United States Patent 10,035,843 (RSV F-binding antibody) — Claims, Validity Pressure Points, and Competitive Landscape

What does US 10,035,843 claim in enforceable terms?

US Patent 10,035,843 is directed to a method of treating and/or preventing RSV-related disorder by administering an antibody (or functional part) that:

1) Specifically binds RSV F protein, and
2) Contains defined CDR sequences (heavy and light chain CDR1/2/3), and
3) Often requires broader sequence identity thresholds and optional IgG1/Fc engineering.

The independent claim 1 is the core. Dependent claims layer specificity (CDR sequences already fixed in claim 1) and then add:

Framework/overall heavy/light sequence homology (claims 2, 13)
Isotype restriction to IgG1 (claims 3, 16, 17)
Fc modifications by Kabat EU-index position sets and specific 252/254/256 substitutions (claims 4-6, 18-20)
Dosing timing relative to infection (claims 7-8)
Patient risk group definitions (claims 9-10)
Combination administration (claims 11-12)

Claim 1: CDR-locked RSV F antibody

Claim 1 requires an antibody or functional part with the following CDRs:

Heavy chain CDRs

CDR1: KLSIH (SEQ ID NO:4)
CDR2: GYEGEVDEIFYAQKFQH (SEQ ID NO:8)
CDR3: LGVTVTEAGLGIDDY (SEQ ID NO:12)

Light chain CDRs

CDR1: RASQIVSRNHLA (SEQ ID NO:20)
CDR2: GASSRAT (SEQ ID NO:24)
CDR3: LSSDSSI (SEQ ID NO:28)

This claim format matters legally: CDR requirements can support enforceability even where the antibody’s full sequence is not recited, but it also creates a strong design-around vector: if a competitor produces an antibody with sufficiently different CDRs (or different epitope-defining residues), it avoids claim 1.

Claim 2: “At least 70% identical” heavy/light sequences

Claim 2 narrows claim 1 by requiring the antibody to include sequence homology to specified full heavy and light sequences:

Heavy chain: ≥70% identical to TABLE-US-00008 (SEQ ID NO:16)
Light chain: ≥70% identical to TABLE-US-00009 (SEQ ID NO:32)

In practice, this “70% identical” language can be both a validity target and a scope risk:

Breadth: 70% identity for ~110 aa variable regions can still admit substantial substitutions, inserts, and deletions while staying within the threshold.
Enablement/definiteness pressure: unless the patent record tightly supports which sequences satisfy the identity computation and how indels are treated, litigants often attack sequence identity bounds as ambiguous or overbroad relative to the disclosure.

Claims 3, 16-17: IgG1 restriction

Claim 3: IgG1 heavy chain
Claim 16: human IgG1 heavy chain
Claim 17: claim 13 version restricted to human IgG1

Claims 4-6 and 18-20: Fc engineering via Kabat EU-index positions

Claims 4 and 18 define a broad set of permissible modification positions across the Fc region using EU numbering by Kabat, and require that modifications include substitutions and/or insertions/deletions at those positions.

Claims 5 and 19 narrow to specific positions:

252, 254, 256

Claims 6 and 20 then narrow the chemistry of those substitutions:

Position 252: substitution with tyrosine
Position 254: substitution with threonine
Position 256: substitution with glutamic acid

So the patent covers at least two “classes” of embodiments:

CDR-defined RSV F binders (claims 1, 13, 14-15, etc.)
CDR-defined binders with engineered Fc (claims 4-6, 18-20)

Claims 7-10: timing and target population

Prophylactic: administered before infection (claim 7)
Therapeutic: administered after infection (claim 8)
Risk: increased risk group includes premature birth, infants <6 weeks, elderly, chronic lung disease, congenital heart disease, hospitalized, or immunocompromised (claims 9-10)

Claims 11-12: combination administration

Claim 11 explicitly references palivizumab and additional RSV-specific antibodies AM14, AM16, AM23, D25. Claim 12 allows at least one other RSV-specific antibody.

This is a practical enforceability lever: even if a competitor’s primary antibody is outside the claim 1 CDR set, they can still infringe if they combine with a claim-covered antibody in a way that triggers these method claims. Method claims can be harder to police, but combination therapy language raises the odds of capture where standard-of-care regimens mix agents.

Where are the biggest legal/technical weak points in the claim set?

A patent portfolio is won and lost on claim construction and prior-art mapping. For US 10,035,843, the most attackable elements are the ones that can be shown to be either already disclosed in RSV F antibody prior art, or obvious in light of standard antibody engineering.

Is the CDR-defined scope vulnerable to prior-art anticipation or obviousness?

RSV F (fusion) is a heavily litigated and heavily published target. The claim 1 requirement is specific CDR sequences, which can reduce anticipation risk versus broader “binds RSV F” claims. But it shifts the question to whether prior art already disclosed antibodies with exactly those CDRs (or functionally equivalent CDRs).

Key issues:

If a single prior art reference already lists those exact CDR sequences (or sequences that, under a court’s construction of CDR boundaries, produce the same CDRs), claim 1 can be anticipated.
If multiple references disclose RSV F antibodies with highly similar CDRs and known frameworks, an obviousness combination argument can still succeed even without exact sequence identity.

Because claim 1 does not require a specific Fc phenotype in the independent claim, the CDRs become the sole “novelty gate” for the antibody binding function. That also means a competitor that can find a similar epitope binder with different CDR motifs can avoid claim 1 and still retain RSV F binding.

Does “70% identical” create overbreadth and indefiniteness leverage?

Claim 2’s “at least 70% identical” to SEQ ID NO:16 (heavy) and SEQ ID NO:32 (light) expands coverage beyond the exact sequences while staying tethered to particular embodiments.

From a validity standpoint, litigants often target identity thresholds as:

Unclear when alignment method (gaps/indels) affects whether sequences qualify
Overbroad where disclosed examples are limited but the homology threshold captures many untested variants

However, for enforceability, identity bounds also let a patentee argue that a competitor’s antibody is “close enough” to fall within the claim, even if it differs at multiple residues, as long as identity stays above 70%.

Are the Fc modification claims vulnerable due to common engineering playbooks?

Fc modifications at Kabat EU positions, especially around the well-known cluster 252/254/256, can be tied to widely taught goals such as altering Fc receptor binding, half-life, or effector function.

From a prior-art/obviousness standpoint:

If the Fc substitutions at or near 252/254/256 are already known in other therapeutic antibodies to achieve predictable Fc behavior, the remaining novelty may rest entirely on the CDR-defined RSV F binding.
If those Fc positions are commonly modified across antibody therapeutics, then claims 4-6 and 18-20 risk being treated as routine engineering.

That dynamic can matter because, in combination claims (e.g., “antibody plus patient timing plus combination agent”), the law sometimes demands a more than routine leap if all other elements are known.

Do combination therapy limitations create enforcement risk for the patentee (and litigation leverage for accused infringers)?

Claims 11-12 depend on administering palivizumab and/or specified antibodies. For infringement:

The patentee must show the accused regimen administers a claim-covered RSV F antibody plus the recited co-therapies, and does so as part of a covered method.
If competitors use different co-therapies or different ordering/timing, the method claims can fail at infringement rather than at validity.

That said, the presence of these dependent claims gives the patentee multiple “paths” to infringement depending on real-world formularies and guideline adherence.

What is the competitive patent landscape implied by the claim structure?

Even without the full prosecution history and the entire cited prior-art graph, the claim language itself indicates what crowded areas US 10,035,843 sits in:

1) RSV F antibody “epitope bins”

The patent is built around a specific RSV F-binding antibody. Industry competitors also pursued RSV F in multiple generations:

Neutralizing epitope-focused F binders (including pre-fusion stabilized constructs in the broader field)
Extended half-life formats
Fc-function tuned variants

Claim 1 locks down CDRs, so it occupies a narrow epitope bin relative to the generic “RSV F binding” space. That narrows infringement reach but can preserve validity if the CDR sequences are not previously disclosed.

2) Antibody format engineering

Claims 3, 14-16 indicate humanized/human embodiments and an IgG1 format. This aligns with standard therapeutic antibody development in the RSV F space.

3) Fc modification industry standardization

The explicit EU-index Kabat position list and the explicit 252/254/256 amino acid chemistry strongly suggests known Fc engineering. The landscape in antibody therapeutics already treats these substitutions as a known toolbox, which compresses the remaining inventive concept toward the RSV F CDR definition.

4) Standard-of-care co-administration

The named inclusion of palivizumab and other antibodies (AM14/AM16/AM23/D25) reflects that the landscape includes multiple RSV F and RSV neutralizing agents. This increases the probability that method combinations are medically plausible and thus fact patterns exist for enforcement.

How does the claim set compare to the dominant RSV F commercial and clinical antibody approaches?

Below is a practical mapping of claim elements to typical industry approaches. This is critical for assessing where competitors are likely to design around.

Design-around levers

Claim element	What it covers	Competitor design-around
CDR1/2/3 sequences in claim 1	Tight epitope definition	Switch to an antibody with different CDR sequences while retaining RSV F binding
≥70% identity to SEQ ID NO:16 and SEQ ID NO:32 (claim 2)	Extended binding to “nearby” variants	Drop below 70% identity via framework/variable-region substitutions while keeping function
IgG1 requirement (claims 3, 16-17)	Format restriction	Use non-IgG1 Fc/isotype (e.g., IgG2/IgG4) or non-IgG formats if feasible
Fc positions list + 252/254/256 substitutions (claims 4-6, 18-20)	Fc-tuned therapeutic phenotype	Avoid those Fc substitutions and/or alter Fc in non-overlapping ways
Admin timing before/after infection (claims 7-8)	Prophylaxis and treatment covered	Argue different administration scheme in practice, especially for prophylaxis/trials
Co-therapy list (claim 11)	Combination regimen capture	Avoid the listed co-administered antibodies in the same treated regimen

Where competitors are likely to stay in-scope

Competitors that:

Use a CDR-defined RSV F antibody with the exact CDR motifs from claim 1, and
Keep IgG1 and use Fc substitutions at 252/254/256, and
Administer in a prophylactic or high-risk clinical window,
face the highest likelihood of infringement.

The highest practical risk is in development programs that intentionally tune antibodies while preserving the original antigen-binding site.

What do the dependent claim themes imply about infringement scenarios?

The dependent claims outline fact patterns that are likely to be found in clinical practice:

Infant prophylaxis (risk group definitions + timing before infection)
Therapeutic use in hospitalized/immunocompromised (timing after infection)
Regimens involving palivizumab or other RSV antibodies (claims 11-12)

If the accused product is a human IgG1 RSV F-binding antibody with the claim 1 CDR set, then infringement analysis will hinge on:

exact CDR boundary definitions
whether Fc includes the specific Kabat EU position substitutions
whether the accused regimen matches the timing and combination limitations in the asserted dependent claims

Key takeaways

US 10,035,843 enforces an RSV F antibody defined primarily by exact CDR sequences in claim 1, with additional tightening via ≥70% identity to specified heavy/light sequences (claim 2) and optional but potent Fc engineering (claims 4-6 and 18-20).
Most validity and obviousness pressure shifts onto whether the exact CDR motifs (or functional equivalents under CDR boundary construction) appear in earlier RSV F antibody disclosures, and whether Fc modifications at Kabat EU 252/254/256 are routine or already taught.
Design-around is feasible primarily by changing the CDR sequences (avoiding claim 1) or by moving off the IgG1 and/or 252/254/256 Fc substitution pattern (avoiding dependent claims).
Combination and timing dependent claims (palivizumab/AM14/AM16/AM23/D25; before/after infection) increase infringement pathways in real-world clinical scenarios, but they also create narrower infringement requirements tied to regimen facts.

FAQs

Is RSV F binding alone enough to infringe US 10,035,843?
No. Claim 1 requires the antibody to contain the specific heavy and light CDR sequences.
Do the claims cover any RSV F antibody with similar CDRs?
The claims cover antibodies that match the listed exact CDR sequences (claim 1). Dependent claims add ≥70% identity to specified heavy/light sequences.
How significant are the Fc edits in the patent’s scope?
Claims 4-6 and 18-20 introduce a structured Fc modification regime based on Kabat EU numbering, and they can narrow scope to embodiments with Y/T/E at 252/254/256.
Does the patent cover both prophylaxis and treatment?
Yes. Claims 7 and 8 cover administration before and after RSV infection.
Does the patent cover combination therapy with palivizumab?
Yes. Claim 11 specifically allows administering the claim-covered method along with palivizumab and named other RSV-specific antibodies.

References

[1] United States Patent 10,035,843 (claims as provided in the prompt).

Applicant	Tradename	Biologic Ingredient	Dosage Form	BLA	Approval Date	Patent No.	Expiredate
Swedish Orphan Biovitrum Ab (publ)	SYNAGIS	palivizumab	For Injection	103770	June 19, 1998	⤷ Start Trial	2036-02-12
Swedish Orphan Biovitrum Ab (publ)	SYNAGIS	palivizumab	Injection	103770	July 23, 2004	⤷ Start Trial	2036-02-12
>Applicant	>Tradename	>Biologic Ingredient	>Dosage Form	>BLA	>Approval Date	>Patent No.	>Expiredate

Patent: 10,035,843

Summary for Patent: 10,035,843