Details for Patent: 5,962,016

Summary for Patent: 5,962,016

Title:	Multivesicular liposomes utilizing neutral lipids to modify in vivo release
Abstract:	The rate of release of encapsulated active compound from a multivesicular liposomal (MVL) formulation is modified by selection of a neutral lipid component. A family of MVL formulations containing different slow:fast release neutral lipid molar ratios display different release rates depending upon the molar ratio of the fast release neutral lipid to the slow release neutral lipid in each member. Incubation in plasma or a plasma-like medium at in vivo temperatures so as to obtain a release rate curve for each allows selection from among the members of the family of a liposomal formulation with a desired rate of release in vivo.
Inventor(s):	Randall C. Willis
Assignee:	Pacira Pharmaceuticals Inc
Application Number:	US08/974,296
Patent Claim Types: see list of patent claims	Use; Dosage form;

United States Patent 5,962,016 (Multivesicular Liposomes): Scope, Claim Coverage, and US Patent Landscape

US Patent 5,962,016 protects a specific multivesicular liposome architecture and composition for controlled release of a biologically active compound. The core claim scope is built around (i) a defined slow-release/fast-release neutral lipid pair and (ii) a defined amphipathic lipid plus aqueous encapsulation of the active. Dependent claims then narrow to neutral lipid melting points and specific molar-ratio windows, with a final method claim tied to administering the claimed liposome to achieve a desired release rate.

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What is US Patent 5,962,016 claiming and what is the practical scope of protection?

Answer: 5,962,016 claims a multivesicular liposome containing (1) a neutral lipid component defined by a slow-release neutral lipid selected from a named trio and (2) a fast-release neutral lipid selected from a named pair, mixed at specified molar ratios, plus an amphipathic lipid, with a biologically active compound encapsulated in water. A method claim covers administering that liposome to a subject to deliver the active at a desired release rate.

Claim 1: composition scope that drives infringement risk

Claim 1 is a three-part composition that must all be met for literal infringement:

1. Neutral lipid component

   • Contains slow-release neutral lipid selected from:
     • triolein
     • tripalmitolein
     • trimyristolien
     • trilaurin
     • tricaprin
     • mixtures of these
   • Contains fast-release neutral lipid selected from:
     • tricaprylin
     • tricaproin
     • mixtures of these
   • Slow:fast neutral lipid molar ratio must fall in:
     • about 1:1 to 1:100

2. Amphipathic lipid

   • Not specified in the claim text you provided; the claim requires that an amphipathic lipid is present. This is a key scope lever: it can be broad if the specification defines common candidates (e.g., phospholipids, sphingomyelin, cholesterol-containing systems), but the claim language you gave still requires an “amphipathic lipid” category.

3. Encapsulated biologically active compound in water

   • The active must be “encapsulated in water in the liposome,” meaning it sits in an aqueous compartment consistent with a multivesicular liposome.

Practical consequence: If a competitor uses a multivesicular liposome but substitutes neutral lipids outside the named slow/fast sets, it avoids Claim 1’s literal scope. If they remain within the named lipid sets but use slow:fast ratios outside 1:1 to 1:100, they also avoid literal coverage. If they are within that ratio range but use a different encapsulation format (e.g., active distributed in nonaqueous phases or surface conjugated only), they may avoid “encapsulated in water” limitations.

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Claim 2: melting point narrowing

Claim 2 limits Claim 1 by requiring:

• Melting point of the neutral lipid component is about or below 37°C.

This claim can be used as a “design-around detector.” If the neutral lipid mixture includes higher melting species or results in a neutral-lipid component melting behavior above 37°C, it may fall outside Claim 2 (but still potentially inside Claim 1).

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Claim 3: total lipid fraction limitation

Claim 3 limits Claim 1 by specifying:

• Molar ratio of neutral lipid component to all lipids in the liposome is about 0.01 to about 0.21.

This is a composition fraction constraint. Competitors with higher neutral lipid loading (or lower, depending on the effective meaning of “all lipids”) can reduce Claim 3 risk while still remaining inside Claim 1.

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Claims 4 and 5: tighter slow:fast ratio windows

Claim 4 narrows Claim 1 to:

• slow:fast neutral lipid = about 1:1 to 1:27

Claim 5 narrows further to:

• slow:fast neutral lipid = about 1:1 to 1:18

Claim hierarchy implication: Claims 4 and 5 are narrower than Claim 1. In litigation, the patentee can use Claim 1 broadly while also targeting Claim 4/5 if the accused formulation’s ratio is tighter.

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Claim 6: method-of-use framing tied to the composition

Claim 6 covers:

• A method for administering a biologically active compound at a desired release rate comprising administering the liposome of Claim 1 to a subject.

Practical consequence: This method claim likely tracks the composition directly. If the composition is outside Claim 1, Claim 6 generally collapses because it depends on administering the Claim 1 liposome.

Data point that matters: “desired release rate” is a functional recitation. Functional language can broaden interpretation, but because Claim 6 depends on Claim 1, structural limitations remain the dominant driver.

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How does the neutral lipid ratio define multivesicular liposome release behavior in Claim 1?

Answer: The slow:fast neutral lipid ratio (about 1:1 to 1:100) is the main controllable variable for the system’s release kinetics, with slow-release neutrals (triglycerides like triolein and related saturated analogues) paired against faster-release neutrals (tricaprylin/tricaproin).

Claim 1’s lipid sets: what is included and what is excluded

Included slow-release neutrals: triolein, tripalmitolein, trimyristolien, trilaurin, tricaprin (and mixtures).
Included fast-release neutrals: tricaprylin, tricaproin (and mixtures).

Excluded by omission: Any other neutral lipids (even if commonly used in lipid drug delivery) are not within the enumerated lists.

Ratio windowing strategy used by the patent

• Broadest window (Claim 1): 1:1 to 1:100
• Narrow windows (Claims 4/5):
  • up to 1:27
  • up to 1:18
• Total neutral lipid loading constraint (Claim 3): 0.01 to 0.21 molar fraction vs. all lipids

Design-around map (composition-level):

• Move outside slow lipid list
• Move outside fast lipid list
• Use slow:fast ratio above 1:100 (or below 1:1 depending on interpretation)
• Use total neutral lipid fraction outside 0.01 to 0.21
• Adjust melting behavior so neutral lipid component melting point is above 37°C (to avoid Claim 2)

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What formulations are covered: what counts as “multivesicular” and “amphipathic lipid”?

Answer: The claim text you provided requires a “multivesicular liposome” and at least one “amphipathic lipid,” but it does not specify which amphipathic lipids. That typically means breadth will be governed by the specification and the ordinary meaning of amphipathic lipid in the field.

Multivesicular liposome: infringement implications

To fall within the claim, the structure must be multivesicular, meaning it has multiple internal vesicles or compartments capable of encapsulating aqueous payloads. If an accused product is instead a unilamellar liposome, niosome, polymeric micelle, or solid lipid nanoparticle, Claim 1’s “multivesicular liposome” limitation becomes a gating issue.

Amphipathic lipid: breadth lever

Because Claim 1 does not enumerate amphipathic lipid species, the scope can be broad if the patent specification lists common phospholipids and lipid excipients. At the claim text level, an amphipathic lipid must be present; if an accused formulation is neutral-lipid-dominant with non-amphipathic surfactants, it may reduce literal risk.

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When does US Patent 5,962,016 lose exclusivity in the US and when do generic risks start?

Answer: Without the filing and priority data, and without the patent’s full bibliographic record, the exclusivity timeline cannot be calculated from the claim text alone. Nothing in the provided information includes filing/issue dates, USPTO status, term adjustments, or maintenance history.

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What prior art likely overlaps: how could novelty and obviousness attacks affect 5,962,016’s enforceability?

Answer: The claim’s novelty rests on the specific neutral-lipid pairing and ratio windows inside a multivesicular liposome with aqueous encapsulation. Without the specification’s details and the patent’s prosecution history (and without knowing the priority date), it is not possible to identify the actual cited references or map exact anticipation/obviousness patterns.

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What generic entry risks exist for products that use tricaprylin/tricaproin with triolein-based neutrals?

Answer: Risk is highest where an accused multivesicular liposome uses:

• slow neutral lipid from the enumerated set (e.g., triolein)
• fast neutral lipid from the enumerated set (tricaprylin and/or tricaproin)
• a slow:fast molar ratio within about 1:1 to 1:100
• amphipathic lipid present
• biologically active compound encapsulated in water
• and, depending on the specific product’s composition and melting behavior, potentially also meeting Claims 2–5 narrowing limits.

High-risk pattern (Claim 1 capture):
A controlled-release multivesicular liposome formulation built from triolein + tricaprylin (or tricaproin) within the ratio band.

Lower-risk patterns (common design-around levers):

• Replace triolein with an unlisted slow neutral lipid
• Replace tricaprylin/tricaproin with an unlisted fast neutral lipid
• Shift ratio outside the window
• Change the system type so payload is not aqueous-encapsulated in a multivesicular liposome

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What patent claims are most likely to be asserted: Claim 1 vs. Claims 2–5 vs. Claim 6?

Answer: Claim 1 is the most likely anchor in enforcement because it is the broadest and does not require the melting point constraint (Claim 2) or the neutral lipid fraction constraint (Claim 3) or the narrower ratio subranges (Claims 4–5). Claim 6 is likely asserted only if the accused formulation meets Claim 1.

Litigation posture inference from claim structure

• Patentee typically pleads all dependent claims once Claim 1 infringement is alleged, using them as alternative coverage if the defendant’s formulation details vary across products or lots.
• Claim 2–5 are composition-parameter claims that can be supported with formulation analytics (DSC for melting point, lipid quantitation for ratios, compositional fraction calculations).

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How strong is the patent estate around 5,962,016 for controlled-release multivesicular liposomes?

Answer: The scope you provided identifies a strong claim nucleus in lipid selection and ratio design. But the “patent estate strength” across related continuations, divisionals, family members, or other asserted patents cannot be established without the complete US family set, publication numbers, and claim sets beyond the single patent.

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What is the likely claim interpretation approach for the ratio and “about” terms?

Answer: The claim uses “about” for ratio endpoints and melting point, which generally invites a tolerance range around the numeric boundaries. The magnitude of tolerance is a factual/legal question driven by the specification’s definitions.

Ratio terms that will matter in claim construction

• “about 1:1 to 1:100”
• “about or below 37°C”
• “about 0.01 to about 0.21”
• “about 1:1 to 1:27”
• “about 1:1 to 1:18”

Consequence for analysis

Even small parameter shifts can decide whether the formulation “falls into” a claim range. For litigation, compositional measurement method and conversion rules (molar basis and “all lipids” definition) become central.

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How does this patent compare with typical multivesicular liposome patents: what is distinctive here?

Answer: Many multivesicular liposome patents focus on:

• manufacturing processes (spray drying, extrusion, sonication parameters),
• general multivesicular structures,
• broad lipid categories.

This patent’s claims are distinctive because they are compositionally constrained to specific slow and fast neutral lipid species with explicit molar ratio ranges and, in dependent claims, melting point and neutral lipid loading fraction.

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Key Takeaways

• US 5,962,016 protects multivesicular liposomes defined by a slow-release/fast-release neutral lipid pairing using enumerated triglyceride sets and a slow:fast molar ratio of about 1:1 to 1:100.
• The claims require an amphipathic lipid and a biologically active compound encapsulated in water.
• Dependent claims further narrow to:
  • neutral lipid component melting point about or ≤ 37°C (Claim 2),
  • neutral lipid fraction vs. all lipids 0.01 to 0.21 (Claim 3),
  • tighter slow:fast ratio windows up to 1:27 (Claim 4) and 1:18 (Claim 5).
• The method claim (Claim 6) is tied to administering the Claim 1 liposome to achieve a desired release rate.
• Without the patent’s bibliographic record and family data, exclusivity timelines and the broader US landscape cannot be quantified from the provided claim text alone.

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FAQs

1. Can a multivesicular liposome avoid infringement if it uses triolein but replaces tricaprylin/tricaproin with a different fast neutral lipid?
2. If a formulation’s slow:fast neutral lipid ratio is 1:28, does Claim 1 still apply even if it fails Claim 4?
3. How do “about” ranges on molar ratios and melting point typically affect infringement analyses for lipid formulations?
4. Is Claim 6 independently enforceable if the accused product is outside the exact composition limits of Claim 1?
5. What analytics are typically used to prove compliance with neutral lipid molar ratios, DSC melting point, and aqueous encapsulation in multivesicular liposomes?

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References

1. US Patent 5,962,016 (claim text provided in prompt).

Drugs Protected by US Patent 5,962,016

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 5,962,016

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Australia	6317898
Australia	731038
Canada	2277956
Canada	2564120