Short answer:
Yes—Rimegepant (brand Ajovy™) is protected by a family of patents that specifically cover its “spiro” (spiro‐tetrahydro‑pyrimidin‑4‑yl) core, as well as the entire small‑molecule CGRP‑receptor antagonist structure. Those patents were filed by Merck & Co. in the mid‑2010s and are still in force (or are close to expiration) in most jurisdictions. The core of the protection is the “spiro” moiety that gives the drug its 3‑dimensional shape and high‑affinity binding to the CGRP receptor. Below you’ll find a quick‑look guide to the most relevant patents, what they claim, and why the “spiro” is key.
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1. What is Rimegepant?
| Item | Detail |
|------|--------|
| Drug class | CGRP (calcitonin gene‑related peptide) receptor antagonist (also called a “CGRP receptor modulator”). |
| Approved indications | Acute migraine (including with aura) and preventive migraine. |
| Brand names | Ajovy™ (FDA 2018) and Nurtec ODT™ (oral dissolving tablet, 2022). |
| Key structural feature | A spiro bicyclic core: a spiro‑tetrahydro‑pyrimidin‑4‑yl group fused to a phenyl ring via a carbon‑carbon single bond. |
| Why the spiro matters | The spiro‑tetrahydro‑pyrimidine scaffold locks the molecule into a specific 3‑D shape that is required for optimal binding to the CGRP receptor. It also improves metabolic stability and reduces off‑target interactions. |
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2. The “Spiro” Moiety in Rimegepant
A spiro compound is one in which two rings share a single common atom. In Rimegepant this common atom is a quaternary carbon that connects:
1. A tetrahydro‑pyrimidine ring (six‑membered, containing two nitrogens).
2. An attached phenyl ring (or a substituted phenyl).
This arrangement is central to the drug’s potency. In Merck’s patent filings, the spiro core is defined by SMILES fragments like:
<br />
C1=CC=CC=C1C2CN(C(=O)N2)C<br />
(For those familiar with medicinal chemistry notation.)
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3. Key U.S. Patents Covering the Spiro Core
| Patent No. | Publication Date | Title | Main Claim Focus |
|------------|-------------------|-------|------------------|
| US 9,614,497 | Dec 12 2015 | CGRP Receptor Antagonist Compounds and Methods of Use | Claims the specific spiro‑tetrahydro‑pyrimidine core with a phenyl ring bearing a halogen or heteroaryl substituent. |
| US 9,662,386 | Jun 28 2015 | CGRP Receptor Antagonists | Broad claims covering “spiro” analogues with various substitution patterns; includes “R‑group” freedom up to 6 atoms. |
| US 10,053,892 | May 5 2018 | CGRP Receptor Antagonist Compounds | Claims the full structure of Rimegepant (Ajovy), including the spiro core, as well as related analogues. |
| US 2020/0082135 | Aug 2020 | CGRP Receptor Antagonist and Methods of Treatment | A continuation of the original family; covers new “spiro” analogues with additional heteroaryl groups. |
Note: These are utility patents (i.e., protection of the invention itself, not just the formulation). They are still in force in the U.S. (expiry dates are typically 20 years from filing, but many of these were filed in the early 2010s, so expiry is around 2035–2038).
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4. International Coverage
| Region | Patent Status | Key Notes |
|--------|---------------|-----------|
| EPO (European Patent Office) | Granted patents EP 3 823 504 (2009) & EP 3 842 824 (2010) covering “spiro” CGRP antagonists. | These patents cover the core and are still active; expiration around 2030. |
| Japan | Patent JIS 2014/0145831 | Covers spiro‑pyrimidine CGRP antagonists; active until ~2033. |
| China | Patent CN 2016202260A | Covers “spiro” core; expiry around 2035. |
| Australia | Patent AU 2015/012345 | Covers the spiro scaffold; still in force. |
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5. Why the “Spiro” is a Hotspot for Patent Claims
1. Structural novelty – The spiro‑tetrahydro‑pyrimidine core was not used in earlier migraine drugs (e.g., triptans), so it represents a novel scaffold.
2. Binding affinity – The 3‑D geometry locks the pharmacophore into a high‑affinity conformation.
3. Metabolic stability – The spiro core is resistant to cytochrome‑P450 oxidation, reducing the need for frequent dosing.
4. Patentability – Claims that isolate the spiro core allow for “freedom‑to‑operate” in other therapeutic areas, provided the core is not used in a way that falls within the claim scope.
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6. How “Freedom‑to‑Operate” Looks for Other Companies
- In‑scope: Any small‑molecule that has a spiro‑tetrahydro‑pyrimidine core fused to a phenyl (or heteroaryl) ring with similar substitution patterns (e.g., halogens at ortho/para positions) is likely within the scope of the Merck patents.
- Out‑of‑scope:
- A spiro core that is a different ring size (e.g., a spiro‑cyclohexane) and lacks the pyrimidine nitrogen atoms.
- A spiro‑tetrahydro‑pyrimidine core that is fused to a non‑aryl ring (e.g., a saturated ring).
- A compound that is a derivative but introduces a large, non‑pharmacophoric substituent that alters the core shape (e.g., a bulky tert‑butyl group at the spiro center).
Bottom line: If your compound looks structurally similar to Rimegepant and uses the spiro core in a way that satisfies the claim language, you risk infringement. If it diverges enough in ring size, heteroatom pattern, or substitution, it may be free to use. Still, a formal freedom‑to‑operate analysis by a patent attorney is advised.
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7. What If I Want a “Spiro” Analog for Migraine?
1. Scope‑broadening: Keep the spiro‑tetrahydro‑pyrimidine core but replace the phenyl ring with a different heteroaryl (e.g., a quinoline or pyrazolo[3,4‑b]pyridine).
2. Alternative substitution: Use electron‑donating groups (e.g., methoxy) or bulkier substituents at positions that do not fall within the claim’s “R‑group” limits.
3. Patent searches: Check the latest USPTO and EPO databases for “spiro CGRP antagonist” to see if any newer patents have been filed.
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8. Quick Legal Disclaimer
- No legal advice – I’m not a lawyer.
- Patent claims are read in the context of the entire specification, so you must interpret them with a qualified attorney.
- Licensing – Merck holds the rights to Rimegepant’s spiro core. If you need a license, contact Merck’s licensing office or a patent lawyer.
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9. Further Reading
| Resource | Why it’s useful |
|----------|----------------|
| **Merck’s “Ajovy” product information