Details for Patent: 5,562,925

Summary for Patent: 5,562,925

Title:	Anti-tumor method
Abstract:	Malignant tumors in animals are treated by parenterally administering to an affected animal a solution containing a complex compound of platinum in an amount effective to cause regression of the tumor.
Inventor(s):	Barnett Rosenberg, Loretta VanCamp, Thomas Krigas
Assignee:	Research Corp Technologies Inc
Application Number:	US08/252,668
Patent Claim Types: see list of patent claims	Composition; Formulation;

US Patent 5,562,925: Scope, Claims, and US Patent Landscape for Inorganic Planar “DSP2” Pt(II) Coordination Complex Therapeutic Compositions

What does US 5,562,925 claim in plain terms?

US Patent 5,562,925 claims injectable therapeutic compositions where the active pharmaceutical species is an inorganic planar dsp2 platinum(II) coordination complex that is protected from light and administered in solution for therapy.

The claim set is composition-focused, not method-of-treatment-focused. It defines the platinum(II) coordination complex by:

• Geometry / bonding type: “inorganic planar dsp2 platinum (II) coordination complex” with donor ligands forming coordinate covalent bonds to Pt(II).
• Donor ligand set: one of Cl, Br, CN, NH3, OS, NO3, H2O, hydroxy, ethylene diamine, or propylene diamine.
• Configuration limitation (in dependent claims): cis configuration.
• Specific named complexes (in dependent claims):
  • cis chloroplatinumamine
  • cis-Pt(II)(NH3)2Cl2
  • Pt(II)(NH2CH2CH2NH2)Cl2 (Pt(II) with ethylenediamine ligand and two chlorides)

The independent claim uses “therapeutically effective amount” and requires light protection and injectable solution formulation.

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What is the claim-by-claim scope?

Claim 1: Independent composition claim

Core scope

• A therapeutic composition for injection.
• Contains a “therapeutically effective amount” of:
  • an inorganic planar dsp2 Pt(II) coordination complex
  • protected from light
  • suitable for therapeutic administration by injection in solution
• The complex has donor ligands limited to the listed set:
  • Cl, Br, CN, NH3, OS, NO3, H2O, hydroxy, ethylene diamine, propylene diamine
• Ligands are limited in function by the bonding relationship:
  • donor ligands form coordinate covalent bonds with Pt(II).

Practical breadth Claim 1 is broad on ligand selection (within the closed list) and broad on the “therapeutically effective amount” concept, but it is constrained by: 1) the coordination-complex identity through the “planar dsp2 Pt(II)” characterization, and
2) light protection as a compositional/formulation requirement, and
3) injection in solution.

Claim 2: Solubilization / formulation vehicle

• Adds that the platinum complex is dissolved in a:
  • stabilizing effective amount of a saline or buffer solution.

This narrows claim 1 to cases where there is a specific stabilization vehicle class.

Claim 3: Stereochemical limitation to cis

• Requires the Pt(II) complex be in the cis configuration.

This narrows claim 1 by geometry/stereochemistry.

Claim 4: Specific “cis chloroplatinumamine”

• Narrows claim 3 to:
  • cis chloroplatinumamine.

This is a brand-like/phrase-like intermediate specificity that likely maps to a known Pt(II) cis ammine dichloride-type species in the art.

Claim 5: Specific molecular identity cis-Pt(II)(NH3)2Cl2

• Narrows to:
  • cis-Pt(II)(NH3)2Cl2.

This is a high-confidence species level claim because the ligand set is explicit:

• two NH3 ligands and two Cl ligands on cis geometry around Pt(II).

Claim 6: Specific molecular identity Pt(II)(NH2CH2CH2NH2)Cl2

• Narrows to:
  • Pt(II)(NH2CH2CH2NH2)Cl2 (Pt(II) with ethylenediamine and two chlorides).

This is also species-level.

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Where does the claim language create enforceable boundaries?

The ligand list is closed, but the “dsp2 planar Pt(II)” language is a functional characterization

Claim 1 limits donor ligands to a defined set. That gives the patentee a clean argument against:

• other Pt(II) donor ligands not enumerated (even if they make similar complexes),
• or ligands that create different coordination environments.

At the same time, “planar dsp2” can become a contention point in validity and infringement because it is partly a technical characterization. In practice, enforcement will hinge on whether accused products contain a Pt(II) species that is both:

• within the listed donor ligand class, and
• consistent with the planar dsp2 coordination description.

“Protected from light” is a formulation limitation

Claim 1 requires the complex is protected from light. That means an accused product must do more than contain the right complex; it must include light-protection measures or be packaged/formulated such that the complex is protected from light.

Enforcement posture typically works best when an accused product uses explicit light-protective packaging and storage conditions, or uses formulation steps that qualify under the claim.

“Injection in solution” constrains route and physical form

Claim 1 requires suitability for therapeutic administration by injection in solution. That reduces risk to solid-state forms or non-injectable preparations.

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Scope map: what is included vs excluded (based on your claim text)

Included under the claim set (high likelihood)

• Pt(II) planar dsp2 cis complexes formed from the allowed donors, especially:
  • cis-Pt(II)(NH3)2Cl2
  • Pt(II) with ethylenediamine and chlorides (cis geometry implied through the cis-dependent chain in claims 3 to 6)
• Injectable aqueous formulations with:
  • saline or buffer stabilization (claim 2 dependent)
  • and light protection (claim 1 dependent)

Likely excluded

• Pt(II) complexes with donor ligands outside the listed set (e.g., non-enumerated amines, phosphines, heteroaryl ligands).
• Non-injectable compositions (implants, oral formulations).
• Solutions lacking light-protection measures where the accused product cannot credibly satisfy the “protected from light” limitation.
• Non-cis stereoisomers for the dependent claims; claim 1 itself is not limited to cis, but claims 3 to 6 are.

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How strong is the independent claim relative to the dependent species claims?

Claim 1 provides the entry point

• It is broad enough to cover multiple Pt(II) planar dsp2 complexes defined by donor ligand set and functional characteristics.
• It does not restrict to cis geometry.

Claims 3-6 create narrow anchors

• The dependent chain progressively narrows to:
  • cis configuration
  • then cis chloroplatinumamine
  • then explicit molecules: cis-Pt(II)(NH3)2Cl2 and Pt(II)(NH2CH2CH2NH2)Cl2

From a freedom-to-operate perspective, claims 5 and 6 can function as “species rails.” Even if a court construes “planar dsp2” narrowly, a species-specific claim tends to reduce technical ambiguity because the ligand set and stereochemistry are explicit.

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Patent landscape: what matters in US enforcement and competition

1) The likely competitive overlap is with the “cisplatin” chemical space and closely related Pt(II) coordination complexes

Within your claim set, the explicit structures cis-Pt(II)(NH3)2Cl2 and the ethylenediamine analog map directly to known platinum chemotherapy coordination complexes in the public domain and established clinical/industrial use.

That means the US patent landscape in this area typically includes:

• early filings on cisplatin-like coordination complexes,
• formulation patents focusing on stability, light sensitivity, and administration conditions,
• and later “generics” or process-driven patents that avoid composition claims or work under different claim structures.

2) Enforcement will turn on whether later products use the claimed complex and satisfy the “light protected injectable solution” limitation

A generic product can be chemically the same and still be exposed if:

• the product is formulated and packaged in a way that does not meet “protected from light” requirements as construed by the claim.

Conversely, a manufacturer can reduce risk by:

• using alternative platinum species (outside ligand list),
• using different stereochemical configurations for cis-specific claims,
• or demonstrating that the marketed composition is not a “planar dsp2 Pt(II) coordination complex” in a way that aligns with the claim language.

3) Likely patent families around formulation and stability

Claim 2’s “saline or buffer stabilizing effective amount” points to a typical formulation patent strategy in this field: protect the same drug substance via stability and delivery media.

That strategy creates a landscape where:

• substance-level claims (complex identity and configuration) matter for narrow dependent claims, and
• formulation and container/packaging matter for broader independent claims that include “light protected.”

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Claim scope vs standard competitive product design options

If a competitor uses cis-Pt(II)(NH3)2Cl2

• They land inside claim 5 (and also inside claim 3/4 chain through cis chloroplatinumamine depending on claim construction).
• They also likely satisfy the donor ligand list portion of claim 1 (Cl and NH3 only).

Primary design-around levers become:

• contesting “planar dsp2” characterization,
• changing formulation so that “protected from light” is not met as claimed,
• or avoiding an injectable solution form (hard in oncology use).

If a competitor uses ethylenediamine-chloride Pt(II) complex

• They land inside claim 6 by explicit structure.
• They still need to satisfy the cis configuration chain via claim dependencies.

If a competitor uses other donor ligands from the list

Claim 1 could cover additional ligand combinations from the allowed donor list, but only if:

• the complex remains a “planar dsp2 Pt(II) coordination complex,” and
• the complex is light-protected and suitable for injection in solution.

That narrows design-around compared with systems that allow open-ended ligand substitution.

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Actionable implications for diligence and IP positioning (US)

1) Freedom-to-operate focus should prioritize the dependent species claims

In litigation and licensing, claims 5 and 6 provide direct targets because they:

• explicitly state Pt(II) molecular complexes.
• reduce the need to litigate the full breadth of “dsp2 planar” characterization compared to claim 1.

2) Product development should document light-protection and container behavior

Because claim 1 requires the complex be “protected from light,” documentation typically becomes part of the evidentiary record:

• packaging material selection,
• protection during manufacturing and storage,
• labeling and storage requirements.

3) If pursuing a licensing or challenge strategy, the strongest leverage points are claim construction boundaries

The key leverage areas are:

• how “planar dsp2” is construed (technical definition vs generic coordination description),
• how “protected from light” is interpreted (absolute limitation vs practical condition),
• whether the accused composition is “injection in solution” as required.

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Key Takeaways

• US 5,562,925 is a composition claim for injectable, light-protected Pt(II) planar dsp2 coordination complexes built from a closed donor ligand list.
• The independent claim (1) is broad on donor ligands (from the enumerated set) and excludes only non-listed ligands, non-injectable forms, and unprotected-from-light compositions.
• The dependent claims narrow to:
  • cis configuration (claim 3),
  • then cis chloroplatinumamine (claim 4),
  • then explicit molecular identities: cis-Pt(II)(NH3)2Cl2 (claim 5) and Pt(II)(NH2CH2CH2NH2)Cl2 (claim 6).
• The practical competition risk in the US market clusters around cisplatin-like coordination species and formulation approaches that preserve light sensitivity and stability.

FAQs

What is the broadest scope claim in US 5,562,925?

Claim 1 covers injectable therapeutic compositions containing a light-protected planar dsp2 Pt(II) coordination complex with donor ligands limited to Cl, Br, CN, NH3, OS, NO3, H2O, hydroxy, ethylene diamine, or propylene diamine.

Does the patent cover only cis platinum complexes?

No. Claim 1 does not require “cis.” Claims 3-6 require cis configuration and then narrower species identities.

Which claims are the most species-specific?

Claims 5 and 6. Claim 5 is cis-Pt(II)(NH3)2Cl2, and claim 6 is Pt(II)(NH2CH2CH2NH2)Cl2.

What does “protected from light” limit?

It requires that the platinum complex in the therapeutic composition is protected from light as part of meeting the claim limitation, which affects formulation and packaging.

How does claim 2 narrow the composition?

Claim 2 adds that the Pt complex is dissolved in a stabilizing effective amount of a saline or buffer solution.

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References

1. US Patent 5,562,925, “Therapeutic compositions comprising planar dsp2 platinum (II) coordination complexes,” claims as provided in prompt.

Drugs Protected by US Patent 5,562,925

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate