Details for Patent: 4,882,452

Summary for Patent: 4,882,452

Title:	Process for the preparation of ifosfamide having improved properties
Abstract:	Ifosfamide having improved properties is obtained by crystallization from a solvent mixture selected from the group consisting of (a) a mixture of diethyl ether and a C1 -C3 alkanol or (b) a mixture of diisopropyl ether and a C1 -C3 alkanol under specific controlled conditions.
Inventor(s):	Jurgen Engel, Siegfried Muller, Werner Laubner
Assignee:	Asta Medica GmbH
Application Number:	US07/163,586
Patent Claim Types: see list of patent claims	Composition; Compound; Process;

Scope and Claims Analysis of US Patent 4,882,452 (Ifosfamide Crystalline Forms and Preparation Processes) and the U.S. Patent Landscape

US 4,882,452 is a crystalline-form and crystallization-process patent centered on specific needle-shaped, prismatic ifosfamide crystals and tightly bounded process parameters (solvent system, seeding conditions, controlled cooling, and isolation). The estate is narrow in claim language but potentially impactful in practice because the ranges are engineered around particle size, aspect ratio, and quality metrics that map to manufacturability and performance of injectable drug substance.

What exactly is US 4,882,452 claiming for ifosfamide crystalline form?

US 4,882,452 contains eight claims you provided that fall into two buckets: (i) the product-by-properties crystalline form (claim 1) and (ii) the process to make it (claims 2-6), plus (iii) downstream pharmaceutical composition and an aqueous injection-ready solution with specified pH and loading (claims 7-8).

Claim 1: “needle-shaped prismatic crystalline ifosfamide” defined by particle size, aspect ratio, and a manufacturability metric

Claim 1 is a product-by-structure-with-quantitative-parameters claim. It requires all of the following:

1. Morphology

   • “Needle-shaped prismatic crystalline” ifosfamide.

2. Particle size distribution constraint

   • At least 70% of crystals must fall in 150–550 μm.

3. Aspect ratio (length:width)

   • Individual crystals must have length-to-width ratio of 3.5:1 to 8:1.

4. Quality/reproducibility metric tied to filling tests

   • The crystals have a maximum average relative standard deviation (RD or deviation from desired value at filling tests) between 0.90% and 2% of 1.4%.

This is not a generic “crystallized ifosfamide” claim. The combination of:

• a threshold on distribution (≥70% within a window),
• a morphological window (aspect ratio),
• and a process-performance proxy (RD relative standard deviation in filling tests) makes the claim less susceptible to obvious design-around by using different polymorphs or “similar” needles.

Practical implication for infringement analysis

To prove infringement of claim 1, a patentee typically must show that the accused ifosfamide drug substance batches produce crystals meeting all three property prongs simultaneously, including the filling-test deviation metric. That creates a higher evidentiary bar for enforcement, but it also increases value because it is targeted to specific production outcomes rather than broad morphology.

Claim 7: pharmaceutical composition tied to the claimed crystalline ifosfamide

Claim 7 requires:

• A pharmaceutical carrier or medium, plus
• “a pharmaceutically effective amount of ifosfamide according to claim 1.”

So claim 7 is dependent on claim 1 and inherits its product property limitations.

Claim 8: injection-ready aqueous solution with pH and 10% loading

Claim 8 requires:

• The aqueous solution of “ifosfamide according to claim 1,”
• pH 5.5 to 6, and
• 10% by weight crystals,
• described as suitable for therapeutic use as an injection solution.

Claim 8 narrows the downstream application even further than claim 7, tying infringement to a specific formulation parameter set (pH and concentration) plus the underlying crystal form.

What exactly does claim 2 require in the crystallization process?

Claim 2 is a multi-step process claim that reads like a manufacturing recipe with defined solvent systems and controlled thermal handling:

(a) Form a solution in a specified ether/alkanol solvent mixture

The solvent system is restricted to one of two groups:

1. Diethyl ether + C1–C3 alkanol, or
2. Diisopropyl ether + C1–C3 alkanol

In both cases:

• Volume ratio of alkanol : ether is 1:1 to 1:200
• Solvent mixture amount is 100–2000 mL per 100 g ifosfamide.

This is a broad ratio range (1:1 to 1:200), but it is still bounded to specific functional solvent types and two ether classes.

(b) Seed with pure ifosfamide at defined temperature

• Seeding occurs with pure ifosfamide,
• at temperature -20°C to +25°C,
• and stirring continues “for several hours” at the seeding temperature.

This is an essential step because it imports the “pure ifosfamide” seed concept, which can become a bottleneck for knockoffs if the seed material is controlled as a reference crystal population.

(c) Optionally cool evenly by stirring over 8–48 hours

Cooling is “optional,” but where done it must satisfy:

• Cooling duration 8–48 hours
• Temperature cooled from seeding temperature down to 0°C to -5°C
• Seeding takes place at a temperature above 0°C (expressly stated as a proviso)
  • “provided that the temperature is above 0°C when seeding takes place”
  • This proviso links the seeding temperature to the cooling mode.

That proviso matters for claim construction: the cooling schedule can only be combined with the seeding step if seeding temperature is above 0°C.

(d) Isolate and dry the resulting crystals

• Standard endpoint, but it closes the process chain.

Claims 3–6: narrower process embodiments

These dependent claims lock down specific versions of the general process in ways that can matter for both novelty and design-around.

Claim 3: solvent specificity

• Solvent mixture in (a) is diethyl ether + methanol.

This is a narrower embodiment than claim 2.

Claim 4: seeding temperature > 11°C

• Seeding in (c) (as written in your claim set) takes place at a temperature greater than 11°C.

Because claim dependencies sometimes reflect drafting artifacts, enforcement typically focuses on the meaningful temperature limitation; the key for risk is the seeding temperature window.

Claim 5: seeding temperature 14–20°C

• Seeding takes place at 14°C to 20°C.

This is a tightly bounded operational window.

Claim 6: controlled cooling via linear temperature reduction

• Cooling to filtering temperature uses a cooling bath in thermal contact with solution to obtain controlled, even, and linear temperature reduction.

This adds a hardware/method constraint that can be difficult to “accidentally” meet.

What is the overall claim architecture and how narrow is the patent?

Core protection: crystallization-to-specific-crystal-quality

The patent is built around:

• a specific product morphology and distribution (claim 1),
• a specific crystallization solvent/seed/cooling recipe (claim 2),
• and downstream formulation targets (claims 7–8).

Why narrow claim language still carries risk

Even narrow patents can control manufacturing if:

• the process is used in commercial production, and
• the produced crystals meet the property windows used in claim 1.

For licensing and litigation, claim 1 product-by-properties and claim 2 process provide two enforcement paths:

• Product infringement: show that commercial ifosfamide batches are “according to claim 1.”
• Process infringement: show that manufacturing uses the specific solvent and thermal sequence.

How strong is US 4,882,452 likely to be for U.S. enforceability and validity?

Based solely on the claim text you provided, the validity profile has two opposing features:

• Strength-inducing features

  • Claim 1 ties to quantitative distributions and an unusual “filling test” deviation metric. That kind of specificity can support novelty if prior art disclosed only generic needle crystals or qualitative morphology.
  • Process claim 2 includes a defined solvent-family constraint plus seeding and cooling time/temperature parameters. That combination can differentiate over general crystallization techniques.

• Vulnerability-inducing features

  • If prior art already disclosed needle-shaped ifosfamide with similar particle size windows and aspect ratios, claim 1 may face obviousness attacks unless the “filling test relative standard deviation” metric is clearly linked to the claimed form and was not taught.
  • Process claim 2 spans a wide solvent ratio range (1:1 to 1:200) and solvent volume (100–2000 mL per 100 g), which can reduce differentiation if older patents disclosed overlapping solvent systems and temperatures.

A full “strength” assessment normally requires the patent’s specification, cited references, prosecution history, and later case law. That information is not present in your prompt, so only the claim-structure implications can be stated here.

What would be the likely design-around strategies against these claims?

Design-around is easiest to conceptualize along three axes: crystal property axis, process recipe axis, and formulation axis.

1) Avoid claim 1 by failing one property prong

• Use an ifosfamide crystal population where <70% lies in 150–550 μm.
• Or shift aspect ratio outside 3.5:1 to 8:1.
• Or disrupt the quality metric relating to filling-test deviation (0.90% to 2% of 1.4%).

Even if morphology stays needle-like, falling short on one quantitative requirement breaks claim 1.

2) Avoid claim 2 by changing at least one required process element

• Use a different solvent system outside the ether + C1–C3 alkanol framework, or change ether type away from diethyl/diisopropyl.
• Change solvent volume-per-mass ratio outside 100–2000 mL per 100 g.
• Seed at a temperature outside -20°C to +25°C.
• Eliminate or change the defined “several hours” seeding hold.
• If using the cooling mode, remove compliance with the 8–48 hour controlled stirring cooling and/or the endpoint -5°C to 0°C constraint.
• Use a non-thermal-contact cooling method that does not produce “linear temperature reduction” as required by claim 6.

3) Avoid claim 7–8 by formulation parameters

• For claim 8 specifically: change pH outside 5.5–6 or adjust concentration away from 10% by weight crystals, or use a crystal form not “according to claim 1.”

How does this interact with generic and biosimilar risk models?

Ifosfamide is a small-molecule chemotherapeutic, so “biosimilar” models do not apply. The relevant risk frameworks are:

• Hatch-Waxman generic drug substance bioequivalence and IP barriers,
• Paragraph IV challenges to Orange Book patents (if listed),
• and product-manufacturing process IP that can persist even if the active ingredient is the same.

A patent like US 4,882,452 can be triggered both by:

• the drug substance (crystal form) and
• the drug product (aqueous pH and concentration).

What is the Orange Book status of US 4,882,452 for ifosfamide?

This cannot be answered from your prompt because it requires Orange Book data (listed patents, expiration, and the associated drug products). Without that source information, no definitive status can be provided.

What about U.S. patent expiration timing for 4,882,452?

This cannot be determined from your prompt because expiration depends on:

• filing date,
• any priority claims,
• potential PTA,
• and whether it has lapsed, terminally disclaimed, or adjusted.

Key Takeaways

• US 4,882,452 is principally a claim-set targeting needle-shaped prismatic ifosfamide crystals defined by strict quantitative property windows (≥70% of crystals in 150–550 μm, aspect ratio 3.5:1 to 8:1) and a filling-test deviation metric (0.90% to 2% of 1.4%).
• Claim 2 protects a specific crystallization recipe using ether + C1–C3 alkanol solvent families, a defined seeding temperature range with pure ifosfamide and a hold, and optionally a controlled stirring cooling schedule over 8–48 hours to 0°C to -5°C, followed by isolation and drying.
• Dependent claims 3–6 narrow embodiments to specific solvents (diethyl ether/methanol), seeding temperature windows (for claims 4–5), and controlled linear cooling via a thermally contacted cooling bath (claim 6).
• Downstream formulation claims 7–8 tie infringement to the claimed crystal form plus specific aqueous solution pH (5.5–6) and 10% by weight crystal loading.

FAQs

1. If my ifosfamide crystals are needle-shaped, can I still infringe claim 1?
   Yes if the crystal batch meets the quantitative constraints on particle size distribution (≥70% in 150–550 μm), aspect ratio (3.5:1 to 8:1), and the filling-test deviation metric.

2. Does claim 2 require cooling in step (c)?
   Cooling in step (c) is “optional,” but if used it must meet the specified 8–48 hour evenly stirred cooling profile and endpoint temperatures with the seeding temperature proviso.

3. Can a different seeding solvent or non-pure seed avoid claim 2?
   Changing the solvent family or seeding conditions outside the defined temperature range can avoid claim 2, and using seeds that are not “pure ifosfamide” can also break the claim as written.

4. Would changing injection solution pH avoid claim 8?
   Yes, because claim 8 requires pH 5.5 to 6 and 10% by weight crystals that are “according to claim 1.”

5. Is this a biosimilar-style patent risk?
   No. The claims are about a small-molecule chemotherapeutic drug substance form and its manufacturing and formulation, aligning with generic small-molecule IP risk rather than biologics.

References (APA)

1. United States Patent 4,882,452.

Drugs Protected by US Patent 4,882,452

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

Foreign Priority and PCT Information for Patent: 4,882,452

Foriegn Application Priority Data
Foreign Country	Foreign Patent Number	Foreign Patent Date
Germany	3707154	Mar 06, 1987

International Family Members for US Patent 4,882,452

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
Austria	63121
Canada	1305970
Germany	3805329