US Patent 12,599,553 (Atorvastatin Oral Aqueous Suspension) Claim Scope, Overlap Risk, and U.S. Patent Landscape

US 12,599,553 claims a specific liquid oral atorvastatin aqueous suspension defined by composition and critical process/particle-size constraints: 4 mg/mL atorvastatin, 2% w/w suspending system split between carboxymethyl cellulose sodium (0.7% w/w) and magnesium aluminum silicate (1.3% w/w), no surfactant, and atorvastatin d90 of 1 to 15 µm. Downstream dependent claims narrow preservative, co-solvent, sweetener, flavoring, and pH (5–10 or 6–9). The practical enforcement hook is the combination of (i) the specific suspending system proportions and (ii) the no-surfactant + particle-size requirement.

This analysis maps the claim boundaries, identifies where generic or “authorized” liquid competitors would face literal infringement risk, and frames the likely surrounding patent estate based on standard U.S. small-molecule formulation claim patterns around atorvastatin suspensions (composition-of-matter style and formulation parameter dependent claims).

What is the claim scope of US 12,599,553 for an atorvastatin aqueous oral suspension?

Core independent claim (Claim 1) defines a tightly bounded product concept:

Claim 1: elements that must all be met

An aqueous suspension for oral administration comprising:

Atorvastatin: about 4 mg/mL
Suspending agent system (2% w/w total):
- Carboxymethyl cellulose sodium about 0.7% w/w
- Magnesium aluminum silicate about 1.3% w/w
Pharmaceutically acceptable excipients selected from:
- co-solvent
- preservative
- sweetener
- buffer
- flavoring agent
Vehicle: water
No surfactant in the suspension
Particle size requirement: atorvastatin d90 from 1 µm to 15 µm

Functional meaning of the particle size limitation

The d90 constraint is a measurable quality attribute. It functions as a de facto process/quality gate: even if composition is close, a formulation that does not achieve d90 (1–15 µm) would avoid literal infringement.

Materiality of the “no surfactant” requirement

Claim 1 requires that the aqueous suspension does not contain a surfactant. That is not limited to nonionic surfactants; it is framed broadly. A competitor that adds any surfactant (to stabilize wetting/redispersion) would likely fall outside the literal scope, assuming the surfactant is present in the formulation.

Composition constraint has a “two-ingredient split”

The suspending system is specified not only as a pair, but as a proportional mix totaling 2% w/w:

CMC sodium: 0.7% w/w
Mg aluminum silicate: 1.3% w/w

This reduces design-around space compared with claims that merely require “a suspending agent comprising CMC and magnesium aluminum silicate” without fixed ratios.

What do the dependent claims add (preservatives, co-solvents, sweeteners, flavoring, pH)?

Dependent claims narrow claim 1 by selecting excipients and/or defining their quantitative ranges. The infringement risk increases with each limitation that is satisfied.

Claim 2: fixed atorvastatin concentration

Atorvastatin present in an amount of 4 mg/mL (a narrowing from “about 4 mg/mL” in Claim 1)

A product at 3.5–4.4 mg/mL could still be “about 4 mg/mL,” but a competitor at a non-4 value could avoid Claim 2 while still potentially falling into Claim 1.

Claims 3 and 6: preservative amount

Preservative present from 0.01% w/w to 0.5% w/w (Claims 3 and 6)
Claim 6 also cross-requires that preservative selection is from the specified list.

Claims 4, 5, 6, 7, 8: co-solvent and preservative identity

Claim 4: co-solvent selected from:
- alcohol
- glycerin
- polyhydric alcohol
- propylene glycol
- combinations
Claim 5: preservative selected from:
- benzyl alcohol
- chlorobutol
- chlorocresol
- alkyl ester of paraben
- phenol
- phenyl ethanol
- sodium benzoate
- propylene glycol
- chloroform
- combinations
Claim 7/8: preservative comprises alkyl ester of paraben, with 0.01–0.5% w/w

Key scope implication: if a competitor uses a preservative not in the listed set (e.g., certain modern alternatives), it can avoid dependent claims 5–8, but still might meet Claim 1 if Claim 1 excipients include a preservative broadly and if that “preservative” term in claim 1 is not read to require the dependent claim list.

However, because dependent claims are optional requirements for infringement of that dependent claim, a typical assertion strategy is:

assert Claim 1 for product composition/particle size/no surfactant + suspending system ratio
assert dependent claims if the competitor uses one of the enumerated excipients and matches the ranges

Claims 9 and 10: sweetener identity and amount

Claim 9: sweetener selected from:
- sucrose, glucose, glycerin, sorbitol, saccharin sodium, sucralose, aspartame, acesulfame potassium
- combinations
Claim 10: sweetener present 0.1% w/w to 2% w/w

Claim 11: flavoring agent amount

Flavoring agent present 0.01% w/w to 2.0% w/w

Claims 12 and 13: pH

Claim 12: pH ranges from 5 to 10
Claim 13: pH ranges from 6 to 9

Because 6–9 is a subset of 5–10, Claim 13 is the narrower target.

Where is the infringement “hot zone” vs. where design-arounds are most plausible?

Hot zone (high literal infringement probability)

A competitor is at highest risk if it matches all of these simultaneously:

atorvastatin near 4 mg/mL
CMC sodium at ~0.7% w/w
magnesium aluminum silicate at ~1.3% w/w
no surfactant
d90 1–15 µm
and uses at least one of the enumerated excipient categories in ways that also meet dependent ranges (if asserted)

Most effective design-around levers

Particle size (d90)
- Avoid by shifting d90 outside 1–15 µm. This is a quality attribute; it is achievable by milling/dispersing control.
Suspending system composition
- Avoid the exact 0.7%/1.3% split totaling 2% w/w. Even if the total is 2%, changing the ratio can evade literal infringement.
Surfactant inclusion
- Claim 1 demands “does not contain a surfactant.” Adding a surfactant (and documenting it is present) can potentially avoid Claim 1 literally, though the formulation must still meet safety and stability.
Atorvastatin concentration
- If the product is not “about 4 mg/mL” (and not exactly 4 mg/mL), Claim 1/2 risk shifts, but Claim 1 uses “about,” which usually provides some tolerance.

Design-around limits

If a competitor changes excipient identity (e.g., preservative or sweetener), it may avoid dependent claims but still be exposed to Claim 1 unless the change affects the key elements: suspending system split, no surfactant, and d90.

How does US 12,599,553 compare with typical atorvastatin formulation patent estates in the U.S.?

Across small-molecule liquid formulation patents, U.S. claim structures tend to cluster into:

composition parameters (specific excipient sets, ranges, pH)
quality attributes (particle size, dissolution, redispersibility)
stability-related constraints (preservative and pH windows)
no surfactant / wetting agent exclusions
sometimes method-of-manufacture claims

US 12,599,553 is most consistent with a formulation patent designed to block ready-to-use generics/biosimilar analogs (though atorvastatin is small molecule, so the “biosimilar” term is not applicable) by forcing a match to measurable formulation attributes rather than only to “use” or “dosage.”

What other patents likely matter around this claim for U.S. exclusivity and freedom-to-operate?

A complete landscape requires the patent document text, assignee, and prosecution history. With only the claim excerpts provided, the most defensible landscape framing is structural: US 12,599,553 is a formulation claim that usually coexists with other patents in the same portfolio class that typically cover:

Other atorvastatin liquid dosage forms
- different strengths (e.g., 10 mg/5 mL, 20 mg/5 mL equivalents)
- different viscosities (different suspending agents or thickener systems)
Alternative suspending systems
- different combinations or ratios of CMC, HPMC, xanthan gum, microcrystalline cellulose, gums, silicas
Different particle size targets
- separate patents for d90 windows, or for d50/d10 constraints
Wetting and redispersion strategies
- patents that include surfactants and those that exclude them, creating a “fork” in claim coverage
Preservative and pH optimization
- additional patents focused on preservative selection/range and buffer systems
Manufacturing methods
- milling/dispersion processes to achieve the d90 range

For enforcement, plaintiffs typically assert the formulation claim(s) that overlap the accused product’s measurable attributes (particle size and excipient system).

What generic entry risks exist for an atorvastatin oral suspension under US 12,599,553?

Risk profile for a would-be generic liquid

If an ANDA filer (or applicant for a 505(b)(2)) develops an aqueous suspension for oral administration, the litigation risk pivots on:

whether the formulation uses the same CMC sodium + magnesium aluminum silicate split
whether it includes any surfactant
the achieved d90 particle size
and whether the strength is exactly or “about” 4 mg/mL

Why particle size testing is central

A generic manufacturer can often mirror excipient identities but may struggle to match d90 due to:

differences in milling equipment and dispersion steps
differences in batch viscosity and wetting
differences in filtration or homogenization

That makes d90 a high-utility test in infringement.

Which claim elements would be most contested in litigation (scope and evidence)?

“Does not contain a surfactant”
- Dispute likely turns on analytical detection and classification of excipients as surfactants.
d90 particle size (1–15 µm)
- Likely dispute around measurement method (laser diffraction vs microscopy), sample preparation, and stability-induced changes.
Suspending agent ratio
- Dispute about whether “about 0.7%” and “about 1.3%” includes the accused formulation’s actual % by w/w.

Dependent claims would be tested if the accused formulation uses the listed excipients and stays within the same ranges.

Claim-by-claim scope map (what must be present for each claim to read on the product)

Claim	Additional limitations beyond Claim 1	Literal read requirement for an accused formulation
1	Water vehicle; suspending system; no surfactant; d90 1–15 µm; excipients categories included	Must match all core elements
2	Atorvastatin exactly 4 mg/mL	Must be at 4 mg/mL (or within “about” if court construes; claim text says “amount of 4 mg/mL”)
3	Preservative 0.01–0.5% w/w	Preservative within range
4	Co-solvent selection list	Uses only from enumerated co-solvents (or combinations)
5	Preservative selection list	Uses only from enumerated preservatives
6	Preservative selection list + 0.01–0.5% w/w	Both identity and range
7	Preservative comprises alkyl ester of paraben	Paraben ester as preservative
8	Paraben ester preservative 0.01–0.5% w/w	Both identity and range
9	Sweetener selection list	Uses only from enumerated sweeteners
10	Sweetener 0.1–2% w/w	Must fall within range
11	Flavoring agent 0.01–2.0% w/w	Must fall within range
12	pH 5–10	Must fall within range
13	pH 6–9	Must fall within range

Key Takeaways

US 12,599,553 is anchored by a specific suspending system ratio (0.7% CMC sodium + 1.3% magnesium aluminum silicate in 2% total) plus no surfactant and a measured d90 particle size of 1–15 µm.
The infringement “hot zone” is the combination of composition + particle size + surfactant exclusion. Excipient identity/range limits in dependent claims mostly matter for narrower claim targets and damages theories.
The most defensible design-arounds are to move the formulation outside the d90 window, change the suspending agent ratio, or include a surfactant (while maintaining the required stability/quality attributes for an oral suspension).

FAQs

What particle-size test would determine infringement for atorvastatin d90 in US 12,599,553?

d90 must be shown to be within 1–15 µm using the measurement method that the court accepts for “d90” in the context of the formulation’s particle distribution.

Can a product avoid US 12,599,553 by changing only the preservative?

Changing preservative alone can avoid dependent claims 5–8, but it does not avoid Claim 1 unless the change affects the core limitations: suspending system split, no surfactant, and d90.

Does “about 4 mg/mL” broaden Claim 1 enough for different strengths?

It provides flexibility versus Claim 2. A product far from 4 mg/mL could avoid Claim 1, but exact tolerance is ultimately construed in litigation.

Is pH a likely standalone infringement issue under the dependent claims?

Yes for dependent claims 12–13 if the accused product’s pH falls outside 5–10 or 6–9, respectively. Claim 1 itself does not specify pH.

What is the cleanest design-around if the formulation must stay surfactant-free?

Change the suspending agent ratio away from 0.7%/1.3% and/or shift d90 outside 1–15 µm.

References

United States Patent No. 12,599,553 (claims provided in prompt).

Applicant	Tradename	Generic Name	Dosage	NDA	Approval Date	TE	Type	RLD	RS	Patent No.	Patent Expiration	Product	Substance	Delist Req.	Patented / Exclusive Use	Submissiondate
Cmp Dev Llc	ATORVALIQ	atorvastatin calcium	SUSPENSION;ORAL	213260-001	Feb 1, 2023		RX	Yes	Yes	12,599,553	⤷ Start Trial	Y				⤷ Start Trial
>Applicant	>Tradename	>Generic Name	>Dosage	>NDA	>Approval Date	>TE	>Type	>RLD	>RS	>Patent No.	>Patent Expiration	>Product	>Substance	>Delist Req.	>Patented / Exclusive Use	>Submissiondate

Country	Patent Number	Estimated Expiration	Supplementary Protection Certificate	SPC Country	SPC Expiration
European Patent Office	3468606	⤷ Start Trial
World Intellectual Property Organization (WIPO)	2017212409	⤷ Start Trial
>Country	>Patent Number	>Estimated Expiration	>Supplementary Protection Certificate	>SPC Country	>SPC Expiration

Details for Patent: 12,599,553

Which drugs does patent 12,599,553 protect, and when does it expire?

Summary for Patent: 12,599,553