US Patent 6,270,757: IL-11 plus glycine (and buffered variants)
What does the patent claim, in plain technical terms?
US 6,270,757 claims protein compositions built around interleukin-11 (IL-11) or des-Pro-IL-11 formulated with glycine, with optional buffering agents (histidine or phosphate) and defined concentration windows.
Claim set map (scope and what changes the “inventive point”)
| Claim group |
Core composition |
Key quantitative limits |
Claim dependency impact |
| Base IL-11 + glycine |
IL-11 + glycine |
Glycine: 50 to 600 mM; IL-11: 0.1 to 20 mg/mL |
Broadest enabling anchor is claim 1 |
| Narrow IL-11 and glycine exemplars |
IL-11 + glycine |
IL-11 ~5.0 mg/mL; glycine about 300 mM; also about 150 mM |
Likely supports written description and enablement, narrows infringement “numerically” |
| Buffered formulation |
IL-11 + glycine + buffer |
Buffer is histidine or phosphate; phosphate 5 to 20 mM; histidine 5 to 40 mM |
Adds formulation stability angle and additional numerical fences |
| Fixed embodiments |
IL-11 + glycine + specific buffer concentrations |
Examples: 5.0 mg/mL IL-11 + 300 mM glycine + 10 mM sodium phosphate; and 20 mM histidine |
Converts formulation space into literal infringement targets |
| Variant protein: des-Pro-IL-11 |
des-Pro-IL-11 + glycine |
Same glycine window as IL-11 series; IL-11 window reused as des-Pro IL-11 window (0.1 to 20 mg/mL) |
Variant extends to alternate processing/sequence form while preserving excipient logic |
| Fixed embodiment for des-Pro |
des-Pro-IL-11 + glycine |
5.0 mg/mL des-Pro-IL-11 + 300 mM glycine |
Numeric locking for commercial formulations |
The claim language you provided (collapsed)
- Claim 1: “composition comprising IL-11 and glycine.”
- Claims 2-4: glycine 50 to 600 mM, with specific instantiations at ~300 mM and ~150 mM.
- Claims 5-7: IL-11 0.1 to 20 mg/mL, with ~5.0 mg/mL, including the ~5.0 mg/mL IL-11 + ~300 mM glycine combination.
- Claims 8-16: IL-11 + glycine + buffer, where the buffer is histidine or phosphate; phosphate ~5 to 20 mM with ~10 mM fixed; histidine ~5 to 40 mM with ~20 mM fixed.
- Claim 15-16: fixed exemplars:
- ~5.0 mg/mL IL-11 + 300 mM glycine + 10 mM sodium phosphate
- ~5.0 mg/mL IL-11 + 300 mM glycine + 20 mM histidine
- Claims 17-20: same excipient logic for des-Pro-IL-11 with glycine 50 to 600 mM; includes ~5.0 mg/mL and ~300 mM glycine exemplar.
What is the patent landscape likely doing with “protein + amino acid + buffer”?
The practical reading: the claims try to lock a formulation region defined by:
- Protein identity: IL-11 or des-Pro-IL-11
- Primary stabilizing excipient: glycine at tens to hundreds of mM
- Optional buffering: phosphate (5-20 mM) or histidine (5-40 mM)
- A small set of exemplar “commercial-like” anchor points: IL-11 ~5 mg/mL, glycine ~300 mM, buffer ~10 mM (phosphate) or ~20 mM (histidine)
In portfolio terms, this is a classic “composition of matter” formulation lock that can be asserted against downstream product formulations that sit inside the numeric windows.
Critical analysis of claim strength
Are the claims likely broad enough to capture many commercial formulations?
Yes, based on the numeric breadth of the key excipients.
Breadth by quantitative fences
- Glycine: 50 to 600 mM is wide. That alone captures a large portion of typical protein stabilization ranges for small amino acids.
- IL-11 concentration: 0.1 to 20 mg/mL is wide; it covers dilute to relatively concentrated protein solutions.
- Buffer choice: histidine or phosphate keeps the formulation options open for accused products.
- Buffer concentration windows:
- phosphate: 5 to 20 mM
- histidine: 5 to 40 mM
These ranges are also non-trivial and align with common buffering strengths.
The “anchor exemplars” tighten infringement risk
Even if a competitor designs a formulation outside the broad ranges, the fixed claims (for ~5 mg/mL IL-11 and 300 mM glycine, plus ~10 mM sodium phosphate or ~20 mM histidine) create high-value targets. In practice, many commercial formulations converge on a handful of workable conditions.
Does claim construction risk collapsing the breadth (enablement/definiteness/interpretation)?
The claim terms you provided are straightforward and likely “definite” at the chemistry level:
- “composition comprising” typically reads as open-ended, not requiring absence of other components.
- “amount ranges from about” supports some latitude, but still anchors to testable concentration.
The main construction risk is interpretive rather than textual:
- Whether “about” establishes a measurable tolerance wide enough to cover adjacent formulations. This affects infringement and noninfringement margins.
- Whether IL-11 and des-Pro-IL-11 include specific processing heterogeneity (sequence variants, truncations, purity profiles). If an accused product uses an IL-11 preparation containing mixed forms, claim coverage may hinge on whether the product “comprises” the claimed species.
Is novelty likely weak because similar excipients were known?
The patent’s apparent strategy (protein + glycine + optional buffer) can run into a common obstacle in biologics formulation patents: the argument that the formulation is an expected optimization of routine excipients.
Without the specification and prosecution history text, the strongest actionable assessment is structural:
- The claims do not include many mechanistic or functional limitations (no explicit stability improvement metrics, no pH range, no solubility/aggregation performance criteria).
- That structure invites an anticipation/obviousness attack from earlier protein formulation disclosures that use glycine as a stabilizer and include common buffers like histidine and phosphate.
From a litigation readiness standpoint, the enforceability usually depends on whether the patent can credibly show:
- a specific, non-routine selection of concentrations for glycine and buffer for IL-11 (and des-Pro-IL-11), and
- a demonstrated technical effect tied to the claimed ranges.
The claim set as provided reads like it is built on range and combination coverage, not on method-of-use performance requirements. That tends to make novelty and nonobviousness hinge on evidence inside the specification.
Do the des-Pro-IL-11 claims materially expand infringement coverage?
They expand coverage in a targeted way.
- des-Pro-IL-11 + glycine is claimed with the same glycine window (50 to 600 mM) and IL-11 concentration window (0.1 to 20 mg/mL) and the same “commercial” exemplar (about 5 mg/mL and about 300 mM glycine).
- If a competitor avoids IL-11 and uses a processed form (des-Pro-IL-11), the formulation is still potentially captured.
This also reduces design-around space: companies cannot simply swap protein processing form unless they move outside the glycine range or avoid the specific protein species.
Design-around pressure points (what a competitor could do)
Given the claims as written, the primary design-around levers are:
- Remove glycine entirely (claims 1, 8, 17 depend on glycine presence).
- Move glycine outside 50 to 600 mM (e.g., use lower than 50 mM or higher than 600 mM), recognizing “about” could still matter.
- Avoid IL-11 or des-Pro-IL-11 as the active protein species (use other engineered IL-11 analogs).
- If staying within IL-11 + glycine, choose buffer strategy carefully to avoid literal overlap of phosphate/histidine claims. However, claims 1 and 17 do not require a buffer, so buffer removal does not avoid the base claims.
In other words: the “hardest” design-around is often removing glycine or avoiding the protein form.
Market and litigation relevance (what products are most at risk)
The risk concentrates on injectable or pharmaceutical solutions of IL-11 where formulation typically includes:
- an excipient like glycine (or similar amino acids),
- buffering agents like histidine/phosphate,
- and concentrations that can align with ~5 mg/mL protein loading.
The claim set is built to catch precisely those typical development endpoints.
What the claims say about the “buffer system” and stability premise
The patent asserts compositional inclusion of:
- histidine as an alternative buffering member; and
- sodium phosphate as another member; with numeric ranges.
Notably, you did not provide any pH ranges or additional excipients (e.g., polysorbates, salts other than phosphate, tonicity agents). The claims, as provided, are narrowly focused on the three components (protein, glycine, and optionally one buffer species). That focus:
- simplifies infringement analysis (fewer moving parts),
- but also increases vulnerability to prior art showing the same selection of components for similar proteins, even if pH and other stabilizers differ.
Patent landscape: how this single patent likely sits in a cluster
For a biologic formulation space, IL-11 is typically surrounded by:
- platform patents (formulation stabilizers like sugars/amino acids, lyophilization systems),
- device and delivery patents,
- and dosing regimen patents.
US 6,270,757, as described by the claim set, is a formulation composition patent centered on glycine and buffer members for specific IL-11 protein species.
This makes it more like a “core excipient lock” than a “method-of-treatment lock.” In litigation, such patents often face:
- validity challenges based on routine formulation knowledge, and
- scope arguments around concentration interpretation and component presence.
Claim-by-claim infringement reading (high-level)
Below is a practical infringement lens: if a product contains the stated components at stated concentrations (and “about” overlaps), it can map to multiple claim levels.
| Product formulation condition |
Potentially implicated claim(s) |
| IL-11 + glycine present within glycine 50-600 mM and IL-11 0.1-20 mg/mL |
Claim 1, 2, 5 |
| IL-11 about 5 mg/mL and glycine about 300 mM |
Claim 7 |
| IL-11 about 5 mg/mL and glycine about 150 mM |
Claim 4/6 combined through Claim 1 base and numeric dependent claims (depending on exact mapping) |
| IL-11 + glycine + histidine |
Claims 8, 9, 13, and fixed exemplar 16 if 20 mM |
| IL-11 + glycine + sodium phosphate |
Claims 8, 9, 10, 11, and fixed exemplar 15 if 10 mM |
| des-Pro-IL-11 + glycine within ranges |
Claims 17-19 and base des-Pro equivalents |
| des-Pro-IL-11 about 5 mg/mL + glycine about 300 mM |
Claim 20 |
Validity attack surfaces (what typically matters in this class)
1) Obviousness from protein stabilization art
Because glycine is a common formulation excipient, the critical question is whether IL-11 requires:
- an unexpected selection of glycine range, or
- a particular synergy between IL-11 (or des-Pro-IL-11) and glycine.
Your claim set does not encode any functional test result in the claims. That pushes technical evidence into the specification and prosecution record.
2) Anticipation by exact compositions or close overlaps
If any earlier disclosure taught IL-11 (or the des-Pro form) in glycine at similar concentrations and in similar buffers, anticipation risk rises. Range-based claims can be anticipated by overlapping ranges depending on how “about” is treated and the extent of overlap.
3) “About” tolerance and quantification
In litigation, parties fight “about”:
- how much deviation is acceptable,
- what measurement method and sampling conditions apply (especially for mM at specific temperature/ionic strength).
Your claims give both wide ranges and fixed exemplars. Fixed exemplars tend to reduce tolerance arguments but can be avoided by designing outside those points.
Key Takeaways
- US 6,270,757 is a formulation composition patent that claims IL-11 or des-Pro-IL-11 with glycine, plus optional histidine or phosphate buffering, using broad numeric ranges and several fixed “anchor” concentrations.
- The most infringement-relevant elements are glycine presence and the numeric fences 50 to 600 mM and IL-11 (or des-Pro-IL-11) 0.1 to 20 mg/mL, plus optional buffer windows phosphate 5 to 20 mM and histidine 5 to 40 mM.
- The des-Pro-IL-11 claims reduce a common design-around strategy (switching IL-11 processing form) and keep coverage tethered to the same excipient logic.
- The claim structure is vulnerable to an obviousness narrative if prior art shows glycine and common buffers were routine for protein stabilization without a specific IL-11-linked technical effect expressed in the claims.
FAQs
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What is the core invention claim in US 6,270,757?
A composition comprising IL-11 (or des-Pro-IL-11) and glycine, with optional inclusion of a buffer selected from histidine or phosphate.
-
What glycine concentration range is claimed for IL-11 formulations?
50 to 600 mM glycine (with specific exemplars at about 300 mM and 150 mM).
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What IL-11 concentration range is claimed?
0.1 to 20 mg/mL (with a specific exemplar at about 5.0 mg/mL).
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How do the buffer claims narrow the formulation?
If a buffer is included, it must be histidine (about 5 to 40 mM; exemplar about 20 mM) or phosphate (about 5 to 20 mM as sodium phosphate; exemplar about 10 mM).
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Does the patent cover des-Pro-IL-11 formulations?
Yes. It claims des-Pro-IL-11 + glycine across the glycine range, including a fixed exemplar of about 5.0 mg/mL des-Pro-IL-11 and about 300 mM glycine.
References (APA)
- United States Patent No. 6,270,757.
