United States Patent 9,387,191 Ferric Citrate Tablet Patent Landscape: Claim Scope, Variants, and US Exclusivity Risk Map
US Patent 9,387,191 claims specific solid oral dosage formulations of ferric citrate with tightly defined core composition ranges, lubricant identity, and performance specifications tied to USP <711> dissolution, friability, moisture (LOD), and disintegration time. The claims are narrow in structure and performance, creating a formulation-design “escape hatch” for generics that can alter one or more claim-critical parameters (especially moisture window, starch and lubricant ranges, and dissolution/disintegration thresholds) while still meeting FDA quality specs.
What do the claims of US 9,387,191 cover for ferric citrate tablets?
Core concept: A ferric citrate tablet with a defined high ferric citrate content (90 to 92 wt%), a pregelatinized starch binder/disintegrant component at specified levels, and a low-percentage lubricant (magnesium stearate or calcium stearate), plus a coating, where the finished tablet meets strict friability, dissolution (USP <711>), and moisture (LOD) criteria; dependent claims further lock in lubricant type, dose mass (≈1000 mg ferric citrate), and disintegration time.
Claim chart summary (independent vs dependent)
| Claim |
Ferric citrate core wt% |
Pregelatinized starch wt% |
Lubricant wt% |
Key performance limits |
Moisture (LOD) |
Disintegration |
| 1 |
~90–92% |
~4.5–30% |
~0.5–3% |
Friability ≤1% w/w; ≥80% dissolved ≤60 min (USP <711) |
<10% |
≤30 min (via dependent claim 5) |
| 6 |
~90–92% |
~4.5–30% |
~0.5–3% |
Same friability and dissolution |
5–10% |
≤30 min (via dependent claim 10) |
| 11 |
~90–92% |
~1.5–15% |
~0.5–3% |
Friability ≤1%; ≥80% dissolved ≤60 min |
5–10% |
≤30 min (via dependent claim 15) |
| 16 |
fixed formulation |
fixed |
fixed |
Friability ≤1%; disintegration <15 min; ≥80% dissolved ≤60 min |
fixed 8.84% |
<15 min |
Structural claim scope boundaries embedded in the language
- Ferric citrate content: roughly 90–92 wt% for claims 1/6/11; fixed in claim 16 (87.6 wt%).
- Pregelatinized starch range is a major differentiator:
- Broadest: ~4.5–30 wt% (claims 1 and 6)
- Narrower: ~1.5–15 wt% (claim 11 and downstream)
- Lubricant composition is constrained only by identity via dependent claims:
- Claim 1/6/11 recite “a lubricant” (no identity in those independent claims)
- Dependent claims specify lubricant is magnesium stearate or calcium stearate (claims 2–3, 7–8, 12–13)
- Performance gating conditions:
- Friability ≤1% w/w
- Dissolution: at least 80% ferric citrate dissolved in ≤60 minutes by USP <711>
- Moisture (LOD):
- Claim 1: <10%
- Claims 6 and 11: 5–10%
- Claim 16: 8.84%
- Disintegration: dependent claims cap at ≤30 min; claim 16 requires <15 min
Practical legal implication of those boundaries
The claims combine composition ranges and finished product parameters. A competitor can reduce infringement risk by changing (i) starch level, (ii) moisture window, (iii) disintegration performance, or (iv) lubricant identity. Because the language ties dissolution to USP <711> and uses a “≥80%” threshold, generic formulations must match not just material amounts but dissolution kinetics under that test method.
How narrow are the “moisture content” and “USP <711> dissolution” limitations for infringement?
Moisture content (LOD) is a claim-critical gating parameter
- Claim 1: moisture content <10%
- Claim 6 and 11: moisture content between 5% to 10%
- Claim 16: moisture content 8.84%
Effect on design-around: A formulation that can be manufactured and released consistently with LOD below 5% or above 10% may fall outside claims 6/11 while still meeting other quality requirements. Claim 1 is broader (only “<10%”), so moving above 10% is more effective for escaping claim 1 scope, assuming manufacturability and stability allow.
USP <711> dissolution constraint is also gating
All independent claims you provided include the same dissolution condition:
- Tablet must have at least 80% ferric citrate dissolved in ≤60 minutes using USP <711>.
Effect on design-around: Faster or slower dissolution can matter; however, the claim as written is satisfied by meeting or exceeding the dissolution criterion. Many formulations that meet FDA dissolution specs may still land within this performance envelope, so the most useful escape routes remain moisture and composition windows.
Which dependent claim elements most constrain competitors (magnesium stearate vs calcium stearate)?
Dependent claims tighten the lubricant identity:
- Magnesium stearate: claims 2, 7, 12
- Calcium stearate: claims 3, 8, 13
Lubricant identity vs lubricant “range” argument
The independent claims allow “a lubricant” at ~0.5–3 wt%. Dependent claims then limit that lubricant to either magnesium stearate or calcium stearate.
Infringement risk profile:
- If a generic uses a lubricant other than magnesium or calcium stearate, it can reduce exposure to dependent claims while remaining at risk under the independent claims (since the independent claims still require only “a lubricant” and not a specific one, as provided).
- If a generic uses magnesium or calcium stearate, it increases risk of dependent-claim capture, provided the rest of the composition and performance elements are met.
What is the coverage difference between claims 1, 6, and 11?
All three share: 90–92 wt% ferric citrate, starch, lubricant, coating, friability ≤1%, ≥80% dissolution in ≤60 min (USP <711>).
They diverge on:
- Moisture LOD requirement
- Claim 1: LOD <10%
- Claims 6 and 11: LOD 5–10%
- Pregelatinized starch range
- Claim 1: starch ~4.5–30%
- Claim 6: starch ~4.5–30% (same as claim 1)
- Claim 11: starch ~1.5–15% (narrower)
- Disintegration
- Both claim 1 and 6 use disintegration ≤30 min via dependent claims (5 and 10)
- Claim 11 uses disintegration ≤30 min via dependent claim 15
Takeaway: Claims 6/11 are more selective because of the LOD band (5–10%) and, in claim 11, the starch lower bound and upper bound.
How does claim 16 change the landscape with fixed composition and faster disintegration?
Claim 16 is a “snapshot” claim with fixed parameters:
- Ferric citrate: 87.6 wt%
- Pregelatinized starch: 10 wt%
- Calcium stearate: 2.4 wt%
- Tablet moisture: 8.84% (LOD)
- Friability ≤1%
- Disintegration <15 minutes
- Dissolution: ≥80% in ≤60 min (USP <711>)
Effect on infringement risk: A competitor’s formulation that meets the broader claims 1/6/11 could still avoid claim 16 by not matching the fixed composition triplet (ferric citrate/starch/lubricant) and, more importantly, by not achieving disintegration <15 min plus LOD 8.84%.
Because claim 16 is likely narrower than range-based independent claims, it typically functions as an additional claim layer to catch a specific preferred manufacturing window.
What patent estate features are implied by these claim types for ferric citrate?
Based on the claim structure you provided, the patent estate is likely built around:
- Formulation composition claims (core fractions of ferric citrate and starch; small lubricant percentage)
- Finished-product performance constraints (friability, dissolution, disintegration)
- Process-independent composition capture (no explicit manufacturing step is visible in the claim text you provided)
- Alternate dependent claim families for lubricant identity and specific tablet strengths/masses (e.g., “approximately 1000 mg ferric citrate”)
That combination is common in formulation patents meant to:
- preserve “product by formulation” exclusivity for specific release profiles and mechanical properties; and
- make generic design-around harder unless a developer can decouple moisture and release characteristics.
What US exclusivity and generic entry risks exist tied to this patent?
Key point: Your claim set is formulation-specific, so the primary risk for a generic applicant is paragraph IV exposure if it files under FDA ANDA (small molecules) with a formulation that meets the same composition/performance envelope.
Risk drivers to map for any ANDA challenger
- Does the ANDA tablet hit friability ≤1%?
- Does it hit ≥80% dissolution in ≤60 min by USP <711>?
- What is the tablet moisture LOD at release and in stability?
- What starch level is used and does it fall within claim windows?
- Does the lubricant match magnesium or calcium stearate?
- Does the formulation disintegrate within ≤30 minutes (or <15 minutes for the fixed claim 16)?
- Does the ANDA tablet strength align with “approximately 1000 mg ferric citrate” if the challenger expects those dependent claims to matter.
How should a competitor evaluate likely claim infringement without knowing other patents in the family?
A competitor can treat the claims as a multi-variable “AND gate.” If any element fails (e.g., LOD outside claimed bands or starch outside the range), that claim may not be met. The highest priority in a freedom-to-operate analysis is usually the elements that are hardest to control across sites and lots.
For this patent, the “hard to control” cluster is typically:
- moisture (LOD),
- dissolution profile under USP <711>, and
- disintegration time.
Which claim elements are most likely to be litigated in US formulation patent disputes?
Formulation disputes usually turn on whether the accused ANDA product meets the claimed objective test outcomes. For this patent, the most litigation-relevant objective terms are:
- USP <711> dissolution (≥80% in ≤60 minutes)
- Friability (≤1% w/w)
- Moisture content (LOD) (bands and the specific fixed 8.84%)
- Disintegration time (≤30 minutes and <15 minutes)
Composition ranges can also be litigated, but objective dissolution/friability/moisture outcomes often drive expert test designs.
Key takeaways
- US 9,387,191 is a ferric citrate tablet formulation patent built around narrow composition ranges and objective performance constraints: friability ≤1%, USP <711> dissolution ≥80% in ≤60 minutes, and LOD moisture windows.
- Claim scope is three-layered: range-based composition claims (claims 1/6/11) plus a fixed preferred embodiment (claim 16) with calcium stearate at 2.4 wt%, LOD 8.84%, and disintegration <15 minutes.
- For generic design-around, the highest leverage elements are LOD moisture bands, pregelatinized starch range, and disintegration time. Lubricant identity matters for the dependent claim set when magnesium/calcium stearate is used.
- Litigation and ANDA risk concentration is most likely around whether the accused product meets USP <711> dissolution, friability, and LOD targets.
FAQs
1) Does US 9,387,191 require a specific tablet coating composition?
The claims require “a coating” but do not, in the provided claim text, specify coating ingredients or thickness, so the coating requirement mainly functions as a structural element rather than a composition-limited feature.
2) If a generic’s tablet meets dissolution and friability but has LOD below 5%, does it avoid claims 6 and 11?
Claims 6 and 11 require LOD between 5% and 10%, so LOD below 5% can avoid those independent claims, while claim 1 remains potentially relevant if LOD is still <10%.
3) Can using a lubricant other than magnesium stearate or calcium stearate avoid the dependent claims?
It can avoid dependent-claim capture tied to those specific lubricant identities, but independent claims still require only “a lubricant” within the recited range unless additional dependent limitations apply.
4) What performance parameter is most likely to be measured under dispute?
USP <711> dissolution and LOD moisture are likely highest-frequency metrics because they use defined test methods and thresholds in the claims.
5) What makes claim 16 strategically important for enforcement?
Claim 16 fixes the formulation and tightens performance with disintegration <15 minutes and LOD 8.84%, allowing enforcement against products matching that specific manufacturing window even if a competitor avoids the broad range claims.
References
- United States Patent No. 9,387,191 (claims provided by user).
