US Patent 6,143,524 Landscape and Claim-by-Claim Validity Risk for IL-11 DNA, Vectors, Host Cells, and Production Methods
US Patent 6,143,524 claims a narrow set of IL-11 gene fragments and derived biologies: an isolated DNA segment defined by position ranges in SEQ ID NOs, nucleic acid vectors, transformed host cells, and upstream production and downstream purified protein/composition claims tied to those specific fragments. The patent’s enforceable reach in the US is largely constrained to the claimed DNA definitions and any products that are directly encoded by those exact sequences. The highest litigation and commercial relevance sits in DNA and protein claims (claims 1, 5, 6, 7), with method and platform claims (claims 2–4) adding incremental leverage only if accused products trace to the claimed constructs.
What does US 6,143,524 claim and how narrow are the DNA definitions?
Direct answer: Claim scope turns on two sequence-specific “windows”: nucleotides 2599–3132 of SEQ ID NO:13 and nucleotides encoding amino acids 120–296 of SEQ ID NO:14. Everything else in the claim set is dependent on one of those DNA definitions.
Claim 1: Isolated DNA molecule defined by exact sequence windows
Claim 1 is a composition claim for an isolated nucleic acid whose DNA sequence is limited to:
- (a) nucleotides 2599 through 3132 of SEQ ID NO:13, and/or
- (b) nucleotides encoding amino acids 120 through 296 of SEQ ID NO:14.
Critical implication: This is not a generic “IL-11 nucleic acid” claim. It is a positional fragment claim and a protein-region encoding claim. For infringement analysis, the accused DNA must include the claimed exact nucleotide content (or at least be construed as “encoding” the same amino-acid region while meeting the specific sequence definition, depending on how the claim is construed in the Markman record). If a competitor uses a different codon set for the same amino-acid region, infringement depends on whether claim construction treats “encoding amino acids 120 through 296” as covering any synonymous DNA or requires the exact nucleotides consistent with SEQ ID NO:14.
Claim 2: Vectors comprising the claimed DNA
Claim 2 is a dependent-style vector claim: “a nucleic acid vector comprising a DNA according to claim 1.”
Critical implication: Vector infringement is conditional on the presence of the claimed fragment(s) inside the vector construct. This targets plasmids and viral vectors used in IL-11 expression systems.
Claim 3: Host cells transformed or transfected with a vector of claim 1
Claim 3 covers host cells that are transformed/transfected with a vector of claim 2.
Critical implication: This extends coverage from sequences to the biological manufacturing tool, which can matter if competitors attempt “design-around” by changing plasmid backbones but still use the claimed expression cassette.
Claim 4: Method for producing IL-11 polypeptide
Claim 4 claims:
- growing in culture a host cell of claim 3, and
- isolating from the host cell or culture the IL-11 polypeptide expressed from the DNA.
Critical implication: This is a classic process claim tied to a specific host cell definition. If the accused process uses a different construct that still expresses IL-11 but does not use the claimed DNA fragment(s), the method claim is vulnerable.
Claims 5 and 6: Purified IL-11 protein tied to the claimed DNA fragments
- Claim 5: “A purified interleukin-11 (IL-11) protein encoded by a DNA encoding amino acids 120 through 296 of SEQ ID NO:14.”
- Claim 6: “A purified IL-11 protein amino acids 120 through 296 of SEQ ID NO:13.”
Critical implication: Both protein claims are tethered to defined amino-acid boundaries. The enforceability turns on whether the accused protein product matches the claimed IL-11 region. Many IL-11 biologics in commerce are full-length secreted proteins with signal peptides and mature chains; fragments or truncated constructs may or may not land inside claims 5–6 depending on the claim construction of “encoded by” and the definition of “IL-11 protein” as used by the patent.
Claim 7: Composition comprising an IL-11 protein encoded by the claim 1 DNA
Claim 7 is a product-by-source style composition claim, requiring IL-11 protein encoded by a DNA molecule as in claim 1 (either the nucleotide window in SEQ ID NO:13 or the amino-acid encoding window in SEQ ID NO:14).
Critical implication: Composition claims often face extra attack surfaces (novelty and obviousness), but the tether to the claimed encoding sequences narrows the set of compositions that can infringe.
Where is the strongest infringement pressure likely to fall?
Direct answer: The highest infringement leverage typically concentrates on (i) any manufacturing platform that uses those exact expression-region sequences and (ii) any purified product whose sequence maps to the claimed amino-acid boundaries.
IL-11 manufacturing realities that map to the claim structure
- If a commercial IL-11 product is produced using expression constructs that contain the claimed IL-11 region exactly as defined in the patent’s SEQ IDs, then claims 1–4 are the most relevant for manufacturing and supply chain discovery.
- If a commercial product uses different boundaries (for example, full-length IL-11 with different processing, alternate isoforms, or different truncation points), then claims 5–7 become the main focus, but they still require the protein to match the claimed region boundaries.
Design-around pressure points
Competitors can reduce risk by:
- changing the encoded region to fall outside amino-acid 120–296,
- using alternate codon sequences if claim construction treats the claim as requiring the exact nucleotide sequence rather than mere synonymous encoding,
- using different IL-11 expression constructs that do not include the exact nucleotide window 2599–3132 of SEQ ID NO:13.
Because claim 1 is limited to positional nucleotide windows and specific SEQ IDs, the space for design-around is larger than for claims that cover full-length IL-11 coding sequences or broadly defined IL-11 variants.
What is the likely priority and filing era, and how does that affect novelty/obviousness?
Direct answer: The patent number (US 6,143,524) places the application in the late-1990s/early-2000 filing window, aligning with the era when IL-11 gene cloning and early recombinant expression were actively published.
Critical implication: For that time period, novelty for “recombinant IL-11” is often less persuasive than for very specific DNA fragments and defined boundaries. A court or PTAB would typically treat broad IL-11 recombinant concepts as known, pushing validity toward whether the particular sequence windows and encoded amino-acid region were non-obvious over prior IL-11 sequences and recombinant expression teachings.
How strong is the patent estate for IL-11 sequence fragments like 120–296?
Direct answer: The patent’s strength is most credible on the exact claimed region definitions, but those definitions still face obviousness risk given the availability of IL-11 sequences and recombinant expression methods during the relevant period.
Claim strength by category
- Claims 1, 5, 6, 7 (sequence and protein region tied): Strongest if the claimed region boundary and exact sequence window correspond to a feature that was not disclosed in prior art or was not an obvious selection.
- Claims 2–4 (vector, host cell, method): Usually dependent on claim 1. If claim 1 is invalid or narrowed, dependent coverage collapses. Their independent value is limited unless there are separate patentable distinctions in the vector/host/process descriptions in the specification.
Typical invalidity theories for this claim set
- Anticipation: a prior reference discloses the same DNA fragment or the same IL-11 region coding sequence and a recombinant expression system with comparable purification.
- Obviousness: a prior reference teaches recombinant IL-11 and sequence-based selection of expressed regions; combining that with known molecular cloning techniques can render the exact fragment selection obvious.
- Indefiniteness / construction pressure: sequence-range claims can trigger interpretive disputes if the SEQ IDs’ content is not clearly mapped in the claim language or if “encoding amino acids” is construed broadly versus narrowly.
What claims are most exposed to design-around in generic or biosimilar manufacturing?
Direct answer: Claims tied to a specific amino-acid region and exact nucleotide range are easier to route around than claims covering full-length IL-11 or broadly defined IL-11 analogs.
Practical design-around levers
- Express full-length IL-11 with different domain boundaries such that the mature product is not restricted to 120–296 in the same way the patent defines it.
- Use constructs that encode IL-11 but replace the exact codon window so the nucleotide range is not literally present (depending on how “encoding” is construed).
- Use alternate signal peptides and processing strategies that produce a different mature region mapping, pushing products outside claim 5–7 definitions.
Orange Book and FDA exclusivity status: what does this patent likely map to?
Direct answer: US 6,143,524 is a gene/protein and production patent family typical of pre-therapeutic-genomics era. It is not a modern formulation, device, or generic exclusivity patent by itself; its enforcement in an Orange Book context depends on whether it was listed for an IL-11 drug in the Orange Book with a corresponding NDA/BLA.
Key limitation embedded in the claim set: the claims are directed to a defined IL-11 region encoded by the claimed DNA. If the relevant marketed product is a different IL-11 molecule or uses a different sequence boundary, the linkage to Orange Book listing relevance may be weak even if the patent is listed.
What patent litigation and PTAB challenges affect this IP?
Direct answer: A complete analysis of litigation and PTAB outcomes requires an identification of the patent’s in-force status, assignment history, and whether it is tied to a specific IL-11 product and real-world defendant portfolio. No litigated docket, settlement, or PTAB institution record is provided in the prompt.
Critical impact: Without docket-linked data, any statement about active enforcement, settlements, or invalidation outcomes would be unsupported.
Which IL-11 products could be implicated and how does the claim language narrow the match?
Direct answer: The claim language most closely implicates recombinant IL-11 constructs and products that encode an IL-11 region corresponding to amino acids 120–296 and that include the specific nucleotide windows defined in SEQ ID NO:13/14.
Matching logic used in infringement analysis
- Determine the accused IL-11 protein sequence and whether it contains the claimed amino-acid region 120–296 as a contiguous part of the “purified IL-11 protein” product.
- Determine the accused DNA used in manufacturing and whether it contains the exact nucleotide range 2599–3132 of SEQ ID NO:13, or encodes amino acids 120–296 using the sequence corresponding to SEQ ID NO:14.
- Map the accused vector and host cell constructs to claim 2–4.
Key commercial takeaway: if the marketed IL-11 product is produced using common expression cassettes encoding full-length IL-11, a key question is whether the patent’s claimed “120–296” is treated as encompassing that mature protein or whether the patent is effectively restricted to a truncated or region-specific product.
What other patents typically cluster around this one?
Direct answer: IL-11 recombinant expression portfolios usually include:
- full-length IL-11 coding sequence claims,
- specific engineered variants, signal peptides, and secretion cassettes,
- purification and formulation claims for the recombinant protein,
- method-of-use claims for indications like wound healing, immune modulation, or GI indications depending on the product.
Risk to enforcement: if those adjacent patents cover broader scope, this patent’s fragment claims might not be the dominant barrier; conversely, if those broader claims are weakened, this one can be the last remaining sequence-specific anchor.
Timeline: where this patent sits for exclusivity and enforcement planning
Direct answer: The critical enforcement window for any US utility patent is its term and any terminal disclaimers, adjusted for filing date, priority, and PTA (patent term adjustment). The prompt provides no filing date or PTA data for US 6,143,524, so a precise expiration timeline cannot be computed from the provided information.
Operational implication: plan freedom-to-operate around whether this patent (and related family members) is still within term and whether it is listed for the specific IL-11 NDA/BLA.
Key takeaways
- US 6,143,524 is a sequence-fragment-centric IL-11 IP bundle: isolated DNA, vectors, host cells, production methods, and purified proteins/compositions all hinge on two strict sequence definitions (nucleotide window 2599–3132 of SEQ ID NO:13; nucleotide sequence encoding amino acids 120–296 of SEQ ID NO:14).
- The patent’s commercial enforceability is conditional on whether competitor manufacturing uses the same gene region boundaries and whether claim construction treats “encoding” as covering synonymous sequences or only the exact sequences tied to the SEQ IDs.
- Vector/host/method claims (2–4) are downstream of claim 1 and typically fail or narrow together with claim 1.
- Protein and composition claims (5–7) can still be design-aroundable if products are full-length IL-11, different isoforms, or different processing boundaries that change the asserted amino-acid region mapping.
FAQs
1) Do claim 5 and claim 6 cover full-length IL-11 or only region 120–296?
The claims are tethered to IL-11 “protein encoded by” DNA encoding amino acids 120–296 and to a “purified IL-11 protein amino acids 120–296,” so product coverage depends on how IL-11 is defined in the patent and whether the purified product is interpreted as the region-specific protein versus the entire IL-11 polypeptide.
2) Can competitors avoid infringement by changing codons for amino acids 120–296?
Risk turns on claim construction for “nucleotides encoding amino acids 120–296 of SEQ ID NO:14.” If the court requires the specific nucleotides, codon substitution can avoid literal infringement; if it is construed functionally, the risk increases.
3) Are vector and host cell claims enforceable without infringing the DNA claim?
No. Claims 2–4 depend on claim 1’s defined DNA. If claim 1 is not met, downstream claims generally do not stand.
4) Does a method of producing recombinant IL-11 infringe if it uses a different expression cassette but still expresses IL-11?
It infringes only if the host cell is transformed/transfected with a vector comprising the claim 1 DNA and the expressed IL-11 polypeptide is the product of that system as claimed.
5) How would Orange Book listing change the practical enforcement of US 6,143,524?
If the patent is listed for a specific IL-11 NDA/BLA, it can create regulatory bottlenecks for generic or biosimilar entry. If it is not listed or is listed for a mismatched IL-11 molecule/sequence boundary, practical barriers are reduced.
References (APA)
- United States Patent 6,143,524.
