Patent 8,916,131 Landscape: What Claims Cover for Aqueous-Ethanol Radiopharmaceuticals With Polysorbate (US8916131)
US Drug Patent 8,916,131 claims a radiopharmaceutical composition defined by an aqueous ethanol carrier, a specific polysorbate concentration band, and a broad formulation pH window. The core protection is composition-level: carrier medium (aqueous ethanol) plus polysorbate surfactant at 0.25-2.5% w/v (with dependent claims narrowing to 0.5-1.0% w/v and polysorbate 80) and a pH of 4.0 to 10.5.
What does US 8,916,131 claim protect for radiopharmaceutical compositions?
Answer: A composition comprising (1) an aqueous ethanol carrier medium, (2) polysorbate at 0.25-2.5% w/v, and (3) formulation pH 4.0-10.5, framed for use as a radiopharmaceutical composition.
Scope of independent claim 1 (composition definition)
Claim 1 is written as a radiopharmaceutical composition with three limiting formulation parameters:
- Biocompatible carrier medium of aqueous ethanol
- The claim requires an aqueous ethanol system described as “biocompatible” and the medium is “aqueous ethanol,” not an aqueous-only system and not a non-ethanol cosolvent system.
- Polysorbate content: 0.25-2.5% w/v
- This is a concentration-limited surfactant element. The infringement-relevant question usually becomes whether an accused product is within the claimed w/v range and uses a polysorbate species covered by the claim structure.
- pH of 4.0 to 10.5
- The claim has a broad pH window that spans from mildly acidic to strongly basic conditions. That breadth increases the probability that many radios are formulated within range, depending on their buffering and stability requirements.
Dependent claims narrow but do not change the carrier system concept
- Claim 2 narrows polysorbate to 0.5-1.0% w/v.
- Claim 3 specifies the polysorbate species as polysorbate 80.
Practical reading: Claim 1 gives the broadest numerical protection. Claims 2 and 3 create nested narrower protection for tighter concentration and for Tween 80 specifically.
How broad is the pH range (4.0 to 10.5) and what does it imply for design-around?
Answer: Claim 1 covers formulations buffered or adjusted to anywhere between pH 4.0 and 10.5, which substantially reduces the value of pH-only design-arounds.
pH element is a strong infringement hook
- The pH range is a numerical limitation. Any formulation outside the range would avoid this element, but staying outside may be incompatible with:
- radiolabel stability,
- chelator integrity,
- hydrolysis or aggregation risk,
- solubility constraints for the target drug (which the claim does not specify in the excerpt).
Where design-arounds typically occur
Within the claimed framework, design-around efforts usually shift on:
- Surfactant concentration (move below 0.25% w/v or above 2.5% w/v),
- Surfactant identity (use a non-polysorbate surfactant or a different polysorbate species not covered by dependent claims, while still risking claim 1 if “polysorbate” remains generic to the independent claim),
- Carrier medium (remove ethanol or replace with a different cosolvent system so it is no longer “aqueous ethanol”),
- pH (move below 4.0 or above 10.5).
Given the claim’s broad pH band, pH-only changes are the least attractive unless a formulation can be engineered without degrading the radiopharmaceutical’s stability.
How does the polysorbate concentration limit (0.25-2.5% w/v) constrain competitors?
Answer: The claimed surfactant concentration is a numerical gate. Products with polysorbate concentrations outside 0.25-2.5% w/v avoid at least claim 1. Claim 2 adds an additional tighter gate of 0.5-1.0% w/v.
Claim 2 creates an even tighter “sweet spot” exposure band
If a competitor uses:
- 0.5-1.0% w/v polysorbate, it hits both claim 1 (because it sits inside 0.25-2.5) and claim 2.
If a competitor uses:
- 0.25-0.5% w/v or 1.0-2.5% w/v, it is within claim 1 but outside claim 2.
If a competitor uses:
- <0.25% w/v or >2.5% w/v, it avoids claim 1 (and thus avoids claim 2 as well).
Polysorbate 80 specificity in claim 3
Claim 3 is limited to polysorbate 80. Even if a competitor uses polysorbate at 0.25-2.5% w/v, claim 3 only applies if the species is polysorbate 80.
What happens if a competitor uses polysorbate but not polysorbate 80?
Answer: In your claim set, claim 1 reads on “polysorbate” generically, while claim 3 reads on polysorbate 80 specifically.
Likely infringement posture from the excerpt alone
- A competitor using polysorbate 20, polysorbate 40, or other polysorbate members would still potentially satisfy claim 1 if the carrier and pH and concentration align.
- The competitor would avoid claim 3 if not using polysorbate 80, but claim 1 would remain in play.
Design-around logic
If a company wants to avoid claim 3 specifically, it can swap polysorbate 80 for a different polysorbate. That is only a partial design-around if claim 1’s “polysorbate” term remains satisfied.
Which carrier systems avoid “aqueous ethanol” (and thus avoid claim 1)?
Answer: Any formulation that is not an aqueous ethanol biocompatible carrier medium can fall outside claim 1.
Carrier medium is a limiting element
From the excerpt, claim 1 requires:
- “biocompatible carrier medium of aqueous ethanol.”
This implies that:
- Removing ethanol entirely (pure aqueous, with alternative solubilizers) may avoid the element.
- Replacing ethanol with a different cosolvent (e.g., propylene glycol, polyethylene glycol, glycerol, DMSO analogs, or cyclodextrin systems) may also avoid “aqueous ethanol.”
“Aqueous ethanol” boundary issues
If accused formulations contain ethanol as a minority component inside a mixed solvent system, infringement will turn on claim construction of “aqueous ethanol carrier medium.” Without the full claim language, the practical risk is that regulators and litigators may interpret “aqueous ethanol” broadly as any composition where ethanol is present in an aqueous carrier as the defining cosolvent.
What formulation competitors are most likely at risk under US 8,916,131?
Answer: Radiopharmaceutical products formulated with:
- aqueous ethanol as a cosolvent,
- polysorbate at 0.25-2.5% w/v,
- pH 4.0-10.5,
- and particularly products using polysorbate 80 with 0.5-1.0% w/v.
High-risk formulation patterns
- Ethanol-water preparation with Tween 80 at roughly 0.5-1.0% w/v,
- Buffered solutions across typical radiopharmaceutical pH targets (commonly buffered near neutral to mild acidity, but the claim covers a wide range).
Lower-risk patterns
- Polysorbate-free formulations,
- Polysorbate outside the range,
- Non-ethanol cosolvent systems,
- pH outside 4.0-10.5.
How does US 8,916,131 compare with typical radiopharmaceutical formulation IP (surfactant + cosolvent + pH)?
Answer: The claim’s strength is that it ties three formulation variables together (aqueous ethanol + polysorbate band + pH window). Many radiopharmaceutical patents focus on chelators, radionuclides, labeling methods, or specific active radiopharmaceutical compounds. This patent is composition-level for a formulation vehicle that can be applied across radiopharmaceuticals.
Composition vehicle patents typically create broad licensing pressure
If this formulation approach is used broadly in multiple radios, the risk is product-platform coverage rather than a single drug. The main limitation is that the radiopharmaceutical composition must meet all three formulation limits simultaneously.
What method-of-use, labeling, or manufacturing claims are included?
Answer: The excerpt you provided contains only composition claims (independent claim 1 and dependent claims 2-3). There is no information here indicating method-of-use, labeling, or manufacturing claims.
What that means for enforcement
- The alleged act usually becomes the sale/use/manufacture of the specific formulation meeting claim elements.
- Design-around strategies can focus on formulation variables rather than clinical indications or manufacturing steps.
How long does US 8,916,131 remain in force, and what affects expiration timing?
Answer: Expiration timing cannot be calculated from the excerpt alone because the filing date, patent term adjustments, and any terminal disclaimers are not provided.
Key drivers for term
- Provisional/application filing date,
- Nonprovisional filing date,
- Patent term adjustment (P.T.A.),
- Terminal disclaimers and any later-filed family members that may affect effective exclusivity.
What Orange Book status, FDA listing, or Paragraph IV challenges apply?
Answer: No Orange Book data or FDA listing information is included in the excerpt, and the analysis cannot map this patent to a specific listed drug or NDA/BLA number.
What patent landscape analysis can be concluded from only claims 1-3?
Answer: From claim structure alone, this patent is best categorized as a formulation composition IP covering a radiopharmaceutical carrier system with aqueous ethanol, polysorbate at defined concentration, and pH range.
Claim-by-claim coverage matrix (based strictly on your excerpt)
| Claim |
Key limitations in excerpt |
Practical coverage implication |
| 1 |
Aqueous ethanol biocompatible carrier + polysorbate 0.25-2.5% w/v + pH 4.0-10.5 |
Core composition-level formulation protection |
| 2 |
Claim 1 plus polysorbate 0.5-1.0% w/v |
Narrower band within claim 1 |
| 3 |
Claim 1 plus polysorbate is polysorbate 80 |
Species-specific to Tween 80 |
How strong is the claim set for litigation outcomes?
Answer: Strength is driven by numerical constraints that are straightforward to test in formulation characterization and by the breadth of pH.
Elements that are relatively “verifiable”
- Polysorbate concentration (% w/v): typically measurable via standard analytical chemistry.
- pH: measurable at time of testing and potentially tied to formulation specs.
- Presence of ethanol in an aqueous carrier: testable by composition analysis.
Main risk areas for enforcement
- Claim construction of “aqueous ethanol carrier medium.”
- Whether a competitor’s “carrier” qualifies as “aqueous ethanol” if ethanol is present only as a minor component.
- Stability-driven formulation changes: if pH or polysorbate concentration drift outside specs, actual infringement may turn on whether the accused product meets claim limits at relevant times.
What generic entry risks exist if this formulation is widely used?
Answer: If the industry standard for a given radiopharmaceutical includes aqueous ethanol plus polysorbate within the claimed band and pH range, generic or competitor entry risks rise because a design-around must change at least one of the three limiting parameters.
Likely licensing triggers
- If multiple products use the same formulation platform, this patent can become a cross-product licensing position.
- If competitors need polysorbate 80 specifically, claim 3 adds further leverage.
Key Takeaways
- US 8,916,131 claims a radiopharmaceutical composition platform defined by aqueous ethanol carrier, polysorbate 0.25-2.5% w/v, and pH 4.0-10.5.
- Claim 2 tightens exposure to 0.5-1.0% w/v polysorbate.
- Claim 3 specifically targets polysorbate 80, but claim 1 appears to cover polysorbate generically.
- The most direct design-arounds change at least one of: ethanol/carrier system, polysorbate concentration, or pH outside 4.0-10.5.
FAQs
1) Does changing from polysorbate 80 to another polysorbate avoid US 8,916,131?
Avoids claim 3 if not using polysorbate 80, but may still fall within claim 1 if polysorbate remains and concentration and pH and aqueous ethanol are within limits.
2) If a competitor sets pH to 3.9, does that avoid claim 1?
Yes, based on claim 1’s pH requirement of 4.0 to 10.5, moving below 4.0 avoids that limitation.
3) What polysorbate concentration range avoids claim 2?
Any level outside 0.5-1.0% w/v avoids claim 2, but still may infringe claim 1 if within 0.25-2.5% w/v.
4) Is the carrier ethanol requirement binary or proportional?
The excerpt says “biocompatible carrier medium of aqueous ethanol,” so infringement turns on whether the accused formulation is construed as an aqueous ethanol carrier system.
5) Are radiolabeling or chelation steps part of this claim set?
The excerpt contains only composition elements; it does not indicate method-of-use or labeling/manufacturing steps.
References
- United States Patent 8,916,131. (Claims excerpt provided in prompt).
