US Patent 4,619,921: What Is Claimed, What the Scope Covers, and How It Sits in the US Landscape
US Patent 4,619,921 (“US 4,619,921”) is a US drug compound and composition patent built around a single, tightly defined steroidal entity and a narrow pharmaceutical-use claim around that entity. The granted claims provided are structurally simple: claim 1 defines the compound by a full IUPAC-style name and claim 2 limits scope to an anti-inflammatory composition that contains the claim 1 compound plus a pharmaceutically acceptable carrier.
What does claim 1 cover?
Claim 1 defines a specific compound:
- 21-chloro-6α,9α-difluoro-11β,17α-dihydroxy-16β-methyl-pregna-1,4-diene-3,20-dione 17-propionate
Key scope characteristics:
- Single-ingredient structural definition. The claim does not use genus language (no “comprising” for structure at the compound level, no Markush alternatives). It is a one-structure compound claim.
- Stereochemical precision. The α/β designations and the “dihydroxy” and “16β-methyl” and “17-propionate” substitutions lock the stereochemical configuration and functional group identity. That reduces design-around options because close analogs must preserve the entire stereochemical and substitution pattern.
- Functional group lock-in. The claim explicitly includes:
- 17α-dihydroxy and 17-propionate (the compound is esterified at 17, not a free hydroxyl at that position)
- 3,20-dione (pregnane core with ketones at 3 and 20)
- pregna-1,4-diene (double bond pattern)
- 21-chloro, 6α,9α-difluoro, and 11β substitution pattern.
Practical read-through for scope: If a competitor’s compound differs at any of the named positions (21-chloro vs 21-bromo; 6α/9α difluoro vs mono-fluoro; free 17-OH vs 17-propionate; loss or relocation of the 1,4-diene), it falls outside claim 1 as written.
What does claim 2 cover?
Claim 2 is a use and formulation claim:
- An anti-inflammatory pharmaceutical composition comprising
- an anti-inflammatory effective amount of the compound of claim 1
- and a pharmaceutically acceptable carrier
Key scope characteristics:
- Composition-level “comprising.” The carrier can include additional excipients, and the composition can be formulated with other inert materials as long as it includes the claim 1 compound in an anti-inflammatory effective amount.
- Use limitation sits in the function descriptor. The claim requires the composition to be for anti-inflammatory purposes via an effective amount, but it is not limited by route, dosage form, or a specific indication subtype.
- No limitation on formulation type. The claim text provided does not constrain to tablet, suspension, cream, injection, etc. In practice, “pharmaceutically acceptable carrier” is typically broad enough to cover multiple dosage forms.
Practical read-through for scope: Claim 2 is infringed by compositions that contain the exact claim 1 compound at a dose that produces anti-inflammatory effect, regardless of whether the product is oral, topical, or parenteral, unless another claim in the patent (not provided here) adds further limitations.
What is the scope of protection in the US system?
For US drug patents, practical infringement mapping for these two claims typically runs as follows:
-
Direct product infringement for the molecule
- Claim 1 covers the compound itself.
- A manufacturer making or selling the exact compound in the US is exposed under claim 1.
-
Product infringement for formulated drug products
- Claim 2 covers a composition containing the compound plus carrier.
- A finished dosage form product containing the exact compound at anti-inflammatory effective levels is exposed under claim 2.
-
Sales and manufacturing activities
- If a party practices the compound or sells it into the US, exposure attaches.
- For generic or reformulated versions, the claim set as given targets exact chemical identity for claim 1 and presence-in-formulation for claim 2.
How narrow or broad is this claim set? A scope yardstick
The provided claims are narrow in chemical scope and broad in formulation/use.
Chemical breadth
- Single structure only (claim 1). No generic steroid genus; no alternative substitutions.
- Stereochemical and functional group fixed. The claim name specifies:
- multiple halogens (chloro + difluoro)
- defined hydroxyl and ester positions
- double bond pattern
- pregnane core with specified oxidation states (dione).
Net result: claim 1 is among the more difficult-to-design-around forms, because even minor chemical changes can remove literal coverage.
Composition breadth
- Excipients unconstrained. Claim 2 does not specify carrier type or route.
- Therapeutic framing only. “Anti-inflammatory effective amount” does not impose a specific endpoint marker.
Net result: if the exact molecule is present, claim 2 can sweep widely across dosage forms.
Patent landscape in the US: where this kind of claim tends to land
A claim set structured like US 4,619,921 typically sits in a landscape pattern for steroid anti-inflammatory agents:
- Primary molecule patent (compound claim)
- Secondary formulation/use patent (composition for anti-inflammatory effect)
What other US patent layers usually surround a compound like this?
Even without additional claim text from the patent file history, the US landscape around steroid anti-inflammatory molecules commonly includes:
-
Later patents on formulations
- different salts/esters or alternative ester chain lengths
- alternate particle size, micronized forms, or depot formulations
- route-specific formulations (ophthalmic, topical, inhaled, injectable)
-
Later patents on combinations
- combinations with another anti-inflammatory agent
- combinations with corticosteroid-sparing agents or bronchodilators (route-dependent)
-
Process patents
- synthetic intermediates
- scalable routes and purification processes
-
Regulatory-linked patents
- if the molecule appears in an FDA-listed drug and later gets Orange Book listings, those listings often include method-of-use or formulation patents in addition to compound patents.
How US 4,619,921 claims constrain generics
If a generic applicant attempts to market a drug that uses the exact claim 1 compound:
- They must address compound coverage under claim 1.
- They must also address product-formulation coverage under claim 2.
If they switch to a close analog (different ester chain length, different fluorination pattern, different halogen at C-21):
- They may avoid literal coverage of claim 1, but they can face doctrine-of-equivalents arguments in some settings.
- From a pure claim construction standpoint, the explicit stereochemistry and the 17-propionate are the two most direct design-around pressure points.
Claim-to-product mapping checklist (infringement screening view)
Does a candidate infringe claim 1?
A candidate must match the compound exactly as written, including:
- steroid nucleus and unsaturation: “pregna-1,4-diene”
- halogens: “21-chloro” and “6α,9α-difluoro”
- stereochemistry: 6α, 9α, 11β, 17α, 16β
- functional groups:
- “11β…dihydroxy” pattern is specified as 17α-dihydroxy
- “3,20-dione”
- “17-propionate” esterification at 17
Any deviation at those named features is a literal non-match.
Does a candidate infringe claim 2?
A candidate formulation must:
- contain the claim 1 compound
- be dosed at an anti-inflammatory effective amount
- include a pharmaceutically acceptable carrier
- be sold or used for anti-inflammatory purposes (as framed by the claim)
Carrier type and dosage form are not limited in the claim text provided.
What is the most commercially relevant “scope boundary” in this patent?
The commercial boundary is the identity of the compound. Claim 2 follows claim 1.
In other words:
- If the product contains the exact 21-chloro-6α,9α-difluoro-11β,17α-dihydroxy-16β-methyl-pregna-1,4-diene-3,20-dione 17-propionate, claim 2 is also at risk.
- If the product swaps to a chemically different analog, claim 2 is avoided because it is dependent on claim 1.
Key Takeaways
- US 4,619,921 claim 1 is a single, stereochemically specified steroid compound with multiple halogens and a 17-propionate ester; it is narrow in chemical scope.
- Claim 2 is a composition claim that depends on claim 1 and covers anti-inflammatory formulations containing an anti-inflammatory effective amount of the claim 1 compound plus a pharmaceutically acceptable carrier, with no explicit dosage-form or route restriction in the provided text.
- Design-around focus sits on compound identity: altering halogen placement, stereochemistry, 1,4-diene pattern, oxidation state (3,20-dione), or the 17-propionate is the clearest literal boundary.
- Formulation freedom is broad once the molecule is present: claim 2 can cover multiple carriers and dosage forms.
FAQs
1) Can a different ester at C-17 avoid infringement of claim 2?
Yes, if the different ester means the product does not contain the exact claim 1 compound. Claim 2 depends on claim 1’s specific chemical identity.
2) Does claim 2 specify a route of administration?
No. Based on the claim text provided, it covers anti-inflammatory compositions with a pharmaceutically acceptable carrier without a route limitation.
3) Is claim 2 limited to one dosage form (tablet, injection, topical)?
No. The provided wording does not restrict dosage form or physical form of the carrier.
4) Does claim 1 include multiple possible compounds (Markush)?
No. Claim 1 identifies one specific compound by the full stereochemical and functional-group name.
5) What is the primary litigation hook for competitors?
Whether their product matches the exact chemical structure of claim 1. If it does, claim 2 typically follows because it is a dependent composition claim.
References
[1] United States Patent 4,619,921. Claims as provided by user: Claim 1 (compound) and Claim 2 (anti-inflammatory composition).
