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US RE39548 patent landscape: Interleukin-5 (IL-5) recombinant antibody claims, scope, and US enforcement risk

RE39548 is a US reissue patent that recites engineered humanized recombinant antibodies targeting human interleukin-5 (IL-5), with claims centered on (i) variable-domain “composite” designs using murine monoclonal 39D10 donor residues and human acceptor frameworks (Kabat numbering), and (ii) specific heavy/light variable region sequence identities and/or encoded sequences (SEQ ID NOs cited in the claims). The practical patent landscape risk is highest for antibodies that (a) retain the claimed IL-5-binding paratope residue sets from 39D10 and (b) use the same Kabat framework “human group I light / group III heavy” backbones or encode the same heavy/light variable regions by SEQ ID numbers.

What is US Patent RE39548 and what does it actually claim for IL-5 antibodies?

Core subject matter. RE39548 claims recombinant antibody molecules that specifically bind human IL-5. The antibody format is defined at the variable-domain level: a composite heavy chain variable domain and a composite light chain variable domain built from human acceptor framework residues plus murine 39D10 donor residues. The claims also include composition claims with pharmaceutically acceptable carriers.

Key claim architecture.

Claim 1: Composite variable domains with acceptor framework residues and donor residues from murine monoclonal 39D10, using Kabat numbering. Donor residue sets are explicitly enumerated for heavy and light variable regions.
Claim 2: Limits acceptor frameworks to human group III heavy chain and human group I light chain frameworks.
Claim 3: Adds alternative sequence-based definition: heavy variable region is residues 20-135 of SEQ ID No:28, light variable region is residues 21-128 of SEQ ID No:26.
Claim 4: Pharmaceutical composition comprising the claimed antibody + carrier.
Claim 5 (in your excerpt): A second explicit donor-residue enumeration that differs from claim 1 in listed residue positions (notably different donor/framework residue positions are named).
Claim 6: Encoded variable regions defined by heavy chain variable region encoded by SEQ ID No:27 and light chain variable region encoded by SEQ ID No:25.
Claim 7: Composition corresponding to claims 5 or 6.

How to read the scope

The binding determinant is residue-specific. The claim language is not limited to “humanized antibodies” in the abstract. It is tethered to enumerated Kabat positions derived from a particular murine monoclonal (39D10) and tied to explicit framework residue sets.
Framework identity narrows non-equivalents. Claim 2 makes the framework choice specific (human group III heavy / group I light). That narrows design-around routes that use other human framework families even if they keep the same donor residues.
Sequence claims create cleaner infringement analysis. Claims 3 and 6 provide “sequence capture” via SEQ ID-defined variable regions, which usually reduces ambiguity relative to residue-only constructs.

Which parts of RE39548 are residue-defined versus sequence-defined?

Residue-defined claims

Claim 1: Composite variable domain with donor residues from 39D10 heavy chain and light chain variable regions; donor residues are enumerated at specified Kabat framework positions.
Claim 2: Specifies the human framework group (group III heavy / group I light) for the acceptor residues.
Claim 5: Another composite residue enumeration (different subset of residue positions than claim 1 as shown in your excerpt).

Sequence-defined claims

Claim 3: Heavy variable region is SEQ ID No:28 residues 20-135; light variable region is SEQ ID No:26 residues 21-128.
Claim 6: Heavy variable region SEQ ID No:27 and light variable region SEQ ID No:25 encoded.

Composition

Claims 4 and 7: Antibody + pharmaceutically acceptable carrier/diluent/excipient.

Implication for infringement

Residue-only constructs can still be designed around by shifting human framework residue sets or making substitutions at non-donor framework positions that change antibody humanization while avoiding the claimed donor residue pattern.
Sequence-defined claims are more brittle for competitors if they use the same variable-region sequences (or sequences that fall within exact claimed residue boundaries).

What murine 39D10-derived donor residue sets does RE39548 require?

From the text you provided, Claim 1 requires donor residues from murine monoclonal antibody 39D10 with the following enumerations (Kabat numbering):

Heavy chain variable donor residues: SEQ ID No:6 at residues 31-35, 50-65, 95-102 and framework residues 23, 24, 27-30, 37, 49, 73, 76, 77, and 78.
Light chain variable donor residues: SEQ ID No:8 at residues 24-34, 50-56, 89-97 and framework residues 22, 68, and 71.

Claim 5 (as shown) requires a donor set that is similar but not identical:

Heavy chain donor residues: SEQ ID NO:6 at residues 31-35, 50-65, 95-102 and framework residues 24, 27-30, 37, 49, 73, 76 and 78.
Light chain donor residues: SEQ ID NO:8 at residues 24-34, 50-56, 89-97 and framework residues 68 and 71.

Practical effect

Claim 1 and Claim 5 target two close but distinct composite residue mappings. That matters for design-around: a competitor can sometimes avoid one set by changing just a framework donor residue position that is present in one enumeration but absent in the other.
However, Claim 2 and sequence claims (3 and 6) can still catch variants that otherwise avoid the residue enumerations.

How does RE39548 define human frameworks (group I light, group III heavy) and what does that mean for design-around?

Claim 2 is explicit:

Acceptors for heavy chain variable domain: human group III heavy chain residues
Acceptors for light chain variable domain: human group I light chain residues

This is a critical limitation because many “humanized” candidates use other framework families (group II, group IV, etc.). Even if a competitor maps the same 39D10 CDRs or donor residues, switching the framework family can avoid exact match to the claimed framework residue set.

Design-around risk assessment

High risk: Candidates using the same human framework group plus the same donor residues.
Medium risk: Candidates with different framework groups but identical or near-identical variable-region sequences that still match SEQ ID-defined sequences in claims 3 and 6.
Lower risk: Candidates using different framework families and also varying the variable-region sequences away from the specific SEQ ID-defined sequences.

Which US claims in RE39548 are most enforceable against a competing IL-5 antibody?

Most enforceable elements usually are the sequence claims (claims 3 and 6) because they can be asserted based on exact variable-region sequence identity or exact encoded SEQ ID-defined strings.

Claim 3 uses bounded residue ranges from SEQ ID 28 (heavy) and SEQ ID 26 (light). This can be powerful if competitor variable regions match those ranges exactly.
Claim 6 ties directly to heavy and light variable regions encoded by SEQ ID 27 and SEQ ID 25, which typically means fewer interpretive degrees of freedom.

Residue enumerations (claims 1 and 5) are enforceable too, but infringement analysis can turn on claim construction disputes about the mapping between Kabat positions and actual sequence positions (especially if any parties argue numbering-system differences or alignment choices).

Composition claims (claims 4 and 7) follow the infringement of the antibody itself. They are usually not the main battleground.

When does RE39548 lose exclusivity and what matters for term/expiration analysis?

No enforceable exclusivity timeline can be provided from the claim text alone. US patent reissue terms depend on the original application filing dates, reissue history, and whether the reissue changed claims or corrected defects, which controls term adjustment. Patent term and exclusivity dates are not extractable from the provided claim excerpts.

What is the Orange Book status of RE39548?

RE39548 is a reissue patent. Orange Book listing is tied to an approved drug and NDA/BLA label as well as the listed patent type (drug substance, drug product, method-of-use). The provided excerpt does not identify the associated product, NDA/BLA number, or Orange Book listing.

Orange Book status cannot be determined from the claim text you supplied.

How would a Paragraph IV challenge typically be framed against RE39548?

A typical generic or biosimilar-leaning challenge would argue one or more of the following:

Non-infringement: the generic’s antibody variable regions do not contain the claimed donor residue sets and/or do not match the SEQ ID-defined sequences.
Invalidity: anticipation/obviousness based on earlier IL-5 antibody humanization disclosures or earlier identification of 39D10-derived donor residue mapping.
Indefiniteness or claim construction: disagreements about Kabat numbering alignment or variable region boundaries.

However, the specific validity and infringement landscape requires knowing the original patent family members, publication numbers, and the approved IL-5 antibody product to map to known prior art and litigation.

What prior art vectors are most relevant to RE39548’s claim type?

Based on the claim structure, the most relevant prior art categories are:

Earlier IL-5 neutralizing antibodies (especially humanized versions derived from a murine IL-5 antibody).
Humanization frameworks using Kabat numbering with explicit donor residues from murine parent antibodies.
Sequence disclosures for heavy/light variable regions matching SEQ ID-defined fragments.

The claim is drafted to be sequence- and residue-specific, which often means competitors attack validity by showing that the specific residue permutations were already disclosed, or obvious combinations were known.

What licensing or settlement posture is likely when claims are this residue/sequence-specific?

A residue- and sequence-specific reissue claim set usually produces:

Faster non-infringement mapping for counsel using sequence alignment.
Higher leverage for the patentee when competitor variable regions are close to the SEQ ID-defined sequences.
Settlement likelihood increases when competitors’ engineering teams converge on “same paratope, same framework family” designs, because claim charts become straightforward.

The actual licensing posture is product and history dependent and cannot be stated from the excerpt alone.

Which IL-5 antibodies are most likely in the competitive firing line?

RE39548 targets IL-5 specifically and references a murine monoclonal 39D10. In practice, that points to antibodies engineered from or related to the 39D10 parental murine IL-5 antibody. But the competitor list depends on identifying the drug name tied to RE39548.

Competitor identification is not possible from the provided claim text alone.

What is the risk for generic vs biosimilar pathways for IL-5 antibodies?

Recombinant antibodies are generally biologics and are not approved via generic NDA pathways. Exclusivity and entry risk depends on biosimilar regulation, reference product exclusivity, and patent use codes (Orange Book biologics listing in US). Without the associated BLA/NDA and listed patent numbers, the entry-risk assessment cannot be made.

How strong is the patent estate for RE39548-style humanized antibody claims?

Strength is a function of:

How many independent claims are sequence- or residue-captured
Whether the reissue covers multiple claim sets that were previously allowed
Whether there are parallel family members covering formulations, full-length antibody, Fc engineering, conjugates, dosing regimens, and manufacturing methods

From your excerpt, RE39548 includes at least two residue-specific claim variants (claims 1 and 5) and two sequence-specific anchors (claims 3 and 6), plus composition claims. That internal redundancy tends to increase enforceability.

But overall estate strength requires the full family list and related US publication/patent numbers, which are not provided.

Key Takeaways

RE39548 claims IL-5 binding recombinant antibodies defined by composite variable-domain engineering using murine 39D10 donor residues inserted into human acceptor frameworks (Kabat numbering).
Scope tightens materially under Claim 2 (human group III heavy / group I light framework selection).
Enforceability risk against competitors is highest for variable regions that match the SEQ ID-defined heavy/light fragments in Claims 3 and 6.
Two related residue maps appear in Claims 1 and 5, creating multiple “rings” of capture that design-around must thread.
Exclusivity timing, Orange Book status, Paragraph IV/biosimilar entry scenarios, litigation posture, and competitor targets cannot be derived from the excerpt alone.

FAQs

Do claims 3 and 6 in RE39548 capture full antibody sequences or only variable-region fragments?
They capture specific heavy and light variable-region sequences or bounded residue ranges as defined by SEQ ID references in the claims excerpt.
How do Kabat numbering systems affect infringement analysis for composite humanized antibodies?
Kabat numbering anchors claim positions; infringement often hinges on correct alignment of the accused sequence to those numbered residues.
Can a competitor avoid RE39548 by using the same CDR residues but swapping human framework families?
Claim 2 restricts framework family selection, and residue/sequence claims may still capture variants even if CDR-only approaches are used.
Is RE39548 limited to therapeutic use against IL-5 only or broader cytokine binding?
The claims are limited to antibodies “specifically bind human Interleukin-5 antigen,” which is a functional binding limitation to IL-5.
Are composition claims (claims 4 and 7) independent patent protection or derivative?
They are derivative of the claimed antibodies in the independent claims referenced in the excerpt.

References

No external sources are provided in the prompt excerpt, and no patent bibliographic identifiers beyond RE39548 are included.

Title:	Interleukin-5 specific recombinant antibodies
Abstract:	An effective anti-IL-5 recombinant antibody molecule comprising heavy and/or light chain antigen-binding residues from a donor antibody.
Inventor(s):	Bodmer; Mark William (Cambridge, GB), Athwal; Diljeet Singh (London, GB), Emtage; John Spencer (Del Mar, CA)
Assignee:	Celltech R&D Limited (Slough, Berkshire, GB)
Application Number:	10/012,579
Patent Claims:	see list of patent claims
Patent landscape, scope, and claims summary:	US RE39548 patent landscape: Interleukin-5 (IL-5) recombinant antibody claims, scope, and US enforcement risk RE39548 is a US reissue patent that recites engineered humanized recombinant antibodies targeting human interleukin-5 (IL-5), with claims centered on (i) variable-domain “composite” designs using murine monoclonal 39D10 donor residues and human acceptor frameworks (Kabat numbering), and (ii) specific heavy/light variable region sequence identities and/or encoded sequences (SEQ ID NOs cited in the claims). The practical patent landscape risk is highest for antibodies that (a) retain the claimed IL-5-binding paratope residue sets from 39D10 and (b) use the same Kabat framework “human group I light / group III heavy” backbones or encode the same heavy/light variable regions by SEQ ID numbers. What is US Patent RE39548 and what does it actually claim for IL-5 antibodies? Core subject matter. RE39548 claims recombinant antibody molecules that specifically bind human IL-5. The antibody format is defined at the variable-domain level: a composite heavy chain variable domain and a composite light chain variable domain built from human acceptor framework residues plus murine 39D10 donor residues. The claims also include composition claims with pharmaceutically acceptable carriers. Key claim architecture. Claim 1: Composite variable domains with acceptor framework residues and donor residues from murine monoclonal 39D10, using Kabat numbering. Donor residue sets are explicitly enumerated for heavy and light variable regions. Claim 2: Limits acceptor frameworks to human group III heavy chain and human group I light chain frameworks. Claim 3: Adds alternative sequence-based definition: heavy variable region is residues 20-135 of SEQ ID No:28, light variable region is residues 21-128 of SEQ ID No:26. Claim 4: Pharmaceutical composition comprising the claimed antibody + carrier. Claim 5 (in your excerpt): A second explicit donor-residue enumeration that differs from claim 1 in listed residue positions (notably different donor/framework residue positions are named). Claim 6: Encoded variable regions defined by heavy chain variable region encoded by SEQ ID No:27 and light chain variable region encoded by SEQ ID No:25. Claim 7: Composition corresponding to claims 5 or 6. How to read the scope The binding determinant is residue-specific. The claim language is not limited to “humanized antibodies” in the abstract. It is tethered to enumerated Kabat positions derived from a particular murine monoclonal (39D10) and tied to explicit framework residue sets. Framework identity narrows non-equivalents. Claim 2 makes the framework choice specific (human group III heavy / group I light). That narrows design-around routes that use other human framework families even if they keep the same donor residues. Sequence claims create cleaner infringement analysis. Claims 3 and 6 provide “sequence capture” via SEQ ID-defined variable regions, which usually reduces ambiguity relative to residue-only constructs. Which parts of RE39548 are residue-defined versus sequence-defined? Residue-defined claims Claim 1: Composite variable domain with donor residues from 39D10 heavy chain and light chain variable regions; donor residues are enumerated at specified Kabat framework positions. Claim 2: Specifies the human framework group (group III heavy / group I light) for the acceptor residues. Claim 5: Another composite residue enumeration (different subset of residue positions than claim 1 as shown in your excerpt). Sequence-defined claims Claim 3: Heavy variable region is SEQ ID No:28 residues 20-135; light variable region is SEQ ID No:26 residues 21-128. Claim 6: Heavy variable region SEQ ID No:27 and light variable region SEQ ID No:25 encoded. Composition Claims 4 and 7: Antibody + pharmaceutically acceptable carrier/diluent/excipient. Implication for infringement Residue-only constructs can still be designed around by shifting human framework residue sets or making substitutions at non-donor framework positions that change antibody humanization while avoiding the claimed donor residue pattern. Sequence-defined claims are more brittle for competitors if they use the same variable-region sequences (or sequences that fall within exact claimed residue boundaries). What murine 39D10-derived donor residue sets does RE39548 require? From the text you provided, Claim 1 requires donor residues from murine monoclonal antibody 39D10 with the following enumerations (Kabat numbering): Heavy chain variable donor residues: SEQ ID No:6 at residues 31-35, 50-65, 95-102 and framework residues 23, 24, 27-30, 37, 49, 73, 76, 77, and 78. Light chain variable donor residues: SEQ ID No:8 at residues 24-34, 50-56, 89-97 and framework residues 22, 68, and 71. Claim 5 (as shown) requires a donor set that is similar but not identical: Heavy chain donor residues: SEQ ID NO:6 at residues 31-35, 50-65, 95-102 and framework residues 24, 27-30, 37, 49, 73, 76 and 78. Light chain donor residues: SEQ ID NO:8 at residues 24-34, 50-56, 89-97 and framework residues 68 and 71. Practical effect Claim 1 and Claim 5 target two close but distinct composite residue mappings. That matters for design-around: a competitor can sometimes avoid one set by changing just a framework donor residue position that is present in one enumeration but absent in the other. However, Claim 2 and sequence claims (3 and 6) can still catch variants that otherwise avoid the residue enumerations. How does RE39548 define human frameworks (group I light, group III heavy) and what does that mean for design-around? Claim 2 is explicit: Acceptors for heavy chain variable domain: human group III heavy chain residues Acceptors for light chain variable domain: human group I light chain residues This is a critical limitation because many “humanized” candidates use other framework families (group II, group IV, etc.). Even if a competitor maps the same 39D10 CDRs or donor residues, switching the framework family can avoid exact match to the claimed framework residue set. Design-around risk assessment High risk: Candidates using the same human framework group plus the same donor residues. Medium risk: Candidates with different framework groups but identical or near-identical variable-region sequences that still match SEQ ID-defined sequences in claims 3 and 6. Lower risk: Candidates using different framework families and also varying the variable-region sequences away from the specific SEQ ID-defined sequences. Which US claims in RE39548 are most enforceable against a competing IL-5 antibody? Most enforceable elements usually are the sequence claims (claims 3 and 6) because they can be asserted based on exact variable-region sequence identity or exact encoded SEQ ID-defined strings. Claim 3 uses bounded residue ranges from SEQ ID 28 (heavy) and SEQ ID 26 (light). This can be powerful if competitor variable regions match those ranges exactly. Claim 6 ties directly to heavy and light variable regions encoded by SEQ ID 27 and SEQ ID 25, which typically means fewer interpretive degrees of freedom. Residue enumerations (claims 1 and 5) are enforceable too, but infringement analysis can turn on claim construction disputes about the mapping between Kabat positions and actual sequence positions (especially if any parties argue numbering-system differences or alignment choices). Composition claims (claims 4 and 7) follow the infringement of the antibody itself. They are usually not the main battleground. When does RE39548 lose exclusivity and what matters for term/expiration analysis? No enforceable exclusivity timeline can be provided from the claim text alone. US patent reissue terms depend on the original application filing dates, reissue history, and whether the reissue changed claims or corrected defects, which controls term adjustment. Patent term and exclusivity dates are not extractable from the provided claim excerpts. What is the Orange Book status of RE39548? RE39548 is a reissue patent. Orange Book listing is tied to an approved drug and NDA/BLA label as well as the listed patent type (drug substance, drug product, method-of-use). The provided excerpt does not identify the associated product, NDA/BLA number, or Orange Book listing. Orange Book status cannot be determined from the claim text you supplied. How would a Paragraph IV challenge typically be framed against RE39548? A typical generic or biosimilar-leaning challenge would argue one or more of the following: Non-infringement: the generic’s antibody variable regions do not contain the claimed donor residue sets and/or do not match the SEQ ID-defined sequences. Invalidity: anticipation/obviousness based on earlier IL-5 antibody humanization disclosures or earlier identification of 39D10-derived donor residue mapping. Indefiniteness or claim construction: disagreements about Kabat numbering alignment or variable region boundaries. However, the specific validity and infringement landscape requires knowing the original patent family members, publication numbers, and the approved IL-5 antibody product to map to known prior art and litigation. What prior art vectors are most relevant to RE39548’s claim type? Based on the claim structure, the most relevant prior art categories are: Earlier IL-5 neutralizing antibodies (especially humanized versions derived from a murine IL-5 antibody). Humanization frameworks using Kabat numbering with explicit donor residues from murine parent antibodies. Sequence disclosures for heavy/light variable regions matching SEQ ID-defined fragments. The claim is drafted to be sequence- and residue-specific, which often means competitors attack validity by showing that the specific residue permutations were already disclosed, or obvious combinations were known. What licensing or settlement posture is likely when claims are this residue/sequence-specific? A residue- and sequence-specific reissue claim set usually produces: Faster non-infringement mapping for counsel using sequence alignment. Higher leverage for the patentee when competitor variable regions are close to the SEQ ID-defined sequences. Settlement likelihood increases when competitors’ engineering teams converge on “same paratope, same framework family” designs, because claim charts become straightforward. The actual licensing posture is product and history dependent and cannot be stated from the excerpt alone. Which IL-5 antibodies are most likely in the competitive firing line? RE39548 targets IL-5 specifically and references a murine monoclonal 39D10. In practice, that points to antibodies engineered from or related to the 39D10 parental murine IL-5 antibody. But the competitor list depends on identifying the drug name tied to RE39548. Competitor identification is not possible from the provided claim text alone. What is the risk for generic vs biosimilar pathways for IL-5 antibodies? Recombinant antibodies are generally biologics and are not approved via generic NDA pathways. Exclusivity and entry risk depends on biosimilar regulation, reference product exclusivity, and patent use codes (Orange Book biologics listing in US). Without the associated BLA/NDA and listed patent numbers, the entry-risk assessment cannot be made. How strong is the patent estate for RE39548-style humanized antibody claims? Strength is a function of: How many independent claims are sequence- or residue-captured Whether the reissue covers multiple claim sets that were previously allowed Whether there are parallel family members covering formulations, full-length antibody, Fc engineering, conjugates, dosing regimens, and manufacturing methods From your excerpt, RE39548 includes at least two residue-specific claim variants (claims 1 and 5) and two sequence-specific anchors (claims 3 and 6), plus composition claims. That internal redundancy tends to increase enforceability. But overall estate strength requires the full family list and related US publication/patent numbers, which are not provided. Key Takeaways RE39548 claims IL-5 binding recombinant antibodies defined by composite variable-domain engineering using murine 39D10 donor residues inserted into human acceptor frameworks (Kabat numbering). Scope tightens materially under Claim 2 (human group III heavy / group I light framework selection). Enforceability risk against competitors is highest for variable regions that match the SEQ ID-defined heavy/light fragments in Claims 3 and 6. Two related residue maps appear in Claims 1 and 5, creating multiple “rings” of capture that design-around must thread. Exclusivity timing, Orange Book status, Paragraph IV/biosimilar entry scenarios, litigation posture, and competitor targets cannot be derived from the excerpt alone. FAQs Do claims 3 and 6 in RE39548 capture full antibody sequences or only variable-region fragments? They capture specific heavy and light variable-region sequences or bounded residue ranges as defined by SEQ ID references in the claims excerpt. How do Kabat numbering systems affect infringement analysis for composite humanized antibodies? Kabat numbering anchors claim positions; infringement often hinges on correct alignment of the accused sequence to those numbered residues. Can a competitor avoid RE39548 by using the same CDR residues but swapping human framework families? Claim 2 restricts framework family selection, and residue/sequence claims may still capture variants even if CDR-only approaches are used. Is RE39548 limited to therapeutic use against IL-5 only or broader cytokine binding? The claims are limited to antibodies “specifically bind human Interleukin-5 antigen,” which is a functional binding limitation to IL-5. Are composition claims (claims 4 and 7) independent patent protection or derivative? They are derivative of the claimed antibodies in the independent claims referenced in the excerpt. References No external sources are provided in the prompt excerpt, and no patent bibliographic identifiers beyond RE39548 are included. More… ↓ ⤷ Start Trial

Applicant	Tradename	Biologic Ingredient	Dosage Form	BLA	Approval Date	Patent No.	Expiredate
Teva Respiratory, Llc	CINQAIR	reslizumab	Injection	761033	23-Mar-16	RE39548	2021-12-07
>Applicant	>Tradename	>Biologic Ingredient	>Dosage Form	>BLA	>Approval Date	>Patent No.	>Expiredate

Country	Patent Number	Estimated Expiration
South Africa	954990	⤷ Start Trial
World Intellectual Property Organization (WIPO)	9535375	⤷ Start Trial
United States of America	6734286	⤷ Start Trial
United States of America	6316227	⤷ Start Trial
United States of America	5998586	⤷ Start Trial
United States of America	2002042089	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration

Patent: RE39548

Summary for Patent: RE39548