US Patent 5,385,839: Claim-by-Claim Analysis and US Patent Landscape
What does US 5,385,839 claim, in technical terms?
US 5,385,839 centers on a genetic construct built around the immediate-early promoter-regulatory region of human cytomegalovirus (hCMV) and its use in transfer vectors and transformed host cells. The claims are drafted in a classic early-biotech format: broad functional linkage language plus host-cell coverage.
Core claim elements across the set
Across claims 1, 2, and 7, the patent’s technical “anchor” is the same:
- DNA element: “immediate-early promoter-regulatory region of human cytomegalovirus”
- Regulatory architecture: the element acts as a promoter-regulatory region within a transfer vector
- Downstream payload (claims 2 and 5): a heterologous gene positioned downstream and operatively linked
- Application vehicle (claims 3, 4, 5, 6): transformed host cells, including eukaryotic and mammalian embodiments
Claim-by-claim parsing
| Claim |
What it covers (plain technical mapping) |
Scope character |
| 1 |
A transfer vector that contains the hCMV immediate-early promoter-regulatory region |
Broad product claim to a class of vectors |
| 2 |
Claim 1 vector with a heterologous gene downstream and operatively linked to that region |
Broader than specific transgenes; limited by structural linkage |
| 3 |
Host cell transformed with the vector of claim 1 |
Broad organism-independent transformation/use claim |
| 4 |
Host cell transformed with the vector of claim 2 |
Broad payload-included host coverage |
| 5 |
Eukaryotic host cell transformed with a vector containing both the hCMV immediate-early promoter-regulatory region and downstream heterologous gene operatively linked |
More explicit vector-host relationship |
| 6 |
Mammalian host cell variant of claim 5 |
Narrows species class to mammalian cells |
| 7 |
Host cell engineered by recombinant DNA technology to contain the hCMV immediate-early promoter-regulatory region |
A second route to “same DNA element” coverage; overlaps claim 3/5 in effect |
How strong is claim scope against obviousness and prior art?
The claims are not limited to:
- a particular hCMV immediate-early promoter variant (e.g., IE1/IE2 subtype specifics, transcript-specific arrangements),
- a particular heterologous gene or expression cassette design beyond “downstream and operatively linked,”
- a particular delivery method (transfection, viral delivery, stable integration),
- a particular cell type beyond eukaryotic and mammalian categories.
That structure matters because early-biotech prior art commonly disclosed:
- hCMV immediate-early regulatory sequences used as strong promoters in expression cassettes,
- vectors in which a downstream heterologous gene is operatively linked to the promoter,
- transformed eukaryotic or mammalian host cells containing the cassette.
In other words, claim breadth increases the risk that at least part of the claim set will be treated as an expected substitution of well-known promoter regulatory sequences into a standard expression-vector architecture.
Where are the technical “pressure points” in claim wording?
1) “Immediate-early promoter-regulatory region”
This phrase typically invites disputes over what exact nucleic acid boundaries qualify as the claimed “region.” If the patent specification defines a precise sequence, competitors can design around by using:
- adjacent promoter elements not included in the claimed boundary,
- promoter fragments shorter or longer than the defined regulatory region,
- alternative hCMV promoter formats (or other viral immediate-early promoters) that may not meet the claimed definition.
If the specification does not lock down boundary length or sequence identity, the claim can look like a functional category and becomes vulnerable to prior art that discloses promoter activity without matching the claim’s implicit definition.
2) “Transfer vector”
“Transfer vector” is frequently used in viral vector contexts, but it can also mean a plasmid vector used to transfer/express an engineered cassette. If prior art shows the same regulatory element used in ordinary expression plasmids, claim language may not prevent obviousness.
3) “Heterologous gene positioned downstream and operatively linked”
This is a standard expression-cassette formulation. Prior art commonly satisfies this in generic ways:
- any transgene placed downstream with promoter-driven expression,
- typical polyA usage and transcription terminator coupling.
The claim does not require:
- specific enhancer arrangements,
- specific transcription start site mapping beyond the promoter region,
- specific insulator elements,
- viral packaging compatibility, or
- integration chemistry.
4) Host-cell transformation claims
Claims 3, 4, 5, 6, and 7 are product-by-process-ish in practice: they cover cells “transformed” or “engineered” with the described DNA elements. For novelty and non-obviousness, the most decisive question becomes whether the prior art already described mammalian cells containing the same promoter-regulatory DNA element used in expression vectors.
How does the claim set compare to typical CMV promoter prior art patterns?
Most early CMV promoter patent and literature disclosures follow this general pattern:
- Identify a viral regulatory region with strong activity in mammalian cells.
- Provide DNA constructs where the viral promoter drives a downstream gene.
- Introduce those constructs into eukaryotic or mammalian host cells.
- Report expression.
US 5,385,839’s claims track that blueprint. Without additional structural constraints, the patent’s novelty likely rests on the specific inclusion and definition of the hCMV immediate-early promoter-regulatory region and on how the claim is tied to “transfer vector” and “operatively linked” language, which may still collapse into standard expression-cassette design.
What does the claim set imply for enforcement and infringement design-around?
What is hardest to design around
- If competitors use the same hCMV immediate-early promoter-regulatory region as defined in the patent, their vectors and transduced cells risk falling within claims 1 and 7, and their expression cassettes risk falling within claims 2 and 5.
What is easier to design around
- Use a different viral promoter (even another hCMV element) or a different immediate-early promoter variant that does not meet the patent’s defined boundaries.
- Use a cellular promoter or hybrid regulatory design rather than the claimed hCMV immediate-early promoter-regulatory region.
- Keep the region present but alter cassette architecture so the gene is not “operatively linked” as construed (for example, by disrupting transcriptional linkage, or creating a non-functional orientation).
- Avoid “transfer vector” characterization by using architectures that do not qualify under the claim interpretation (this depends heavily on claim construction).
How broad is the US claim coverage in functional terms?
| Category |
Claim coverage |
Practical breadth |
| Vector |
Any transfer vector containing the hCMV immediate-early promoter-regulatory region |
Very broad |
| Payload |
Any heterologous gene downstream and operatively linked |
Very broad |
| Host |
Any transformed host cell; then eukaryotic; then mammalian |
Extremely broad |
| Engineering method |
Recombinant DNA engineering containing the regulatory region |
Broad and overlapping |
That combination creates a large infringement surface for anyone building expression cassettes or vector systems that use the hCMV immediate-early promoter regulatory region as the key driver.
US patent landscape: where similar coverage typically appears
The landscape relevant to this type of claim is usually populated by:
- patents and publications disclosing CMV immediate-early promoters in expression vectors,
- patent families claiming vectors and host cells using viral immediate-early promoter elements to drive transgene expression in mammalian cells,
- method and system patents that include the regulatory region as part of broader vector platforms (adenoviral, retroviral, AAV, plasmid expression, etc.).
Even if a competitor’s product uses a viral delivery system, claim scope can still be reached because the asserted claims here are not limited to a specific delivery vehicle. The regulatory element itself drives the infringement analysis.
Landscape drivers
In US enforcement practice, the key competitive families usually cluster around:
- CMV promoter sequence identity and boundary definitions
- expression cassette architecture (promoter, downstream gene orientation, polyA/termination)
- host-cell specificity (mammalian cells are broadly included in many families)
- vector system context (plasmid expression versus viral transfer vectors)
Because US 5,385,839 claims do not tie to a delivery platform, the prior art most likely to challenge it is prior art describing the promoter element in standard expression cassettes rather than promoter usage in only a single delivery system.
What is the most likely validity posture for the claim set?
Given the generic architecture, the patent’s validity would likely face an attack in one or more ways:
- Anticipation: A single prior art reference discloses the same hCMV immediate-early promoter-regulatory region used in a transfer vector with downstream heterologous gene and transformed mammalian cells.
- Obviousness: Multiple references establish:
- the promoter region’s use and strong mammalian expression function,
- standard cassette designs operatively linking promoters to transgenes,
- routine transformation into eukaryotic or mammalian cells.
- Claim construction vulnerabilities:
- if “immediate-early promoter-regulatory region” is construed narrowly, the claim may not cover many common promoter constructs,
- if construed broadly, it overlaps more prior art.
Does claim 7 duplicate claims 1 and 3?
Claim 7 covers host cells engineered using recombinant DNA to contain the immediate-early promoter-regulatory region. This is effectively a host-cell embodiment of claim 1’s DNA element.
- Claim 1: vector with the regulatory region
- Claim 3: host cell transformed with that vector
- Claim 7: host cell engineered to contain the regulatory region via recombinant DNA
So the claim set creates redundant coverage paths for the same underlying DNA element. In an infringement landscape, this increases the chance a competitor’s process lands within at least one independent claim family.
Strategic implications for R&D and investment decisions
A. If you build CMV-driven expression systems
Your exposure is most sensitive to:
- exact promoter-region sequence used,
- cassette boundaries and whether your design matches the claimed “immediate-early promoter-regulatory region,”
- your orientation and whether the downstream gene is “operatively linked.”
B. If you invest in platform vectors
Because claims extend to host cells and general vector architecture, platform investors should map:
- whether the platform depends on CMV immediate-early promoter elements,
- whether competitors have alternative promoter architectures that avoid the claimed region.
C. If you pursue a freedom-to-operate strategy
A practical read of the claim set suggests the highest-risk area is any mammalian expression system using the hCMV immediate-early promoter-regulatory region as a primary transcriptional control element.
Key Takeaways
- US 5,385,839 claims a broad class of vectors and transformed mammalian host cells defined primarily by inclusion of the hCMV immediate-early promoter-regulatory region.
- Claims 2 and 5 cover essentially any downstream heterologous gene that is operatively linked, making the payload largely non-limiting.
- Host-cell claims (3, 4, 5, 6, 7) broaden enforcement beyond the vector itself, reducing the effectiveness of “vector-only” design carve-outs.
- The strongest validity challenge risk comes from prior art that discloses CMV immediate-early promoter sequences driving transgene expression in mammalian cells via standard expression cassette architecture.
- Design-around most plausibly depends on sequence boundary differences for the promoter region, substitution with a different promoter, or cassette architecture that avoids “operatively linked” construction under claim interpretation.
FAQs
-
What DNA element is the main basis of infringement risk in US 5,385,839?
The hCMV immediate-early promoter-regulatory region that must be present in the vector or engineered into the host cell.
-
Does the patent require a specific transgene?
No. Claims 2 and 5 only require a heterologous gene downstream and operatively linked; the transgene identity is not limited.
-
Are mammalian host cells covered even if the delivery method differs?
Yes. Claims 5 and 6 cover transformed eukaryotic and mammalian host cells, so many delivery contexts can still fall within the claims if the regulatory DNA element and cassette architecture are present.
-
Do the claims protect the vector only, or also the cells?
Both. Independent claim coverage spans transfer vectors (claims 1 and 2) and transformed host cells (claims 3-7).
-
Where is the main design-around lever likely to be?
In practice, the main lever is whether the promoter used matches the patent’s claimed hCMV immediate-early promoter-regulatory region boundaries/definition and whether the downstream gene is truly operatively linked.
References
- U.S. Patent No. 5,385,839.
