Executive summary: U.S. Patent 5,547,933 claims non-naturally occurring, recombinant human erythropoietin (EPO) glycoproteins with glycosylation distinct from human urinary EPO, with downstream composition and use claims covering (i) mammalian expression products (including CHO), (ii) isolation from transformed/ transfected host cells, (iii) molecular-weight shifts versus urinary EPO by SDS-PAGE, and (iv) pharmaceutical compositions and methods for EPO therapy, including treatment of kidney dialysis patients to raise hematocrit. The estate is heavily rooted in broad genus claims to “non-naturally occurring” EPO products defined primarily by glycosylation divergence and biological activity rather than by a single, concrete glycoform sequence or site-specific structure. That drafting choice expands literal coverage potential but increases invalidity exposure under later-developed antibody/glyco-structure enablement standards and obviousness-type reasoning for recombinant EPO expressed in common mammalian hosts.

United States Patent 5,547,933 claims analysis: recombinant EPO with altered glycosylation, CHO expression, and dialysis hematocrit uses

What does U.S. Patent 5,547,933 claim protection cover for recombinant erythropoietin?

Short answer: The patent protects (1) recombinant EPO glycoproteins defined by non-natural glycosylation and in vivo erythropoietic activity, (2) recombinant production in mammalian hosts (with specific leader-sequence emphasis in one embodiment), and (3) EPO compositions and dosing methods for therapy, including dialysis hematocrit increases.

Core product protection (claims 1, 3, 4, 5, 6)

Claim 1 is the main independent claim. It requires:

A non-naturally occurring EPO glycoprotein product.
In vivo biological activity: increased production of reticulocytes and red blood cells via bone marrow.
Glycosylation differs from human urinary erythropoietin.

Claim 3 recasts this as a mammalian host cell expression product of an exogenous DNA sequence encoding human EPO, tied to the same in vivo activity.

Claims 4 and 5 narrow the production method “product-by-process” style:

Claim 4 requires growth of host cells transformed/transfected with an isolated DNA encoding the human EPO amino acid sequence set out in Fig. 6 (or fragments), then isolation of a glycosylated polypeptide.
Claim 5 instead requires growth with a DNA sequence encoding the leader sequence of human EPO set out in Fig. 6, again followed by isolation.

Claim 6 expands host choice: expression in a non-human eukaryotic host, with an emphasis on average carbohydrate composition differing from naturally occurring EPO.

Host and cell-line limitations (claims 7, 8)

Claim 7 adds a host limitation: “non-human mammalian cell.”
Claim 8 narrows further: CHO cell.

These claims matter for enforcing around alternatives:

Many recombinant EPO products are made in mammalian systems and may fall within CHO-linked glycosylation ranges even if the exact glycoform distribution differs.

Measurement-oriented limitation (claim 2)

Claim 2 adds an evidentiary measurement constraint:

Higher molecular weight than human urinary EPO by SDS-PAGE.

In practice, this is a structural/biophysical hook. But SDS-PAGE shift can be influenced by multiple factors beyond glycosylation (sample preparation, reduction conditions, glycan processing heterogeneity), which can become a litigation focal point for claim construction and infringement proof.

Composition and method claims (claims 9–14)

Claims 9 and 12: pharmaceutical composition comprising the claimed glycoprotein and a pharmaceutically acceptable diluent/carrier.
Claims 10 and 13: administering the composition to a mammal for EPO therapy.
Claims 11 and 14: treating kidney dialysis patients by administering an effective amount to increase hematocrit.

These downstream claims generally track standard EPO-label indications. If the product claim is weak or non-infringed, the composition and method claims typically fall with it. If the product claim is enforceable, the therapy claims can add leverage in settlements, especially where generic or biosimilar entrants seek narrow non-infringing positioning.

How do the claims define “non-naturally occurring” glycosylation, and what does that mean legally?

Short answer: The patent defines coverage by glycosylation difference from human urinary EPO and by “non-naturally occurring” status tied to recombinant expression. That leaves infringement to two proof routes: (i) glyco-profile comparison, and (ii) functional erythropoietic activity consistent with EPO.

Functional activity vs. structural definition

The independent claims repeatedly include the functional requirement that the product “caus[es] bone marrow cells to increase production of reticulocytes and red blood cells.” This is effectively an EPO activity limitation.

For infringement, a patent holder can argue:

Recombinant EPO inherently meets the biological function, so the main differentiator is glycosylation.

A challenger can argue:

The patent is overbroad because recombinant EPO expressed in mammalian hosts is routinely “non-naturally occurring” compared to urinary EPO, making the glycosylation-difference limitation difficult to treat as a meaningful narrow structural boundary.

Glycosylation difference language and enforcement

Claim 1: “glycosylation which differs from that of human urinary erythropoietin.”
Claim 6: “average carbohydrate composition which differs.”

The claims do not specify:

a glycan composition list,
site occupancy on Asn residues,
exact glycoform distribution (e.g., percentage of sialylated biantennary structures),
or a specific isoform set.

That absence can enlarge literal coverage but makes validity and claim-definiteness/infringement disputes more likely in later-era glycoprotein patent practice.

SDS-PAGE higher molecular weight hook

Claim 2 allows a measurable proxy for glycosylation changes. Litigation commonly turns on:

whether the competitor’s preparation shows higher MW under the asserted SDS-PAGE conditions,
whether differences arise from glycosylation rather than assay variance.

Which patent scope is strongest: product-by-process, glycosylation difference, or CHO host claims?

Short answer: CHO and leader-sequence embodiments may be easier to target factually, but the broadest independent claim (claim 1) is the biggest practical enforcement lever. Product-by-process claims (claims 4 and 5) are powerful if the accused product is made by the same process steps, but they are also typically the most litigation-intensive due to process ambiguity.

**Claim 1 vs. claims 4–5 (product-by-process risk)

Claims 4 and 5 define the product as “the product of the process” that includes:

specific host cell growth conditions,
transformation/transfection with DNA encoding Fig. 6 EPO sequence (claim 4) or Fig. 6 leader sequence (claim 5),
isolation of glycosylated polypeptide.

If a competitor uses a different construct, host, leader, or expression system, those product-by-process boundaries can create non-infringement arguments. Meanwhile, if the competitor produces a glycoprotein that matches the claim’s glycosylation and activity requirements, the case may proceed under claim 1 regardless.

CHO limitation (claims 7–8) as a carve-in for certain biosimilar-like production

CHO is common for glycoproteins and is frequently used for EPO biosimilars. A CHO-made product may still differ from urinary EPO in glycosylation, satisfying claim 1. But if the accused product is made in another mammalian host (e.g., human cell lines, baby hamster kidney derivatives, or engineered lines), claim 8 may not read onto it.

Molecular weight requirement (claim 2) narrows but can be met indirectly

Even where glycosylation differs, MW may or may not be higher depending on assay conditions and glycan processing. That makes claim 2 a narrower dependent claim that can be used as an additional infringement pillar when SDS-PAGE evidence is favorable.

What patents protect recombinant EPO glycoproteins with altered glycosylation around this era?

Short answer: During the recombinant EPO expansion of the late 1980s and early 1990s, the patent landscape clustered around (i) recombinant DNA constructs and expression systems, (ii) glycoprotein variants defined by glycosylation or processing, and (iii) therapeutic compositions and methods. U.S. 5,547,933 sits in that core cluster but is framed broadly around glycosylation difference versus urinary EPO rather than a single expressed isoform.

Landscape relevance to enforcement

Construct patents typically control DNA sequences and expression platforms.
Glycoform/processing patents control the “product identity” under biosimilar/glycoprotein comparisons.
Therapeutic use patents are often less differentiating and tend to collapse if product-level claims are invalid or not infringed.

This portfolio structure matters in licensing and litigation strategy: the “strongest” leverage often tracks to the protein identity claims, not the dosing claims.

When does U.S. Patent 5,547,933 lose exclusivity and can generics or biosimilars enter?

Short answer: The patent’s enforceable life is governed by U.S. utility term (and any patent-term adjustments), starting from earliest effective priority and ending after the statutory term from grant/filing (subject to adjustments). Without the filing/priority and PTA details, no precise expiration date can be stated from the claim text alone.

Practical exclusivity mechanics for EPO in the U.S.

For EPO products, market entry typically depends on:

U.S. patent listings in the Orange Book for the reference product (if applicable to the same active ingredient form and strength),
later-filed patents directed to formulation, method-of-use, or biosimilar comparability,
and biosimilar-specific considerations for biologics licensing.

This patent’s claims are product and method claims, which generally correspond to high-stakes barriers to generic/biosimilar entry.

What is the Orange Book status of U.S. Patent 5,547,933 and where is it listed for EPO products?

Short answer: Orange Book listing is product-specific and requires pairing the patent number with a particular FDA-approved NDA and listed active ingredient. That mapping cannot be produced from the provided material alone.

Why the mapping matters

If the patent is listed only against certain EPO products (e.g., specific strengths or dosage forms), then the enforcement reach against other branded EPOs may be limited even if the claimed molecule concept is similar.

How strong is the patent estate based on claim drafting: broad genus glycoproteins vs. narrow glyco-structure?

Short answer: The estate strength for infringement is medium to high in concept (because recombinant EPO in mammalian hosts typically differs from urinary EPO glycosylation), but the claim strength for validity is vulnerable due to broad functional and comparative glycosylation language without concrete structural definition.

Strength for infringement

The claims cover a wide range of “non-naturally occurring” EPO glycoproteins.
They do not require a specific glycan structure, isoform count, or exact glycosylation sites in the claims provided.
The biological activity requirement will likely be met by most EPO-like molecules.

Validity risk themes

A challenger typically attacks:

enablement and written description for a broad genus defined by comparative glycosylation without explicit structural boundaries,
obviousness over known recombinant EPO expression in mammalian hosts that already yield non-urinary glycosylation patterns,
anticipation by earlier recombinant EPO patents, especially where the only difference is glycosylation.

What patent litigation issues are likely for U.S. 5,547,933 (infringement proof and claim construction)?

Short answer: Litigation will likely center on glycosylation comparison evidence, SDS-PAGE assays, host expression method, and whether the accused product fits the “non-naturally occurring” glycosylation difference requirement.

Key infringement evidence

Glycoprotein mass and electrophoresis profiles (including SDS-PAGE under comparable conditions for claim 2).
Glycopeptide mapping and carbohydrate analysis to demonstrate “differs from human urinary EPO.”
Construct and host cell records, especially to test claim 5 leader-sequence dependence and claim 8 CHO status.

Key claim construction disputes

Scope of “glycosylation differs” (binary difference vs. statistically meaningful divergence).
Treatment of product-by-process claims 4 and 5.
Whether “average carbohydrate composition” in claim 6 is sufficient to define a specific product identity.

How does this patent compare to later EPO/biosimilar patent strategies focused on glycoform similarity?

Short answer: 5,547,933 uses comparative divergence from urinary EPO and broad non-natural status. Later strategies in biosimilars emphasize:

analytical characterization to show similarity or differences in glycosylation and isoforms,
detailed structural analytics,
and product-specific formulations.

So, enforcement under 5,547,933 can be fact-intensive and may look less like modern glycoform “fingerprinting” and more like comparative functional and analytical demonstrations versus urinary EPO standards.

Which drug or company products are most likely to be implicated by the scope of 5,547,933?

Short answer: The claim scope maps to recombinant EPO products made in mammalian cells, including CHO-based manufacturing, and to their approved therapeutic use in anemia of renal disease and dialysis settings. Company identification cannot be reliably produced from the provided information alone.

What generic or biosimilar entry risks exist under this claim set?

Short answer: If a candidate product uses mammalian-cell recombinant EPO with glycosylation that differs from human urinary EPO and preserves EPO activity, it risks literal coverage under claim 1. Dependent claims 8 and 5 add host and leader-sequence boundaries that can create partial design-around options.

Design-around paths implied by the claims

Avoid CHO expression to target claim 8, though claim 1 may still read if glycosylation differs from urinary EPO.
Use a different leader sequence than Fig. 6 to attempt to reduce claim 5 fit.
Target glycosylation profiles to approximate urinary EPO glycosylation. That is difficult given typical mammalian glycosylation processing, but if achieved, it could be an infringement avoidance strategy against claim 1’s “differs from urinary” requirement.

Key Takeaways

U.S. 5,547,933 protects recombinant EPO glycoproteins defined by non-naturally occurring status, EPO biological activity, and glycosylation divergence from urinary EPO, plus product-by-process embodiments and CHO limitations.
Dependent claims add measurable narrowing (SDS-PAGE higher molecular weight) and production-specific features (Fig. 6 amino acid sequence vs. Fig. 6 leader sequence).
Downstream composition and therapy claims cover EPO therapy and kidney dialysis hematocrit increase, but their enforceability largely depends on product-level infringement and validity.
The breadth of comparative glycosylation language expands potential infringement scope while increasing validity and proof challenges due to lack of concrete, site-specific or isoform-specific structure in the claim text provided.

FAQs

Does claim 1 require a specific glycan structure or just “difference” vs urinary EPO?
It requires glycosylation that “differs from that of human urinary erythropoietin,” without specifying structure in the provided claim text.
Can a non-CHO mammalian host avoid claim 8 but still infringe claim 1?
Yes. Claim 8 is CHO-limited, but claim 1 is not; infringement can still occur if the glycosylation difference and activity requirements are met.
How is claim 2 typically proven in infringement cases?
By SDS-PAGE demonstrating higher apparent molecular weight relative to human urinary EPO under comparable assay conditions.
Are claims 4 and 5 easier or harder to enforce than claim 1?
They are often harder to enforce consistently because they are tied to specific DNA encoding details and process steps, though they can provide stronger hooks when the accused process is documentable.
Do the dialysis hematocrit methods (claims 11 and 14) create independent barriers if the product claim falls?
Typically they do not; method-of-use claims depend on the accused use of a product that fits the claimed composition/product scope.

References

U.S. Patent 5,547,933.

Title:	Production of erythropoietin
Abstract:	Disclosed are novel polypeptides possessing part or all of the primary structural conformation and one or more of the biological properties of mammalian erythropoietin (\"EPO\") which are characterized in preferred forms by being the product of procaryotic or eucaryotic host expression of an exogenous DNA sequence. Illustratively, genomic DNA, cDNA and manufactured DNA sequences coding for part or all of the sequence of amino acid residues of EPO or for analogs thereof are incorporated into autonomously replicating plasmid or viral vectors employed to transform or transfect suitable procaryotic or eucaryotic host cells such as bacteria, yeast or vertebrate cells in culture. Upon isolation from culture media or cellular lysates or fragments, products of expression of the DNA sequences display, e.g., the immunological properties and in vitro and in vivo biological activities of EPO of human or monkey species origins. Disclosed also are chemically synthesized polypeptides sharing the biochemical and immunological properties of EPO. Also disclosed are improved methods for the detection of specific single stranded polynucleotides in a heterologous cellular or viral sample prepared from, e.g., DNA present in a plasmid or viral-borne cDNA or genomic DNA \"library\".
Inventor(s):	Lin; Fu-Kuen (Thousand Oaks, CA)
Assignee:	Kirin-Amgen, Inc. (Thousand Oaks, CA)
Application Number:	08/487,774
Patent Claims:	see list of patent claims
Patent landscape, scope, and claims summary:	Executive summary: U.S. Patent 5,547,933 claims non-naturally occurring, recombinant human erythropoietin (EPO) glycoproteins with glycosylation distinct from human urinary EPO, with downstream composition and use claims covering (i) mammalian expression products (including CHO), (ii) isolation from transformed/ transfected host cells, (iii) molecular-weight shifts versus urinary EPO by SDS-PAGE, and (iv) pharmaceutical compositions and methods for EPO therapy, including treatment of kidney dialysis patients to raise hematocrit. The estate is heavily rooted in broad genus claims to “non-naturally occurring” EPO products defined primarily by glycosylation divergence and biological activity rather than by a single, concrete glycoform sequence or site-specific structure. That drafting choice expands literal coverage potential but increases invalidity exposure under later-developed antibody/glyco-structure enablement standards and obviousness-type reasoning for recombinant EPO expressed in common mammalian hosts. United States Patent 5,547,933 claims analysis: recombinant EPO with altered glycosylation, CHO expression, and dialysis hematocrit uses What does U.S. Patent 5,547,933 claim protection cover for recombinant erythropoietin? Short answer: The patent protects (1) recombinant EPO glycoproteins defined by non-natural glycosylation and in vivo erythropoietic activity, (2) recombinant production in mammalian hosts (with specific leader-sequence emphasis in one embodiment), and (3) EPO compositions and dosing methods for therapy, including dialysis hematocrit increases. Core product protection (claims 1, 3, 4, 5, 6) Claim 1 is the main independent claim. It requires: A non-naturally occurring EPO glycoprotein product. In vivo biological activity: increased production of reticulocytes and red blood cells via bone marrow. Glycosylation differs from human urinary erythropoietin. Claim 3 recasts this as a mammalian host cell expression product of an exogenous DNA sequence encoding human EPO, tied to the same in vivo activity. Claims 4 and 5 narrow the production method “product-by-process” style: Claim 4 requires growth of host cells transformed/transfected with an isolated DNA encoding the human EPO amino acid sequence set out in Fig. 6 (or fragments), then isolation of a glycosylated polypeptide. Claim 5 instead requires growth with a DNA sequence encoding the leader sequence of human EPO set out in Fig. 6, again followed by isolation. Claim 6 expands host choice: expression in a non-human eukaryotic host, with an emphasis on average carbohydrate composition differing from naturally occurring EPO. Host and cell-line limitations (claims 7, 8) Claim 7 adds a host limitation: “non-human mammalian cell.” Claim 8 narrows further: CHO cell. These claims matter for enforcing around alternatives: Many recombinant EPO products are made in mammalian systems and may fall within CHO-linked glycosylation ranges even if the exact glycoform distribution differs. Measurement-oriented limitation (claim 2) Claim 2 adds an evidentiary measurement constraint: Higher molecular weight than human urinary EPO by SDS-PAGE. In practice, this is a structural/biophysical hook. But SDS-PAGE shift can be influenced by multiple factors beyond glycosylation (sample preparation, reduction conditions, glycan processing heterogeneity), which can become a litigation focal point for claim construction and infringement proof. Composition and method claims (claims 9–14) Claims 9 and 12: pharmaceutical composition comprising the claimed glycoprotein and a pharmaceutically acceptable diluent/carrier. Claims 10 and 13: administering the composition to a mammal for EPO therapy. Claims 11 and 14: treating kidney dialysis patients by administering an effective amount to increase hematocrit. These downstream claims generally track standard EPO-label indications. If the product claim is weak or non-infringed, the composition and method claims typically fall with it. If the product claim is enforceable, the therapy claims can add leverage in settlements, especially where generic or biosimilar entrants seek narrow non-infringing positioning. How do the claims define “non-naturally occurring” glycosylation, and what does that mean legally? Short answer: The patent defines coverage by glycosylation difference from human urinary EPO and by “non-naturally occurring” status tied to recombinant expression. That leaves infringement to two proof routes: (i) glyco-profile comparison, and (ii) functional erythropoietic activity consistent with EPO. Functional activity vs. structural definition The independent claims repeatedly include the functional requirement that the product “caus[es] bone marrow cells to increase production of reticulocytes and red blood cells.” This is effectively an EPO activity limitation. For infringement, a patent holder can argue: Recombinant EPO inherently meets the biological function, so the main differentiator is glycosylation. A challenger can argue: The patent is overbroad because recombinant EPO expressed in mammalian hosts is routinely “non-naturally occurring” compared to urinary EPO, making the glycosylation-difference limitation difficult to treat as a meaningful narrow structural boundary. Glycosylation difference language and enforcement Claim 1: “glycosylation which differs from that of human urinary erythropoietin.” Claim 6: “average carbohydrate composition which differs.” The claims do not specify: a glycan composition list, site occupancy on Asn residues, exact glycoform distribution (e.g., percentage of sialylated biantennary structures), or a specific isoform set. That absence can enlarge literal coverage but makes validity and claim-definiteness/infringement disputes more likely in later-era glycoprotein patent practice. SDS-PAGE higher molecular weight hook Claim 2 allows a measurable proxy for glycosylation changes. Litigation commonly turns on: whether the competitor’s preparation shows higher MW under the asserted SDS-PAGE conditions, whether differences arise from glycosylation rather than assay variance. Which patent scope is strongest: product-by-process, glycosylation difference, or CHO host claims? Short answer: CHO and leader-sequence embodiments may be easier to target factually, but the broadest independent claim (claim 1) is the biggest practical enforcement lever. Product-by-process claims (claims 4 and 5) are powerful if the accused product is made by the same process steps, but they are also typically the most litigation-intensive due to process ambiguity. Claim 1 vs. claims 4–5 (product-by-process risk) Claims 4 and 5 define the product as “the product of the process” that includes: specific host cell growth conditions, transformation/transfection with DNA encoding Fig. 6 EPO sequence (claim 4) or Fig. 6 leader sequence (claim 5), isolation of glycosylated polypeptide. If a competitor uses a different construct, host, leader, or expression system, those product-by-process boundaries can create non-infringement arguments. Meanwhile, if the competitor produces a glycoprotein that matches the claim’s glycosylation and activity requirements, the case may proceed under claim 1 regardless. CHO limitation (claims 7–8) as a carve-in for certain biosimilar-like production CHO is common for glycoproteins and is frequently used for EPO biosimilars. A CHO-made product may still differ from urinary EPO in glycosylation, satisfying claim 1. But if the accused product is made in another mammalian host (e.g., human cell lines, baby hamster kidney derivatives, or engineered lines), claim 8 may not read onto it. Molecular weight requirement (claim 2) narrows but can be met indirectly Even where glycosylation differs, MW may or may not be higher depending on assay conditions and glycan processing. That makes claim 2 a narrower dependent claim that can be used as an additional infringement pillar when SDS-PAGE evidence is favorable. What patents protect recombinant EPO glycoproteins with altered glycosylation around this era? Short answer: During the recombinant EPO expansion of the late 1980s and early 1990s, the patent landscape clustered around (i) recombinant DNA constructs and expression systems, (ii) glycoprotein variants defined by glycosylation or processing, and (iii) therapeutic compositions and methods. U.S. 5,547,933 sits in that core cluster but is framed broadly around glycosylation difference versus urinary EPO rather than a single expressed isoform. Landscape relevance to enforcement Construct patents typically control DNA sequences and expression platforms. Glycoform/processing patents control the “product identity” under biosimilar/glycoprotein comparisons. Therapeutic use patents are often less differentiating and tend to collapse if product-level claims are invalid or not infringed. This portfolio structure matters in licensing and litigation strategy: the “strongest” leverage often tracks to the protein identity claims, not the dosing claims. When does U.S. Patent 5,547,933 lose exclusivity and can generics or biosimilars enter? Short answer: The patent’s enforceable life is governed by U.S. utility term (and any patent-term adjustments), starting from earliest effective priority and ending after the statutory term from grant/filing (subject to adjustments). Without the filing/priority and PTA details, no precise expiration date can be stated from the claim text alone. Practical exclusivity mechanics for EPO in the U.S. For EPO products, market entry typically depends on: U.S. patent listings in the Orange Book for the reference product (if applicable to the same active ingredient form and strength), later-filed patents directed to formulation, method-of-use, or biosimilar comparability, and biosimilar-specific considerations for biologics licensing. This patent’s claims are product and method claims, which generally correspond to high-stakes barriers to generic/biosimilar entry. What is the Orange Book status of U.S. Patent 5,547,933 and where is it listed for EPO products? Short answer: Orange Book listing is product-specific and requires pairing the patent number with a particular FDA-approved NDA and listed active ingredient. That mapping cannot be produced from the provided material alone. Why the mapping matters If the patent is listed only against certain EPO products (e.g., specific strengths or dosage forms), then the enforcement reach against other branded EPOs may be limited even if the claimed molecule concept is similar. How strong is the patent estate based on claim drafting: broad genus glycoproteins vs. narrow glyco-structure? Short answer: The estate strength for infringement is medium to high in concept (because recombinant EPO in mammalian hosts typically differs from urinary EPO glycosylation), but the claim strength for validity is vulnerable due to broad functional and comparative glycosylation language without concrete structural definition. Strength for infringement The claims cover a wide range of “non-naturally occurring” EPO glycoproteins. They do not require a specific glycan structure, isoform count, or exact glycosylation sites in the claims provided. The biological activity requirement will likely be met by most EPO-like molecules. Validity risk themes A challenger typically attacks: enablement and written description for a broad genus defined by comparative glycosylation without explicit structural boundaries, obviousness over known recombinant EPO expression in mammalian hosts that already yield non-urinary glycosylation patterns, anticipation by earlier recombinant EPO patents, especially where the only difference is glycosylation. What patent litigation issues are likely for U.S. 5,547,933 (infringement proof and claim construction)? Short answer: Litigation will likely center on glycosylation comparison evidence, SDS-PAGE assays, host expression method, and whether the accused product fits the “non-naturally occurring” glycosylation difference requirement. Key infringement evidence Glycoprotein mass and electrophoresis profiles (including SDS-PAGE under comparable conditions for claim 2). Glycopeptide mapping and carbohydrate analysis to demonstrate “differs from human urinary EPO.” Construct and host cell records, especially to test claim 5 leader-sequence dependence and claim 8 CHO status. Key claim construction disputes Scope of “glycosylation differs” (binary difference vs. statistically meaningful divergence). Treatment of product-by-process claims 4 and 5. Whether “average carbohydrate composition” in claim 6 is sufficient to define a specific product identity. How does this patent compare to later EPO/biosimilar patent strategies focused on glycoform similarity? Short answer: 5,547,933 uses comparative divergence from urinary EPO and broad non-natural status. Later strategies in biosimilars emphasize: analytical characterization to show similarity or differences in glycosylation and isoforms, detailed structural analytics, and product-specific formulations. So, enforcement under 5,547,933 can be fact-intensive and may look less like modern glycoform “fingerprinting” and more like comparative functional and analytical demonstrations versus urinary EPO standards. Which drug or company products are most likely to be implicated by the scope of 5,547,933? Short answer: The claim scope maps to recombinant EPO products made in mammalian cells, including CHO-based manufacturing, and to their approved therapeutic use in anemia of renal disease and dialysis settings. Company identification cannot be reliably produced from the provided information alone. What generic or biosimilar entry risks exist under this claim set? Short answer: If a candidate product uses mammalian-cell recombinant EPO with glycosylation that differs from human urinary EPO and preserves EPO activity, it risks literal coverage under claim 1. Dependent claims 8 and 5 add host and leader-sequence boundaries that can create partial design-around options. Design-around paths implied by the claims Avoid CHO expression to target claim 8, though claim 1 may still read if glycosylation differs from urinary EPO. Use a different leader sequence than Fig. 6 to attempt to reduce claim 5 fit. Target glycosylation profiles to approximate urinary EPO glycosylation. That is difficult given typical mammalian glycosylation processing, but if achieved, it could be an infringement avoidance strategy against claim 1’s “differs from urinary” requirement. Key Takeaways U.S. 5,547,933 protects recombinant EPO glycoproteins defined by non-naturally occurring status, EPO biological activity, and glycosylation divergence from urinary EPO, plus product-by-process embodiments and CHO limitations. Dependent claims add measurable narrowing (SDS-PAGE higher molecular weight) and production-specific features (Fig. 6 amino acid sequence vs. Fig. 6 leader sequence). Downstream composition and therapy claims cover EPO therapy and kidney dialysis hematocrit increase, but their enforceability largely depends on product-level infringement and validity. The breadth of comparative glycosylation language expands potential infringement scope while increasing validity and proof challenges due to lack of concrete, site-specific or isoform-specific structure in the claim text provided. FAQs Does claim 1 require a specific glycan structure or just “difference” vs urinary EPO? It requires glycosylation that “differs from that of human urinary erythropoietin,” without specifying structure in the provided claim text. Can a non-CHO mammalian host avoid claim 8 but still infringe claim 1? Yes. Claim 8 is CHO-limited, but claim 1 is not; infringement can still occur if the glycosylation difference and activity requirements are met. How is claim 2 typically proven in infringement cases? By SDS-PAGE demonstrating higher apparent molecular weight relative to human urinary EPO under comparable assay conditions. Are claims 4 and 5 easier or harder to enforce than claim 1? They are often harder to enforce consistently because they are tied to specific DNA encoding details and process steps, though they can provide stronger hooks when the accused process is documentable. Do the dialysis hematocrit methods (claims 11 and 14) create independent barriers if the product claim falls? Typically they do not; method-of-use claims depend on the accused use of a product that fits the claimed composition/product scope. References U.S. Patent 5,547,933. More… ↓ ⤷ Start Trial**

Applicant	Tradename	Biologic Ingredient	Dosage Form	BLA	Approval Date	Patent No.	Expiredate
Amgen Inc.	EPOGEN/PROCRIT	epoetin alfa	Injection	103234	June 01, 1989	5,547,933	2015-06-07
Amgen Inc.	EPOGEN/PROCRIT	epoetin alfa	Injection	103234		5,547,933	2015-06-07
Amgen Inc.	PROCRIT	epoetin alfa	Injection	103234		5,547,933	2015-06-07
>Applicant	>Tradename	>Biologic Ingredient	>Dosage Form	>BLA	>Approval Date	>Patent No.	>Expiredate

Country	Patent Number	Estimated Expiration
South Africa	849625	⤷ Start Trial
World Intellectual Property Organization (WIPO)	8502610	⤷ Start Trial
United States of America	4703008	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration

Patent: 5,547,933

Summary for Patent: 5,547,933