US Patent 6,221,633 claims and US patent landscape for engineered insulin derivatives
US 6,221,633 protects engineered insulin derivatives defined by specific amino-acid substitutions in the insulin A- and B-chains (notably B3 and B27/B28/B29), plus a set of downstream protection layers: specific sequences (SEQ ID NOs 3-11), manufacturing processes using expression vehicles and precursor-release steps, nucleic acids/expression constructs/host cells, and pharmaceutical compositions and therapeutic use (diabetes treatment).
Business impact: the claims are broad at the concept level (insulin derivatives defined by residue-position rules), then narrow into species claim fences (particular residue combinations and explicit sequence IDs). Any generic/biosimilar or follow-on “insulin analog” would need to avoid infringement by changing at least one of the critical structural anchors (B3 basic residue substitution and the B27/B28/B29 neutral/acidic replacement logic) and, depending on product form, may also need to design around the formulation/depot cocrystallization and manufacturing process layers.
What does US 6,221,633 claim: insulin derivatives with B3 basic residue and B27/B28/B29 neutral/acidic changes?
Core claim architecture (Claim 1):
- An insulin derivative (or physiologically tolerable salt).
- B3 of the B-chain: Asn replaced by a naturally occurring basic amino acid residue (i.e., a basic residue defined by the claim as naturally occurring and basic).
- B27, B28 or B29: at least one position replaced by another naturally occurring neutral or acidic amino acid residue.
- Claim scope therefore turns on two structural “hot spots”:
- B3 substitution chemistry category (basic).
- B27/B28/B29 substitution category (neutral/acidic), with “at least one” position changed.
How the claim expands in dependent claims:
- Dependent claims enumerate which basic residues can occupy B3: His, Lys, Arg (Claims 9-12).
- Dependent claims enumerate which neutral/acidic residues can occupy B27/B28/B29:
- Neutral/acidic set is implemented by species lists including Asp (acidic) and Glu (acidic) (Claims 13-22).
- There is also a neutral subset (Claims 25-27) using Ile (neutral).
Other structural anchors inside Claim 1’s variable regime (Claim 2 onwards):
Claim 2 introduces a larger formula I and adds positional constraints for many residues across A- and B-chains. This matters in non-infringement design because infringement does not only require the B3 and B27/B28/B29 criteria; it may require matching the defined overall structure under formula I.
Which amino-acid positions define infringement risk under Claims 1-22?
High-leverage positions:
- B3: must be basic (His/Lys/Arg species fall under Claims 9-12).
- B27/B28/B29: at least one must be neutral or acidic (neutral via Ile; acidic via Asp/Glu in the enumerated dependents).
Additional restriction positions that tighten claim scope in Claim 2 and its dependents:
- B1: Phe or hydrogen (Claim 2), with a tighter dependent that can make “Phe absent” a distinct sub-class (Claim 43).
- B30: –OH or amino-acid residue (Claim 2) with species dependent coverage (Claims 3-7, 5-7).
- A21: Asn replaced by Asp/Gly/Ser/Thr/Ala is covered (Claim 42 plus Claim 33 species).
- There are also explicit dependent sequences with full B-chain sequences (SEQ ID NOs 3-5, etc.) and full A/B precursor sequences (SEQ ID NOs 6-11).
Net effect: A product that matches the “B3 basic + B27/B28/B29 neutral/acidic” concept but deviates at additional constrained residues could still fall outside the formula I boundary. Conversely, a product that matches those additional residue rules would be harder to design around.
How do specific claim species work: SEQ ID NOs 3-11 and sequence-locked coverage?
US 6,221,633 contains both:
- genus rules (position-based categorical substitutions), and
- species lock-ins using explicit SEQ ID NO sequences.
Sequence species that likely map to marketed or prototype molecules
The patent explicitly claims both derivative sequences and precursors. Key anchors:
B-chain sequences:
- SEQ ID NO 3 (Claim 23): begins “Phe Val Lys Gln His Leu Cys Gly Ser His Leu Val Glu Ala Leu Tyr Leu Val Cys Gly Glu Arg Gly Phe Phe Tyr Thr Pro Glu Thr”
- SEQ ID NO 4 (Claim 28): “Phe Val Lys Gln His Leu Cys Gly Ser His Leu Val Glu Ala Leu Tyr Leu Val Cys Gly Glu Arg Gly Phe Phe Tyr Thr Ile Lys Thr”
- SEQ ID NO 5 (Claim 31): “Phe Val Lys Gln His Leu Cys Gly Ser His Leu Val Glu Ala Leu Tyr Leu Val Cys Gly Glu Arg Gly Phe Phe Tyr Ile Pro Lys Thr”
Precursor sequences (full precursor including A-chain portion and B-chain portion with processing context):
- SEQ ID NO 6 (Claim 24): precursor sequence starting “Met Ala Thr Thr Ser Thr Gly Asn Ser Ala Arg Phe Val ... Asn ...”
- SEQ ID NO 7 (Claim 29): precursor sequence differing in the region around B3/B30-related edits versus SEQ ID NO 6.
- SEQ ID NO 8 (Claim 32): another precursor species.
- SEQ ID NO 9 (Claim 34): A-chain sequence species.
- SEQ ID NO 10 (Claim 34): B-chain sequence species for the A21-derived variant.
- SEQ ID NO 11 (Claims 33-35 and 50-54): a precursor species tied to the Asn/Asp substitution at A21 (“Asn in position 21 replaced by Asp”).
Why sequence-locked claims matter for competition
Sequence-defined claims reduce freedom. If a competitor’s molecule is equivalent but uses a different backbone processing route, it may still infringe if the final amino-acid sequence falls within claimed SEQ IDs or within formula I with the required positional identities.
What manufacturing/process claims exist: expression vehicles, precursor constructs, and precursor release?
US 6,221,633 pushes protection beyond the molecule into how it is made.
Process claim spine (Claims 24, 29, 32, 35, 45)
These are “replicable expression vehicle” and “host cell expression” claims with defined precursor linkage logic:
- Build an expression vehicle with a DNA sequence coding for a precursor.
- The patent defines a link between A1 (A-chain position) and B30 (B-chain position) via a peptide chain of formula II where R¹(n) has n amino acid residues and n ranges 0 to 34.
- The B-chain is modified by covalent linkage at B1 via formula III where R²(m) has m amino acid residues and m ranges 0 to 40, with p = 0, 1, or 2.
- Express in a host cell.
- Release the insulin derivative from the precursor using chemical and/or enzymatic methods.
Host cell scope (Claims 46-49)
- Claim 46: host cell can be bacterium.
- Claim 47: bacterium can be E. coli.
- Claim 48: host cell can be yeast.
- Claim 49: yeast can be Saccharomyces cerevisiae.
Implication: a manufacturing process using bacterial or yeast expression routes that implements the defined precursor linkage and release steps is a meaningful infringement vector, even if formulation is redesigned.
Which nucleic-acid and expression-vehicle claims exist (Claims 55-64)?
The patent adds a second manufacturing/IP layer through genetic material coverage:
- Isolated or purified nucleic acid coding for precursors with sequence selected from SEQ ID NOs 11, 6, 8, 7 (Claim 55).
- Dependent nucleic acid claims lock each SEQ ID number (Claims 56, 59, 61, 63).
- Expression vehicle includes nucleic acids corresponding to each SEQ ID (Claims 57, 60, 62, 64).
- Host cell transformed with the expression vehicle (Claim 58).
Infringement mechanics: Even if the active insulin is made by a third party, suppliers of DNA constructs and expression systems can fall into direct liability if the claimed nucleic acids/expression vehicles are used.
What composition and use claims exist: injectable solutions, depots, and diabetes treatment?
Pharmaceutical preparation claims (Claims 36-39)
- Claim 36: pharmaceutical preparation comprising the insulin derivative and/or salt of Claim 1.
- Claim 37: includes dissolved, amorphous, and/or crystalline forms.
- Claim 38: adds “depot auxiliary.”
- Claim 39: depot auxiliary is protamine sulfate and the insulin derivative/salt is present with protamine sulfate in a cocrystallizate.
Injectable solution claim (Claim 41)
- Injectable solution having insulin activity comprising the pharmaceutical preparation in dissolved form.
Therapeutic use claim (Claim 40)
- Method for treatment of diabetes mellitus by administering an effective amount of the Claim 36 preparation.
Practical read-through: this layered structure means design-around has to consider both molecule and product form:
- A competitor that changes the active sequence might still face infringement if the exact claimed cocrystallizate/protamine depot formulation is used and the active still falls within Claim 1.
- A competitor that changes formulation alone is unlikely to escape if the active remains within the claimed structural boundaries.
How strong is the patent estate for US 6,221,633 specifically, given its claim breadth vs. specificity?
Strength profile:
- Broad conceptual hook: Claim 1 covers any insulin derivative meeting the B3 basic substitution and B27/B28/B29 neutral/acidic substitution logic.
- Species tightening: the patent then narrows to explicit combinations via dependent claims and SEQ IDs.
- Multi-layer coverage: molecule + sequences + manufacturing + nucleic acids + formulation + therapeutic use.
Litigation posture likely supported by multiple claim types:
- Infringement can be pled on (i) molecule sequence, (ii) manufacturing precursor construct/release process, (iii) DNA construct/expression vehicle, and (iv) formulation form factor (protamine sulfate cocrystallizate).
Critical vulnerability (from a design-around perspective):
- The claims require meeting positional constraints across A and B. A competitor that edits only B3 or only B27/B28/B29 may miss the full formula I requirement if other constrained residues do not align.
- The claims also constrain specific residues and provide “absent/present” limitations (Claims 43-44), enabling potential escape routes by removing Phe at B1 or B30 functionality, depending on how formula I is interpreted.
When does US 6,221,633 lose exclusivity: filing-date mechanics and likely term?
No reliable expiration timetable can be produced from the information provided. A patent’s expiration depends on:
- priority and filing dates,
- whether it is a continuation/divisional,
- patent term adjustments,
- potential terminal disclaimers.
Because those dates are not included here, an accurate exclusivity timeline cannot be generated for this specific patent.
What Orange Book status applies to US 6,221,633 for insulin products?
No Orange Book applicability can be determined from the provided inputs. Orange Book listings require drug product–patent mapping (application/holder/NDC), which is not included in the prompt.
Which generic entry risks exist for US 6,221,633?
Generic risk assessment depends on whether the claimed insulins are the same active as a generic candidate and on FDA pathway status (referenced drug, biosimilarity, and interchangeability). The prompt provides only claim text and not the FDA product mapping needed to determine:
- whether a competitor product would be “generic” vs. “biosimilar,”
- whether any marketed insulin analogs have sequences that align with SEQ ID coverage,
- whether Paragraph IV litigation has been filed.
No such mapping can be computed accurately from the provided information alone.
What patent litigation affects US 6,221,633?
No litigation docket can be identified from the provided information. Litigation status requires case captions, case numbers, or at least the relevant parties and jurisdictions.
Key Takeaways
- US 6,221,633 is not limited to an insulin molecule concept. It covers a structured insulin derivative genus (B3 basic substitution + B27/B28/B29 neutral/acidic substitution) and then extends protection through sequence-locked species (SEQ ID NOs), manufacturing processes (expression vehicle, precursor linkage, host expression, precursor release), nucleic acids and expression constructs, and pharmaceutical formulations including protamine sulfate cocrystallizates, plus diabetes treatment method claims.
- The most actionable infringement probes for competitors are:
- whether their active amino-acid sequence satisfies Claim 1’s B3 and B27/B28/B29 positional rules and falls within the formula I bounds,
- whether their manufacturing uses the claimed precursor linkage formulas II/III, host cell expression, and release steps,
- whether their genetic constructs match the claimed nucleic acid sequences/vehicles,
- whether their dosage form uses the claimed protamine sulfate cocrystallizate framework.
- Exclusivity timing, Orange Book listing, and litigation posture cannot be determined from the prompt.
FAQs
1) Does US 6,221,633 require both B3 and B27/B28/B29 substitutions to be infringed?
Yes. Claim 1 requires Asn at B3 replaced by a basic naturally occurring residue and at least one of B27/B28/B29 replaced by a neutral or acidic naturally occurring residue.
2) Are sequence-defined claims (SEQ ID NOs 3-11) broader or narrower than the positional genus claims?
They are narrower in coverage because they lock specific amino-acid sequences or precursor sequences, but they can provide clearer infringement proofs if a product matches the stated SEQ IDs.
3) Can a competitor avoid infringement by changing only the formulation (for example, not using protamine)?
Not if the active insulin derivative still falls within Claim 1 (or the specific sequence dependents). Formulation changes may matter for Claim 39 but do not remove molecule/process liability.
4) Do the process claims protect only chemical synthesis or also recombinant production?
They explicitly cover recombinant expression vehicle construction, host cell expression, and precursor release using chemical and/or enzymatic methods.
5) Do nucleic-acid/expression-vehicle claims create risk for suppliers of DNA constructs?
Yes. Claims 55-64 cover isolated/purified nucleic acids, expression vehicles, and a transformed host cell aligned to specific precursor sequences.
References
- United States Patent 6,221,633. (Provided claim text in prompt).
