Patent: 4,530,787

Summary for Patent: 4,530,787

Title:	Controlled oxidation of microbially produced cysteine-containing proteins
Abstract:	Method of oxidizing reduced cysteine-containing microbially produced synthetic proteins, such as synthetic IFN-.beta. or synthetic IL-2, in a controlled manner so that the synthetic proteins have the same disulfide bridging as their native counterparts. The oxidation employs o-iodosobenzoate as oxidizing agent and is carried out in an aqueous medium at a pH at least about one-half pH unit less than the pK.sub.a of the cysteines to be oxidized, a synthetic protein concentration of less than about 5 mg/ml, and an oxidizing agent:protein mol ratio that is at least stoichiometric, provided that the oxidizing agent is in excess in the terminal portion of the reaction.
Inventor(s):	Shaked; Ze\'ev (Berkeley, CA), Wolfe; Sidney N. (Richmond, CA)
Assignee:	Cetus Corporation (Emeryville, CA)
Application Number:	06/661,902
Patent Claims:	see list of patent claims

US Patent 4,530,787 Landscape: What the Oxidation Process and Cystine-Containing IFN-β/IL-2 Claims Cover, How They Differ, and Where the Claim Scope Faces Erosion

United States Patent 4,530,787 covers a specific oxidative refolding/oxidation approach for microbially produced proteins that start fully reduced at cysteines and need selective intramolecular cystine formation with low mispairing and oligomerization. The asserted claim architecture is two-tier: (1) a process claim set built around reaction conditions using o-iodosobenzoate at pH below the cysteine pKa, constrained protein concentration and stoichiometric reagent ratios with terminal excess; and (2) composition/preparation claims focused on the resulting cystine-disulfide pattern matching native IL-2 or IFN-β, plus quantitative limits on oligomers and misbridged disulfide isomers.

The practical risk profile is driven by whether competitors can design around (a) the oxidant identity (o-iodosobenzoate), (b) the pH window “at least about one-half pH unit below” cysteine pKa, (c) concentration and reagent stoichiometry, and (d) the endpoint composition specs (oligomer threshold, and <15 wt% misbridged isomer threshold). For litigation and licensing, the key question is whether a competing oxidation/refolding method that uses a different oxidant or different control strategy can still reach products meeting the same disulfide-identity and impurity limits.

What patents protect the selective oxidation (cysteine to cystine) of fully reduced microbially produced proteins like US 4,530,787?

US 4,530,787 is an oxidation-process and product-quality patent centered on controlled cysteine oxidation to obtain correct intramolecular disulfide bridging with minimal overoxidation and low oligomer/mispairing. Its claim language ties scope to both method conditions and product structure/impurity limits.

Core claim concept: controlled cystine formation using o-iodosobenzoate under pH/conc/reagent constraints

Claim 1 anchors the estate with a controlled oxidation method:

• Starting material: microbially produced synthetic protein with fully reduced cysteines and amino acid sequence substantially identical to the useful protein sequence, including cysteines that form intramolecular cystine in the useful protein.
• Oxidant: o-iodosobenzoate.
• Medium: aqueous.
• pH: “at least about one-half pH unit below the pKa of said cysteines.”
• Protein concentration: less than about 5 mg/mL.
• Stoichiometry: mol ratio oxidant-to-protein at least stoichiometric, with proviso that o-iodosobenzoate is in excess in the terminal portion of the reaction.
• Outcome assurance: selective oxidation to form cystine with minimal overoxidation and minimal formation of nonconforming cysteine groups or oligomers.

This is a narrow-to-medium method claim because it is condition-specific (pH relative to cysteine pKa, protein concentration ceiling, stoichiometry plus terminal excess). Many oxidation/refolding processes will miss one or more conditions even if they achieve native-like disulfide patterns.

Downstream composition claims: disulfide bridging identity plus quantitative impurity thresholds

Claims 16–20 and 17–20 push the estate into product characterization territory:

• Composition/preparation derived from synthetic microbially produced, unglycosylated protein (for claim 17/19) and containing correct disulfide bridging as native IL-2 or native IFN-β.

• Product impurity constraints:

  • “substantially free of oligomers”
  • less than about 15% by weight isomers having disulfide bridging different from native
  • in dependent claims, less than about 1% by weight oligomers.

• Specific IL-2 and IFN-β embodiments:

  • claim 21: des-ala IL-2.sub.ser125
  • claim 22: IFN-β.sub.ser17

For infringement, the “right product” requirement can be powerful: a process may be similar, but if it yields a product profile that fails the disulfide isomer or oligomer thresholds, the composition claims are harder to land.

Therapeutic scope is IL-2 and IFN-β centered

Claims 3–4, 7–11 tie method coverage to lymphokines and specifically IFN-β or IL-2, with pH windows narrowed further:

• Claim 5: pH below about 9.
• Claim 6: pH between 5.5 and 9.
• Claim 7: IL-2, pH 6.5 to 7.5.
• Claim 8: IFN-β, pH 6.5 to 9.0.
• Claims 10–11 add mol ratio range 1:1 to 5:1 and concentration range 0.3 to 0.7 mg/mL.

Purification and processing details

• Claim 12: purification using gel filtration method.
• Claim 13: filtration using a G-25 Sephadex desalting column.

This adds another potential design-around vector. Competitors using different purification (e.g., ion exchange, tangential flow filtration, chromatography platforms not using G-25 Sephadex desalting) can avoid those dependent claims.

Mutein concept

• Claim 15 covers muteins of biologically active proteins where at least one cysteine residue is deleted or replaced by another amino acid and cystine formation is controlled for biological activity.

This can extend product coverage to engineered disulfide architectures, but still anchored to the “cysteines which in the useful protein are linked intramolecularly” concept.

Critical scope boundary: “substantially identical” amino acid sequence

The process claim 1 includes proteins with amino acid sequences “substantially identical” to the useful protein sequence. That phrase is a litigation flashpoint: competitors producing variants that are not “substantially identical” to native IL-2 or IFN-β sequence could argue noninfringement. The composition claims are more directly tied to native disulfide bridging patterns and impurity limits rather than “substantially identical” alone.

How strong is the claim set against process variants?

• Stronger against competitors who use the same oxidant class and the same strict pH/conc/stoichiometry control to drive correct intramolecular cystine.
• Weaker if competitors shift:
  • oxidant chemistry (different iodinane/halogen donor),
  • pH control strategy (not “0.5 pH unit below cysteine pKa”),
  • or protein concentration regime (avoid <5 mg/mL and/or 0.3–0.7 mg/mL ranges).
• The composition claims can be tougher to design around if the competitor’s product consistently achieves native disulfide bridging with low misbridged isomers and oligomers below thresholds, regardless of method.

When does US 4,530,787 lose exclusivity and what does that imply for generic or biosimilar risk?

US 4,530,787 is an older US patent (issued in 1985). Without the exact filing date, claim-by-claim expiry in the US cannot be stated precisely here. Do not rely on generic “20 years from filing” assumptions without verifying the application filing date, continuation status, and any term adjustments.

From a competitive perspective, the practical implication is that the patent’s method and product claims are likely expired or near-expired in the US, shifting risk from patent-based exclusivity to (a) remaining unexpired continuations in the same family and (b) any newer patents covering formulation, manufacturing, or analytics.

Because the user request asks for a “comprehensive and critical analysis” including exclusivity timelines, that requires family data (filing, priority, continuations, term adjustments) and Orange Book/BPCIA status for IL-2/IFN-β products. That dataset is not provided here, so a complete exclusivity timeline cannot be produced.

How do claims 1–15 (process) compare with claims 16–22 (composition) for infringement risk?

The estate is best understood as two different infringement regimes.

Process claims: conditional control of the oxidation reaction

• Infringement tracks whether a defendant performs the same oxidation operation with:
  • o-iodosobenzoate,
  • controlled pH relative to cysteine pKa,
  • protein concentration constraints,
  • oxidant-to-protein mol ratios including terminal excess,
  • and selective oxidation outcomes framed as minimizing overoxidation and mispairing.

Design-around strategy in litigation practice often focuses on changing one or more “hard” parameters (oxidant, pH relative offset, protein concentration, stoichiometry scheme, terminal excess technique) rather than trying to dispute the chemistry after the fact.

Composition claims: the final product quality profile

Claims 16–20 (and 21–22) create a “product-by-spec” hook:

• Correct disulfide bridging as native IL-2 or native IFN-β,
• low oligomers and low misbridged disulfide isomer content.

Design-around can target process and still reach product compliance, but the composition claims then become the end barrier. Conversely, if a competitor tolerates higher misbridged disulfide isomer fractions or oligomers above the thresholds, it can avoid composition claim infringement even if it produces correct bridging for the majority.

Which is more enforceable?

• Process claims can be harder to prove absent discovery into reaction conditions and manufacturing logs.
• Composition claims can be easier if the competitor’s product is tested by the same analytics used for disulfide mapping and oligomer quantification.
• Dependent claims tied to specific purification (G-25 Sephadex) raise both enforceability and design-around options.

What formulations and purification steps are explicitly protected by US 4,530,787?

US 4,530,787 does not claim a broad drug formulation matrix (excipients, buffers, stabilizers) in the claim set provided. It focuses on intermediate purification after oxidation:

• Gel filtration purification is claimed (claim 12).
• Specifically, G-25 Sephadex desalting is claimed (claim 13).

That is narrow. A manufacturer using different desalting (desalting columns other than G-25 Sephadex, membrane diafiltration, or different chromatography) could avoid dependent claims 12–13 while still potentially falling within claim 1 if reaction conditions match.

What patent estate surrounds US 4,530,787 for IL-2 and IFN-β (method-of-use, manufacturing, and formulation) and how do they interact?

A complete “landscape” requires the rest of the patent family, citations, and the broader patent set in the IL-2 and IFN-β manufacturing space (oxidants/refolding reagents, disulfide isomer control, purification, stability, delivery). That requires:

• the full patent family (continuations/divisionals),
• cited references and citing patents,
• and product-linked regulatory documents (Orange Book listings for IL-2/IFN-β products or biosimilar licensure data under BPCIA for IFN-β).

No such bibliographic data is included in the prompt. Per constraint, an analysis that claims “which patents” or “which companies” without the underlying dataset cannot be produced here.

How does this patent compare with competing disulfide-refolding patents for biologic cystine-containing proteins?

Within the claims provided, the competitive differentiator is the specificity of oxidation control parameters:

• Oxidant: o-iodosobenzoate.
• pH control: at least about 0.5 pH unit below cysteine pKa.
• Concentration: <5 mg/mL with preferred range for IL-2/IFN-β embodiments (0.3–0.7 mg/mL).
• Reagent ratio with terminal excess.

Many refolding patents in the field (not identified here by number) typically pivot on:

• different oxidants/reductants,
• redox buffers,
• temperature/time control,
• or cell-free oxidative folding in the presence/absence of catalysts.

US 4,530,787’s combination of oxidant identity plus pH offset plus concentration constraints narrows its claim coverage against methods that do not replicate that control strategy. But it retains relevance if competitors use the same o-iodosobenzoate chemistry and the same “terminal excess” approach to manage kinetics and avoid mispairing.

What patent litigation and Paragraph IV challenges exist for IL-2 or IFN-β tied to this patent?

Paragraph IV challenges are relevant for small molecules and certain biologic-like non-biologics in Orange Book contexts; for protein biologics under BPCIA, the analog is biosimilar litigation and patent dance/early resolution. The prompt does not provide:

• parties,
• venue,
• case numbers,
• or whether US 4,530,787 is asserted in any specific dispute.

A credible litigation mapping cannot be constructed from the claim text alone.

What is the Orange Book status and FDA regulatory status impact for IL-2 and IFN-β products under this patent?

Orange Book listings apply to approved drug products that are not biologics. IL-2 and IFN-β are biologics with BLA frameworks and do not generally map cleanly to Orange Book exclusivity. The prompt does not provide product names, BLAs, biosimilar sponsors, or reference products, so a regulatory-status analysis cannot be completed.

Key Takeaways

• US 4,530,787 claim coverage is anchored to a controlled oxidation process using o-iodosobenzoate in aqueous media at pH at least about 0.5 unit below cysteine pKa, with protein concentration below 5 mg/mL and stoichiometric oxidant-to-protein ratios plus terminal excess.
• Claims 16–22 shift from process conditions to product specs: correct native disulfide bridging plus strict limits on oligomers and misbridged disulfide isomers (<15 wt% total misbridged isomers; <1 wt% oligomers in dependents).
• Infringement risk splits by claim type: process defenses target reaction conditions; product defenses target analytical compliance with disulfide mapping and oligomer/mispairing thresholds.
• The dependent claims add additional design-around options: G-25 Sephadex desalting (claim 13) and IL-2/IFN-β-specific pH and concentration/molar ratio windows (claims 7–11).
• A comprehensive exclusivity timeline, family landscape, and litigation/regulatory mapping cannot be produced from the claim text alone because the necessary bibliographic and FDA/Orange Book/BPCIA data are not present.

FAQs

1. What does “pH at least about one-half pH unit below the pKa of said cysteines” constrain in practice?
   It hard-codes relative acidity control, limiting process freedom versus patents that specify an absolute pH or broader buffer regime.

2. If a competitor uses a different oxidant than o-iodosobenzoate, can the process still infringe claim 1?
   Claim 1 requires o-iodosobenzoate, so changing oxidant identity is a primary design-around path.

3. How do oligomer limits affect product infringement for IL-2 and IFN-β preparations?
   The claims set explicit weight-percent thresholds for oligomers (substantially free; <1 wt% in dependents), making analytical outcomes central.

4. Do the composition claims protect only IL-2 and IFN-β, or broader cystine-containing proteins?
   The provided dependent compositions are specifically IL-2 and IFN-β, while claim 1 covers “useful protein” more generally within the intramolecular cystine-forming framework.

5. What role does gel filtration and G-25 Sephadex desalting play in the patent’s enforceability?
   It is only in dependent claims (12–13), so it can be avoided without necessarily escaping claim 1.

References

1. U.S. Patent 4,530,787, “Preparative process for oxidizing a microbially produced synthetic protein…,” issued 1985.

Details for Patent 4,530,787

Applicant	Tradename	Biologic Ingredient	Dosage Form	BLA	Approval Date	Patent No.	Expiredate
Bayer Healthcare Pharmaceuticals Inc.	BETASERON	interferon beta-1b	For Injection	103471	July 23, 1993	4,530,787	2004-10-17

International Patent Family for US Patent 4,530,787

Country	Patent Number	Estimated Expiration
Austria	108186
Austria	196769
Canada	1233172
Germany	156354