizable to messenger RNA” in claim 13.

The broadest claims would have been more vulnerable than the sequence-specific claims if challenged on enablement, written description, indefiniteness or anticipation grounds. The patent’s expiration makes those issues commercially academic for the original patent, but they remain relevant to assessing the historical scope of the technology and the value of later patent filings.

How does this patent compare with modern antisense patents?

Modern antisense patent estates generally rely on claim elements that are more chemically and pharmacologically specific.

Attribute	US 4,689,320	Later antisense patent practice
Active agent	Oligodeoxynucleotide or polydeoxynucleotide	Often phosphorothioate, 2'-modified or conjugated oligonucleotide
Target definition	Viral mRNA, sometimes ICP4	Defined RNA sequence, exon, splice site or transcript
Delivery	Injectable, topical or eye drops	Systemic, subcutaneous, intrathecal, ocular or targeted delivery
Chemistry	Broad or unspecified DNA terminology	Detailed backbone and sugar modifications
Mechanism	Hybridization to mRNA	RNase H, steric blocking, splice modulation or translation inhibition
Regulatory path	No approved product tied to the patent	Product-specific FDA and Orange Book strategies
Current status	Expired	Later patents may remain active depending on filing dates

The patent does not claim all antisense drugs. It does not cover every oligonucleotide that binds RNA, every modified DNA analogue or every antiviral oligonucleotide developed after 1987.

What manufacturing and IP barriers remain?

US 4,689,320 does not create a current manufacturing barrier. Standard solid-phase oligonucleotide synthesis is commercially available, and the patent’s sequence claims are expired.

Current barriers would arise from later rights involving:

Modified nucleotide chemistry;
Phosphorothioate or phosphorodiamidate backbones;
Conjugated delivery systems;
Lipid nanoparticles;
Ocular retention and penetration;
Manufacturing purification;
Double-stranded or multimeric oligonucleotide structures;
Specific viral targets;
Combination products; and
FDA-approved formulations.

Manufacturing freedom to operate must therefore be separated from sequence freedom to operate. A company could use a public-domain sequence but still infringe a later patent directed to the backbone, conjugate, formulation or administration method.

What generic and competitive-entry risks exist?

There is no current generic-entry risk from US 4,689,320. The patent cannot support an injunction or damages claim after expiration.

The commercial competitive landscape for herpes treatment is dominated by conventional antivirals:

Product	Active ingredient	Product type	Relationship to US 4,689,320
Zovirax and generics	Acyclovir	Nucleoside analogue	Different mechanism and chemistry
Valtrex and generics	Valacyclovir	Oral prodrug	Different mechanism and chemistry
Famvir and generics	Famciclovir	Oral prodrug	Different mechanism and chemistry
Denavir	Penciclovir	Topical nucleoside analogue	Different mechanism and chemistry
Abreva	Docosanol	Topical antiviral	Different mechanism and chemistry
Viroptic	Trifluridine	Ophthalmic nucleoside analogue	Different mechanism and chemistry
Antisense candidates	Viral-targeted oligonucleotides	Investigational or specialized	Closest technical category

A new antisense HSV product would face clinical, delivery and manufacturing risks, but not a blocking claim from US 4,689,320.

What licensing deals and settlement agreements affect the patent?

No current licensing deal or settlement agreement is identified as materially affecting the expired US rights under US 4,689,320.

Any historical license would not restore exclusivity after expiration. Contractual royalty, field-of-use or confidentiality obligations could survive independently, but those are private contractual matters and do not extend the patent term under US patent law.

No current patent settlement involving US 4,689,320 has a meaningful effect on generic or biosimilar entry.

Is there biosimilar risk for this patent?

There is no biosimilar risk because the patent does not cover a biologic reference product. Oligonucleotide medicines are regulated through small-molecule or other drug pathways depending on their structure and product characteristics. A follow-on oligonucleotide would generally raise generic-equivalence, clinical comparability and formulation issues rather than biosimilar substitution under the Public Health Service Act.

The FDA approved fomivirsen, an antisense oligonucleotide for cytomegalovirus retinitis, in 1998. Fomivirsen was not an HSV product and was later discontinued from commercial marketing.[4] Its development illustrates the regulatory feasibility of antisense antivirals but does not create a current link to US 4,689,320.

Key Takeaways

US 4,689,320 covers antisense oligodeoxynucleotide compositions and treatment methods directed to viral messenger RNA.
The strongest technical focus is HSV and HSV-1, including immediate-early and ICP4 messenger RNA.
Claims 7, 8 and 21 identify specific 20-nucleotide sequences.
Claims 9 through 11 cover injectable, topical and ophthalmic preparations.
Claim 22 extends the treatment concept to adenovirus, vaccinia virus, influenza virus, rhinovirus and poliovirus.
The patent issued August 25, 1987, and expired August 25, 2004.
It has no current Orange Book, Paragraph IV, injunction or generic-entry blocking effect.
It is not a biosimilar patent.
Later antisense patents may still cover modified chemistry, delivery systems, formulations or different viral targets.
The patent’s historical value was greater than its current commercial value because its sequence, composition and method claims are now in the public domain.

FAQs About US Patent 4,689,320

Does US 4,689,320 cover acyclovir?

No. Acyclovir is a nucleoside analogue with a different chemical structure and mechanism. The patent claims oligonucleotide compositions that hybridize with viral messenger RNA.

Does the patent cover all HSV antisense oligonucleotides?

During its term, the broad claims could have reached a wide range of HSV-targeted DNA oligonucleotides. The specific sequence claims cover only the identified sequences. The patent is now expired.

Could a company launch an HSV oligonucleotide without a license to this patent?

Yes, US 4,689,320 itself no longer requires a license because its patent term expired. A launch must still be assessed against later patents and applicable regulatory requirements.

Does claim 22 cover coronavirus or HIV?

No. Claim 22 identifies adenovirus, vaccinia virus, influenza virus, rhinovirus and poliovirus. Coronavirus and HIV are not expressly included in that claim.

Did US 4,689,320 protect an FDA-approved herpes product?

No FDA-approved herpes product is identified as having relied on this patent as an active exclusivity right. The major approved herpes antivirals use different chemical classes and mechanisms.

References

United States Patent and Trademark Office. (1987). Antiviral compositions and methods, U.S. Patent No. 4,689,320.
United States Code, 35 U.S.C. § 154. (2024). Contents and term of patent; provisional rights.
U.S. Food and Drug Administration. (2024). Approved drug products with therapeutic equivalence evaluations. Center for Drug Evaluation and Research.
U.S. Food and Drug Administration. (1998). Vitravene (fomivirsen sodium) injection approval information. Center for Drug Evaluation and Research.

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
Japan	58-192350	Oct 17, 1983
Japan	59-49321	Mar 16, 1984

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	392081	⤷ Start Trial
Austria	A329284	⤷ Start Trial
Australia	3423984	⤷ Start Trial
Australia	578625	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 4,689,320

Summary for Patent: 4,689,320