Details for Patent: 6,248,726

Summary for Patent: 6,248,726

Title:	Method of peritoneal dialysis using glucose polymer solutions
Abstract:	There is described polysaccharides of high molecular weight for use in peritoneal dialysis. The polysaccharides are capable of dialysing human serum for long periods of time without causing damage to the peritoneum and are also capable of preventing loss of polymer from the peritoneum to the serum.There is also described a method of making the polysaccharides and pharmaceutical formulations containing them.
Inventor(s):	Ranulph Michael Alsop, Raymond Brian Forrester, David John Manning
Assignee:	N M ROTHSCHILD & SONS Ltd , Innovata Ltd
Application Number:	US07/954,686
Patent Claim Types: see list of patent claims	Use; Formulation;

US Patent 6,248,726 Scope, Claims, and US Patent Landscape for Glucose-Polymer Dialysis Solutions (Method of Treatment)

US 6,248,726 claims a dialysis treatment method using a specific aqueous glucose-polymer mixture derived from starch hydrolysis, defined by molecular-weight distribution cutoffs and a range-limited weight-average and number-average molecular weight. The claims are narrowly tethered to (i) the polymer source (starch hydrolysis), (ii) dialysis/serum dialysis purpose, and (iii) quantitative molecular-weight parameters. Claim 4 further limits the solution by adding amino acids.

What patents protect US 6,248,726’s specific dialysis-by-glucose-polymer solution concept in the US?

US 6,248,726’s protection theory is method-of-treatment rather than a composition per se. The enforceable scope is therefore tied to performance of the claimed treatment using the claimed polymer mixture and parameters. In practice, infringement risk is highest for:

1. dialysis center procedures or commercial dialysis solutions that are sold and used as part of a protocol, and
2. manufacturers who supply a dialysis fluid composition meeting the molecular-weight specifications and marketed for “dialysis of serum” in a “method of treatment” context.

How does claim language shape the protective boundary?

Key limiting phrases and what they do to claim scope:

• “Method of treatment of a human requiring dialysis of the serum”
  Requires the patient is a human, the method is a “treatment,” and the dialyzed target is serum.

• “By use of an aqueous solution”
  The method uses an aqueous solution rather than an administered bolus composition.

• “Physiologically acceptable mixture of glucose polymers derived from the hydrolysis of starch”
  Locks polymer origin to starch hydrolysis and requires physiological acceptability.

• Molecular-weight distribution requirements (core novelty driver)

  • At least 50% by weight of polymers with MW 5,000 to 30,000
  • Weight average MW 5,000 to 50,000
  • Number average MW 2,890 to 8,000
  • Optional limits in dependent claims:
    • Up to 20% by weight polymers with MW 800 to 10,000
    • Less than 5% by weight polymers with MW >100,000

• Claim 4: “aqueous solution further comprises amino acids”
  Adds an additional ingredient limitation.

Patent landscape implications

Because the claims are defined by tight molecular-weight parameters, the landscape “forks” into two competitive design spaces:

1. Starch-derived glucose polymers with overlapping MW distributions
   These are the primary infringement risk zone if used in serum dialysis protocols as claimed.

2. Alternative polymer sources or substantially different MW distributions
   These design around the claim by changing starch hydrolysis origin, shifting weight-average or number-average MW outside ranges, changing the fraction in the 5,000 to 30,000 band, or reducing/raising high-MW tail fractions (>100,000).

How strong are the claims on novelty and breadth for infringement and licensing?

Claim 1: the independent claim’s real breadth

Claim 1 is broad in that it covers any physiologically acceptable starch-hydrolysis glucose-polymer mixture meeting the MW constraints and used in serum dialysis treatment. It does not specify a particular dialysis mode (hemodialysis vs peritoneal dialysis) in the text provided; it only requires dialysis of serum using the claimed aqueous solution.

But Claim 1 is narrow on MW definitions:

• Concentration banding: at least 50% by weight between 5,000 and 30,000 MW
• Two different averaging metrics:
  • weight-average: 5,000 to 50,000
  • number-average: 2,890 to 8,000
• Implicitly limits distribution shape even before considering Claims 2 and 3.

A court typically treats numeric ranges as strong claim limitations. As a result, the claim’s practical scope is likely to track what an accused polymer mixture would test to under standard molecular-weight analysis methods.

Dependent claim fallbacks

• Claim 2: “up to 20% by weight… 800 to 10,000”
  This limits low-MW fraction. It is a typical “distribution-shape” narrowing that helps distinguish from mixtures with a large oligosaccharide fraction.

• Claim 3: “less than 5% by weight… >100,000”
  This limits high-MW tail. A mixture with a heavy fraction of very high-MW polymers would fall outside Claim 1’s “weight-average 5,000 to 50,000” constraints anyway in many cases, but Claim 3 adds an explicit high-MW cap that can distinguish borderline compositions.

• Claim 4: adds amino acids
  This likely narrows further to dialysis fluids or solutions containing amino-acid components.

What do the molecular-weight limitations mean for design-around strategies?

For patent strategy and infringement screening, the molecular-weight parameters operate like “numerical claim predicates.” Below is how parties usually analyze whether a polymer mixture hits or avoids the claimed ranges.

Core decision points for a serum dialysis glucose-polymer mixture

1. Does ≥50 wt% fall between 5,000 and 30,000 MW?
   This is the most direct distribution threshold.

2. Do the averages fall within limits simultaneously?

   • weight-average (5,000–50,000)
   • number-average (2,890–8,000)

3. Is the high-MW tail below 5 wt% above 100,000 MW?
   If the mixture has a significant long-chain tail, Claim 3 can be a key differentiator.

4. Does the low-MW fraction stay at or below 20 wt% in 800–10,000 MW?
   Claim 2 narrows the lower tail.

5. If marketing the formulation with amino acids, does Claim 4 apply?
   Amino acids alone do not automatically prove infringement, but a solution that meets Claim 1’s MW constraints and includes amino acids would satisfy Claim 4.

Does US 6,248,726 read on hemodialysis “dialysate” products or only on specific solution types?

Based on the claim text provided, it reads on use of an aqueous solution in a serum dialysis treatment. That can include a broad set of dialysis modalities if the serum is dialyzed using the specified solution. The patent does not specify:

• a dialysis device,
• a particular tonicity/osmolality target,
• a specific ionic composition,
• or whether the glucose polymers are the primary solute in a dialysate/hemofiltration fluid.

So scope turns on whether the solution used in the patient procedure meets the MW constraints and is used for serum dialysis as part of a “method of treatment.” This kind of claim often creates infringement exposure for product labels, IFUs, and protocol instructions that tie the polymer solution to serum dialysis treatment.

Which claim elements are most likely to be litigated in US 6,248,726 disputes?

1) Molecular-weight characterization methodology

Numeric ranges invite disputes over measurement:

• whether the accused mixture is measured as-received vs after purification,
• which analytical method is used (e.g., chromatography calibration, light scattering, intrinsic viscosity),
• and how the polymer is fractionated for “weight-percent” determination.

2) “Derived from the hydrolysis of starch”

This limits polymer origin. Litigation often focuses on whether the polymer is genuinely produced by hydrolyzing starch and whether processing steps create a substantially different polymer type.

3) “Dialysis of the serum”

Accused parties may contest whether the procedure truly involves dialysis of serum versus another fluid compartment or whether the method is performed in a way that the “serum dialysis” requirement is satisfied.

4) Amino acids in Claim 4

If a marketed dialysis solution includes amino acids, Claim 4 becomes relevant. If not, only Claims 1–3 are at issue.

What patent expiration or exclusivity timelines matter for licensing and generic entry?

No timing analysis can be produced from the claim text alone. US patent term and expiration depend on:

• earliest effective filing,
• non-provisional vs continuation chain,
• any patent term adjustment (PTE),
• and whether there are regulatory exclusivity extensions (not typical for ordinary patents, but relevant to related waivers/links in some landscapes).

No reliable expiration date can be stated without the patent’s bibliographic data and prosecution history.

How does US 6,248,726 compare with other starch-derived glucose polymer patents in dialysis and infusion?

The claim architecture is consistent with a class of carbohydrate polymer technology where differentiation comes from:

• distribution profile (weight-percent bands),
• MW averaging metrics,
• and caps on low and high MW fractions.

In practice, comparison across the space typically hinges on whether other patents claim:

• different MW bands,
• different averaging metrics,
• different starting feedstock (e.g., different polysaccharide sources),
• different uses (e.g., volume expansion, plasma substitution, hemofiltration, osmotic agents),
• or specific additives (electrolytes, amino acids, buffering systems).

For infringement and freedom-to-operate, the most important comparison is not the “use in dialysis” label but whether the competitor’s polymer composition is analytically within the same MW distribution and averaging ranges.

What formulations are protected by US 6,248,726 (and what are not)?

Protected by the claim set as provided

• Aqueous solution used in serum dialysis treatment
• Containing starch-hydrolysis glucose polymer mixture that is physiologically acceptable and meets:
  • ≥50 wt% polymers between 5,000–30,000 MW
  • weight-average MW 5,000–50,000
  • number-average MW 2,890–8,000
• Plus dependent narrowing:
  • Claim 2: up to 20 wt% in 800–10,000 MW
  • Claim 3: <5 wt% >100,000 MW
  • Claim 4: solution further comprises amino acids

Not protected (based on limitations alone)

• Solutions that do not meet the numeric MW distribution and averaging constraints.
• Solutions where the glucose polymers are not derived from hydrolysis of starch.
• Methods that do not use an aqueous solution in serum dialysis as the treatment context.
• Additive compositions are not claimed unless they fall within Claim 4 (amino acids) while satisfying Claim 1.

What regulatory status or Orange Book listing applies to US 6,248,726?

No data can be produced from the claim text regarding:

• drug product identity,
• FDA approval,
• Orange Book listing,
• or listed patents/claims.

Those determinations require FDA product and Orange Book listing data that is not contained in the provided claim excerpt.

What generic entry risks exist for competing dialysis solutions using different polymer MW distributions?

Given the numeric nature of the claim, entry risk increases sharply when a competitor:

• uses starch-hydrolyzed glucose polymers,
• and formulates a dialysis solution with MW distribution and averages overlapping Claim 1 (and possibly Claims 2–3),
• and markets or uses it for serum dialysis as a method of treatment.

A competitor that shifts the mixture:

• outside the 5,000–30,000 MW at ≥50 wt% requirement,
• or outside the weight-average 5,000–50,000 and number-average 2,890–8,000 constraints,
• or increases high-MW tail fractions above the <5 wt% >100,000 limitation (at least relative to dependent claim 3), can often reduce direct infringement likelihood because numeric claim predicates are strict.

What patent litigation affects freedom-to-operate for US 6,248,726?

No litigation history is derivable from the claim text alone. A proper landscape requires case captions, courts, parties, asserted claims, and final outcomes.

What are the commercial implications for companies developing starch-derived glucose polymer dialysis solutions?

Commercially, the key issue is whether the company’s polymer supply chain can consistently reproduce the required MW distributions. If manufacturing variability causes excursions outside:

• ≥50 wt% between 5,000–30,000 MW,
• weight-average 5,000–50,000,
• number-average 2,890–8,000, then the product can drift into or out of the claimed scope depending on batch.

For licensing strategy, the bargaining point is typically either:

• a license tied to a defined manufacturing specification that fits the patent claims, or
• design-around by moving the polymer distribution outside the claim predicate ranges.

Key Takeaways

• US 6,248,726 claim scope is dominated by strict molecular-weight distribution and averaging limits for starch-derived glucose polymer mixtures used as an aqueous solution in serum dialysis treatment.
• The principal infringement risk zone is products/protocols that reproduce the required weight-percent distribution (≥50 wt% in 5,000–30,000 MW) and simultaneously meet both weight-average and number-average MW ranges.
• Dependent claims narrow further by limiting low-MW fraction (Claim 2), high-MW tail (>100,000 MW) (Claim 3), and requiring amino acids in the solution (Claim 4).
• Design-around is analytically driven: shifting polymer MW distribution or averages can move products outside the numeric predicates that define Claim 1.

FAQs

1. How do I determine whether a starch-hydrolyzed glucose polymer mixture meets Claim 1’s MW averaging and wt% band limits?
2. What manufacturing controls reduce batch-to-batch risk of falling within US 6,248,726’s claimed molecular-weight distribution?
3. If a dialysis solution includes amino acids, does Claim 4 automatically apply?
4. What parts of the claim are most likely to fail in an infringement analysis: serum dialysis context, starch-derived origin, or molecular-weight compliance?
5. If a competitor’s polymer mixture has a small high-MW tail (>100,000), how does that affect exposure under Claim 3?

References

1. United States Patent 6,248,726.

Drugs Protected by US Patent 6,248,726

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: 6,248,726

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
United Kingdom	BA85/15842	Jun 22, 1985

International Family Members for US Patent 6,248,726

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	106410
Australia	5881186
Australia	594060