Details for Patent: 6,147,204

Summary for Patent: 6,147,204

Title:	Nucleic acid ligand complexes
Abstract:	PCT No. PCT/US96/06171 Sec. 371 Date Oct. 28, 1997 Sec. 102(e) Date Oct. 28, 1997 PCT Filed May 2, 1996 PCT Pub. No. WO96/34876 PCT Pub. Date Nov. 7, 1996This invention discloses a method for preparing a therapeutic or diagnostic complex comprised of a nucleic acid ligand and a lipophilic compound or non-immunogenic, high molecular weight compound by identifying a nucleic acid ligand by SELEX methodology and associating the nucleic acid ligand with a lipophilic compound or a non-immunogenic, high molecular weight compound. The invention further discloses complexes comprising one or more nucleic acid ligands in association with a lipophilic compound or non-immunogenic, high molecular weight compound.
Inventor(s):	Larry Gold, Paul G Schmidt, Nebojsa Janjic
Assignee:	Gilead Sciences Inc
Application Number:	US08/945,604
Patent Claim Types: see list of patent claims	Use;

US Patent 6,147,204 Landscape: Scope, Claim Boundaries, Enforceability, and Key Design-Around Routes

US 6,147,204 claims a class of nucleic-acid ligands covalently linked to a lipophilic or a non-immunogenic high molecular weight carrier, where the complex has improved pharmacokinetic properties versus the nucleic-acid ligand alone. The claims also funnel into PEG/dextran/albumin/magnetite conjugates and liposome/cholesterol/dialkyl or diacyl glycerol formulations, plus optional co-loaded or membrane-projected therapeutic/diagnostic agents and targeting (intercellular or intracellular).

The patent’s economic leverage is concentrated in three repeatable claim drivers:

1. Covalent linkage of a nucleic-acid ligand to a specified class of hydrophobic or high-MW carrier.
2. A functional requirement: improved pharmacokinetics relative to the nucleic-acid ligand alone.
3. Optional but high-value packaging into lipid constructs (especially liposomes) with defined placement of the nucleic-acid ligand (encapsulated vs protruding) and defined ligand presentation (projecting into/out of the membrane).

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What does US 6,147,204 claim for nucleic acid ligand complexes, and what is the core invention boundary?

Core independent claim theme (Claim 1)

Claim 1 is the gatekeeper. It covers a therapeutic or diagnostic complex comprising:

• A Nucleic Acid Ligand with a specific binding affinity to a Target molecule defined as a three-dimensional chemical structure other than a polynucleotide.
• The nucleic acid binds the target predominantly via Watson-Crick base pairing or triple helix binding.
• A restriction: the nucleic-acid ligand is not a nucleic acid that has the known physiological function of being bound by the target molecule.
• The nucleic acid ligand is covalently linked to either:
  • a lipophilic compound, or
  • a non-immunogenic, high molecular weight compound.
• A performance restriction: the complex has improved pharmacokinetic properties vs the nucleic acid ligand alone.

Practical boundary: The claim is not just “aptamer conjugate.” It is a specific nucleic acid ligand type (selected by binding mode and target definition), covalent conjugate chemistry, and an explicit PK improvement requirement.

How the claim definition narrows the nucleic-acid ligand universe

Claim 1’s binding mechanics and target definition narrow coverage to nucleic acids that bind to:

• non-polynucleotide 3D chemical structures (not another polynucleotide sequence),
• through mechanisms that predominantly depend on:
  • Watson-Crick base pairing, or
  • triple helix binding.

The “not having the known physiological function of being bound by the target molecule” is a carve-in limitation aimed at excluding biologically natural ligand-target relationships.

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What patents protect nucleic-acid-ligand conjugates with PEG, liposomes, and cholesterol under US 6,147,204?

US 6,147,204 is itself the key document you provided, but its internal claim architecture identifies the protection themes that would likely be asserted across family members (if any) and continuation filings. Within this patent, the following dependent claims materially expand scope into formulation and materials:

Non-immunogenic, high molecular weight carriers (PEG/dextran/albumin/magnetite)

• Claim 4: nucleic acid ligand + non-immunogenic, high molecular weight compound
• Claim 5: carrier selected from polyethylene glycol, dextran, albumin, magnetite
• Claim 6: PEG specifically

Lipophilic carriers (cholesterol, dialkyl glycerol, diacyl glycerol)

• Claim 7: nucleic acid ligand + lipophilic compound
• Claim 8: lipophilic compound selected from cholesterol, dialkyl glycerol, diacyl glycerol
• Claim 9: cholesterol
• Claim 10: dialkyl glycerol

Lipid constructs and liposome-specific positioning

• Claim 11-13: lipid construct = lipid bilayer vesicle, i.e., liposome
• Claim 14-16: liposome embodiments repeated for the other arm (lipophilic vs PEG arm)
• Claim 23-24: nucleic acid ligand location:
  • encapsulated within interior of the liposome (Claim 23)
  • protrudes from exterior of the liposome (Claim 24)

Nucleic-acid attachment to a second lipophilic compound and membrane projection

• Claim 25: nucleic acid covalently attached to a second lipophilic compound
• Claim 26: attachment via linker
• Claims 27-28: projection orientation:
  • projecting out of exterior surface (Claim 27)
  • projecting into interior (Claim 28)

Optional co-administered agents (therapeutic/diagnostic)

• Claim 29-32: additional agent can be:
  • encapsulated in interior (Claim 30)
  • protruding from membrane or exterior surface (Claims 31-32)

Targeting to preselected location and cellular compartment

• Claim 33: targets complex to preselected location
• Claim 34-35: target is intercellular or intracellular
• Claim 36: cellular uptake enhanced vs nucleic acid ligand alone

PEG-linked additional agent

• Claims 37-39: additional agent covalently/noncovalently linked to PEG and covalently linked embodiment

Takeaway: The “protection map” inside the claims is already highly structured: carriers, lipid constructs, ligand spatial orientation, and additional payload presentation.

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How broad is the wording on targets, binding modes, and what does “three-dimensional chemical structure other than a polynucleotide” exclude?

Target definition is both functional and structural

Claim 1’s target is:

• a three-dimensional chemical structure,
• other than a polynucleotide,
• and bound predominantly through base pairing or triple helix.

This implies:

• It is trying to capture synthetic binding targets including proteins, small molecules, and other non-polynucleotide entities that a nucleic-acid ligand binds to via sequence-mediated pairing/structure recognition (not just generic “binds target”).

Exclusion: “known physiological function of being bound”

Claim 1 also excludes nucleic acids that are natural ligands for biologically known target binding functions. The boundary is not framed as “specific sequence” but as a biological function exclusion.

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Does “improved pharmacokinetic properties” create a strength or an indefiniteness risk in US litigation?

Functional PK limitation is central to Claim 1

Claim 1 requires:

• improved pharmacokinetic properties relative to the nucleic acid ligand alone.

In enforceability terms, this is a performance limitation tied to comparison.

• Strong when prosecution history and spec support measurable PK improvement.
• Attackable when accused complexes do not clearly show PK improvement or when the comparison is not like-for-like.

From a claim construction perspective, the phrase is still:

• objective in direction (improved PK),
• but can be litigated on:
  • what PK metrics matter (half-life, clearance, distribution, bioavailability),
  • what the baseline “nucleic acid ligand alone” means (same sequence, same chemistry without carrier).

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What do Claims 2–3 cover about ligand identification and enrichment methods, and how might that be asserted?

Claim 2 method wrapper

Claim 2 adds a method component specifying how the nucleic acid ligand was identified from a candidate mixture:

• (a) contact candidate mixture with the target; partition nucleic acids with increased affinity from remainder
• (b) partition the increased-affinity nucleic acids
• (c) amplify to yield ligand-enriched mixture

Claim 3 iterative refinement

• Claim 3 adds repeating steps (b) and (c).

Enforcement logic: If manufacturing includes a ligand selection workflow matching these steps, then method claims like Claim 2–3 can be asserted even if the final complex is produced with different handling steps. That said, actual enforceability depends on whether the asserted activity falls within the claim’s method steps.

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What is covered for liposome formulations: encapsulation vs protrusion and covalent attachment to lipid components?

US 6,147,204’s liposome coverage is detailed through placement and attachment topology.

Placement options

• Encapsulated nucleic acid ligand (Claim 23)
• Protruding nucleic acid ligand from exterior (Claim 24)
• With second lipophilic compound attachment:
  • projects out of exterior surface (Claim 27)
  • projects into interior (Claim 28)

Lipid construct definitions

• “Lipid construct is a lipid bilayer vesicle” (Claim 11/14/17/20, depending on claim chain)
• “Lipid bilayer vesicle is a liposome” (Claim 13/16/19/22)

Co-therapy and diagnostics placement

• Additional agent encapsulated (Claim 30)
• Additional agent protruding from membrane/exterior (Claims 31-32)

Design implication: A competitor seeking to avoid this patent’s liposome geometry likely needs to change either:

• the covalent conjugate requirement, or
• the explicit topology (encapsulated vs protruding vs projected via membrane-anchored second lipophilic construct), or
• the PK-improvement claim premise if performance is materially different.

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How does this patent compare to common aptamer conjugate strategies: PEGylation, cholesterol conjugates, and lipid nanoparticles?

PEGylated aptamer-like constructs

Many aptamer therapeutics use PEGylation to increase half-life. Claim 1 + Claims 4–6 specifically cover:

• nucleic acid ligand covalently linked to non-immunogenic high molecular weight compounds,
• with PEG explicitly included.

Cholesterol conjugates

Cholesterol conjugation is a widely used half-life extension method. Claim 7–9 capture:

• lipophilic compound arm including cholesterol.

Lipid nanoparticles beyond liposomes

The claims in your excerpt lock into lipid bilayer vesicles and liposomes. If a competing system uses a different lipid architecture (not a bilayer vesicle), or uses non-covalent lipid association, it may fall outside these dependent claim chains, but may still risk Claim 1 if the covalent conjugate plus PK improvement matches.

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When does US 6,147,204 lose exclusivity, and how does that timing drive generic or biosimilar risk?

No USPTO term/exclusivity date can be derived from the claim text alone. Without patent issue date, filing date, and any PTA/terminal disclaimer, exclusivity timing cannot be computed accurately here.

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What Paragraph IV or Hatch-Waxman generic entry risks exist for a nucleic acid ligand-liposome conjugate patent?

US 6,147,204’s subject matter is a therapeutic or diagnostic nucleic-acid ligand complex. Hatch-Waxman Paragraph IV filings typically map to small-molecule drugs and some biologics do not follow this structure. Without the associated marketed product(s), Orange Book listings, and FDA application numbers, it is not possible to identify:

• whether any NDA/ANDA mapping exists for the claimed complex,
• whether any applicant would file a Paragraph IV certification referencing this patent,
• or how litigation would be triggered.

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Commercial and litigation leverage: which claim elements are most likely to be asserted?

Most assertion-friendly elements

• Covalent linkage between nucleic acid ligand and carrier (Claim 1).
• Carriers enumerated in dependents:
  • PEG (Claim 6),
  • cholesterol (Claim 9),
  • dextran/albumin/magnetite (Claim 5),
  • dialkyl/diacyl glycerols (Claims 10 and 8).
• Liposome topology:
  • encapsulated ligand (Claim 23),
  • protruding ligand (Claim 24),
  • projected ligand via second lipophilic compound (Claims 25–28),
  • co-loaded or surface protruding additional agent (Claims 29–32).

Most challengeable elements

• “Improved pharmacokinetic properties” compared to nucleic acid ligand alone. This is a performance test that can be litigated on measurement methodology and baseline comparability.
• Target definition: “three-dimensional chemical structure other than a polynucleotide” and binding “predominantly depends on Watson/Crick base pairing or triple helix binding.” Competitors using different binding modalities or targeting polynucleotide targets can argue non-infringement.

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Claim chart style mapping (accused product decision points)

Accused product feature	Matches US 6,147,204 Claim 1?	Why it matters
Nucleic acid ligand binds a target with sequence-mediated Watson-Crick or triple helix	Yes if “predominantly depends”	Binding mechanism is a core limiter
Target is non-polynucleotide 3D chemical structure	Yes if target fits	Excludes polynucleotide targets
Nucleic acid ligand is not a naturally physiologically bound nucleic acid	Often disputed	Limits to non-physiological-function ligands
Covalent linkage to carrier	Yes if covalent	Biggest practical boundary for design-around
Carrier is lipophilic or non-immunogenic high MW compound	Yes if within enumerated classes	PEG/cholesterol arms increase risk
Complex shows improved PK vs nucleic acid alone	Must be shown	Performance limitation can decide validity/infringement
Liposome formulation with ligand encapsulated or protruding	Matches dependent claims	Depends on topology and construction
Additional therapeutic/diagnostic agent placement (interior vs exterior)	Matches dependents	Often product-specific

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Design-around pathways implied by the claim language

These are derived directly from claim elements rather than external portfolio assumptions:

1. Break covalency
   If the nucleic-acid ligand associates non-covalently with the lipophilic/high-MW component, Claim 1’s “covalently linked” requirement is a direct avoidance lever.

2. Change carrier class
   Use a high-MW carrier not falling within the “non-immunogenic, high molecular weight compound” concept as construed, or avoid the specified subclasses (PEG/dextran/albumin/magnetite) in dependents.

3. Avoid liposome bilayer vesicle architecture
   If the platform is not a liposome or does not function as a lipid bilayer vesicle, dependent claim chains may not match.

4. Use different ligand binding mode or target type
   If targeting uses binding mechanisms not predominantly Watson-Crick/triple helix, or targets polynucleotides, risk to Claim 1 decreases.

5. Engineer to eliminate PK “improved” profile
   If pharmacokinetics are not improved versus the nucleic-acid ligand alone under like-for-like conditions, the performance limitation becomes an infringement dispute.

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Key Takeaways

• US 6,147,204 covers covalently linked nucleic-acid ligand complexes with sequence-mediated binding (Watson-Crick or triple helix) to non-polynucleotide 3D targets, plus a requirement of improved pharmacokinetics versus the nucleic-acid ligand alone.
• Coverage expands into PEGylated and cholesterol/glycerol lipophilic conjugates and into liposome formats with specified ligand and payload placement (encapsulated vs protruding).
• The strongest infringement vectors are covalent conjugation and liposome topology. The strongest litigation pressure points are the PK improvement limitation and the target/binding-mechanism definition.

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FAQs

1) Does US 6,147,204 cover non-covalent PEG-aptamer complexes?

No. Claim 1 requires the nucleic acid ligand to be covalently linked to the lipophilic or high-MW carrier.

2) Can a liposomal formulation still infringe if the nucleic acid ligand is not encapsulated or protruding?

Dependent claims require specific placement (e.g., interior encapsulation or protrusion). If placement does not match those dependents, infringement analysis would turn on whether the product still satisfies Claim 1 without relying on the liposome dependents.

3) What targets are excluded by the “other than a polynucleotide” language?

Targets that are polynucleotides are excluded by the claim definition of the target as “three-dimensional chemical structure other than a polynucleotide.”

4) Are cholesterol and PEG both explicitly within the patent’s dependent claim scope?

Yes. PEG is explicitly included (Claim 6). Cholesterol is explicitly included (Claim 9).

5) Does the patent require that the ligand be selected by enrichment and amplification?

Claims 2–3 include a ligand identification method with contacting, partitioning, and amplification. Whether those method steps apply depends on whether the asserted claim is a method claim and whether the activity being challenged matches those steps.

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References (APA)

1. United States Patent 6,147,204. (n.d.). Claims as provided by user (excerpt).

Drugs Protected by US Patent 6,147,204

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate

Foreign Priority and PCT Information for Patent: 6,147,204

PCT Information
PCT Filed	May 02, 1996	PCT Application Number:	PCT/US96/06171
PCT Publication Date:	November 07, 1996	PCT Publication Number:	WO96/34876

International Family Members for US Patent 6,147,204

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
European Patent Office	0957929		91252	Luxembourg
European Patent Office	0957929		300234	Netherlands
European Patent Office	0957929		PA2006004	Lithuania
European Patent Office	0957929		CA 2006 00021	Denmark
European Patent Office	0957929		SPC024/2006	Ireland