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Patent landscape, scope, and claims: |
Scope, Claims, and U.S. Patent Landscape for U.S. Patent 4,647,447
U.S. Patent 4,647,447 claims NMR (MRI) diagnostic methods that use paramagnetic chelate salts where (i) the chelated metal is selected by atomic-number ranges that cover key paramagnetic ions and (ii) the counterion/salt is physiologically compatible, frequently using aminopolycarboxylate chelators (notably DTPA derivatives) paired with multivalent metal ions and pharmaceutically acceptable bases. The claims also include method dosing ranges, timing relative to imaging, and alternative salt/counterion systems (including N-methylglucamine and disodium-type salts) plus formulation variants (liposomes).
What is the core claim scope of U.S. 4,647,447?
The patent has two main claim “tracks” in substance:
- Direct method claims using a specific chelate-salt definition (Claim 1 and dependent claims 2 to 23; plus liposome variant in Claim 18).
- Broader “improvement in NMR tomography” method claims using paramagnetic salts of metal chelates with defined ligand families, including an expanded formulation and administration window, and additional dependent examples (Claims 24 to 68).
Claim 1: method using an NMR diagnostic medium defined by a chelated paramagnetic metal and specific counterion/salt architecture
Claim 1 requires:
- Activity: performing an NMR diagnostic procedure in a patient by administering an NMR diagnostic medium and then performing an NMR measurement step to image at least a portion of the patient body.
- Diagnostic medium definition: the medium comprises a physiologically compatible salt of:
- (a) an anion of a complexing acid, and
- (b) at least one central ion of an element with atomic number 21–29, 42, 44, or 57–83 chelated with that complexing acid.
- Salt/formula constraints: salts of formula I or II (with additional chemical definitions through Markush-style variables).
- Complexing ligand and counterion substituent definitions: the claim includes extensive structural variables (A, R1-R4, W, V, m, Z, R4, w), plus the rule that:
- at least two substituents Y are metal ion equivalents for an element with atomic numbers 21–29, 42, 44, or 57–83.
Business translation: Claim 1 is broad across multiple metals in the specified atomic-number ranges and across multiple aminocarboxylate-like or related complexing acid families described by the variables. It is still anchored to a “chelate-salt responsive to NMR” concept and to the specific structural variable framework of the complexing acid anion/counterion architecture.
Claims 2 to 23: concentration ranges plus extensive specific metal-ligand salt examples
These claims tighten Claim 1 by adding:
- Salt concentration windows (Claims 2, 3, 4) in μmole to mole and mmol/l implied ranges.
- Specific named salts (Claims 5 to 23), including:
- Gadolinium(III) complexes with DTPA (diethylenetriaminepentaacetic acid) in monosodium/mono-N-methylglucamine, disodium, or related forms.
- Iron(III) complexes of DTPA in di-N-methylglucamine or disodium forms.
- Manganese(II) complexes of DTPA in disodium forms.
- Bismuth(III) complexes of DTPA in di-N-methylglucamine forms.
- Ytterbium(III) DTPA complex disodium.
- Ho(III), La(III), Sm(III) DTPA complex disodium.
- Dy(III) DTPA complex in the broader set (also see later dependent claims in Claim 48 for dysprosium).
- Formulation variant: liposomes charged with the gadolinium(III)-DTPA complex (Claim 18).
Business translation: This block gives claim value in litigation by embedding numerous embodiments, especially across Gd, Fe, Mn, Bi, Yb, Ho, La, Sm, and also shows counterion flexibility between sodium, disodium, and N-methylglucamine-based systems.
Claims 24 to 68: broader “improvement” in NMR tomography, with ligand family expansion and administration parameters
Claim 24 states:
- Imaging by NMR tomography.
- Prior to tomography, administer a pharmaceutical agent affecting relaxation times to enhance contrast.
- The agent comprises:
- a paramagnetic, physiologically compatible salt of a complex of:
- a lanthanide ion atomic numbers 57–70, or
- a transition metal ion atomic numbers 21–29, 42, or 44,
- and a pharmaceutically acceptable carrier.
Dependent claims (25 to 68) then add:
- Salt concentration range (Claim 25): 1 μmole to 1 mole.
- Expanded ligand structures (Claim 26):
- Complexed ion is lanthanide 57–70 or transition metal 21–29, 42, 44.
- Ligand must be one of:
- an aminopolycarboxylic acid selected from NTA, HEEDTA, DTPA, HEDIDA, etc., or
- a defined formula ligand with nitrogen-based substituents, or
- another aminopolycarboxylic acid formula with defined ranges (m, n) and substituent class R5 (C4-12 alkyl, alkenyl, cycloalkyl, aralkyl, aryl, etc.).
- Timing window: administration about 15–60 minutes before tomography (Claim 27).
- Dose range: 1–100 μmol/kg intravenously (Claim 28).
- pH: 6.5–7.5 (Claim 29).
- Isotonicity: blood isotonic (Claim 30).
- Solvent concentration: 5–250 mmol/l in water (Claim 31).
- Acid/base counterion types (Claim 32 and 33): inorganic/organic salts; list includes HCl, H2SO4, acetic acid, citric acid, amino acids, NaOH, glucamine/N-methylglucamine, ethanolamine, diethanolamine, morpholine, lysine, ornithine, arginine.
- Further dependent examples:
- Ligand examples anchor to DTPA and related aminopolycarboxylates (Claims 34 to 39).
- Many specific paramagnetic complex salts:
- Ni(II)-EDTA with N-methylglucamine (Claim 66),
- Co(II)-EDTA with diethanolamine (Claim 67),
- Cu(II)-EDTA with di-diethanolamine (Claim 68),
- plus other salts listed earlier (Claims 45 to 59) including Mn(II)-EDTA disodium, Gd(III)-EDTA systems, Ni2 complex chloride hydrate, Cu(II) complex with a large aza-bicyclic chelator, etc.
Business translation: The “improvement” claims convert the patent from a narrow “specific salt formula” concept (Claim 1) into a broader contrast-agent delivery claim with explicit clinical administration parameters and a Markush ligand framework that still focuses on aminopolycarboxylate complexing systems and related nitrogen-containing chelators.
What claim elements most constrain scope versus broaden it?
Most constraining elements
- Metal atomic-number selection is still specific:
- Claim 1: atomic numbers 21–29, 42, 44, or 57–83.
- Claims 24–68: narrowed to lanthanide 57–70 plus transition metals 21–29, 42, 44.
- Chelate/ligand definition: Claim 1 uses formula-driven variables; Claims 24–26 explicitly require ligand membership in defined aminopolycarboxylic acids (including classic chelators such as DTPA/EDTA/NTA derivatives) or defined alternative formula classes.
- Salt physiologic compatibility and physiologic counterions: the claims do not cover arbitrary anions; they require physiologically compatible salt forms and list typical pharma bases and acids in dependent claims.
Most broadening elements
- Markush metal coverage by atomic-number ranges enables design-around resistance across multiple paramagnetic ions.
- Counterion flexibility: sodium, disodium, N-methylglucamine, di-lysine, di-diethanolamine, tri-diethanolamine, morpholine, etc.
- Form-factor expansion: Claim 18 covers liposomes charged with gadolinium-DTPA complex.
- Operational clinical parameters appear in later dependent claims, but broad independent coverage remains centered on the method-with-paramagnetic-chelate-salt concept (Claims 24 and 1).
How does the patent map to existing MRI contrast-agent categories?
U.S. 4,647,447 targets an MRI contrast delivery approach based on:
- Paramagnetic chelates of lanthanides and selected transition metals.
- Aminopolycarboxylate ligands, including:
- DTPA derivatives (diethylenetriaminepentaacetic acid),
- EDTA derivatives (ethylenediaminetetraacetic acid),
- NTA (nitrilotriacetic acid),
- HEEDTA and related HEDIDA-style ligands.
- Common pharmaceutically acceptable counterions/bases such as:
- Na-based salts,
- N-methylglucamine (glucamine),
- amino acids and polyamine alcohols like ethanolamine/diethanolamine.
Key strategic point: the claim language is sufficiently structured to cover the typical “chelate + physiologically compatible counterion + IV or oral administration + pre-scan timing” pattern used across many early gadolinium contrast agents, while still leaving room for alternative transition-metal chelates.
What is the dependent-claim “embodiment set” strength for infringement and validity?
Named salt examples in Claims 5–23 (Claim 1 dependencies)
The dependent claims explicitly recite multiple concrete species. This strengthens enforceability because:
- it demonstrates possession of a wide range of metal-ligand-counterion embodiments, and
- it gives multiple entry points for literal infringement mapping.
Concrete examples include:
- Gd(III)-DTPA salts: mono sodium/mono N-methylglucamine, disodium, and other DTPA derivative salts (also see Claim 13 and Claim 16 in the provided text).
- Fe(III)-DTPA salts: di-N-methylglucamine and disodium.
- Mn(II)-DTPA salts: disodium.
- Bi(III)-DTPA salts: di-N-methylglucamine.
- Yb(III)-DTPA salts: disodium.
- Ho(III)-DTPA salts: disodium.
- La(III)-DTPA salts: disodium.
- Sm(III)-DTPA salts: disodium.
- DTPA derivative described as 13,23-dioxo-... pentaazapentatriacontanedioic acid with Gd salts (Claim 16 and Claim 23).
Administration parameter dependencies in Claims 27–33 (Claim 26 dependencies)
- Timing: 15–60 minutes before NMR tomography.
- IV dose: 1–100 μmol/kg.
- pH: 6.5–7.5.
- isotonicity: blood isotonic.
- aqueous concentration: 5–250 mmol/l.
These dependencies are relevant for both:
- infringement theory where a specific clinical regimen matches, and
- validity challenges if earlier art exists on those process parameters.
What does the claim architecture imply for patent landscape and design-around?
High-risk design spaces
Any product or method that matches all of the following will be within the patent’s gravitational center:
- NMR/MRI diagnostic use of a paramagnetic chelate salt.
- Chelated metal is in the specified atomic-number sets.
- Chelating ligand is within the claimed aminopolycarboxylate or defined formula ligand classes.
- Counterion is one of the physiologically compatible salt systems (commonly sodium, N-methylglucamine, amino-acid bases, ethanolamine-type bases).
- Administration aligns with typical IV timing and dose.
Lower-risk design spaces (from a literal-reading perspective)
- Avoiding the claimed ligand classes (the aminopolycarboxylic acids and the explicit formula ligand classes) reduces overlap.
- Using metals outside the specified atomic-number sets reduces overlap (especially for Claim 24-68).
- Using non-physiologically compatible salt anions would be out of scope, but practically that is unlikely for MRI indications.
- Avoiding the explicit timed administration window and dosing range can reduce infringement for dependent claims, though not necessarily for independent claims.
How to think about enforceable scope by claim level
| Claim level |
What it covers most directly |
Primary business risk for competitors |
| Claim 1 |
NMR imaging method with physiologically compatible salt of complexed paramagnetic ions using a formula-defined chelate architecture |
Broad metal coverage plus explicit diagnostic-medium concept |
| Claims 2–23 |
Specific concentration ranges plus numerous named salt examples (Gd/Fe/Mn/Bi/Yb/Ho/La/Sm DTPA systems; liposomes) |
Literal mapping to known contrast-agent species |
| Claim 24 |
NMR tomography contrast enhancement by administering paramagnetic physiologically compatible complex salt with lanthanide 57–70 or transition metals 21–29, 42, 44 |
Core “contrast agent administration” claim level |
| Claims 26–33 |
Expanded ligand families plus administration timing/dose/pH/isotonic aqueous concentration and common counterions |
Higher confidence infringement mapping if product matches regimen and ligand class |
| Claims 65–68 |
Additional “improvement” formulations with specified acyclic/cyclic complexing agents containing N/P/O/S |
Narrower, but adds coverage breadth for alternative chelators |
Where the patent likely sits in the MRI IP timeline (by substance, not by filing dates)
Based on the claim content, the patent reflects an era focused on:
- EDTA/DTPA/NTA-type chelators and their physiologic salt forms,
- early MRI contrast dosing and physicochemical constraints (pH, isotonicity),
- early formulation variants like liposomes,
- broad Markush metal coverage including gadolinium and several transition metals.
This matters for landscape because many later MRI agents refine:
- chelate stability, thermodynamic/kinetic stability,
- macrocyclic scaffolds,
- and improved safety profiles.
U.S. 4,647,447 still remains a risk anchor for metal-chelate salt administration approaches that use aminopolycarboxylate families and conventional counterions.
Key claim elements checklist for landscape screening
Use this as a literal “hit list” when evaluating competitor products, protocols, and reformulations:
- Method type: NMR diagnostic procedure with imaging (tomography) after administration.
- Agent type: paramagnetic physiologically compatible salt of a metal chelate.
- Metal scope:
- Claim 1: atomic numbers 21–29, 42, 44, 57–83.
- Claims 24–68: lanthanides 57–70; transition metals 21–29, 42, 44.
- Ligand scope:
- Claim 24/26: aminopolycarboxylic acids (NTA, HEEDTA, DTPA, HEDIDA) and defined formula ligand classes.
- Salt/counterion scope:
- physiologically compatible acids/bases including sodium, N-methylglucamine (glucamine), ethanolamine/diethanolamine, amino acids.
- Regimen (dependent claims):
- 15–60 minutes pre-scan timing,
- 1–100 μmol/kg IV,
- pH 6.5–7.5,
- blood isotonic,
- 5–250 mmol/l aqueous concentration.
Key Takeaways
- U.S. 4,647,447 claims NMR/MRI diagnostic methods using paramagnetic chelate salts and defines scope by metal atomic-number ranges, chelating ligand families, and physiologically compatible counterions.
- Claim 1 is anchored to a detailed chelate-salt formula architecture and covers many paramagnetic metal embodiments via Markush variables.
- Claims 24–33 expand into a broad “contrast enhancement by relaxation-time affecting agent” framework with explicit timing, dosing, pH, isotonicity, and aqueous concentration parameters.
- The dependent claims list many concrete chelate species (notably Gd(III)-DTPA salt variants and additional transition-metal chelates), supporting strong infringement mapping where a product matches species and regimen.
- Competitor design-around efforts should focus on moving outside claimed ligand classes and/or metal ranges, since counterion substitution alone is unlikely to escape the broad chelate-salt method framing.
FAQs
1) Does U.S. 4,647,447 cover gadolinium-based MRI contrast agents?
Yes. Multiple dependent claims explicitly recite gadolinium(III) DTPA salt variants (including N-methylglucamine and disodium forms) and Claim 24/26 cover lanthanides in atomic-number 57–70 with aminopolycarboxylate ligand classes. (Claims 5, 6, 12, 13, 16, 17, 23; Claims 24 and 26)
2) What metals are explicitly within the claimed scope?
Claim 1 covers atomic numbers 21–29, 42, 44, and 57–83. Claims 24–68 narrow to lanthanides 57–70 and transition metals 21–29, 42, 44. (Claim 1; Claim 24; Claim 26)
3) Are dosing and timing part of the independent claim scope?
Timing and dosing appear in dependent claims: administration about 15–60 minutes before tomography (Claim 27) and 1–100 μmol/kg IV (Claim 28). The independent method framework exists in Claim 24 and Claim 1 without those specific regimen parameters, but they increase risk for products matching clinical protocols. (Claims 1, 24, 27, 28)
4) Does the patent cover formulations beyond simple solutions?
Yes. Claim 18 includes liposomes charged with the gadolinium(III) complex of diethylenetriaminepentaacetic acid. (Claim 18)
5) Can counterion changes avoid the patent?
Counterion changes alone are unlikely to fully avoid scope because multiple claims require physiologically compatible salts and list many acceptable inorganic/organic base acids and bases including sodium and N-methylglucamine. Escape typically requires leaving the claimed ligand and/or metal spaces rather than only changing the pharmaceutically acceptable salt form. (Claims 32, 33; Claims 5–7, 12–17, 23; Claim 26)
References
[1] United States Patent 4,647,447, “Method for NMR diagnostic procedure using paramagnetic chelate salts,” claims as provided in user prompt.
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