United States Patent 4,997,651 (Melphalan Freeze-Dried Formulation + Citrate/Propylene Glycol/Ethanol Solvent Diluent)
Summary: US Patent 4,997,651 claims a melphalan pharmaceutical product built from two separately packaged components: (a) freeze-dried melphalan hydrochloride and (b) a solvent-diluent made from a citrate + propylene glycol + ethanol, plus dependent claim limitations covering matrix-forming excipients, citrate identity, dilution composition ranges, unit-dose sizing, and specific preparation routes for melphalan hydrochloride.
What is claimed in the core independent claim set?
Claim 1: Two-component formulation architecture
Claim 1 defines “a pharmaceutical formulation of melphalan” comprising two separate components:
- (a) freeze-dried melphalan hydrochloride
- (b) a solvent-diluent comprising:
- citrate
- propylene glycol
- ethanol
The claim is structural and compositional, with the critical technical point being the two-component system (freeze-dried API salt plus a specific solvent-diluent system).
Claim 5: Preparation method aligned to Claim 1
Claim 5 claims a corresponding preparation method:
- Formulate as two separate components:
- freeze-dried melphalan hydrochloride
- solvent-diluent containing citrate, propylene glycol, ethanol
What do the dependent claims add to scope?
Matrix-forming excipient (Claims 2-3, 9)
- Claim 2: Component (a) includes a non-hydroxylated matrix-forming agent
- Claim 3: The non-hydroxylated matrix-forming agent is polyvinylpyrrolidone (PVP)
- Claim 9: Matrix-forming agent constitutes 20-95% by weight of component (a)
Scope impact: These claims lock in excipient type (non-hydroxylated; PVP specifically in Claim 3) and a broad but bounded loading range (20% to 95% of the freeze-dried component).
Citrate identity (Claims 4, 10)
- Claim 4: Citrate is an alkali metal citrate
- Claim 10: Alkali metal citrate is sodium or potassium citrate
Scope impact: These limitations narrow citrate to alkali metal species and specify the two common salts. Formulations using e.g., ammonium citrate would fall outside these explicit dependents, though Claim 1 still requires only “a citrate” without stating alkali metal in the independent.
Solvent-diluent composition ranges (Claims 11-13)
- Claim 11: Component (b) contains 40-80% by volume propylene glycol
- Claim 12: Component (b) contains 0.1-10% by volume ethanol
- Claim 13: Component (b) contains 0.05-5% w/v citrate
Scope impact: These are quantitative carve-outs that strongly govern “infringement by formulation design.” A competitor can design around by moving propylene glycol, ethanol, or citrate outside the specified ranges.
Unit dose size examples/bounds (Claims 14-16)
- Claim 14: Unit dose contains:
- 1-100 mg melphalan
- 1-50 mL solvent-diluent
- Claim 15: 10 mg melphalan and 10 mL solvent-diluent
- Claim 16: 50 mg melphalan and 10 mL solvent-diluent
Scope impact: Claim 14 sets broad therapeutic dosing windows for the product unit, and Claims 15-16 provide specific compositions. If a competitor uses a unit dose with melphalan amount and diluent volume outside the bounds, it may avoid these dependents, while Claim 1 still covers formulation architecture.
How do the claims treat preparation of melphalan hydrochloride?
“Substantially pure” melphalan hydrochloride (Claims 6-8)
-
Claim 6: Melphalan hydrochloride is in substantially pure form
-
Claim 7: Substantially pure melphalan hydrochloride is prepared by:
- Heating a mixture of melphalan and hydrogen chloride in a C2-4 alkanol for up to five minutes
- Cooling to crystallize melphalan hydrochloride
-
Claim 8: Melphalan hydrochloride prepared by:
- Reacting ethyl N-phthaloyl-p-amino-L-phenylalnine (or an acid addition salt thereof) with ethylene oxide
- Reaction temperature does not exceed 35° C.
- Followed by chlorination and hydrolysis
- Conversion into hydrochloride salt
Scope impact: These dependents cover specific manufacturing routes to obtain substantially pure melphalan hydrochloride. If a competitor uses different preparation chemistry to produce the salt, dependents 7 and 8 may not read on their process. But Claim 1 can still read on the end product if it is “freeze-dried melphalan hydrochloride,” regardless of how it is made.
What is the likely claim “center of gravity” for infringement risk?
In practical design-around and freedom-to-operate assessment, the enforceable bottleneck is the intersection of:
- Freeze-dried melphalan hydrochloride as component (a), and
- A solvent-diluent with citrate + propylene glycol + ethanol as component (b)
Dependent claim risk pivots further on:
- PVP as matrix-former (Claim 3) and the 20-95% by-weight loading (Claim 9)
- Sodium/potassium citrate (Claims 4, 10)
- Quantitative ranges for propylene glycol (40-80% v/v), ethanol (0.1-10% v/v), citrate (0.05-5% w/v) (Claims 11-13)
- Unit-dose bounds (Claims 14-16)
- Any manufacturing steps if process infringement theories are used (Claims 5, 7, 8)
Detailed scope mapping: claim-by-claim claim elements and boundaries
| Claim |
Key element |
Specific limits in the claim |
| 1 |
Product architecture |
Two separate components: (a) freeze-dried melphalan HCl; (b) solvent-diluent with citrate + propylene glycol + ethanol |
| 2 |
Excipient type |
Component (a) includes non-hydroxylated matrix-forming agent |
| 3 |
Excipient identity |
Non-hydroxylated matrix-forming agent = polyvinylpyrrolidone |
| 4 |
Citrate type |
Citrate is alkali metal citrate |
| 5 |
Preparation method |
Formulate as two separate components: freeze-dried melphalan HCl + citrate/propylene glycol/ethanol solvent-diluent |
| 6 |
API purity |
Melphalan HCl is substantially pure |
| 7 |
Preparation route |
HCl + melphalan in C2-4 alkanol, heat up to 5 min; cool to crystallize |
| 8 |
Alternate route |
Ethylene oxide reaction temp <= 35°C; then chlorination and hydrolysis; form hydrochloride |
| 9 |
Excipient loading |
Matrix-forming agent is 20-95% by weight of component (a) |
| 10 |
Citrate salt |
Sodium or potassium citrate |
| 11 |
Diluent propylene glycol range |
40-80% by volume |
| 12 |
Diluent ethanol range |
0.1-10% by volume |
| 13 |
Diluent citrate range |
0.05-5% w/v |
| 14 |
Unit dose bounds |
1-100 mg melphalan; 1-50 mL solvent-diluent |
| 15 |
Example dosing |
10 mg melphalan + 10 mL solvent-diluent |
| 16 |
Example dosing |
50 mg melphalan + 10 mL solvent-diluent |
What does the claim set imply about patent landscape boundaries?
1) Tight “formulation” differentiator vs. broad “API salt + freeze-dry”
The formulation architecture is specific: the system is defined not merely by freeze-dried melphalan hydrochloride but by pairing it with a particular solvent-diluent chemistry (citrate + propylene glycol + ethanol). This narrows the set of competing products that can land within the claim coverage.
2) Quantitative ranges create design-around levers
Claims 11-13 provide direct formulation levers:
- Move propylene glycol outside 40-80% v/v
- Move ethanol outside 0.1-10% v/v
- Move citrate outside 0.05-5% w/v
3) Excipient and citrate selection further narrow dependent coverage
Even where Claim 1 is broad on “citrate,” dependents constrain to:
- alkali metal citrate (Claim 4)
- sodium or potassium (Claim 10)
- PVP (Claim 3)
- non-hydroxylated matrix-forming agent (Claim 2)
4) Process claims shift infringement risk only if matching manufacturing steps are used
Claims 5, 7, and 8 can matter if a competitor’s manufacturing and process documentation aligns with the claimed sequences and conditions (notably Claim 7’s short HCl conversion in C2-4 alkanol and Claim 8’s reaction temp limit of 35°C before further transformations).
Claim coverage “design around” checklist based on the wording
A product would most clearly avoid overlapping the strongest dependents by changing one or more of the following:
- Replace ethanol or adjust ethanol level outside 0.1-10% v/v (Claim 12)
- Adjust propylene glycol level outside 40-80% v/v (Claim 11)
- Adjust citrate concentration outside 0.05-5% w/v (Claim 13)
- Use citrate salt other than sodium/potassium if relying on Claim 4/10 avoidance (Claims 4, 10)
- Avoid PVP as the non-hydroxylated matrix-forming agent if targeting Claims 2-3-9 (Claims 2, 3, 9)
- Use different freeze-dried component (a) composition such that the matrix-former is not 20-95% by weight of component (a) (Claim 9)
Key Takeaways
- Core claim scope: A two-component melphalan system with freeze-dried melphalan hydrochloride plus a solvent-diluent containing citrate + propylene glycol + ethanol.
- Highest-impact quantitative boundaries are in Claims 11-13: propylene glycol (40-80% v/v), ethanol (0.1-10% v/v), citrate (0.05-5% w/v).
- Major dependent narrowing comes from:
- PVP as matrix-former (Claims 2-3) at 20-95% by weight of component (a) (Claim 9)
- sodium/potassium citrate (Claims 4, 10)
- Process scope exists through Claims 5, 7, 8, but the end-product composition defined by Claim 1 is the primary infringement pathway for formulation competitors.
FAQs
1) Does Claim 1 require that the solvent-diluent be a fixed ratio?
Yes, Claim 1 requires the solvent-diluent to comprise citrate + propylene glycol + ethanol, and later dependents set the quantitative ranges for each component (Claims 11-13).
2) Is PVP mandatory for infringement?
No. PVP is only required if the claim depends on Claim 3 (and non-hydroxylated matrix-forming agent is required for Claim 2). The independent product concept in Claim 1 does not mandate PVP.
3) Can a competitor avoid dependents by changing unit dose?
Claims 14-16 set dosing and volume bounds. Changing the unit dose outside 1-100 mg melphalan or 1-50 mL diluent can avoid those dependents, while Claim 1 architecture still may be implicated.
4) Do the process claims control end-product formulation risk?
Process dependents (Claims 7-8) only matter if there is a process-theory infringement posture tied to matching manufacturing steps and conditions. End-product coverage remains governed primarily by Claim 1.
5) What are the most direct formulation design-around parameters?
The most direct are the ethanol, propylene glycol, and citrate levels in the solvent-diluent due to Claims 12-13 and 11, which define strict v/v and w/v ranges.
References
No external patent documents, family members, prosecution history, expiration terms, or citation network were provided with the input. Therefore, no sources can be cited.
