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United States Patent 5,843,439 (Anti-CD20 Radiolabeled Chimeric and Murine Antibodies) Claims, Scope, and U.S. Patent Estate Analysis

United States Patent 5,843,439 is directed to a B-cell lymphoma treatment sequence using a radiolabeled anti-CD20 antibody as an initial dose followed by subsequent administrations of a chimeric anti-CD20 antibody (produced by transfectoma TCAE 8, ATCC 69119). The independent claim is a tightly sequenced method claim that couples (a) a first radiolabeled murine or chimeric anti-CD20 antibody to (b) later dosing with the same chimeric antibody source. The dependent claims expand dosing frequency, stem cell harvesting/reinfusion, and radiolabel selection (I-131, In-131, In-111, Y-90). The patent landscape around this concept in the U.S. is dominated by earlier and adjacent anti-CD20 antibody IP (chimeric vs murine, radiolabeling, conjugation and dosing regimens, and transplant-associated conditioning), with 5,843,439’s practical leverage concentrated in infringement cases where a challenger uses the specific antibody sources and the claimed administration order.

What does U.S. Patent 5,843,439 claim for B-cell lymphoma treatment?

Core claim architecture: what must be proven for infringement

Independent claim 1 requires all of the following elements as a sequence:

A first administration period (step (i)) in which a patient with B-cell lymphoma receives a radiolabeled anti-CD20 antibody.
The administered radiolabeled anti-CD20 antibody must be one of two specifically identified antibody sources:
- Chimeric anti-CD20 produced by transfectoma TCAE 8 (ATCC 69119), or
- Murine anti-CD20 secreted by hybridoma identified as ATCC HB 11388**.
Subsequent administration after step (i) (step (ii)) of at least one dosage of a chimeric anti-CD20 antibody produced by TCAE 8 (ATCC 69119).

Infringement therefore hinges on two tight constraints:

Antibody identity/source (ATCC deposits tied to particular producers).
Treatment sequencing (radiolabeled anti-CD20 first, chimeric anti-CD20 later).

Claim 1 is not a general “anti-CD20 + radiolabel” claim

The claim is not drafted as:

“Any radiolabeled anti-CD20 followed by any anti-CD20”
“Any chimeric anti-CD20 after radiolabeled anti-CD20”
“Radiolabeled antibody therapy for B-cell lymphoma”

It is drafted as a two-stage regimen with source-specific antibodies. That drafting choice narrows infringement risk for generic method substitutes that use different murine/humanized variants, different clonotypes, different chimeric constructs, or different manufacturing cell lines.

Which parts of claim 1 are most likely to be litigated in U.S. anti-CD20 patent cases?

(1) Do the “TCAE 8 (ATCC 69119)” and “HB 11388 (ATCC HB 11388)” identities map to accused products?

The claim ties infringement to antibodies produced by those particular deposited organisms. In U.S. practice, this typically turns into an evidentiary fight over:

whether the accused chimeric anti-CD20 is the same construct and is produced by the same transfectoma line (or an equivalent that still meets the “produced by” requirement),
whether the radiolabeled antibody used in the first step is truly murine HB 11388 antibody vs a different murine precursor,
whether the accused radiolabeled antibody is the same antibody “selected from the group consisting of” the two options.

A challenger can often narrow exposure by switching from the claimed ATCC-identified antibody material to an alternative anti-CD20 (for example, a later-generation chimeric or humanized variant, or a different radiolabeled anti-CD20 entity with different binding epitopes or sequences).

(2) Sequencing and timing: what counts as “subsequently” and “at least one dosage”?

The claim requires:

step (i) is a first administration period with a radiolabeled antibody, then
step (ii) is administration of chimeric anti-CD20 after step (i).

This creates litigation pressure around regimen labeling and protocol: even if the same patient receives both agents, the case turns on whether the clinical plan matches the claim’s order.

(3) Radiolabel identity: claim scope is expanded but not universally required by claim 1

Claim 1 does not enumerate radiolabels. Claim 7 does, but it only applies when pleaded as a dependent claim. The radiolabel selection becomes crucial if a challenger uses a radiolabel outside the listed set and the patentee asserts only claim 1.

What do dependent claims 2-7 add to the infringement scope?

Claim 2: multiple post-radiolabel chimeric doses

Claim 2 covers the situation where multiple dosages of chimeric anti-CD20 are administered after the initial radiolabeled step. This does not broaden claim 1 to “single dose” protocols, but it adds coverage to common clinical patterns of repeated chimeric dosing following imaging/conditioning with radiolabeled anti-CD20.

Claim 3 and 4: whether the initial radiolabeled dose is murine or chimeric

Claim 3: radiolabeled antibody in step (i) is radiolabeled murine anti-CD20 secreted by ATCC HB 11388.
Claim 4: radiolabeled antibody in step (i) is radiolabeled chimeric anti-CD20 produced by TCAE 8 (ATCC 69119).

These dependent claims map to two factual scenarios. Claim 4 is especially significant because it captures regimens that begin with radiolabeled chimeric anti-CD20, then continue with non-radiolabeled (or differently radiolabeled) chimeric anti-CD20.

Claim 5 and 6: autologous transplant elements

Claim 5: includes harvesting peripheral stem cells (PSC) or bone marrow (BM) prior to treatment.
Claim 6: reinfuses the harvested PSC/BM after treatment.

These dependent claims link radiolabeled anti-CD20 regimens with transplant workflows. If the accused treatment includes transplant conditioning steps, claim 5/6 become the likely asserted hooks for coverage.

Claim 7: allowed radiolabel list

Claim 7 specifies that the radiolabel contained in the step-(i) radiolabeled antibody is selected from:

Iodine (131),
Indium (131),
Indium (111),
Yttrium (90).

This is a classic narrowing dependent clause. A protocol using a different radioisotope (or a different radiolabeling chemistry that changes the “radiolabel contained in said radiolabeled antibody”) may avoid claim 7 even if claim 1 is asserted.

What radiolabels and regimen design features are most critical to validity and claim construction?

Radiolabels implicated by claim 7

From an infringement standpoint, the isotopes in claim 7 cover the common radiolabeled antibody set used in older conditioning and lymphoma targeting strategies:

I-131 and Y-90 are beta emitters often used in cytotoxic radioimmunotherapy.
In-111 is a gamma emitter historically used for imaging and dosimetry and sometimes therapy depending on configuration.
In-131 appears in some radioimmunotherapy contexts, though it is less common than I-131 or Y-90 in routine practice.

Regimen design: staged radioimmunotherapy followed by chimeric anti-CD20

The claim reflects a design where the radiolabeled anti-CD20 step is a “first” systemic or targeted conditioning phase, then chimeric anti-CD20 is administered afterward as a follow-on therapeutic dose. This sequence can overlap with conditioning and consolidation approaches used in earlier lymphoma protocols.

How strong is the patent estate for this “anti-CD20 radiolabel then chimeric” method concept?

Strength depends on how unique the claim is relative to earlier anti-CD20 art

Method claims combining:

radiolabeled anti-CD20,
chimeric anti-CD20 follow-on administration,
and transplant-adjacent components

tend to be vulnerable if earlier patents already disclosed the same sequence and antibody identities. Claim strength therefore turns on whether earlier references disclose all features:

the same antibody source (TCAE 8, ATCC 69119),
the same radiolabeled vs non-radiolabeled staging,
and, if asserted via dependent claims, PSC/BM harvesting and reinfusion.

What limits “obviousness surface area” for 5,843,439

The main narrowing features that reduce prior-art overlap are:

ATCC deposit-linked antibody identity (TCAE 8/ATCC 69119 and HB 11388).
Sequence specificity: radiolabeled anti-CD20 in step (i) followed by chimeric anti-CD20 in step (ii).
Optional transplant tie-in via dependent claims 5/6.

Those limitations can provide stronger separation from generic radioimmunotherapy regimens that do not specify the antibody source or follow-on non-radiolabeled chimeric dosing.

What expands risk: broadness in dosing and isotope selection (at least at the independent-claim level)

Claim 1 does not specify isotope or number of subsequent doses, so a broad set of “radiolabeled anti-CD20 followed by chimeric anti-CD20” protocols could still fall within claim 1, provided they use the ATCC-specified antibodies and sequencing.

What “Orange Book” status applies to this patent?

This patent is a method-of-treatment patent directed to antibody regimens and is not itself an FDA approval. The practical Orange Book relevance is limited because Orange Book listings are drug-product centric (active ingredient/marketing authorization), while method-of-use patents are listed only when tied to a specific approved product and patent submission.

Without the FDA Orange Book listing record for this specific patent and corresponding reference product, no definitive Orange Book status statement can be made here.

How does the claim scope compare with later anti-CD20 IP (rituximab and successors)?

Potential overlap with rituximab-era practices

The chimeric anti-CD20 described as “TCAE 8” aligns with the canonical anti-CD20 therapeutic concept used in commercial development of chimeric antibodies. In modern practice, most large-scale anti-CD20 regimens use:

non-radiolabeled chimeric antibody dosing as primary therapy,
sometimes combined chemotherapy,
and, in selected approaches, radioimmunotherapy conditioning historically in earlier eras.

Key distinction for 5,843,439: it requires radiolabeled anti-CD20 as the first step followed by chimeric anti-CD20 administrations. Many contemporary regimens do not include the radiolabeled initial phase, so they may avoid claim 1 entirely.

Where successor products may still face exposure

If an accused protocol uses a radiolabeled anti-CD20 step and then administers a chimeric anti-CD20 product meeting the ATCC-linked identity requirement, exposure can persist even with later-generation packaging, dosing schedules, and supportive care.

What generic or biosimilar “entry risk” exists for this method claim?

Small-molecule generics are irrelevant

This is an antibody-based method claim. Small-molecule generic entry does not affect it.

Biosimilar risk depends on whether it reproduces the claimed antibody

If a biosimilar produces a chimeric anti-CD20 that matches the claim’s “produced by transfectoma TCAE 8 (ATCC 69119)” requirement, a biosimilar could create method infringement exposure for the prescriber/patient administration, depending on how infringement is argued (especially since method claims focus on the treatment regimen, not the product alone).

Radioimmunotherapy components are the bigger lever

Even if a biosimilar exists for the non-radiolabeled chimeric follow-on doses, the claim’s first step (radiolabeled anti-CD20) is often specific and may be harder to replicate with an unlicensed alternative.

Patent litigation scenarios most consistent with claim 1’s structure

Scenario A: accused protocol uses radiolabeled anti-CD20 first, then rituximab-like chimeric dosing

To infringe claim 1, an accused regimen must:

use a radiolabeled anti-CD20 that is either murine HB 11388 or chimeric TCAE 8 (ATCC 69119),
then administer at least one subsequent dose of chimeric TCAE 8 (ATCC 69119).

Litigation would focus on protocol order, the identity of the antibody material, and labeling/administration data.

Scenario B: transplant conditioning trial

If a clinical protocol includes PSC/BM harvest and reinfusion around a staged radiolabeled anti-CD20 plus chimeric anti-CD20 sequence, claims 5 and 6 become the focal points.

Claims and patent-landscape critical points for licensing and freedom-to-operate

The “ATCC deposit identity” is both a strength and an execution risk

Strength: it narrows the universe of potentially infringing materials.
Execution risk for a licensee: it may require tight supply-chain documentation demonstrating the exact antibody-producing line and identity.

The sequencing requirement is a lever for design-around

A design-around strategy frequently used in method claim disputes is altering the order or removing the radiolabeled initial phase. If the radiolabeled step is removed or moved after chimeric dosing, claim 1’s sequence can fail.

Dependent claims create multiple fallback lanes

Even if a challenger avoids one dependent limitation, the independent claim still captures staged treatment so long as sequencing and antibody identity match.

Key Takeaways

U.S. Patent 5,843,439 is a sequenced method-of-treatment claim for B-cell lymphoma: radiolabeled anti-CD20 first, then follow-on chimeric anti-CD20 produced by transfectoma TCAE 8 (ATCC 69119).
The claim’s most litigation-relevant constraints are (i) ATCC deposit-linked antibody identity and (ii) administration order.
Dependent claims broaden coverage for multiple follow-on doses, murine vs chimeric radiolabeled first steps, and PSC/BM harvest plus reinfusion.
Claim 7 narrows the radiolabel to I-131, In-131, In-111, and Y-90, making isotope selection a key design-around lever for any assertion targeting that dependent claim.
Orange Book implications cannot be stated from the claim text alone because Orange Book listings require product-to-patent mapping.

FAQs

Does claim 1 require the radiolabeled antibody to be a particular isotope?
No. Claim 1 does not list isotopes; isotope specificity appears in dependent claim 7.
Can infringement occur if only a single chimeric anti-CD20 dose is given after the radiolabeled first step?
Yes. Claim 1 requires at least one chimeric dose after step (i); claim 2 adds coverage for multiple doses.
If a protocol uses a radiolabeled anti-CD20 different from ATCC HB 11388 or ATCC 69119, does claim 1 apply?
No, not under the claim language. Claim 1 restricts the radiolabeled anti-CD20 to the two enumerated antibody sources.
Do claims 5 and 6 require transplant procedures for infringement of claim 1?
No. Claim 5/6 are dependent; they add PSC/BM harvest and reinfusion requirements only when those dependent claims are asserted.
Is a biosimilar of the non-radiolabeled chimeric antibody alone enough to trigger infringement risk?
Not by itself if the radiolabeled first step is not performed with the claimed ATCC-identified antibody material in the claimed sequence.

References

U.S. Patent 5,843,439, “Method of treating B-cell lymphoma with radiolabeled anti-CD20 antibody and chimeric anti-CD20 antibody,” claims as provided in prompt.

Title:	Therapeutic application of chimeric and radiolabeled antibodies to human B lymphocyte restricted differentiation antigen for treatment of B cell lymphoma
Abstract:	Disclosed herein are therapeutic treatment protocols designed for the treatment of B cell lymphoma. These protocols are based upon therapeutic strategies which include the use of administration of immunologically active mouse/human chimeric anti-CD20 antibodies, radiolabeled anti-CD20 antibodies, and cooperative strategies comprising the use of chimeric anti-CD20 antibodies and radiolabeled anti-CD20 antibodies.
Inventor(s):	Anderson; Darrell R. (Escondido, CA), Hanna; Nabil (Olivenhain, CA), Leonard; John E. (Encinitas, CA), Newman; Roland A. (San Diego, CA), Reff; Mitchell E. (San Diego, CA), Rastetter; William H. (Rancho Sante Fe, CA)
Application Number:	08/478,967
Patent Claims:	see list of patent claims
Patent landscape, scope, and claims summary:	United States Patent 5,843,439 (Anti-CD20 Radiolabeled Chimeric and Murine Antibodies) Claims, Scope, and U.S. Patent Estate Analysis United States Patent 5,843,439 is directed to a B-cell lymphoma treatment sequence using a radiolabeled anti-CD20 antibody as an initial dose followed by subsequent administrations of a chimeric anti-CD20 antibody (produced by transfectoma TCAE 8, ATCC 69119). The independent claim is a tightly sequenced method claim that couples (a) a first radiolabeled murine or chimeric anti-CD20 antibody to (b) later dosing with the same chimeric antibody source. The dependent claims expand dosing frequency, stem cell harvesting/reinfusion, and radiolabel selection (I-131, In-131, In-111, Y-90). The patent landscape around this concept in the U.S. is dominated by earlier and adjacent anti-CD20 antibody IP (chimeric vs murine, radiolabeling, conjugation and dosing regimens, and transplant-associated conditioning), with 5,843,439’s practical leverage concentrated in infringement cases where a challenger uses the specific antibody sources and the claimed administration order. What does U.S. Patent 5,843,439 claim for B-cell lymphoma treatment? Core claim architecture: what must be proven for infringement Independent claim 1 requires all of the following elements as a sequence: A first administration period (step (i)) in which a patient with B-cell lymphoma receives a radiolabeled anti-CD20 antibody. The administered radiolabeled anti-CD20 antibody must be one of two specifically identified antibody sources: Chimeric anti-CD20 produced by transfectoma TCAE 8 (ATCC 69119), or Murine anti-CD20 secreted by hybridoma identified as ATCC HB 11388. Subsequent administration after step (i) (step (ii)) of at least one dosage of a chimeric anti-CD20 antibody produced by TCAE 8 (ATCC 69119). Infringement therefore hinges on two tight constraints: Antibody identity/source (ATCC deposits tied to particular producers). Treatment sequencing (radiolabeled anti-CD20 first, chimeric anti-CD20 later). Claim 1 is not a general “anti-CD20 + radiolabel” claim The claim is not drafted as: “Any radiolabeled anti-CD20 followed by any anti-CD20” “Any chimeric anti-CD20 after radiolabeled anti-CD20” “Radiolabeled antibody therapy for B-cell lymphoma” It is drafted as a two-stage regimen with source-specific antibodies. That drafting choice narrows infringement risk for generic method substitutes that use different murine/humanized variants, different clonotypes, different chimeric constructs, or different manufacturing cell lines. Which parts of claim 1 are most likely to be litigated in U.S. anti-CD20 patent cases? (1) Do the “TCAE 8 (ATCC 69119)” and “HB 11388 (ATCC HB 11388)” identities map to accused products? The claim ties infringement to antibodies produced by those particular deposited organisms. In U.S. practice, this typically turns into an evidentiary fight over: whether the accused chimeric anti-CD20 is the same construct and is produced by the same transfectoma line (or an equivalent that still meets the “produced by” requirement), whether the radiolabeled antibody used in the first step is truly murine HB 11388 antibody vs a different murine precursor, whether the accused radiolabeled antibody is the same antibody “selected from the group consisting of” the two options. A challenger can often narrow exposure by switching from the claimed ATCC-identified antibody material to an alternative anti-CD20 (for example, a later-generation chimeric or humanized variant, or a different radiolabeled anti-CD20 entity with different binding epitopes or sequences). (2) Sequencing and timing: what counts as “subsequently” and “at least one dosage”? The claim requires: step (i) is a first administration period with a radiolabeled antibody, then step (ii) is administration of chimeric anti-CD20 after step (i). This creates litigation pressure around regimen labeling and protocol: even if the same patient receives both agents, the case turns on whether the clinical plan matches the claim’s order. (3) Radiolabel identity: claim scope is expanded but not universally required by claim 1 Claim 1 does not enumerate radiolabels. Claim 7 does, but it only applies when pleaded as a dependent claim. The radiolabel selection becomes crucial if a challenger uses a radiolabel outside the listed set and the patentee asserts only claim 1. What do dependent claims 2-7 add to the infringement scope? Claim 2: multiple post-radiolabel chimeric doses Claim 2 covers the situation where multiple dosages of chimeric anti-CD20 are administered after the initial radiolabeled step. This does not broaden claim 1 to “single dose” protocols, but it adds coverage to common clinical patterns of repeated chimeric dosing following imaging/conditioning with radiolabeled anti-CD20. Claim 3 and 4: whether the initial radiolabeled dose is murine or chimeric Claim 3: radiolabeled antibody in step (i) is radiolabeled murine anti-CD20 secreted by ATCC HB 11388. Claim 4: radiolabeled antibody in step (i) is radiolabeled chimeric anti-CD20 produced by TCAE 8 (ATCC 69119). These dependent claims map to two factual scenarios. Claim 4 is especially significant because it captures regimens that begin with radiolabeled chimeric anti-CD20, then continue with non-radiolabeled (or differently radiolabeled) chimeric anti-CD20. Claim 5 and 6: autologous transplant elements Claim 5: includes harvesting peripheral stem cells (PSC) or bone marrow (BM) prior to treatment. Claim 6: reinfuses the harvested PSC/BM after treatment. These dependent claims link radiolabeled anti-CD20 regimens with transplant workflows. If the accused treatment includes transplant conditioning steps, claim 5/6 become the likely asserted hooks for coverage. Claim 7: allowed radiolabel list Claim 7 specifies that the radiolabel contained in the step-(i) radiolabeled antibody is selected from: Iodine (131), Indium (131), Indium (111), Yttrium (90). This is a classic narrowing dependent clause. A protocol using a different radioisotope (or a different radiolabeling chemistry that changes the “radiolabel contained in said radiolabeled antibody”) may avoid claim 7 even if claim 1 is asserted. What radiolabels and regimen design features are most critical to validity and claim construction? Radiolabels implicated by claim 7 From an infringement standpoint, the isotopes in claim 7 cover the common radiolabeled antibody set used in older conditioning and lymphoma targeting strategies: I-131 and Y-90 are beta emitters often used in cytotoxic radioimmunotherapy. In-111 is a gamma emitter historically used for imaging and dosimetry and sometimes therapy depending on configuration. In-131 appears in some radioimmunotherapy contexts, though it is less common than I-131 or Y-90 in routine practice. Regimen design: staged radioimmunotherapy followed by chimeric anti-CD20 The claim reflects a design where the radiolabeled anti-CD20 step is a “first” systemic or targeted conditioning phase, then chimeric anti-CD20 is administered afterward as a follow-on therapeutic dose. This sequence can overlap with conditioning and consolidation approaches used in earlier lymphoma protocols. How strong is the patent estate for this “anti-CD20 radiolabel then chimeric” method concept? Strength depends on how unique the claim is relative to earlier anti-CD20 art Method claims combining: radiolabeled anti-CD20, chimeric anti-CD20 follow-on administration, and transplant-adjacent components tend to be vulnerable if earlier patents already disclosed the same sequence and antibody identities. Claim strength therefore turns on whether earlier references disclose all features: the same antibody source (TCAE 8, ATCC 69119), the same radiolabeled vs non-radiolabeled staging, and, if asserted via dependent claims, PSC/BM harvesting and reinfusion. What limits “obviousness surface area” for 5,843,439 The main narrowing features that reduce prior-art overlap are: ATCC deposit-linked antibody identity (TCAE 8/ATCC 69119 and HB 11388). Sequence specificity: radiolabeled anti-CD20 in step (i) followed by chimeric anti-CD20 in step (ii). Optional transplant tie-in via dependent claims 5/6. Those limitations can provide stronger separation from generic radioimmunotherapy regimens that do not specify the antibody source or follow-on non-radiolabeled chimeric dosing. What expands risk: broadness in dosing and isotope selection (at least at the independent-claim level) Claim 1 does not specify isotope or number of subsequent doses, so a broad set of “radiolabeled anti-CD20 followed by chimeric anti-CD20” protocols could still fall within claim 1, provided they use the ATCC-specified antibodies and sequencing. What “Orange Book” status applies to this patent? This patent is a method-of-treatment patent directed to antibody regimens and is not itself an FDA approval. The practical Orange Book relevance is limited because Orange Book listings are drug-product centric (active ingredient/marketing authorization), while method-of-use patents are listed only when tied to a specific approved product and patent submission. Without the FDA Orange Book listing record for this specific patent and corresponding reference product, no definitive Orange Book status statement can be made here. How does the claim scope compare with later anti-CD20 IP (rituximab and successors)? Potential overlap with rituximab-era practices The chimeric anti-CD20 described as “TCAE 8” aligns with the canonical anti-CD20 therapeutic concept used in commercial development of chimeric antibodies. In modern practice, most large-scale anti-CD20 regimens use: non-radiolabeled chimeric antibody dosing as primary therapy, sometimes combined chemotherapy, and, in selected approaches, radioimmunotherapy conditioning historically in earlier eras. Key distinction for 5,843,439: it requires radiolabeled anti-CD20 as the first step followed by chimeric anti-CD20 administrations. Many contemporary regimens do not include the radiolabeled initial phase, so they may avoid claim 1 entirely. Where successor products may still face exposure If an accused protocol uses a radiolabeled anti-CD20 step and then administers a chimeric anti-CD20 product meeting the ATCC-linked identity requirement, exposure can persist even with later-generation packaging, dosing schedules, and supportive care. What generic or biosimilar “entry risk” exists for this method claim? Small-molecule generics are irrelevant This is an antibody-based method claim. Small-molecule generic entry does not affect it. Biosimilar risk depends on whether it reproduces the claimed antibody If a biosimilar produces a chimeric anti-CD20 that matches the claim’s “produced by transfectoma TCAE 8 (ATCC 69119)” requirement, a biosimilar could create method infringement exposure for the prescriber/patient administration, depending on how infringement is argued (especially since method claims focus on the treatment regimen, not the product alone). Radioimmunotherapy components are the bigger lever Even if a biosimilar exists for the non-radiolabeled chimeric follow-on doses, the claim’s first step (radiolabeled anti-CD20) is often specific and may be harder to replicate with an unlicensed alternative. Patent litigation scenarios most consistent with claim 1’s structure Scenario A: accused protocol uses radiolabeled anti-CD20 first, then rituximab-like chimeric dosing To infringe claim 1, an accused regimen must: use a radiolabeled anti-CD20 that is either murine HB 11388 or chimeric TCAE 8 (ATCC 69119), then administer at least one subsequent dose of chimeric TCAE 8 (ATCC 69119). Litigation would focus on protocol order, the identity of the antibody material, and labeling/administration data. Scenario B: transplant conditioning trial If a clinical protocol includes PSC/BM harvest and reinfusion around a staged radiolabeled anti-CD20 plus chimeric anti-CD20 sequence, claims 5 and 6 become the focal points. Claims and patent-landscape critical points for licensing and freedom-to-operate The “ATCC deposit identity” is both a strength and an execution risk Strength: it narrows the universe of potentially infringing materials. Execution risk for a licensee: it may require tight supply-chain documentation demonstrating the exact antibody-producing line and identity. The sequencing requirement is a lever for design-around A design-around strategy frequently used in method claim disputes is altering the order or removing the radiolabeled initial phase. If the radiolabeled step is removed or moved after chimeric dosing, claim 1’s sequence can fail. Dependent claims create multiple fallback lanes Even if a challenger avoids one dependent limitation, the independent claim still captures staged treatment so long as sequencing and antibody identity match. Key Takeaways U.S. Patent 5,843,439 is a sequenced method-of-treatment claim for B-cell lymphoma: radiolabeled anti-CD20 first, then follow-on chimeric anti-CD20 produced by transfectoma TCAE 8 (ATCC 69119). The claim’s most litigation-relevant constraints are (i) ATCC deposit-linked antibody identity and (ii) administration order. Dependent claims broaden coverage for multiple follow-on doses, murine vs chimeric radiolabeled first steps, and PSC/BM harvest plus reinfusion. Claim 7 narrows the radiolabel to I-131, In-131, In-111, and Y-90, making isotope selection a key design-around lever for any assertion targeting that dependent claim. Orange Book implications cannot be stated from the claim text alone because Orange Book listings require product-to-patent mapping. FAQs Does claim 1 require the radiolabeled antibody to be a particular isotope? No. Claim 1 does not list isotopes; isotope specificity appears in dependent claim 7. Can infringement occur if only a single chimeric anti-CD20 dose is given after the radiolabeled first step? Yes. Claim 1 requires at least one chimeric dose after step (i); claim 2 adds coverage for multiple doses. If a protocol uses a radiolabeled anti-CD20 different from ATCC HB 11388 or ATCC 69119, does claim 1 apply? No, not under the claim language. Claim 1 restricts the radiolabeled anti-CD20 to the two enumerated antibody sources. Do claims 5 and 6 require transplant procedures for infringement of claim 1? No. Claim 5/6 are dependent; they add PSC/BM harvest and reinfusion requirements only when those dependent claims are asserted. Is a biosimilar of the non-radiolabeled chimeric antibody alone enough to trigger infringement risk? Not by itself if the radiolabeled first step is not performed with the claimed ATCC-identified antibody material in the claimed sequence. References U.S. Patent 5,843,439, “Method of treating B-cell lymphoma with radiolabeled anti-CD20 antibody and chimeric anti-CD20 antibody,” claims as provided in prompt. More… ↓ ⤷ Start Trial**

Applicant	Tradename	Biologic Ingredient	Dosage Form	BLA	Approval Date	Patent No.	Expiredate
Acrotech Biopharma Inc.	ZEVALIN	ibritumomab tiuxetan	Injection	125019	February 19, 2002	⤷ Start Trial	2015-06-07
>Applicant	>Tradename	>Biologic Ingredient	>Dosage Form	>BLA	>Approval Date	>Patent No.	>Expiredate

Country	Patent Number	Estimated Expiration
South Africa	938466	⤷ Start Trial
World Intellectual Property Organization (WIPO)	9411026	⤷ Start Trial
United States of America	7744877	⤷ Start Trial
United States of America	7422739	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration

Summary for Patent: 5,843,439