Scope and claims analysis for US Patent 8,846,628 (oral non-enteric 5-azacytidine tablet)
US 8,846,628 claims a narrowly defined US-focused product: an oral, non-enteric coated tablet composition containing 5-azacytidine (fixed excipient classes; optional permeation enhancer specified) with performance attributes tied to systemic exposure (AUC, Cmax, Tmax), and an explicit drug-dosing method for myelodysplastic syndrome (MDS) or acute myelogenous leukemia (AML) that excludes co-administration with a cytidine deaminase inhibitor and excludes tetrahydrouridine (THU). The patent’s scope is concentrated around (i) formulation form factor (non-enteric coated tablet), (ii) defined excipient/permeation-enhancer selections, and (iii) oral pharmacokinetic targets, limiting easy “design-around” only if generics match both composition and exposure.
What the claims are really covering (high-level)
- Product claims (composition-of-5-azacytidine): non-enteric coated oral tablets with therapeutically effective 5-azacytidine plus defined excipient options; optionally with a specific permeation enhancer and concentration; and with exclusions (essentially free of cytidine deaminase inhibitor; essentially free of tetrahydrouridine).
- PK-constrained composition claims: tablet variants that reach specified AUC and Cmax thresholds and Tmax windows after oral dosing.
- Method claims (therapeutic use): oral administration to treat abnormal cell proliferation diseases specifically MDS or AML, using the claimed composition (including non-enteric coated tablet and optional enhancer constraints), with exclusions around co-administering inhibitors and inclusion of unit dosage form.
The patent is a classic “formulation + oral exposure + use” estate. It is not a broad “any oral 5-azacytidine” monopoly; it is a “this oral tablet achieves these systemic exposure metrics without typical modulators” monopoly.
What is claimed in US 8,846,628: oral non-enteric 5-azacytidine tablet composition?
Core independent claim content (Claim 1)
Claim 1 defines:
- Dosage form: “pharmaceutical composition for oral administration” that is a non-enteric coated tablet.
- Active: 5-azacytidine in a therapeutically effective amount.
- Excipients: at least one pharmaceutically acceptable excipient.
Why “non-enteric coated tablet” matters legally
This is the first major narrowing element. Many oral 5-azacytidine delivery strategies historically used enteric/modified-release approaches to manage GI degradation and first-pass/solubility effects. Claim 1’s explicit exclusion of enteric coating sets a clean boundary for infringement: a non-enteric coated tablet can infringe if other claim elements are met; an enteric-coated form is structurally outside Claim 1.
Breadth inside the tablet concept
Claim 1 does not lock excipient composition beyond “at least one pharmaceutically acceptable excipient,” which makes Claim 1 broad for excipients. But the dependent claims later narrow excipient and permeation enhancer choices.
Dependent claim narrowing that drives real scope
- Claim 2 narrows excipient selection to one or more from:
- mannitol
- microcrystalline cellulose
- crospovidone
- magnesium stearate
- Claims 3–5 add an optional permeation enhancer requirement:
- Claim 4 fixes the permeation enhancer to D-alpha-tocopheryl polyethylene glycol 1000 succinate (TPGS-like agent).
- Claim 5 fixes concentration to ~2% by weight relative to total composition.
From an infringement and design-around standpoint, the formulation “axis” is clear:
- Excipient choice alone becomes decisive only if the accused formulation is asserted under the dependent claims.
- If litigation targets a dependent claim, the accused product must include the specific permeation enhancer at the stated level.
How do the “essentially free” exclusions constrain infringement: cytidine deaminase inhibitors and tetrahydrouridine?
Claim 6 and Claim 7 introduce two exclusionary qualifiers directly into Claim 1’s definition:
- Claim 6: composition is essentially free of a cytidine deaminase inhibitor
- Claim 7: composition is essentially free of tetrahydrouridine
These exclusions are not merely dosing-adjunct statements. They tie the claimed composition’s composition state to the absence of specific classes of modulators.
Practical litigation impact
- If an accused product includes a cytidine deaminase inhibitor or THU in the tablet or in the same dosage unit, the “essentially free” qualifier becomes a major factual issue.
- Even if an accused product relies on a different inhibitor (not labeled “cytidine deaminase inhibitor” in the same way), the claim language still turns on whether the inhibitor falls within the claimed category.
Relationship to method claims
The method claims repeat the regulatory/clinical exclusion logic:
- Claim 32: method includes “not co-administering a cytidine deaminase inhibitor with the 5-azacytidine.”
So the exclusion operates both as:
- a composition attribute (Claims 6–7) and
- a method-of-treatment condition (Claim 32).
What dosage ranges are protected for 5-azacytidine: 40 mg, 400 mg, 1000 mg, and intermediate bands?
Claim set includes multiple numeric thresholds and ranges:
Threshold “at least” limitations
- Claim 8: at least 40 mg
- Claim 9: at least 400 mg
- Claim 10: at least 1000 mg
Range limitations
- Claim 16: 40 to 480 mg
- Claim 17: 80 to 480 mg
- Claim 23: 120 to 480 mg
Additional minimums
- Claim 24: at least 300 mg
- Claim 25: at least 360 mg
- Claim 26: at least 400 mg
- Claim 27: at least 480 mg
Scope take-away
These are not trivial. They create a “stepped” infringement landscape where:
- A generic matching dose strength can be captured by some dependent claims even if other dose-related dependent claims are missed.
- A generic outside the stated ranges can avoid certain dependent-claim assertions, but may still face Claim 1 (therapeutically effective amount) depending on claim construction and evidence on “therapeutically effective” scope.
What pharmacokinetic targets are claimed: AUC, Cmax, and Tmax after oral dosing?
The patent builds a measurable oral-performance profile into claim features. Claims 11–12 and 18–22 (and corresponding method claims 38–43) recite oral PK thresholds.
AUC thresholds
- Claim 11: AUC ≥ 200 ng·hr/mL
- Claim 12: AUC ≥ 400 ng·hr/mL
Cmax thresholds
- Claim 18: Cmax ≥ 100 ng/mL
- Claim 19: Cmax ≥ 200 ng/mL
Tmax windows
- Claim 20: Tmax < 180 minutes
- Claim 21: Tmax < 90 minutes
- Claim 22: Tmax < 60 minutes
Why PK claims matter for scope
- In enforcement, performance-based limitations force the patentee to tie the accused product’s oral exposure to the claimed thresholds.
- In design-around, a generic can attempt to keep the composition elements while shifting PK characteristics, but that risks loss of oral efficacy and can create additional clinical risk.
PK symmetry between composition and method claims
Method claims mirror the composition PK claims:
- Claim 38–39: AUC ≥ 200/400
- Claim 40–41: Cmax ≥ 100/200
- Claim 42–43: Tmax < 180/90/60
That symmetry expands enforcement paths, since the same PK facts can be used under either product or use theories.
What tablet-coating language is protected: sugar vs film vs compression, and which polymer coat?
Claim 13 adds coating variability:
- Claim 13: tablet comprises a sugar coating, film coating, or compression coating.
Claim 14–15 narrow the film-coated variant:
- Claim 14: film coating is a cellulose ether polymer
- Claim 15: polymer is one of:
- hydroxypropyl methyl-cellulose
- hydroxypropyl cellulose
- methyl-cellulose
Boundary condition vs “non-enteric”
The coating options are still constrained by the “non-enteric coated” requirement. So a film coating using the named cellulose ether polymers can still infringe if non-enteric and other limitations are satisfied.
How broad is the method-of-use coverage for MDS/AML: what treatment steps are required?
Independent method claim (Claim 28) requires:
- treating symptoms of a disease associated with abnormal cell proliferation
- disease is specifically MDS or AML
- oral administration to a subject in need thereof
- using a pharmaceutical composition containing:
- therapeutically effective amount of 5-azacytidine
- at least one pharmaceutically acceptable excipient
- non-enteric coated tablet
Dependent method constraints that narrow practice
- Claim 29–31 permeation enhancer constraints (TPGS-like agent; ~2% by weight).
- Claim 32 “not co-administering a cytidine deaminase inhibitor.”
- Claim 33 single unit dosage form.
- Claim 34 excipient class list (mannitol, MCC, crospovidone, magnesium stearate).
- Claims 35–37 dose thresholds.
- Claims 38–43 PK thresholds.
Enforcement posture
In practice, this is an “intent + administration” claim set. For infringement, the fact pattern needs to show an administration regimen meeting the composition and exclusion conditions, plus exposure profile if asserted under PK-dependent claims.
What would a design-around need to change to evade US 8,846,628 claims?
Key “escape hatches” track the strongest claim limitations:
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Switch from non-enteric to enteric or other release architecture
This directly attacks Claim 1’s and Claim 28’s “non-enteric coated tablet” limitation.
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Change the permeation enhancer (only if the assertion targets Claims 3–5 / 29–31)
Using a different enhancer or different concentration can avoid dependent claims, while Claim 1 may still remain at risk.
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Include THU or a cytidine deaminase inhibitor in the formulation or co-administration regimen
This attacks Claims 6–7 and method Claim 32. Note: this may have clinical implications and could trigger other IP.
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Shift oral PK outcomes away from claimed thresholds
This attacks the PK-dependent dependent claims. It is not a composition design-only approach; it requires achieving a different exposure curve.
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Avoid the stated dose strengths/ranges where dependent claims are asserted
This reduces coverage under the numeric-dependent claim family, though Claim 1’s “therapeutically effective amount” still poses risk.
How many claims are “composition-only” vs “method-of-use,” and what’s the practical overlap?
Based on your claim list, the patent has two major buckets:
- Composition claims: Claims 1–27
- Method claims: Claims 28–43 (dependent to Claim 28)
Overlap effect
The method claims largely restate the composition limitations (non-enteric, excipients, enhancer, exclusions, dose thresholds) and add the therapeutic disease context (MDS/AML). That means the same formulation facts can support either:
- product infringement (composition theory) and
- clinical administration infringement (method theory).
Related patent landscape analysis: what other patent types typically surround oral 5-azacytidine?
Your provided claim text does not include bibliographic or family details for US 8,846,628 itself, and the public record for the patent’s full specification is not in scope of what you provided. Within that boundary, the landscape analysis is limited to claim-structure-driven inference of adjacent IP typically present around this exact technology stack:
Typical neighboring US patent categories
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Drug substance/compound patents (5-azacytidine itself)
Usually long ago issued or expired for nucleoside analogs unless new prodrugs/derivatives exist.
-
Formulation patents
- tablet excipient matrices
- disintegrants/surfactants
- coating systems (film/sugar)
- moisture/instability control
-
Permeation/absorption enhancer patents
- specific enhancers and their inclusion levels
- oral absorption modulation with lipophilic surfactants
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PK-driven oral delivery patents
- exposure thresholds (AUC/Cmax/Tmax) tied to oral bioavailability improvements
-
Combination therapy patents
- co-administration with cytidine deaminase inhibitors (your claims expressly exclude these as “essentially free” or “not co-administer” conditions)
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Therapeutic use patents
- disease-specific indications (MDS/AML)
- symptom or response definitions
Business implication
Given Claim 6–7 and Claim 32 exclusion language, this patent likely positions itself against a co-therapy paradigm. That increases the chance that separate patents exist covering alternative co-therapies (including cytidine deaminase inhibitors and THU), which can become relevant if a generic uses those approaches to avoid infringement.
Timeline and exclusivity: how would this patent map to regulatory exclusivity and generic entry risk?
A timeline requires at least: filing dates, issue date, and any regulatory approvals linked to the claimed formulation. No such data is contained in your prompt. Without that, any specific dates (filing/expiration, regulatory exclusivity end) would be fabricated. Therefore, this analysis stays limited to claim-scope-driven entry-risk logic:
Entry-risk logic that follows from these claim features
- A generic can be “at risk” if it sells an oral non-enteric 5-azacytidine tablet that reaches the claimed PK thresholds in humans, especially if it matches dose strength bands and excludes THU and inhibitors.
- A generic can reduce risk by:
- altering the coating architecture to be enteric/modified-release,
- including THU or a cytidine deaminase inhibitor (if clinically acceptable for the product label),
- using a different enhancer at different concentration,
- or tuning PK outcomes away from AUC/Cmax/Tmax limits.
What patent strength is implied by claim drafting: where is the estate “hard” versus “soft”?
Strength is best assessed by claim elements that are objectively verifiable and hard to change without altering the product.
Hard (high enforceability) elements
- Non-enteric coated tablet: binary structural feature.
- Specific enhancer identity and concentration: TPGS-like agent at ~2% by weight (in dependent claims).
- Explicit exclusions (THU; cytidine deaminase inhibitor “essentially free”): categorical and composition-level.
Soft or litigation-sensitive elements
- “Therapeutically effective amount”: depends on claim construction and evidence.
- “Essentially free”: admits arguments about degree and presence threshold.
- PK metrics: can be contested based on study design, fasting vs fed state, assay variability, and dosing regimen alignment with the patent’s tested conditions.
Key Takeaways
- US 8,846,628 is a formulation-centered oral patent: it targets non-enteric coated tablet delivery of 5-azacytidine with excipient constraints (dependent), optional D-alpha-tocopheryl polyethylene glycol 1000 succinate at ~2% by weight (dependent), and explicit absence of cytidine deaminase inhibitors and tetrahydrouridine.
- The patent’s “hard” enforcement hooks are the structural dosage form limit (non-enteric tablet), specific enhancer identity and level (in dependent claims), and composition/method exclusions.
- The estate also uses oral PK thresholds (AUC, Cmax, Tmax), turning infringement into a measurable bioavailability issue for dependent claims.
- Method claims extend coverage to MDS and AML using the claimed non-enteric oral tablet and repeating exclusions (no cytidine deaminase inhibitor co-administration) and PK constraints.
FAQs
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Does US 8,846,628 cover enteric-coated tablets?
No, the claims require a “non-enteric coated tablet,” so an enteric-coated form is outside the claimed dosage form limitations.
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Can a product avoid infringement by switching permeation enhancers?
It can avoid the dependent enhancer-specific claims if it does not use the claimed enhancer identity and level, but Claim 1 may still create risk if other elements match.
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What’s the infringement impact of adding THU to the tablet?
Adding THU can defeat the “essentially free of tetrahydrouridine” limitation if the product is found to contain THU to the extent that it is no longer “essentially free.”
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Do the AUC/Cmax/Tmax claim limits require clinical batch testing to prove infringement?
If asserted under PK-dependent claims, the patent ties infringement to achieving stated human exposure metrics after oral administration, so exposure data aligned with the claim conditions becomes central.
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Is the indication limited to myelodysplastic syndrome and acute myelogenous leukemia?
Yes. The method claims specifically recite MDS or AML.
References (APA)
- United States Patent No. 8,846,628. (Claims provided in prompt).
