United States Patent 5,538,982 (NK1/Tachykinin Antagonist Antiemesis): Claim Scope, Territory, and US Patent Landscape
United States Patent 5,538,982 is a US-method patent claiming antiemesis by administering an NK receptor antagonist (tachykinin antagonist), with detailed dependent coverage for specific emesis causes and, in the broadest independent claim, a very wide chemical genus of NK1 antagonists defined by multiple structural formulae plus pharmaceutically acceptable salts.
What patents protect NK1 tachykinin antagonist methods for emesis in the US?
Answer (scope anchor): US 5,538,982 protects a method of treatment of emesis (including chemotherapy-induced emesis) by administration of an NK receptor antagonist that is characterized as an NK1 receptor antagonist (tachykinin NK receptor antagonist). The claim set is structured so the chemical definitions in the specification are used to cover many NK1 antagonist compounds and their salts, while the method claims cover many etiologies of nausea/vomiting.
Independent claim 1: what the enforceable scope covers
Claim 1 (core):
A method for the treatment of a mammal suffering from or susceptible to emesis, comprising administering an effective amount of a tachykinin antagonist which is an NK1 receptor antagonist.
Claim construction consequences (high impact):
- “Method for the treatment” makes the claim enforceable against US acts of use (diagnosis or treatment steps), not just sales of API.
- “Mammal” captures humans and non-human animals (practically, enforceability typically targets human medical use).
- “Suffering from or susceptible to emesis” expands beyond active emetic episodes to prophylaxis-like administration.
- “Tachykinin antagonist” + “NK1 receptor antagonist” narrows to antagonists acting at NK1 receptors, but the chemical coverage via formulae is broad.
Dependent claim set: which emesis triggers are explicitly included
Claim 2 lists numerous emesis-inducing contexts:
- Chemotherapy, radiation sickness, radiation therapy
- poisons/toxins
- pregnancy
- vestibular disorders
- post-operative sickness
- gastrointestinal obstruction and reduced motility
- visceral pain, migraine
- altered intracranial pressure (increased or decreased)
- opioid analgesics
Claim 3–6 narrow to chemotherapy-induced emesis, with Claim 4 listing a large menu of chemotherapeutics; Claims 5 and 6 then specifically call out:
- cisplatin (Claim 5)
- cyclophosphamide (Claim 6)
Claim 7 adds non-oncology triggers:
- morphine, ipecacuanha, copper sulphate
Practical enforceability read-through: A product administered to prevent or treat nausea/vomiting caused by these conditions, where the regimen uses a tachykinin/NK1 antagonist matching the patent’s chemical genus, is at higher risk of meeting the method claim elements.
What is the claim coverage for NK1 antagonist compounds under US 5,538,982?
Answer (chemical scope anchor): Claim 1 requires an NK1 receptor antagonist. The patent’s structural coverage is expressed through multiple Markush-style formulae (not fully reprinted here) defining Ar, R, R1, R11 and additional embodiments under STR31, STR32, STR33, and Y/P/Z/R1/R2 variables, plus pharmaceutically acceptable salts.
Markush-style genus breadth: what the formula language implies
From the claim text you provided, the genus includes:
- Aryl definitions (Ar): thienyl, phenyl, fluorophenyl, chlorophenyl, bromophenyl
- Substitution variability: extensive optional substitutions on rings (cyano, nitro, amino, N-monoalkylamino, F/Cl/Br/CF3, alkyl, alkoxy, allyloxy, hydroxy, carboxy, carboxamido, N,N-dialkylcarboxamido)
- Alkyl/alkoxy chain length control: often limited to C1–C4 (or C1–C3) on substituents
- R1 variability: includes multiple heterocycles and fused/functionalized ring systems, including substituted phenyl and heteroaryl options
- R11 variability: branched C3–C4 alkyl, branched alkenyl C5–C6, cycloalkyl C5–C7, furyl/thienyl/pyridyl/indolyl/biphenyl, plus substituted phenyl restrictions (“always other than unsubstituted phenyl, fluorophenyl, chlorophenyl, bromophenyl or alkylphenyl” when other conditions are met)
The formula for alternative embodiments (STR32, STR33) continues the genus concept:
- STR32: defines R1 (H or C1–C6 alkyl), R2 and R3 phenyl/heteroaryl options with 1–3 substituents (C1–C4 alkyl/alkoxy, halogens, I, CF3)
- STR33: defines Y as CH2 repeated 1–3 or another group formula; P is 0–1; Z can be oxygen, sulfur, amino, N-(C1–C3)alkylamino, or substituted methylene with constraints; R1 and R2 have additional ring substituent ranges; again includes pharmaceutically acceptable salts
What this means for “coverage” vs “practical design-around”
- The claims (as you pasted) are consistent with broad structural genus coverage rather than a single lead scaffold.
- A credible design-around must avoid the specific chemical variable combinations that map into the stated formula constraints, plus avoid the NK1 antagonism requirement.
- Because the emesis trigger list is broad, design-around strategies are more likely to focus on chemistry (non-genus chemistry or non-NK1 mechanism) or on shifting into uses that do not fit the claimed emesis indications (though the claim includes “susceptible to emesis,” which makes indication-based carve-outs harder).
When does US 5,538,982 lose exclusivity in the US?
Answer: The patent term for a US utility patent depends on filing date and any patent term adjustments or terminal disclaimers. No filing date, issue date, or PTO/terminal disclaimer information is present in your prompt, so a precise loss-of-exclusivity date cannot be computed from the provided record.
What is the Orange Book status of US 5,538,982?
Answer: Orange Book status requires matching the patent to an FDA-approved drug product code and then checking listed patents for that NDA/ANDA. Your prompt does not include the drug name, NDA/ANDA number, or Orange Book listing, so the Orange Book linkage cannot be established from the supplied information.
What generic entry risks exist for NK1 antagonists covered by US 5,538,982?
Answer (risk framing based on claim structure): The main generic risk arises when:
- The generic ANDA manufactures and sells a competing NK1 antagonist product that is within the chemical genus (or literal equivalents that fall within the Markush variables as construed), and
- Generic entry is paired with label instructions or actual medical use that matches the claimed emesis contexts (including prophylaxis since “susceptible to emesis” is included), especially chemotherapy-induced emesis such as cisplatin and cyclophosphamide.
Because the claims are method-of-treatment, labeling that instructs NK1 antagonist use for these indications can be a key trigger for enforcement. If generic labeling is carved away from the claimed emesis etiologies, a design-around may reduce literal infringement exposure; however, prophylactic wording and broad “susceptible” language can weaken those carve-outs.
Which companies are likely implicated in the NK1 antagonist landscape tied to US 5,538,982?
Answer: The specific companies depend on which NK1 antagonist compounds are within the patent’s claimed formula genera and which of those compounds are FDA-approved and marketed in the US. No active ingredient name(s), NDA/ANDA numbers, or assignees/licensees for US 5,538,982 are provided in your prompt, so entity-level mapping cannot be performed reliably from the supplied data.
How strong is the patent estate around US 5,538,982 for NK1 antiemesis?
Answer (based on claim architecture only): US 5,538,982 has a strong breadth posture on two axes:
- Medical use breadth: many emesis causes are explicitly enumerated, and “susceptible to emesis” expands prophylaxis coverage.
- Chemical breadth: multiple formula embodiments with wide options on ring systems and substitutions suggest broad genus protection.
Litigation leverage implications:
- Broad genus language can create higher infringement surface area against multiple NK1 antagonist candidates and follow-on analogs, depending on claim construction and prosecution history.
- The enumerated chemotherapeutics (including cisplatin and cyclophosphamide) increases practical enforceability in oncology supportive care where NK1 antagonists are commonly used.
What patent litigation affects US 5,538,982?
Answer: Litigation requires case citations, court dockets, and parties. Your prompt does not include litigation records, case numbers, or assignees, so litigation impact cannot be determined.
What formulations are protected by US 5,538,982?
Answer: The claims you provided are method-of-treatment claims and do not explicitly claim a formulation composition (e.g., dosage form, sustained-release matrix, specific excipients). Without additional claim text that recites formulation/dosage/administration device constraints, the protected subject matter is primarily the act of administering the NK1 antagonist for the claimed emesis indications.
Does US 5,538,982 overlap with NK1 antagonist use against chemotherapy-induced emesis (CINV)?
Answer: Yes by claim design. Claim 2–6 explicitly cover:
- emesis induced by cancer chemotherapeutic agents
- including cisplatin and cyclophosphamide
Timing note: For supportive care, NK1 antagonists are often administered before or around chemo dosing. The claim language “suffering from or susceptible to emesis” supports both treatment and prophylaxis timing.
How does US 5,538,982 compare with other NK1 antagonist patents in the US?
Answer: Comparison requires identifying:
- the patent’s active ingredient(s) within the genus,
- priority relationships and continuation/divisional family structure,
- and which other patents claim composition vs method vs specific compounds.
Your prompt does not provide patent family members, assignees, priority dates, or the specific NK1 antagonists targeted, so no defensible comparison can be produced.
Key claim-scope table (from your provided text)
| Claim |
Infringement element emphasized |
Covered emesis / context |
Chemical requirement |
| 1 |
Method for treatment of a mammal with emesis |
“Suffering from or susceptible to emesis” (broad) |
Administer effective amount of a tachykinin antagonist that is an NK1 receptor antagonist |
| 2 |
Additional limitation: type of emesis trigger |
Cancer chemotherapy, radiation sickness/therapy, pregnancy, vestibular, post-operative, GI obstruction, reduced motility, visceral pain, migraine, intracranial pressure changes, opioid analgesics, etc. |
Same as claim 1 |
| 3 |
Narrow trigger |
Cancer chemotherapeutic agent-induced emesis |
Same as claim 1 |
| 4 |
Enumerated chemo agent set |
Long list including cisplatin, cyclophosphamide, doxorubicin, 5-FU, methotrexate, etc. |
Same as claim 1 |
| 5 |
Narrow enumerated chemo agent |
Cisplatin-induced emesis |
Same as claim 1 |
| 6 |
Narrow enumerated chemo agent |
Cyclophosphamide-induced emesis |
Same as claim 1 |
| 7 |
Non-oncology emesis triggers |
Morphine, ipecacuanha, copper sulphate |
Same as claim 1 |
| 8+ (chemical dependency via formulas) |
NK1 antagonist identity |
Not limited by emesis cause beyond claim chain |
Chemical genus per STR31/STR32/STR33 (and salts) |
Key Takeaways
- US 5,538,982 is a method-of-treatment NK1 antagonist patent focused on antiemesis in mammals, with prophylaxis-like reach via “suffering from or susceptible to emesis.”
- Claim 2 and Claim 2–6 drive oncology supportive-care exposure, explicitly listing chemotherapy-induced emesis and naming cisplatin and cyclophosphamide.
- Chemical coverage is broad through multiple Markush-style formula embodiments defining an NK1 antagonist genus plus salts, which increases the number of plausible in-scope NK1 compounds.
- Orange Book status, exclusivity dates, company mapping, and litigation risk cannot be derived from the claim text alone because the FDA product linkage, assignee, and family/timeline data are not included.
FAQs
1) Is US 5,538,982 limited to chemotherapy-induced emesis?
No. Chemistry-induced emesis is one explicit dependent pathway, but the independent claim covers emesis broadly and dependent claim 2 enumerates many non-oncology and mixed etiologies.
2) Does the patent cover both treatment and prevention of nausea/vomiting?
Yes. “Suffering from or susceptible to emesis” supports both active-treatment and prophylactic use.
3) Does the patent protect a specific NK1 antagonist only or a chemical class?
The patent language is consistent with a chemical genus defined by structural formula variables (STR31/STR32/STR33), not a single compound only.
4) Can a generic avoid infringement by omitting cisplatin from its label?
Not reliably, because the claims also cover other chemotherapeutic agents (Claim 4) and broader emesis triggers (Claims 1 and 2).
5) Are formulation-specific dosage forms claimed in US 5,538,982 based on the provided claims?
No. The provided claims are method-of-treatment claims tied to administration of an NK1 antagonist; they do not, as provided, recite excipient/dosage-form limitations.
References (APA)
- United States Patent No. 5,538,982. (Claims excerpt as provided by user).
