United States Patent 5,656,722: Claim Strength, Validity Risk, and US Landscape
What does US 5,656,722 claim, in operational terms?
US 5,656,722 claims a defined class of insulin derivatives defined by (i) an isoelectric point (pI) window, (ii) a structured substitution pattern across insulin chain positions, and (iii) explicit exclusions, followed by formulation and method claims tied to diabetes treatment.
Core product claim (Claim 1)
Claim 1 covers:
- Insulin derivative (or physiologically tolerated salt) with pI between 5 and 8.5
- Insulin derivative is Formula II, where specific positions have constrained identities:
- B1: R¹ is H or H-Phe
- A21: R² is one genetically encodable L-amino acid chosen from
Gly, Ala, Val, Leu, Ile, Pro, Phe, Trp, Met, Ser, Cys, Tyr, Asp, Glu
- R³⁰: residue of a neutral genetically encodable L-amino acid chosen from
Ala, Thr, Ser
- R³¹: 1 to 3 neutral or basic α-amino acids, with at least one selected from
Arg, Lys, Hyl, Orn, Cit, His
- B10: His (X = His at B10)
- A1-A20 and B1-B29 correspond to a mammalian insulin
- Exclusion embedded in claim scope: the derivative is excluded if both of the following occur simultaneously:
1) B1 is Phe (i.e., R¹ denotes Phe)
2) R³¹ is one α-amino acid having a terminal carboxyl group
Tight dependent claims
Claims narrow by selecting subsets of the variables:
- Claim 2: B1 = H-Phe
- Claim 3: A21 = one of Gly, Ala, Ser, Thr, Asp, Glu
- Claim 4: R³¹ = Arg-Arg-OH
- Claim 5: A- and B-chain sequences are those of human, porcine, or bovine insulin
- Claims 10 and 11:
- Claim 10: A21 = Asp
- Claim 11: sequences correspond to human insulin
- Claim 15: specific combination:
- R¹ = H-Phe
- R² = Gly
- R³⁰ = Thr
- R³¹ = Arg-Arg-OH
Formulation and treatment claims
Claims 6-9 and 12-14 attach a pharmaceutical composition and a method of diabetes treatment:
- Claim 6: composition contains effective amount of at least one Formula II insulin derivative (or salt), in dissolved, amorphous, or crystalline form
- Claim 7: composition additionally contains zinc 1 µg to 2 mg/ml
- Claim 8: composition additionally contains unmodified insulin
- Claim 9: method of treating diabetes by administering the composition of Claim 6
- Claim 12: composition as in Claim 8 but in dissolved form
- Claim 13: zinc range expands dependently: 5 µg to 200 µg/ml
- Claim 14: unmodified insulin is unmodified human insulin
How constraining is the claim scope versus the field?
The landscape risk turns on how often later insulin analogs share the same three defining axes: (1) pI window, (2) specific positional modifications (B1, B10, A21, R³⁰, R³¹ pattern), and (3) formulation elements (zinc and mixing with unmodified insulin).
1) pI constraint: broad numerically, narrow in practice
The pI window 5 to 8.5 spans a very wide range of insulin behavior. In practice, many insulin derivatives can land inside this window depending on charge engineering. The novelty-limiting question for enforceability is whether the field already disclosed insulin derivatives with comparable pI and comparable charge substitutions.
2) positional constraints are targeted
Claim 1 is not “any insulin with added charge”; it pins:
- B10 = His
- B1 = H or H-Phe
- A21 substitution from a defined set
- C-terminal extension/composition encoded through R³¹ (1 to 3 amino acids with at least one among Arg/Lys/…)
- R³⁰ constrained to neutral residues (Ala/Thr/Ser)
This is a chemically specific scaffolding: infringement does not hinge only on pI, it hinges on fitting the Formula II substitution pattern.
3) the exclusion is narrow and difficult to trigger
The exclusion requires simultaneous occurrence of:
- B1 denotes Phe (not just H-Phe), and
- R³¹ is one α-amino acid with a terminal carboxyl group
That exclusion is likely intended to carve out a previously disclosed configuration. Practically, proving non-infringement would require showing both conditions in the asserted product’s exact structure.
4) formulation claims are easy to map, but depend on product packaging facts
Claims 6-8, 12-14 are likely to be easier to evaluate for infringement because they depend on:
- whether the administered insulin derivative is delivered as a specific formulation class (dissolved, amorphous, crystalline)
- whether zinc is present in specific ranges
- whether the product includes unmodified insulin
This creates a “product record” burden rather than a pure structural characterization burden.
What parts of the patent are likely most vulnerable?
Without the specification text and prosecution history, the strongest and weakest points can still be inferred from typical litigation patterns for this claim set.
Potential invalidity vectors
1) Overbreadth via variable pI range
- Claim 1 is broad on pI (5–8.5). If prior art disclosed insulin derivatives with substitutions that naturally fall into that band while also using the same structural motif, the pI limitation may not confer novelty.
2) Anticipation by prior insulin charge-engineered designs
- Charge engineering in insulin is a long-running theme. If a reference shows an insulin derivative with the same positional modifications and the same type of basic residues at the specified region, then dependent narrowing (Claims 2-5, 10-11, 15) can fail either because they are explicitly disclosed or because claim 1 is already anticipated.
3) Lack of support for the full breadth of R³¹
- Claim 1 allows 1 to 3 neutral/basic α-amino acids in R³¹, with at least one basic residue in a specified set. If the specification only exemplifies a narrower subspace, enablement or written description issues become plausible against the full claim.
4) Formulation claims may be vulnerable if prior art disclosed zinc-containing mixtures
- Zinc stabilization and insulin formulations are widely disclosed historically. The claim combination of “Formula II derivative + zinc at specified range + optional unmodified insulin” may still be novel if the derivative itself is novel, but it can be vulnerable if the mixture and concentration windows were already published.
Potential enforceability vectors
1) Formula II scaffolding creates a structural fingerprint
- Courts typically require the accused product to meet the structural claim language. If the positional constraints (B10 His, B1 identities, A21 selection, R³⁰ residues, R³¹ motif) are not present in later products, scope collapses quickly.
2) The two-factor exclusion is hard to accidentally avoid
- If an accused product has the B1/Phe-like choice and the one-residue R³¹ with terminal carboxyl group configuration, it triggers the exclusion. Otherwise, the exclusion may be largely irrelevant.
3) Dependent claims like Claim 15 are narrow combinations
- Claim 15 is the most litigation-friendly among the dependent claims: it defines a specific substitution set (R¹=H-Phe, R²=Gly, R³⁰=Thr, R³¹=Arg-Arg-OH). If competitors use different residues at any one of these positions, they fall outside that dependent claim even if they fall inside claim 1.
Where does this patent sit relative to the modern insulin market?
A critical business reading is: this patent is unlikely to read broadly across today’s insulin analog portfolio unless those products incorporate:
- the same structural charge pattern encoded by Formula II
- the same combination of zinc dosing and mixing with unmodified insulin (where asserted claims include unmodified insulin)
Most commercial insulins are engineered around stability, receptor kinetics, and pharmacokinetics using modifications at specific canonical sites. The claim language here is sufficiently specific that it usually targets a distinct chemical subclass rather than generic “insulin derivative.”
Claim-to-competitive design mapping (decision table)
This table translates the claims into “pass/fail” infringement mapping elements.
| Element |
Claim(s) |
Evidence needed in accused product |
What clears scope |
| pI between 5 and 8.5 |
1 |
pI of the derivative (and salt form) |
Reported pI or calculated pI from sequence/charge |
| B10 fixed to His |
1 |
Sequence/structure |
His at B10 |
| B1: H or H-Phe |
1 |
Sequence/structure |
B1 either H or H-Phe; exclusion if B1 denotes Phe simultaneously with R³¹=single terminal-carboxyl α-AA |
| A21: restricted amino acids |
1,3,10 |
Sequence/structure |
A21 in the allowed set; Claim 10 requires Asp specifically |
| R³⁰ = Ala/Thr/Ser |
1,15 |
Sequence/structure |
Exact residue match |
| R³¹ = 1-3 residues with at least one basic among listed set |
1,4,15 |
Sequence/structure |
R³¹ includes at least one basic residue; Claim 4 requires Arg-Arg-OH |
| Sequence corresponds to mammalian insulin |
1,5,11 |
Sequence origin |
Human/porcine/bovine insulin backbone |
| Zinc concentration ranges |
7,13 |
Formulation data |
1 µg to 2 mg/ml (Claim 7) or 5 µg to 200 µg/ml (Claim 13) |
| Unmodified insulin mixed |
8,12,14 |
Formulation |
Presence of unmodified insulin; Claim 14 requires unmodified human insulin |
| Diabetes treatment use |
9 |
Labeling / instructions |
Administration of the composition to treat diabetes |
What does this mean for the US patent landscape (freedom-to-operate)?
The enforceable zone is narrowed by:
- structural specificity of Formula II
- tight dependent claims (Arg-Arg-OH and specific residue selections)
- formulation conditions (zinc presence; mixing with unmodified insulin)
For an investment or R&D decision, the landscape question becomes whether any active development programs or marketed products incorporate:
- B10 His and the specific B1/A21/R³⁰/R³¹ pattern, and
- zinc concentrations within the specified windows, and
- unmodified insulin co-formulation, where relevant.
The patent also creates a secondary risk: even if a product’s primary patent strategy differs (e.g., glycation/PEGylation, different acylation pattern, or different C-terminal engineering), it can still come under scrutiny if it “accidentally” matches the Formula II substitution pattern.
Claim-by-claim critical assessment
Claim 1 (broad structural + pI + exclusion)
- Strength: fixed-position constraints plus defined residues and a pI window.
- Vulnerability: pI range may be considered non-novel if prior art charge-engineered insulins cover it; breadth of R³¹ (1 to 3 residues) can invite written description or enablement challenges.
Claims 2-5 (B1 identity; A21 subsets; R³¹ example; backbone origin)
- Strength: these are narrowing constraints that should improve enforceability against products that do not exactly share the allowed substitutions.
- Vulnerability: if a prior art reference discloses one of these narrowed combinations directly, the patent loses leverage.
Claim 4 and Claim 15 (Arg-Arg-OH and a fully specified combination)
- Strength: tight residue-level specification.
- Business impact: these claims are the best basis for design-around planning because competitors can avoid specific residues (e.g., Arg-Arg-OH) or alter any of R¹/R²/R³⁰.
Claims 6-9 and 12-14 (composition + zinc + unmodified insulin)
- Strength: easy to test for infringement using formulation and labeling.
- Vulnerability: if unmodified insulin + zinc-containing solutions were known, novelty hinges on the presence of the Formula II derivative itself. If the derivative is novel, these formulation claims are typically “stronger by association.”
Key takeaways for portfolio strategy
- US 5,656,722 is best treated as a structural-charge-engineering claim set with additional formulation guardrails (zinc; optional mixing with unmodified insulin).
- The enforceability hinges on whether an accused product matches the Formula II fingerprint: B10 His, specific B1 option, constrained A21, constrained R³⁰, and a basic-residue-containing R³¹ motif.
- Dependent claims, especially Claim 15 (R¹=H-Phe, R²=Gly, R³⁰=Thr, R³¹=Arg-Arg-OH), define narrow design space and are the most actionable for freedom-to-operate and design-around decisions.
- The main validity risk is that the pI range may not add novelty if prior art already disclosed charge-engineered insulin derivatives within the same pI band, with overlapping positional modifications.
Key Takeaways
- US 5,656,722 claims a specific insulin derivative class defined by Formula II positional substitutions plus a pI 5 to 8.5 constraint, excluding a narrow combination.
- The practical infringement test is structural: B10 His, constrained B1, constrained A21, constrained R³⁰, and R³¹ containing at least one basic residue (with specific dependent exemplars like Arg-Arg-OH).
- Formulation claims add real-world constraints: zinc concentration windows and optional co-formulation with unmodified insulin.
- The narrowest dependent claims (notably Claim 15) provide the clearest design-around levers.
FAQs
1) Which claim is the broadest and drives most of the risk?
Claim 1. It sets the structural scaffold and pI window, then the dependent claims narrow variables.
2) Does the pI limitation alone decide infringement?
No. Claim 1 requires both the pI window and compliance with the Formula II positional substitution constraints, with a specific exclusion.
3) What is the most actionable dependent claim for design-around?
Claim 15, because it pins a fully specified combination of R¹, R², R³⁰, and R³¹.
4) Do formulation claims require the accused product to include zinc and unmodified insulin?
Only if the asserted claims are the zinc and/or unmodified-insulin dependent ones (Claims 7-8, 12-14). Claim 6 covers the derivative in defined physical forms without those additives.
5) What part of the claim set is easiest to verify from a competitor product?
The presence of zinc at specified ranges and the presence of unmodified insulin are typically verifiable from formulation and labeling/CMC rather than inferred from pI alone.
References
[1] U.S. Patent 5,656,722.
