Details for Patent: 4,497,744
Summary for Patent: 4,497,744
| Title: | Gentisic acid salts as radiographic scanning agent stabilizers | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Abstract: | Stable compositions, useful as technetium-99m-based scintigraphic agents, comprise gentisic acid or a pharmaceutically-acceptable salt or ester thereof in combination with a pertechnetate reducing agent or dissolved in pertechnetate-99m (99m TcO4 -) solution. The compositions are especially useful in combination with a phosphate or phosphonate material which carries the radionuclide to bone, thus providing a skeletal imaging agent. | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Inventor(s): | Mahdi B. Fawzi | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Assignee: | Mallinckrodt Inc , Malco Inc | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Application Number: | US06/202,962 | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
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Patent Claim Types: see list of patent claims | Compound; | |||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| Patent landscape, scope, and claims: | United States Patent 4,497,744: Claim Scope, Expiration, and Patent Landscape for Stannous Gentisate and Chromous GentisateU.S. Patent No. 4,497,744 contains two narrow composition claims directed to the discrete compounds stannous gentisate and chromous gentisate. The claims do not cover gentisic acid generally, other metal gentisates, pharmaceutical formulations, methods of treatment, manufacturing processes, or combinations with other active ingredients. Based on its 1985 issue date and the pre-1995 patent-term rules, the patent expired no later than February 5, 2002, absent an unusual term adjustment, extension, or terminal disclaimer. The claims therefore present no current U.S. blocking right. What compounds does U.S. Patent 4,497,744 claim?The patent claims two water-soluble metal salts or coordination compounds of gentisic acid:
Gentisic acid is 2,5-dihydroxybenzoic acid. A gentisate is the corresponding deprotonated anion, generally represented as C7H5O4− when one carboxylic proton is removed. The claims are product claims. They do not require a particular therapeutic use, dosage form, route of administration, purity level, manufacturing process, particle size, crystalline form, or formulation excipient. What does “stannous gentisate” mean?“Stannous” denotes tin in the +2 oxidation state. A conventional neutral salt representation would be:
The claim is directed to tin(II), not tin(IV). A stannic gentisate, if separately prepared, would not fall within claim 1 merely because it contains tin and gentisate. The claim may cover hydrates, solvates, or different solid-state forms if the material remains the claimed water-soluble compound. The scope would depend on whether the claimed identity is interpreted to include such forms and whether the form retains the relevant chemical composition. What does “chromous gentisate” mean?“Chromous” denotes chromium in the +2 oxidation state. A conventional neutral salt representation would be:
Chromium(II) compounds are generally sensitive to oxidation. A product that has materially converted to chromium(III) gentisate would raise a different infringement and identity question. Chromic gentisate, meaning chromium(III) gentisate, is not the compound expressly claimed in claim 2. How broad are the claims of U.S. Patent 4,497,744?The claims are chemically narrow but potentially direct. Each claim identifies one named compound and adds the qualification “water-soluble.” Claim-scope analysis
A commercial product could potentially fall within the claims even if it were sold for a different purpose from the patent’s disclosed use. Because the claims are composition claims, the relevant inquiry would be the identity and properties of the compound, not the seller’s stated indication. What compounds are outside the literal scope?The following materials would generally be outside the literal scope unless they contain or convert into the claimed compound:
A formulation containing the claimed compound could still implicate the claim. The presence of excipients, a carrier, a buffer, or a second active ingredient would not necessarily avoid infringement if the claimed compound is present in the accused product. When did U.S. Patent 4,497,744 expire?U.S. Patent 4,497,744 issued on February 5, 1985. For an application subject to the pre-Uruguay Round patent-term regime, the ordinary term was 17 years from issue. On that basis, the patent’s ordinary expiration date was February 5, 2002. [1][2]
The analysis assumes that no unusual patent-term adjustment, patent-term extension, terminal disclaimer, or other record event altered the ordinary expiration date. For a patent issued in 1985, modern 20-year-from-earliest-effective-filing rules generally do not displace the applicable pre-1995 term calculation. [2] An expired patent cannot support a current infringement action for post-expiration conduct. Its disclosure may still be relevant as prior art against later applications claiming the same compounds or closely related compositions. What does the patent claim about formulations and methods of use?Nothing in the two supplied claims expressly claims a formulation or method of use. Formulation patentsClaims 1 and 2 do not recite:
A later patent could attempt to claim one of those features, but it would need to satisfy novelty, nonobviousness, enablement, written-description, and other applicable requirements. The existence of U.S. Patent 4,497,744 would provide an earlier disclosure of the underlying active compound. Method-of-use patentsThe claims do not require treatment of a disease or any other use. They therefore do not create a patent right limited to a particular indication. Conversely, the patent cannot be used to establish exclusivity for a method of treating a disease unless the patent contains separate unprovided method claims. Any later method-of-use patent would face the ordinary prior-art and obviousness consequences of the earlier compound disclosure. A new therapeutic use could remain patentable in some circumstances, but that question would depend on the specific method claim and the evidence supporting it. What is the Orange Book status of stannous gentisate and chromous gentisate?The claims do not establish FDA approval, an approved drug product, or an Orange Book listing. The FDA Orange Book lists approved drug products and related patent and exclusivity information for products approved under the applicable drug-approval pathways. A historical composition patent does not automatically create an Orange Book entry. [3] No Paragraph IV analysis follows from the patent claims alone. Paragraph IV certifications apply to an abbreviated new drug application referencing an approved listed drug and challenging a patent listed for that drug. If no approved reference product and no listed patent exist, there is no ordinary Orange Book Paragraph IV dispute tied to U.S. Patent 4,497,744. [3][4] FDA regulatory statusThe compounds could theoretically be developed as small-molecule drug substances, but the patent claims do not show:
The compounds would be treated as small molecules, not biologics. Biosimilar legislation and the abbreviated pathway under section 351(k) of the Public Health Service Act would not apply. A generic pathway under section 505(j) could become relevant only if an approved reference product existed and the proposed product met the statutory requirements. [4][5] How does this patent affect generic launch risk?The patent itself presents no current launch barrier because it expired in 2002.
A company commercializing stannous gentisate or chromous gentisate today would still need to evaluate other rights, including later patents covering:
Those rights would be separate from the expired compound claims. What manufacturing and technical barriers remain?The patent claims are narrow, but the compounds may present practical development issues. Stannous gentisateTin(II) is susceptible to oxidation to tin(IV). A manufacturing process may need to control:
A later patent could attempt to protect a stabilizing system or a process that preserves the tin(II) state. Such a patent would need to claim more than the already disclosed compound. Chromous gentisateChromium(II) is also oxidation-sensitive and may convert to chromium(III). Development concerns may include:
These technical barriers are not themselves patent rights. They can, however, support process, formulation, or manufacturing patents if a later applicant develops a novel and nonobvious solution. How strong is the patent estate for these compounds?The estate represented by U.S. Patent 4,497,744 is narrow and expired.
During its term, the patent could have been valuable if either compound had entered commercial development, because a direct composition claim is easier to map to a product than a process or use claim. Its commercial value was limited by the absence, in the supplied claims, of formulation, indication, and manufacturing protection. Which companies are challenging U.S. Patent 4,497,744?No current Paragraph IV challenger is implicated by the supplied claims. The patent expired before the modern commercial dispute would ordinarily arise, and the claims do not establish that either compound was the subject of an approved reference drug. The absence of a current Paragraph IV dispute does not exclude historical litigation or later disputes involving related compounds. It means only that this patent does not present a current Orange Book-based challenge pathway on the available claim record. What licensing deals or settlements involve the patent?The claims supplied do not identify any license, assignment, covenant not to sue, settlement, or consent judgment. An expired patent can remain relevant to historical licensing or ownership analysis, but no such transaction should be inferred from the claim language. Any current freedom-to-operate review should distinguish:
How does U.S. Patent 4,497,744 compare with later patent strategies?The patent uses the simplest protection strategy: claim the chemical entity itself. Later pharmaceutical patent programs commonly layer protection across the product lifecycle.
The patent’s compound claims would have been the foundational layer. Because that layer expired and no additional claims are supplied, current commercial protection would need to come from later patents or non-patent rights. Key Takeaways
FAQsAre stannous gentisate and chromous gentisate the same compound?No. Stannous gentisate contains tin(II), while chromous gentisate contains chromium(II). They are distinct chemical entities covered by separate claims. Does U.S. Patent 4,497,744 cover stannic gentisate?Not on the face of the supplied claims. “Stannous” identifies tin(II), while “stannic” ordinarily identifies tin(IV). Does the patent cover sodium gentisate or potassium gentisate?No. The claims specify tin(II) and chromium(II). Alkali-metal gentisates are different compounds. Can an expired composition patent still be cited against a later patent application?Yes. Expiration ends enforceability, but the patent disclosure may remain prior art against later claims, subject to the applicable filing dates and prior-art rules. Would an oxidation-stabilized formulation necessarily infringe the expired patent?The expired patent cannot support a current infringement claim. A later stabilized formulation may have implicated the compound claims during the patent term if it contained the claimed compound, but any current legal analysis would focus on separate, unexpired rights. References
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Drugs Protected by US Patent 4,497,744
| Applicant | Tradename | Generic Name | Dosage | NDA | Approval Date | TE | Type | RLD | RS | Patent No. | Patent Expiration | Product | Substance | Delist Req. | Patented / Exclusive Use | Submissiondate |
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| >Applicant | >Tradename | >Generic Name | >Dosage | >NDA | >Approval Date | >TE | >Type | >RLD | >RS | >Patent No. | >Patent Expiration | >Product | >Substance | >Delist Req. | >Patented / Exclusive Use | >Submissiondate |
International Family Members for US Patent 4,497,744
| Country | Patent Number | Estimated Expiration | Supplementary Protection Certificate | SPC Country | SPC Expiration |
|---|---|---|---|---|---|
| Australia | 4559579 | ⤷ Start Trial | |||
| Australia | 537689 | ⤷ Start Trial | |||
| Canada | 1122524 | ⤷ Start Trial | |||
| Germany | 2960805 | ⤷ Start Trial | |||
| Denmark | 133979 | ⤷ Start Trial | |||
| Denmark | 156411 | ⤷ Start Trial | |||
| >Country | >Patent Number | >Estimated Expiration | >Supplementary Protection Certificate | >SPC Country | >SPC Expiration |
