Crystal Pharma & Bergen v. Eisai: Federal Circuit Affirms Unpatentability
Crystal Pharmaceutical (Suzhou) and Bergen Pharmaceutical challenged Eisai’s US10759779B2 — a patent covering a crystalline form of an orexin receptor antagonist — in a 701-day Federal Circuit appeal. The court issued a Rule 36 affirmance, upholding the underlying finding of unpatentability and ending the challenge.
Federal Circuit seals Eisai orexin patent’s fate with Rule 36 affirmance
Crystal Pharmaceutical (Suzhou) Co., Ltd. and Bergen Pharmaceutical, LLC initiated appellate proceedings before the Court of Appeals for the Federal Circuit on 6 October 2022, challenging an earlier tribunal ruling concerning US10759779B2. The patent, held by Eisai, covers a crystalline form of an orexin receptor antagonist — a pharmacologically significant compound class used in sleep and neurological disorder therapies — along with processes for its preparation and therapeutic use.
The Federal Circuit closed the case on 6 September 2024, issuing a summary affirmance under Federal Circuit Rule 36. This procedural mechanism signals that the appellate panel found no reversible error in the lower tribunal’s determination of unpatentability, and saw no need to issue a written opinion elaborating on its reasoning. The finding of unpatentability was thereby sustained, leaving Eisai’s patent claims without legal protection.
The 701-day duration reflects the typical pace of Federal Circuit patent appeals in complex pharmaceutical matters. The use of Rule 36 — a summary affirmance without opinion — means the public record provides no detailed appellate reasoning, making it difficult to assess precisely which patentability grounds were determinative. What remains unknown is whether obviousness, anticipation, or another § 103/§ 102 basis drove the outcome, and whether Eisai will pursue further remedies such as en banc rehearing or certiorari.
Filing to Unpatentable in 701 days
701-day Federal Circuit appeal — consistent with complex pharma patentability disputes
Federal Circuit affirms: what the unpatentability ruling means for both parties
Rule 36 affirmance: the appellate panel found no reversible error
A Federal Circuit Rule 36 affirmance means the panel unanimously concluded the lower tribunal’s patentability determination was correct and required no separate written explanation. It is not a merits opinion — it produces no new citable precedent — but it is a full and final affirmance. The underlying finding of unpatentability stands with the same legal force as if accompanied by a detailed opinion.
Summary affirmance — no written opinionEisai’s patent remains unpatentable — enforceability extinguished
For Eisai, the affirmance is adverse: the appellate court declined to reverse the unpatentability finding, meaning US10759779B2 cannot be enforced. The crystalline form claims at issue no longer provide exclusivity. Eisai’s options are narrow — a petition for en banc rehearing before the Federal Circuit, or a certiorari petition to the Supreme Court — both of which face very high bars in patent patentability cases.
Patent claims unenforceableCrystal Pharma and Bergen prevail — market entry barrier reduced
Crystal Pharmaceutical and Bergen Pharmaceutical secured the outcome they sought: affirmance of the unpatentability decision removes a patent barrier that could have blocked commercialisation of a competing crystalline orexin antagonist product. With the Federal Circuit upholding the finding, the challengers are positioned to proceed with development or commercialisation activities without the overhang of US10759779B2 infringement risk — subject to any remaining related patents in Eisai’s portfolio.
Key patent barrier removedOrexin antagonist IP landscape opens — but portfolio risk remains
The affirmance suggests that crystalline form patents in the orexin receptor antagonist space are not insurmountable barriers, which may embolden generic and specialty pharma players in this therapeutic category. However, the Rule 36 nature of the ruling produces no guiding precedent. Competitors should audit Eisai’s broader orexin antagonist portfolio — compound patents, method-of-treatment claims, and formulation patents may remain active and enforceable independently of this crystalline form patent.
Broader portfolio audit advisedFull party and counsel information
| Role | Name | Type | Detail |
|---|---|---|---|
| Plaintiff | Crystal Pharmaceutical (Suzhou) Co., Ltd. | Company | Generic pharma challengers — appellants seeking invalidation of US10759779B2Search in Eureka ↗ |
| Co-Plaintiff | BERGEN PHARMACEUTICAL, LLC | Company | Search in Eureka ↗ |
| Defendant | Eisai | Individual | Eisai — Japanese research-based pharmaceutical company, patent holder of US10759779B2Search in Eureka ↗ |
| Plaintiff counsel | Cecil Kyle Musgrove | Attorney | Counsel for Crystal Pharmaceutical (Suzhou) Co., Ltd.Search in Eureka ↗ |
| Plaintiff counsel | Elizabeth Crompton | Attorney | Counsel for Crystal Pharmaceutical (Suzhou) Co., Ltd.Search in Eureka ↗ |
| Plaintiff counsel | Scott A. Cunning II | Attorney | Counsel for Crystal Pharmaceutical (Suzhou) Co., Ltd.Search in Eureka ↗ |
| Plaintiff law firm | Gemini Law LLP | Law Firm | Representing Crystal Pharmaceutical (Suzhou) Co., Ltd.Search in Eureka ↗ |
| Plaintiff law firm | Parker Poe Adams & Bernstein LLP | Law Firm | Representing Crystal Pharmaceutical (Suzhou) Co., Ltd.Search in Eureka ↗ |
| Defendant counsel | Bruce M. Wexler | Attorney | Counsel for EisaiSearch in Eureka ↗ |
| Defendant counsel | Christopher P. Hill | Attorney | Counsel for EisaiSearch in Eureka ↗ |
| Defendant counsel | Melanie R. Rupert | Attorney | Counsel for EisaiSearch in Eureka ↗ |
| Defendant counsel | Michael Wolfe | Attorney | Counsel for EisaiSearch in Eureka ↗ |
| Defendant counsel | Naveen Modi | Attorney | Counsel for EisaiSearch in Eureka ↗ |
| Defendant counsel | Young J. Park | Attorney | Counsel for EisaiSearch in Eureka ↗ |
| Defendant law firm | Paul Hastings, LLP | Law Firm | Representing EisaiSearch in Eureka ↗ |
| Presiding judge | Judge N/A | Judge | Court of Appeals for the Federal CircuitSearch in Eureka ↗ |
Official order — verbatim text
The court’s order — ‘AFFIRMED. See Fed. Cir. R. 36’ — is the Federal Circuit’s most summary form of disposition. It signals that all three panel judges agreed the lower tribunal’s patentability determination was free from reversible error, but declined to elaborate on the legal reasoning. For Eisai, this means the unpatentability finding is final at this appellate level. For the challengers, it validates their position without generating citable precedent that could benefit others in parallel disputes involving related crystalline form patents.
US10759779B2 — Crystalline orexin receptor antagonist solid-state form
US10759779B2 (application no. US16/777121) covers a specific crystalline solid-state form of an orexin receptor antagonist compound, along with the processes used to prepare it and its application in therapy. Orexin receptor antagonists are a pharmacologically important class — dual orexin receptor antagonists (DORAs) are used to treat insomnia and are under investigation for broader neurological indications. Crystalline form patents protect a defined physical structure of an active pharmaceutical ingredient, which can confer advantages in stability, bioavailability, and manufacturability.
Strategically, crystalline form patents are a widely used tool in pharmaceutical lifecycle management — they can extend effective market exclusivity beyond the expiry of primary compound patents. The unpatentability finding against US10759779B2 suggests the claimed crystalline form may have lacked sufficient novelty or non-obviousness over prior art, a common vulnerability for polymorph patents. For competitors developing orexin antagonist products, this outcome reduces one IP barrier, but Eisai’s broader patent estate in this therapeutic area warrants careful and ongoing monitoring.
Should your team run an FTO against US10759779B2 and Eisai’s orexin portfolio?
Any company developing, manufacturing, or commercialising a crystalline orexin receptor antagonist — whether a generic, a 505(b)(2) applicant, or a specialty pharma player — should conduct a thorough FTO analysis before advancing to clinical or commercial stages. Although US10759779B2 has been found unpatentable, Eisai’s orexin antagonist portfolio likely includes compound patents, method-of-treatment claims, and other formulation patents that remain active. A single invalidated crystalline form patent does not clear the entire freedom-to-operate landscape.
PatSnap Eureka’s FTO Search Agent allows R&D and IP teams to map the full Eisai orexin antagonist patent estate in minutes — identifying live claims, expiry dates, and prosecution history flags that may affect design-around options. With the Federal Circuit appeal record now closed, there is no written opinion to rely on for guidance; a proactive, data-driven FTO approach is the most reliable path to commercial clarity in this space.
Run a freedom-to-operate analysis on US10759779B2 to assess your product’s exposure
Run FTO in Eureka →Similar Federal Circuit pharmaceutical patentability appeals
Explore Federal Circuit cases involving pharmaceutical crystalline form and polymorph patent patentability challenges — comparable in technology domain and appellate posture to Case 23-1017.
What this case signals for pharmaceutical crystalline form IP strategy
A Rule 36 affirmance of unpatentability in pharma sends a clear message about the limits of crystalline form patent protection.
Crystalline form patents face heightened vulnerability at the Federal Circuit
This outcome suggests that crystalline polymorph patents — when found unpatentable at the tribunal level — are unlikely to be rescued on appeal without compelling reversible error. Pharma IP teams filing solid-state form patents should ensure robust differentiation over prior art, particularly for known compound classes like orexin antagonists where analogous crystalline forms may already be disclosed.
Rule 36 affirmances leave the record thin — act on what you know now
Without a written Federal Circuit opinion, competitors cannot rely on reasoned guidance about which invalidity grounds were decisive. For FTO purposes, this means the analysis must go back to the underlying tribunal record. Companies in the orexin receptor antagonist space should review that lower-level record closely before making commercialisation decisions based solely on this affirmance.
Crystal v Eisai — key questions answered
The Federal Circuit affirmed the lower tribunal’s finding that US10759779B2 — Eisai’s patent covering a crystalline form of an orexin receptor antagonist — is unpatentable. The court issued a summary affirmance under Federal Circuit Rule 36, meaning no written opinion was produced and the unpatentability determination stands as final at the appellate level.
A Rule 36 affirmance is a summary disposition used by the Federal Circuit when all panel judges agree the lower decision was correct and no written opinion is needed. It carries the same legal weight as a full opinion but produces no new precedent. For Eisai, it means the unpatentable finding on US10759779B2 is final; for the challengers, their appellate victory is confirmed without creating citable guidance.
US10759779B2 covers a crystalline solid-state form of an orexin receptor antagonist, including preparation processes and therapeutic applications. Orexin receptor antagonists are used in sleep disorder treatment and investigated for neurological indications. Crystalline form patents are a key pharmaceutical lifecycle management tool; their invalidation can open market entry opportunities for generic and specialty pharma competitors.
Not necessarily. The invalidation of US10759779B2 removes one crystalline form patent, but Eisai’s orexin antagonist portfolio likely includes additional compound, formulation, and method-of-treatment patents that remain active and enforceable. A comprehensive FTO analysis across Eisai’s full orexin-related patent estate is strongly advisable before any commercialisation decision.
The appellants — acting as plaintiffs in the Federal Circuit appeal — were Crystal Pharmaceutical (Suzhou) Co., Ltd., a Chinese pharmaceutical manufacturer, and Bergen Pharmaceutical, LLC. They were represented by attorneys from Gemini Law LLP and Parker Poe Adams & Bernstein LLP, challenging the patentability of Eisai’s US10759779B2 before the Federal Circuit.
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