Details for Patent: 6,071,534

Summary for Patent: 6,071,534

Title:	Multivesicular liposomes with controlled release of active agents encapsulated in the presence of a hydrochloride
Abstract:	Disclosed are multivesicular liposomes containing biologically active substances, and having defined size distribution, adjustable average size, adjustable internal chamber size and number, and a modulated release of the biologically active substance. The liposomes are made by a process comprising dissolving a lipid component in volatile organic solvents, adding an immiscible aqueous component containing at least one biologically active substance to be encapsulated, and adding to either or both the organic solvents and the lipid component, a hydrochloride effective to control the release rate of the biologically active substance from the multivesicular liposome. A water-in-oil emulsion is made from the two components, the emulsion is immersed into a second aqueous component, and then divided into small solvent spherules which contain even smaller aqueous chambers. The solvents arc finally removed to give an aqueous suspension of multivesicular liposomes encapsulating biologically active substances.
Inventor(s):	Sinil Kim, Stephen B. Howell
Assignee:	Pacira Pharmaceuticals Inc
Application Number:	US09/019,337
Patent Claim Types: see list of patent claims	Process; Device; Dosage form;

US Patent 6,071,534 Multivesicular Liposomes with Hydrohalide-Modeled Release: Claim Scope and US Patent Landscape

US 6,071,534 claims a multivesicular liposome (MVL) architecture built via a water-in-oil emulsion that contains a specified hydrohalide (hydrochloride salts) at a defined concentration range, with the hydrohalide concentration used to modulate in vivo release of an incorporated biologically active substance. Claim scope is dominated by (i) the MVL structure (multiple non-concentric chambers/membranes in a matrix), (ii) the two-immiscible phase emulsion composition and solvent system, and (iii) the presence and concentration of the hydrochloride salt in the emulsion to tune release.

The dependent claims materially narrow lipid classes (zwitterionic/cationic/anionic amphipathic lipids, phospholipids, specified neutral lipids) and provide exemplars of active substances, including cytarabine, opioid analgesics, leuprolide, nucleic acids, interleukin-2, and others.

What patents protect multivesicular liposomes made by hydrohalide-modulated water-in-oil emulsions like US 6,071,534?

Direct protection from US 6,071,534 covers the specific MVL manufacturing scheme and the hydrohalide concentration-based release modulation, independent of the specific therapeutic payload. The active ingredient is broad, including many therapeutic classes, with explicit examples that strengthen enablement and litigation defensibility for those embodiments.

Key protective “pillars” in the claim set

1. MVL structure requirement: multiple non-concentric chambers with membranes distributed in a matrix.
2. Two-immiscible-component formulation:
   • lipid component includes at least one organic solvent, at least one amphipathic lipid, and a neutral lipid lacking a hydrophilic head group.
   • first aqueous component is one phase of the W/O emulsion.
3. Hydrochloride salt in the W/O emulsion:
   • hydrochloride selected from HCl, arginine hydrochloride, histidine hydrochloride, lysine hydrochloride, pyridine hydrochloride, or combinations.
   • concentration range: ~10 mM to ~500 mM.
4. Payload loading and placement:
   • biologically active substance and hydrochloride are independently incorporated into either the lipid component, aqueous component, or both.
5. Solvent-spherule formation + solvent removal:
   • disperse the W/O emulsion containing hydrohalide into a second aqueous component to form solvent spherules.
   • remove organic solvent to form MVL suspended in the second aqueous component.
6. Functional limitation tied to hydrohalide concentration:
   • hydrohalide concentration is “chosen to modulate the in vivo release rate” of the biologically active substance.

H3: What does “multiple non-concentric chambers” do to infringement scope?

This phrase narrows the target product beyond generic “multivesicular” liposomes that may be concentric lamellae or vesicles with different morphology. It focuses on an MVL morphology where chambers are not concentric.

Practical effect: product-by-process or morphology-based proof becomes central. If a competitor’s MVL is formed by a different templating method (eg, layer-by-layer deposition, spray drying with rehydration, thin-film hydration with subsequent phase separation) that yields concentric or differently arranged chambers, it can avoid the structural limitation even if it uses a similar W/O emulsion concept.

H3: What is the “matrix” limitation?

Membranes distributed in a matrix links the structural organization to a continuous scaffold-like arrangement of membranes and compartments, not merely a set of separate vesicles. This again makes morphology and microscopy-based comparatives relevant.

---

Which steps in claim 1 define the manufacturing process and are most infringement-sensitive?

Independent claim 1 is process-centric and product-constrained. The manufacturing steps are not ornamental; they are integral to the “multivesicular liposome produced by a process comprising steps of…”.

H3: Step (a) forming the water-in-oil emulsion

• Two immiscible components:
  1. lipid component: organic solvent(s) + amphipathic lipid(s) + neutral lipid(s) without hydrophilic head group
  2. first aqueous component
• The W/O emulsion contains:
  • hydrochloride (specified salts) at 10–500 mM
  • at least one biologically active substance
• Hydrochloride and drug can be in lipid phase, aqueous phase, or both.

Infringement sensitivity: if a competitor uses a different salt family (eg, bromides, acetates) or omits the hydrohalide entirely, claim 1 is hard to meet. If they use the salt outside the 10–500 mM window, the literal match also fails.

H3: Step (b) dispersing into second aqueous component to form solvent spherules

This step is tied to solvent-spherule formation. Many MVL approaches use double emulsions (W1/O/W2), while others use homogenization and solvent evaporation differently. The claim’s language requires dispersing the W/O emulsion containing hydrochloride into a second aqueous component to form solvent spherules.

Infringement sensitivity: alternate templating that does not form “solvent spherules” as described can create non-infringing design space.

H3: Step (c) removing organic solvent to form MVLs

The solvent removal step defines how the solvent-spherules become MVLs. Competitors can attempt to use different solvent-removal kinetics (dialysis vs evaporation) or different solvent systems. The independent claim still requires solvent removal to form MVLs; dependent claims enumerate typical removal methods (sparging, rotary evaporation, passing gas).

---

How does the hydrohalide concentration “modulate release” shape the claim’s functional scope?

The claim includes a functional requirement: hydrohalide concentration in the W/O emulsion is “chosen to modulate the in vivo release rate.”

H3: What does this mean for literal vs design-around?

• Literal infringement typically requires that the competitor uses the claimed salt(s) at 10–500 mM in the W/O emulsion.
• The “chosen to modulate” language ties the concentration to release behavior. If a product uses the same formulation but does not tune release via hydrohalide concentration (eg, salt is incidental or unintended), plaintiffs may still argue that the concentration choice implies intended modulation. Defendants can argue the functional hook is not met if release modulation is not attributable to hydrohalide concentration.

In practice, the most direct design-around is salt selection (avoid the specified hydrochloride salts), salt placement (only in the second aqueous phase, not in W/O), and concentration (outside 10–500 mM). Morphology deviations also matter (non-concentric chambers limitation).

---

What lipid and solvent combinations are explicitly claimed in dependent claims?

Dependent claims tighten lipid and solvent parameters that can strongly influence freedom-to-operate for “MVL hydrohalide release modulation” platforms.

H3: Amphipathic lipid classes (claims 4–6)

• At least one zwitterionic amphipathic lipid
• or at least one cationic amphipathic lipid
• or at least one anionic amphipathic lipid

H3: Amphipathic lipid as phospholipids (claims 7–8)

If phospholipids are used, claim 7 requires the phospholipid set and claim 8 lists examples:

• phosphatidylcholine
• cardiolipin
• phosphatidylethanolamine
• sphingomyelin
• lysophosphatidylcholine
• phosphatidylserine
• phosphatidylinositol
• phosphatidylglycerol
• phosphatidic acid

H3: Neutral lipids lacking hydrophilic head groups (claims 12–17)

Dependent claims enumerate neutral lipid options:

• triglycerides (examples include triolein, tripalmitolein, trimyristolein, trilinolein, tributyrin, tricaproin, tricaprylin, tricaprin, trilaurin)
• diglycerides (diolein, dipalmitolein)
• propylene glycol ester (mixed diesters of caprylic and capric acids)

Design-around relevance: competitors using substantially different neutral lipid structures outside these classes might avoid dependent claim coverage, but would still potentially fall under claim 1 if their neutral lipid meets “lacking a hydrophilic head group” and the rest of claim 1 is met.

H3: Organic solvent categories (claim 18)

Organic solvent is selected from ethers, hydrocarbons, esters, or combinations.

---

What “biologically active substance” scope exists, and where do the examples narrow?

Claim 1 broadly covers “biologically active substance” and the dependent claims provide specific exemplars.

H3: Broad enumerated therapeutic classes (claim 39)

The claim lists an extensive class range spanning anesthetics, antiasthmatics, cardiac glycosides, antihypertensives, nucleic acids, antibiotics, vaccines, antiarrhythmics, antiangina, hormones, antidiabetics, antineoplastics, immunomodulators, antifungals, tranquilizers, steroids, sedatives, analgesics, vasopressors, antivirals, herbicides, pesticides, proteins, peptides, neurotransmitters, radionuclides, and combinations.

This enumeration is used to support breadth and reduce plausibility challenges for diverse payloads.

H3: Specific drug/product examples (claims 23–32, 35–37)

Examples include:

• cytarabine (23)
• morphine (24)
• hydromorphone (25)
• leuprolide (26)
• nucleic acid (27)
• interleukin-2 (28)
• amikacin (29)
• G-CSF (30)
• insulin (31)
• hepatitis B vaccine (32)
• α-interferon (35)
• methotrexate (36)
• GM-CSF (37)

Infringement relevance: even though claim 1 is broad, these examples can guide claim construction toward MVL delivery of these classes through hydrohalide-tuned release, strengthening arguments that the patent is applicable to liposomal delivery programs using the specified architecture.

---

What do claim 2–3 add about hydrochloride selection?

• Claim 2 limits hydrochloride to hydrochloric acid.
• Claim 3 limits hydrochloride to lysine hydrochloride, histidine hydrochloride, arginine hydrochloride, and combinations.

These dependent claims create clear sub-ranges:

• HCl-only embodiment (claim 2)
• amino-acid hydrochlorides set (claim 3)

If a competitor uses pyridine hydrochloride (included in claim 1 but not in claim 2 or 3), they still potentially infringe claim 1 but would not meet these narrower dependent claims.

---

What do claims 20–22 add about formation and solvent removal methods?

These are procedural sub-elements that can matter for infringement if a competitor uses different hardware or a different process sequence.

• Emulsification of W/O: mechanical agitation, ultrasonic energy, nozzle atomization (20)
• Formation of solvent spherules: mechanical agitation, ultrasonic energy, nozzle atomization, combinations (21)
• Solvent removal: sparging, rotary evaporation, passing gas over solvent spherules, combinations (22)

If a competitor uses supercritical drying, lyophilization of solvent-spherules without the same solvent removal mode, or an alternative solvent-extraction workflow, dependent claims 20–22 may be avoided, while claim 1 may still be met depending on whether the core steps and outcomes align with solvent-spherules and solvent removal required by claim 1.

---

How do the dependent claims about payload placement change the scope?

• Claim 11: lipophilic biologically active substance incorporated into lipid component.
• Claim 19: hydrophilic biologically active substance incorporated into first aqueous component.

These can be used by plaintiffs to narrow to common drug-loading patterns. Competitors can argue non-infringement for these dependent claims by altering loading distribution (eg, lipophilic drug primarily in aqueous, hydrophilic drug in lipid) while still potentially infringing claim 1.

---

US Patent 6,071,534 Landscape: likely adjacent IP risks and infringement pathways

The document title and claim content show an MVL platform defined by hydrohalide-in-W/O at 10–500 mM to tune in vivo release. This tends to intersect with several other patent families that companies typically file around MVLs:

1. MVL formation methods using W/O emulsion and solvent evaporation.
2. MVL morphology control (non-concentric chamber architecture).
3. Lipid composition variations (ionizable lipids, phospholipids vs neutral lipids).
4. Drug loading and stabilization strategies (pH gradients, ion-pairing, salt forms).
5. Controlled release tuning via trapped salts, buffers, or osmotic agents.

Where are the likely “most dangerous” competitor design choices?

Based on claim structure, high-risk convergence points are:

• using the same hydrochloride salt group (HCl, arginine/lysine/histidine hydrochlorides, pyridine hydrochloride)
• using the 10–500 mM concentration in the W/O emulsion
• using W/O to generate solvent-spherules in a second aqueous component
• producing MVLs by removing the organic solvent from solvent spherules
• targeting non-concentric chamber MVL architecture
• loading diverse payloads where hydrohalide modulates in vivo release

A competitor who changes only the payload (eg, swapping cytarabine for insulin) while maintaining the MVL/hydrochloride/release mechanism likely remains within claim 1’s broad “biologically active substance” scope.

What design-around levers are structurally built into the claim language?

The claim provides multiple literal “escape hatches”:

• Hydrochloride salt selection: use a non-covered counterion or non-covered salt.
• Concentration: operate outside 10–500 mM in the W/O.
• Placement: ensure the hydrochloride is not present in the W/O emulsion as required (since claim 1 ties hydrohalide in the W/O emulsion).
• Architecture: avoid non-concentric chamber/matrix distribution, using different MVL structural formation routes.
• Process: avoid solvent-spherule formation as described, or use a fundamentally different solvent-removal workflow that does not form MVLs from solvent-spherules.

---

Orange Book status, Paragraph IV, biosimilar risk, and FDA exclusivity

US 6,071,534 is a drug-delivery technology patent directed to liposomes and is not tied to a single FDA NDA/BLA in the provided information. No Orange Book listing, Paragraph IV certification, or biologics exclusivity linkage can be determined from the claim text alone. The risk profile will be driven by whether any marketed product uses an MVL manufacturing scheme with hydrohalide-in-W/O tuned release matching claim 1’s constraints.

No reliable FDA regulatory status, exclusivity windows, or generic/biosimilar litigation timelines can be constructed from the information provided.

---

Patent estate strength for MVL hydrohalide-modulated release: how strong is claim 1?

Strength drivers

• Clear, mechanically anchored manufacturing steps.
• Specific salt list and concentration window (10–500 mM).
• Explicit MVL architecture language (multiple non-concentric chambers).
• Broad payload scope that can capture multiple product lines under one process umbrella.

Vulnerabilities

• Functional language (“chosen to modulate in vivo release rate”) can be contested if accused products show that release tuning is driven by other variables or that salt concentration is incidental.
• Architecture limitations can be evaded by producing different MVL morphology.
• Dependent claims constrain lipid choices, so a competitor can potentially fall outside dependent claim coverage even if claim 1 still captures them.

---

Litigation posture and settlement-driven design changes

No litigation docket, enforcement timeline, or settlement agreement information is included in the provided record. Without that, no accurate inference about which companies are challenging or being challenged can be made.

---

Key Takeaways

• US 6,071,534 is built around a specific MVL manufacturing concept: W/O emulsion formation containing hydrochloride salts at 10–500 mM, dispersing into a second aqueous phase to form solvent spherules, then removing solvent to yield multivesicular liposomes with multiple non-concentric chambers.
• Claim 1’s main capture range is the combination of (i) MVL structure, (ii) hydrohalide identity and concentration, and (iii) the solvent-spherule/solvent removal process sequence.
• Dependent claims add enforceability hooks on lipid class (zwitterionic/cationic/anionic, phospholipids), neutral lipid exemplars, solvent categories, and specific drug payload examples.
• The most direct design-arounds are changing the hydrochloride salt family, moving outside 10–500 mM, altering salt placement relative to the W/O emulsion requirement, and producing a different MVL chamber architecture that avoids “multiple non-concentric chambers” in a matrix.

---

FAQs

1. What hydrohalide salts are covered in US 6,071,534 and how does the 10–500 mM range affect infringement?
2. Does US 6,071,534 cover multivesicular liposomes where the hydrochloride is added only after emulsification?
3. Which lipid components are most likely to trigger dependent claim coverage under the phospholipid and neutral lipid lists?
4. Can competitors avoid infringement by changing solvent removal method from rotary evaporation to dialysis?
5. How do the explicit payload examples (cytarabine, insulin, leuprolide, G-CSF) influence claim construction for broader “biologically active substances”?

---

References (APA)

1. United States Patent 6,071,534. (n.d.). Multivesicular liposomes having multiple non-concentric chambers with membranes distributed in a matrix produced by a process comprising hydrohalide concentration modulation of release.

Drugs Protected by US Patent 6,071,534

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 6,071,534

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	87823
Australia	1205588
Australia	602190
Canada	1323568