US Patent 4,537,883: Hydrated Lyophilizate Stability and Solubility Claims for Cyclophosphamide
US Patent 4,537,883 claims a specific hydrated lyophilizate composition of cyclophosphamide (as the anhydride) with controlled water content and mannitol content, plus single-dose vial formulations defined by the lyophilizate composition and reconstitution volumes.
The core claim architecture is composition-first (Claims 1-5), followed by formulation dose packaging and reconstitution parameters (Claims 6-16).
What is the claimed invention scope?
1) Product-by-composition: hydrated lyophilizate
Claims 1-5 require a lyophilized solid that is explicitly hydrated (not anhydrous), with three numeric constraints:
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Cyclophosphamide content
- About 20 parts by weight of cyclophosphamide, taken as the anhydride.
-
Water content
- About 1.25 to 2 parts by weight water in Claims 1-4
- About 1.5 parts by weight water in Claim 5
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Mannitol content
- From about 10 to 85 parts by weight in Claim 1
- From about 10 to 40 parts by weight in Claim 2
- From about 10 to 20 parts by weight in Claim 3
- About 15 parts by weight in Claim 4
- From about 10 to 40 parts by weight in Claim 5
Interpretation for scope: the invention is not a general “cyclophosphamide lyophilizate.” It is a hydrated lyophilizate with tight water:cyclophosphamide ratios and a defined mannitol range. Changing water content and manninitol loading is the main design lever that moves products out of the literal ranges.
2) Single-dose packaging and reconstitution
Claims 6-16 narrow the scope from the composition to a single-dose vial formulation:
- Claim 6: “A single dose formulation comprising the hydrated lyophilizate composition of claim 4” in a single dose vial container sized to allow reconstitution with water to yield a desired administration concentration.
- Claims 7-16: specific embodiments that lock in:
- approximate total cyclophosphamide mass per vial,
- mannitol mass,
- water mass in the hydrated lyophilizate,
- and a specified reconstitution volume (water volume) that provides the intended solution volume/concentration.
Key point: Claims 6-16 are not just “any vial containing the lyophilizate.” They require the particular amounts of cyclophosphamide/mannitol/water and the corresponding reconstitution volume.
What do Claims 1-5 cover in numeric ratio terms?
The claims use “parts by weight” anchored to cyclophosphamide (20 parts). The following table maps the claim ranges.
Table 1. Composition parameter ranges by claim (parts by weight)
| Claim |
Cyclophosphamide (anhydride basis) |
Water (parts by weight) |
Mannitol (parts by weight) |
| 1 |
~20 |
~1.25 to 2 |
~10 to 85 |
| 2 |
~20 |
~1.25 to 2 |
~10 to 40 |
| 3 |
~20 |
~1.25 to 2 |
~10 to 20 |
| 4 |
~20 |
~1.25 to 2 |
~15 (about) |
| 5 |
~20 |
~1.5 |
~10 to 40 |
Practical scope take:
- Claim 1 is the broadest for mannitol (10 to 85).
- Claim 2 is narrower (10 to 40).
- Claim 3 is narrower still (10 to 20).
- Claim 4 is narrower again (about 15).
- Claim 5 pins water closer to ~1.5 while keeping mannitol at 10 to 40.
How do Claims 6-16 define the single-dose formulation scope?
Claims 6-16 tie the invention to specific vial content and reconstitution volumes.
Table 2. Single-dose embodiments (absolute masses and reconstitution volumes)
| Claim |
Approx. cyclophosphamide in vial |
Approx. mannitol in vial |
Approx. water in hydrated lyophilizate |
Reconstitution volume (water) |
| 7 |
~100 mg |
75 mg |
7 mg |
(not stated in 7) |
| 8 |
(depends on claim 7) |
(depends on claim 7) |
(depends on claim 7) |
5 mL |
| 9 |
~200 mg |
150 mg |
14 mg |
(not stated in 9) |
| 10 |
(depends on claim 9) |
(depends on claim 9) |
(depends on claim 9) |
10 mL |
| 11 |
~500 mg |
375 mg |
35 mg |
(not stated in 11) |
| 12 |
(depends on claim 11) |
(depends on claim 11) |
(depends on claim 11) |
25 mL |
| 13 |
~1,000 mg |
750 mg |
70 mg |
(not stated in 13) |
| 14 |
(depends on claim 13) |
(depends on claim 13) |
(depends on claim 13) |
50 mL |
| 15 |
~2,000 mg |
1,500 mg |
140 mg |
(not stated in 15) |
| 16 |
(depends on claim 15) |
(depends on claim 15) |
(depends on claim 15) |
100 mL |
Ratio consistency check (scope coherence)
These embodiments are internally consistent with the claimed parts structure:
- 100 mg CP corresponds to 75 mg mannitol and 7 mg water.
- 200 mg CP corresponds to 150 mg mannitol and 14 mg water.
- 500 mg CP corresponds to 375 mg mannitol and 35 mg water.
- 1,000 mg CP corresponds to 750 mg mannitol and 70 mg water.
- 2,000 mg CP corresponds to 1,500 mg mannitol and 140 mg water.
This means the patent scope is aimed at a scalable composition where water and mannitol scale proportionally with cyclophosphamide.
What is the claim dependency structure and why it matters
-
Claims 1-5 define the hydrated lyophilizate composition.
-
Claim 6 uses claim 4 specifically (not claim 1-3 or 5).
- So for vial formulations, the relevant composition is the claim 4 subrange:
- cyclophosphamide: ~20 parts
- water: ~1.25 to 2 parts
- mannitol: ~15 parts (about)
-
Claims 7-16 then specify “approximately” quantitative embodiments that correspond to that composition.
Scope effect
- The composition in claims 1-3 can exist without directly landing in claims 6-16 if a product does not meet the claim 4 mannitol “about 15 parts” constraint.
- Conversely, once a product meets claim 4’s composition constraints, it can fall into the single-dose claim structure when vial format and reconstitution volume match the specified embodiments (claims 8, 10, 12, 14, 16).
Patent landscape analysis: what can be inferred from the claim set alone
Based on the information provided (only the claim text), the patent landscape can be characterized at a technical-claim level, not by enumerating specific competitors’ patents.
Technical “landscape axis” created by this patent
This patent creates an exclusion zone defined by three technical variables:
- Hydration level of the lyophilized cyclophosphamide composition (water about 1.25-2 parts; or about 1.5 in claim 5).
- Bulking/crystallization control via mannitol (10-85, 10-40, 10-20, or about 15 parts).
- Single-dose usability (vial reconstitution volumes matching defined mass loadings).
Where design-arounds usually succeed against this type of claim
From the claim ranges alone, the main ways to avoid literal capture are:
- Move water content outside “about 1.25-2 parts” or “about 1.5 parts” depending on which claim is targeted.
- Move mannitol content outside the relevant subrange, especially:
- outside “from about 10 to 85” for claim 1, and
- outside “from about 10 to 20” for claim 3, and
- outside “about 15 parts” for the vial formulation path (claim 4).
- Use vial formats that do not match the claimed “single dose formulation” mapping to the specific embodiments (100/200/500/1000/2000 mg CP and 5/10/25/50/100 mL reconstitution volumes as written in claims 8/10/12/14/16).
Where overlap risk concentrates
Overlap risk concentrates on products that:
- intentionally create a hydrated cyclophosphamide lyophilizate (not fully dried to anhydrous),
- use mannitol in the same narrow “about 15 parts” regime tied to claim 4,
- and package for reconstitution at the specific volumes tied to those CP loadings.
Claim scope in litigation/clearance terms
Literal infringement focal points
A product faces literal claim risk when it meets all of the following simultaneously:
-
Composition: hydrated lyophilizate with:
- cyclophosphamide at “about 20 parts by weight (anhydride basis),”
- water at “about 1.25 to 2 parts” (or about 1.5 for claim 5),
- mannitol at the relevant range or “about 15 parts” for claim 4.
-
Product form:
- single-dose vial (claim 6) and then one of the specific mass/reconstitution embodiments (claims 8/10/12/14/16).
Design-around focal points
Any of these changes can reduce literal match:
- water content shift,
- mannitol content shift (especially around the claim 4 “about 15 parts” target),
- changing vial reconstitution volume relative to the specified embodiments for the same drug mass.
What is the commercial and formulation relevance of each claim tier?
Claims 1-5: upstream formulation space
These claims drive the medicinal product’s solid-state identity:
- cyclophosphamide in hydrated lyophilizate form,
- water retention controlled into a narrow window,
- mannitol loading chosen within specified ranges.
Claims 6-16: downstream dose-product packaging space
These claims drive the “patient-ready” product:
- vialed single-dose reconstitution with water volumes mapped to cyclophosphamide loadings.
Key Takeaways
- US 4,537,883 claims a hydrated cyclophosphamide lyophilizate with specific water and mannitol loading constraints anchored to cyclophosphamide “about 20 parts by weight (anhydride).”
- Claims 1-3 cover mannitol ranges (10-85, 10-40, 10-20) at the same water window; Claim 4 fixes mannitol at about 15 parts and is the composition predicate for vial formulations.
- Claims 6-16 expand scope to single-dose vial embodiments with specific cyclophosphamide/mannitol/water masses and corresponding reconstitution volumes (5/10/25/50/100 mL for the enumerated CP loads).
- The cleanest technical exposure concentration is products that meet claim 4’s hydrated composition (water about 1.25 to 2 parts; mannitol about 15 parts) and then match one of the reconstitution-volume embodiments.
FAQs
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Is cyclophosphamide required to be “taken as the anhydride”?
Yes. The claims specify cyclophosphamide content “taken as the anhydride” in the part-by-weight definitions.
-
Do the claims require the lyophilizate to contain water (hydrated)?
Yes. Water is explicitly required in the composition ranges (about 1.25-2 parts in most claims; about 1.5 parts in claim 5).
-
Which claim is critical for single-dose vial formulations?
Claim 6 depends on claim 4, making claim 4’s composition (including mannitol “about 15 parts”) the key predicate for the vial scope.
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Are the reconstitution volumes tied to specific cyclophosphamide doses?
Yes. Claims 8, 10, 12, 14, and 16 tie reconstitution volumes (5, 10, 25, 50, 100 mL) to the corresponding approximate cyclophosphamide loadings (100, 200, 500, 1,000, 2,000 mg).
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Can products outside the mannitol ranges still infringe?
Literal infringement depends on meeting the exact claimed ranges for the relevant claim. For the vial pathway (claim 6), mannitol must meet the “about 15 parts” limitation of claim 4.
References
[1] United States Patent 4,537,883, claims (as provided in prompt).
