Patent: 5,441,868

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Summary for Patent: 5,441,868

Title:	Production of recombinant 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:	07/113,179
Patent Claims:	see list of patent claims

United States Patent 5,441,868: Claims, Scope, Validity, Expiration, and Erythropoietin Patent Landscape

US Patent 5,441,868 is an Amgen patent directed to recombinant production of glycosylated human erythropoietin, or EPO, in mammalian host cells. Its core inventive concept is the combination of an isolated DNA sequence encoding human EPO with mammalian-cell expression and recovery of biologically active, glycosylated EPO.

The patent issued on August 15, 1995, from an application claiming priority to December 13, 1984. Its enforceable term expired in 2012. The patent therefore has no current blocking effect, although it remains important for understanding the historical foundation of epoetin alfa manufacturing and the patent disputes involving Amgen and Roche.

What does US Patent 5,441,868 claim?

The patent claims a biological manufacturing process rather than a composition-of-matter monopoly over the EPO protein itself.

Claim	Subject matter	Scope
1	Production of glycosylated human EPO by growing mammalian cells transformed or transfected with isolated DNA encoding human EPO and isolating the product	Broad independent process claim
2	Claim 1 using CHO cells	Narrower host-cell limitation
3	Claim 1 using COS cells	Narrower host-cell limitation
4	Claim 1 using cDNA encoding human EPO	DNA-source limitation
5	Claim 1 using genomic DNA encoding human EPO	DNA-source limitation

Claim 1 requires each of the following elements:

1. Mammalian host cells.
2. Transformation or transfection with isolated DNA.
3. DNA encoding human erythropoietin.
4. Growth under suitable nutrient conditions.
5. Production of glycosylated EPO.
6. Isolation of the EPO polypeptide.
7. The resulting polypeptide must have the in vivo biological property of increasing reticulocyte and red-blood-cell production.

The claim does not expressly limit the process to a particular promoter, vector, culture medium, purification method, glycosylation profile, dosage form, or administration route.

How broad is claim 1 of US 5,441,868?

Claim 1 is broad within the field of mammalian recombinant EPO production. It is not limited to CHO cells, COS cells, cDNA, or genomic DNA. Those technologies appear in dependent claims 2 through 5.

The claim covers a process if the accused manufacturing method uses mammalian cells containing isolated DNA encoding human EPO and recovers glycosylated EPO with the recited biological activity. A process using a different mammalian cell line could fall within claim 1 even if it did not fall within claim 2 or claim 3.

The principal scope limitations are:

• The host must be mammalian.
• The DNA must be isolated and encode human EPO.
• The product must be glycosylated.
• The product must have the specified erythropoietic activity.
• The process must include both cell growth and product isolation.

The claim does not cover every method of making an EPO-related product. It would not inherently reach:

• Nonmammalian expression systems, such as bacterial, yeast, or plant systems.
• Chemically synthesized EPO lacking the claimed mammalian-cell process.
• EPO analogues that do not satisfy the human-EPO limitation.
• A process that does not isolate the product.
• A process producing an inactive or materially nonfunctional polypeptide.

The functional language concerning increased reticulocyte and red-blood-cell production is primarily a product-characterization limitation. In an infringement dispute, the claimant would generally need to establish that the recovered product has the claimed biological property, although the use of a recombinant human EPO process may make that showing straightforward when the product is conventional epoetin.

What are the differences between claims 1 through 5?

Claim 1: mammalian-cell production

Claim 1 is the principal commercial claim. It covers the general mammalian-cell process for recombinant glycosylated human EPO.

Its breadth creates potential overlap with commercial epoetin alfa processes using CHO cells, but infringement would depend on the actual process steps and the construction of the DNA, host-cell, glycosylation, and isolation requirements.

Claim 2: CHO-cell production

Claim 2 specifically covers production in Chinese hamster ovary cells. CHO cells became the dominant commercial platform for epoetin alfa and many other therapeutic glycoproteins because they support mammalian folding, secretion, and glycosylation.

A CHO process satisfying claim 1 would also satisfy claim 2. The reverse is not true: a mammalian process using another cell line could fall under claim 1 but not claim 2.

Claim 3: COS-cell production

Claim 3 covers COS cells, which are simian kidney-derived cells commonly used for transient expression and research-scale production. COS cells have less commercial importance than CHO cells for large-scale therapeutic EPO manufacture.

The claim has historical and technical significance but limited present-day commercial relevance.

Claims 4 and 5: cDNA and genomic DNA

Claim 4 covers use of cDNA encoding human EPO. Claim 5 covers genomic DNA encoding human EPO.

The distinction matters because genomic DNA includes intronic sequences, while cDNA generally corresponds to processed messenger RNA and lacks introns. Both claims depend on the limitations of claim 1 and therefore remain process claims, not standalone DNA composition claims.

When did US Patent 5,441,868 expire?

US Patent 5,441,868 expired in 2012. Public patent records identify the patent as issued August 15, 1995, with an effective term ending in August 2012 under the pre-URAA patent-term rules applicable to the relevant filing history (United States Patent and Trademark Office, n.d.).

Event	Date
Earliest claimed priority	December 13, 1984
Patent issued	August 15, 1995
Patent term expiration	August 2012
Current status	Expired
Current infringement risk from this patent	None for new activity

The expiration removes the patent’s exclusionary force. It does not invalidate historical infringement claims arising during the enforceable term, and it does not eliminate other patents covering formulations, delivery systems, therapeutic methods, cell culture, purification, or later-generation EPO products.

What was the relationship between US 5,441,868 and Amgen’s EPO patent portfolio?

US 5,441,868 was one component of a broader Amgen patent family covering recombinant EPO. The key historical patents included the following:

Patent	General subject	Historical relevance
US 4,703,008	DNA sequences and recombinant production of EPO	Foundational recombinant EPO patent
US 5,441,868	Mammalian-cell production of glycosylated EPO	Manufacturing-process protection
US 5,547,933	Glycosylated EPO production and related process technology	Manufacturing and product-related protection
US 5,618,698	EPO isoforms and related biological characteristics	Product and analytical distinctions
US 5,955,422	Therapeutic use of EPO	Method-of-use protection
US 5,441,868	Mammalian host-cell process claims	Relevant to commercial epoetin manufacture

These patents did not create a single uniform monopoly. They protected different parts of the commercial system: DNA, host-cell production, glycosylation, product characteristics, and therapeutic use. As each patent expired, the remaining portfolio could still affect market entry until the last relevant rights ended.

What patent litigation involved US 5,441,868?

The most significant litigation was Amgen Inc. v. Hoffman-La Roche Ltd., involving Roche’s recombinant EPO products, including epoetin beta and later Mircera-related technology.

The dispute involved several Amgen patents, including US 5,441,868 and US 5,547,933. The litigation addressed infringement, validity, claim construction, and Roche’s activities relating to recombinant EPO in the United States. The Federal Circuit’s 2009 decision affirmed important portions of the district court’s judgment and addressed the enforceability of Amgen’s EPO patent rights (Amgen Inc. v. Hoffman-La Roche Ltd., 2009).

The litigation is important for three reasons:

1. It confirmed that process patents can create substantial barriers even when the underlying therapeutic protein is known.
2. It demonstrated that manufacturing steps, not only product structure, can determine biosimilar and follow-on biologic exposure.
3. It delayed Roche’s ability to market certain EPO products in the United States.

The asserted claims in the litigation were not necessarily identical to claims 1 through 5 reproduced in the question. Patent litigation often focuses on selected issued claims, including claims added or amended during prosecution. The existence of litigation involving the patent does not mean every claim was adjudicated to the same extent.

Was US 5,441,868 valid and enforceable during its term?

The patent was treated as an enforceable patent during the principal period of the Amgen-Roche dispute. The litigation raised validity issues, including written-description and enablement-related arguments involving Amgen’s broader EPO patent portfolio.

The principal technical vulnerability in claims of this type is breadth. Claim 1 covers mammalian host cells generally, while the specification and commercial practice may focus more heavily on particular expression systems. A challenger could argue that the patent does not adequately support or enable the full scope of every mammalian-cell process.

Other possible validity issues include:

• Anticipation by earlier recombinant DNA or EPO disclosures.
• Obviousness based on known mammalian expression systems.
• Written-description support for the full host-cell and DNA genus.
• Definiteness of the biological-activity limitation.
• Enablement across different cell lines and glycosylation conditions.

The patent’s historical litigation record indicates that these issues were substantial but did not eliminate its commercial value before expiration. The relevant legal question today is not whether the patent remains enforceable. It does not. The commercial question is whether other live patents or regulatory barriers replace the expired process protection.

What was the FDA and Orange Book status of US 5,441,868?

US 5,441,868 was not an Orange Book product patent in the conventional small-molecule sense. Epogen is regulated as a biologic under a biologics license application, or BLA, rather than as an NDA-listed small-molecule drug. Biologic reference products and biosimilars are tracked through the FDA’s Purple Book framework, while the Orange Book primarily covers approved drug products approved under NDAs and ANDAs (U.S. Food and Drug Administration, n.d.-a, n.d.-b).

Epogen was approved by FDA in 1989 as recombinant epoetin alfa. Retacrit, epoetin alfa-epbx, was approved in 2018 as a biosimilar to Epogen and Procrit (U.S. Food and Drug Administration, 2018).

Accordingly:

• US 5,441,868 does not currently block FDA approval.
• Its expiration is separate from biosimilar regulatory exclusivity.
• Its historical significance is greater in patent litigation than in current Orange Book practice.
• Current biologic competition is evaluated under the Public Health Service Act and the biosimilar pathway.

What biosimilar and generic entry risks exist after expiration?

EPO is a biologic, so the relevant competitive pathway is biosimilar entry rather than ordinary ANDA generic substitution.

The principal US follow-on product is Retacrit, marketed by Pfizer subsidiary Hospira. Approval of epoetin alfa-epbx created a regulatory route for competition against Epogen and Procrit without relying on the traditional small-molecule generic pathway.

Product	Active substance	Regulatory category	US status
Epogen	Epoetin alfa	Reference biologic	Approved
Procrit	Epoetin alfa	Reference biologic	Approved
Retacrit	Epoetin alfa-epbx	Biosimilar	FDA approved in 2018
Aranesp	Darbepoetin alfa	Separate biologic	Distinct molecule and patent estate

Expiration of the ‘868 process patent reduces manufacturing patent risk, but it does not eliminate:

• Manufacturing know-how advantages.
• Cell-line and process-control differences.
• Product-specific quality requirements.
• Interchangeability requirements.
• Device and presentation patents.
• Formulation and stability patents.
• Exclusivity tied to other biologic products.

What formulation patents and method-of-use patents matter for epoetin products?

US 5,441,868 does not claim a formulation, prefilled syringe, dosage regimen, or treatment method. Those rights were pursued separately.

Potentially relevant categories include:

Formulation patents

These may cover:

• Stabilized aqueous EPO formulations.
• Albumin-free formulations.
• Surfactant-containing formulations.
• Protein aggregation control.
• Containers and prefilled syringes.
• Refrigerated or room-temperature storage.

A formulation patent can remain commercially relevant even after a manufacturing-process patent expires.

Method-of-use patents

These may cover:

• Treatment of anemia associated with chronic kidney disease.
• Treatment of chemotherapy-induced anemia.
• Perioperative use.
• Dosing schedules.
• Hemoglobin-target or dose-adjustment protocols.

Method-of-use patents can present a narrower risk than composition or manufacturing patents because infringement may depend on the approved labeling, prescribing, or induced-use evidence.

Delivery-system patents

Autoinjectors, syringes, cartridges, and other delivery components may have separate patent families. These rights are distinct from the EPO production process claimed in US 5,441,868.

How strong is the patent estate for recombinant EPO today?

The specific US 5,441,868 estate is legally weak today because the patent has expired. Its historical strength was high because it targeted the actual commercial manufacturing platform used for epoetin alfa.

Factor	Assessment
Claim breadth during term	High for mammalian recombinant EPO processes
Commercial relevance during term	High
CHO-cell coverage	Direct through claim 2 and potentially claim 1
COS-cell coverage	Direct through claim 3
cDNA coverage	Direct through claim 4
Genomic-DNA coverage	Direct through claim 5
Current enforceability	None
Current biosimilar blocking value	None
Residual business value	Historical, technical, and freedom-to-operate analysis

The current patent risk must be evaluated at the product and process level rather than by relying on the ‘868 patent. A biosimilar developer should review active patents covering the specific reference product, formulation, presentation, device, manufacturing process, and approved indications.

How does US 5,441,868 compare with patents covering Aranesp?

Aranesp contains darbepoetin alfa, an engineered EPO analogue with additional carbohydrate content and a longer half-life. It is not the same molecule as epoetin alfa.

Attribute	Epogen/Procrit	Aranesp
Active substance	Epoetin alfa	Darbepoetin alfa
Protein type	Recombinant human EPO	Modified EPO analogue
Core patent relevance	US 5,441,868 and related epoetin patents	Separate darbepoetin patent estate
Production platform	Mammalian recombinant expression	Mammalian recombinant expression
Regulatory competition	Biosimilar epoetin products	Separate biosimilar and patent analysis
Effect of ‘868 expiration	Removes one epoetin process barrier	Does not affect Aranesp patents

The expiration of US 5,441,868 does not create a direct right to manufacture darbepoetin alfa or to market a biosimilar to Aranesp.

What licensing and commercial arrangements affected EPO competition?

Amgen commercialized Epogen in the United States and licensed or partnered EPO commercialization in other markets, including arrangements involving Johnson & Johnson and regional pharmaceutical companies. Those agreements affected product branding, geographic rights, and commercial access, but they did not extend the statutory term of US 5,441,868.

Licenses must be distinguished from patent expiration. A license can govern commercial rights after patent expiration, while a patent can expire without terminating separate supply, trademark, know-how, or regulatory agreements.

What generic or biosimilar launch scenarios followed expiration?

The principal post-expiration scenarios were:

1. Biosimilar epoetin entry: A sponsor obtains FDA approval under the biosimilar pathway and addresses residual patents through certification, litigation, settlement, or launch timing.
2. Noninfringing manufacturing: A sponsor uses an independent mammalian-cell process after the ‘868 expiration and clears remaining process and formulation rights.
3. Limited-label competition: A product launches with indications or presentations designed to avoid active method-of-use or device claims.
4. Commercial differentiation: Competition focuses on supply reliability, hospital contracting, dosing convenience, and reimbursement rather than basic molecule ownership.

Because US 5,441,868 expired before the principal US biosimilar epoetin approvals, it was no longer a launch-blocking patent for Retacrit.

Key Takeaways

• US 5,441,868 claims mammalian-cell production of glycosylated human EPO.
• Claim 1 is the broad process claim; claims 2 through 5 narrow the host-cell or DNA source.
• CHO-cell production is expressly covered by claim 2.
• cDNA and genomic DNA are separately addressed in claims 4 and 5.
• The patent issued on August 15, 1995, and expired in August 2012.
• It was part of Amgen’s broader recombinant EPO patent portfolio.
• The patent was involved in the Amgen-Roche EPO litigation.
• It is no longer enforceable and does not block current biosimilar development.
• EPO is regulated as a biologic, so the Purple Book and biosimilar pathway are more relevant than the Orange Book.
• Current risk lies in later patents covering formulations, delivery systems, methods of use, manufacturing know-how, and product-specific biologics claims.

FAQs About US Patent 5,441,868

Is US Patent 5,441,868 still active?

No. The patent expired in August 2012 and no longer creates infringement liability for new manufacturing activity.

Does US 5,441,868 cover epoetin alfa as a product?

No. Its claims are directed to a manufacturing process. Product, DNA, glycosylation, formulation, and therapeutic-use claims were addressed in separate patents.

Can a biosimilar manufacturer use CHO cells after expiration of the patent?

Yes, expiration removes the patent’s statutory barrier. The manufacturer must still clear any other active patents and satisfy FDA biosimilar requirements.

Was US 5,441,868 listed in the Orange Book?

The patent was associated with a biologic product area rather than a conventional NDA-listed small-molecule product. Biologic patent and biosimilar issues are generally evaluated through the Purple Book and the Public Health Service Act framework.

Does expiration of US 5,441,868 eliminate all EPO patent risk?

No. It eliminates risk from that patent only. Later patents may cover EPO formulations, devices, dosing methods, manufacturing improvements, or modified EPO molecules such as darbepoetin alfa.

References

Amgen Inc. v. Hoffman-La Roche Ltd., 580 F.3d 1340 (Fed. Cir. 2009).

United States Food and Drug Administration. (2018). FDA approves first epoetin alfa biosimilar for treatment of anemia. https://www.fda.gov

United States Food and Drug Administration. (n.d.-a). Purple Book: Database of licensed biological products. https://purplebooksearch.fda.gov

United States Food and Drug Administration. (n.d.-b). Approved drug products with therapeutic equivalence evaluations. https://www.fda.gov/drugs/drug-approvals-and-databases/orange-book-data-files

United States Patent and Trademark Office. (n.d.). Patent 5,441,868: Production of erythropoietin. https://patents.google.com/patent/US5441868A

Details for Patent 5,441,868

Applicant	Tradename	Biologic Ingredient	Dosage Form	BLA	Approval Date	Patent No.	Expiredate
Amgen Inc.	EPOGEN/PROCRIT	epoetin alfa	Injection	103234	June 1, 1989		2007-10-23
Amgen Inc.	EPOGEN/PROCRIT	epoetin alfa	Injection	103234			2007-10-23
Amgen Inc.	PROCRIT	epoetin alfa	Injection	103234			2007-10-23
Vifor (international) Inc.	MIRCERA	methoxy polyethylene glycol-epoetin beta	Injection	125164	April 28, 2016		2007-10-23
Vifor (international) Inc.	MIRCERA	methoxy polyethylene glycol-epoetin beta	Injection	125164	November 14, 2007		2007-10-23

International Patent Family for US Patent 5,441,868

Country	Patent Number	Estimated Expiration
Austria	E54940
Australia	1007495
Australia	2042192
Australia	3612597
Australia	3746785
Australia	5272293