Adverio Pharma’s CA2807859A1 Refused: Polymorph Claims Found Obvious
Canada’s Patent Appeal Board recommended refusal of Adverio Pharma GmbH’s application CA2807859A1, covering a specific crystalline modification of riociguat, after finding all four claims obvious over the prior art combined with common general knowledge. The Board concluded the skilled person would have arrived at both the compound form and the pharmaceutical composition claims without inventive ingenuity.
CIPO Panel Finds Riociguat Polymorph Claims Lack Inventive Step
Adverio Pharma GmbH, represented by Smart & Biggar LP, pursued Canadian patent application CA2807859A1 directed to Modification II — a defined crystalline polymorph of methyl {4,6-diamino-2-[1-(2-fluorobenzyl)-1H-pyrazolo[3,4-b]pyridino-3-yl]pyrimidino-5-yl}methyl carbamate, the active pharmaceutical ingredient in the soluble guanylate cyclase stimulator riociguat. Claims 1 to 4 encompassed the specific polymorphic form, a pharmaceutical composition containing it, and a process for its preparation.
The Patent Appeal Board recommended refusal of the application, concluding that claims 1 to 4 did not comply with section 28.3 of the Patent Act because their subject-matter would have been obvious to the skilled person. The Board found that prior art document D1 disclosed the compound and that any gap between D1 and the claimed Modification II would have been bridged by common general knowledge, including well-known methods for producing and characterising polymorphic forms. The pharmaceutical composition claims (claims 2 and 3) were likewise held to require no inventive ingenuity.
The outcome is consistent with a broader pattern at CIPO and other major patent offices in which second-generation polymorph applications face heightened obviousness scrutiny when the parent compound is already disclosed in the prior art. The Board’s reasoning suggests that demonstrating unexpected properties or a non-obvious selection would have been necessary to distinguish the claims. The public record does not indicate whether Adverio Pharma intends to seek judicial review of the refusal recommendation before the Federal Court of Canada.
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Closed 22 August 2025 — duration not available from public record
Application refused on obviousness: what the Board’s finding means
Section 28.3 obviousness: the Board’s standard applied
Section 28.3 of Canada’s Patent Act bars protection for subject-matter that would have been obvious to a skilled person at the claim date, having regard to prior art and common general knowledge. The Board applied the four-step Sanofi framework, concluding that D1 and CGK together rendered Modification II and its compositions obvious — no special technical effect sufficient to confer inventive step was identified in the record.
Obvious — s.28.3 Patent ActRefusal forecloses Canadian patent protection for Modification II
A CIPO refusal recommendation means the application will be refused unless Adverio Pharma successfully seeks judicial review before the Federal Court of Canada. Without a granted patent, the applicant cannot assert Canadian patent rights in Modification II or its compositions, limiting enforcement options in Canada. The public record does not confirm whether an appeal or review is planned.
No Canadian patent grantedAbsence of a granted patent reduces exclusivity risk for generic entrants
Because the application was refused rather than granted, no Canadian patent claiming Modification II of riociguat currently exists from this application. Generic and follow-on manufacturers operating in Canada face reduced risk of infringement claims based on this specific crystalline form, though other granted patents in the riociguat portfolio may still apply and should be independently assessed.
Reduced exclusivity risk (CA)Polymorph patent strategies face tougher CGK bar in Canada
This refusal is consistent with CIPO’s rigorous treatment of polymorph applications where the parent compound is known. Pharmaceutical companies relying on crystalline-form patents to extend market exclusivity should expect scrutiny of whether the specific modification offers unexpected advantages beyond what CGK would predict. Early investment in characterising and documenting non-obvious physical or pharmacological properties is increasingly important for Canadian polymorph prosecution.
Polymorph IP strategy riskFull party and counsel information
| Role | Name | Type | Detail |
|---|---|---|---|
| Plaintiff | Adverio Pharma GMBH (Re) | Company | Pharmaceutical IP applicant — holder of CA2807859A1 covering riociguat Modification IISearch in Eureka ↗ |
| Defendant | Defendant | Individual | N/A — CIPO prosecution; no defendant partySearch in Eureka ↗ |
| Plaintiff law firm | Smart & Biggar, LP | Law Firm | Representing Adverio Pharma GMBH (Re)Search in Eureka ↗ |
| Presiding judge | Judge N/A | Judge | CIPOSearch in Eureka ↗ |
Official order — verbatim text
The Board’s verdict language is precise and far-reaching: it holds that a skilled person armed with D1 and common general knowledge would have arrived at both the crystalline form (claim 1), the pharmaceutical compositions (claims 2–3), and the preparative process (claim 4) without exercising any inventive ingenuity. The explicit reliance on CGK as a bridge — rather than requiring a secondary reference — suggests the Board applied a demanding obviousness standard consistent with post-Sanofi Canadian jurisprudence. For Adverio Pharma, this leaves judicial review as the primary avenue for preserving Canadian protection.
CA2807859A1 — Crystalline Modification II of Riociguat
CA2807859A1 is a Canadian patent application directed to Modification II, a specific crystalline polymorph of methyl {4,6-diamino-2-[1-(2-fluorobenzyl)-1H-pyrazolo[3,4-b]pyridino-3-yl]pyrimidino-5-yl}methyl carbamate — the active ingredient of riociguat, a soluble guanylate cyclase (sGC) stimulator approved for pulmonary hypertension. The claims cover the compound in Modification II form, pharmaceutical compositions incorporating it, and a process for its preparation. Polymorph patents of this type are a recognised strategy to extend exclusivity beyond the primary compound patent.
Riociguat is a commercially significant small molecule in the pulmonary arterial hypertension and chronic thromboembolic pulmonary hypertension space. Crystalline form patents, if granted, can meaningfully extend market exclusivity and complicate generic entry by requiring specific polymorphic form avoidance. The refusal of this application in Canada suggests that the Modification II form was considered an obvious variant of the known compound, potentially opening the Canadian market to formulations of riociguat in this crystalline form without infringement of this specific application.
Should you run an FTO against CA2807859A1?
Any company developing, manufacturing, or commercialising riociguat or structurally related sGC stimulators in Canada should assess the current status of CA2807859A1 and the broader riociguat patent family. Although this specific application has been recommended for refusal, other applications or granted patents in the same family may cover related crystalline forms, formulations, or methods of use. Generic pharmaceutical companies preparing Canadian market entry strategies should not rely solely on this refusal without a full family search.
PatSnap Eureka’s FTO Search Agent can map the full CA2807859A1 patent family across jurisdictions, identify granted counterparts still in force, flag related applications covering alternative riociguat polymorphs, and surface any post-refusal Federal Court proceedings. For R&D and regulatory teams, this provides a structured, evidence-based foundation for Canadian commercialisation risk assessments.
Run a freedom-to-operate analysis on CA2807859A1 to assess your product’s exposure
Run FTO in Eureka →Similar CIPO Polymorph Obviousness Cases & Pharma Patent Refusals
Explore related Canadian patent prosecution cases involving pharmaceutical polymorph obviousness challenges before CIPO and the Patent Appeal Board.
What this case signals for pharmaceutical polymorph IP in Canada
The refusal of CA2807859A1 highlights the evidential bar that polymorph applications must clear at CIPO to survive an obviousness challenge.
CGK gap-bridging is decisive in Canadian polymorph prosecution
The Board’s conclusion that common general knowledge would bridge any gap between D1 and Modification II underscores that applicants must proactively address CGK in prosecution. Filing declarations from experts or data showing unexpected properties before the examiner raises the issue can significantly change the outcome.
Composition and process claims offer no shelter if the compound is obvious
Claims 2–4 covering pharmaceutical compositions and preparation processes fell with claim 1. Where the core compound claim is held obvious, dependent formulation and process claims typically cannot independently survive unless they introduce a separate inventive concept — a critical drafting consideration for pharma IP teams.
Adverio v Defendant — key questions answered
The Patent Appeal Board recommended refusal of CA2807859A1, finding claims 1–4 obvious under section 28.3 of the Patent Act. The Board held that a skilled person would have used well-known methods to produce the Modification II crystalline form and formulate it as a pharmaceutical composition without any inventive ingenuity, given prior art document D1 and common general knowledge.
CA2807859A1 is a Canadian patent application filed by Adverio Pharma GmbH covering Modification II, a specific crystalline polymorph of methyl {4,6-diamino-2-[1-(2-fluorobenzyl)-1H-pyrazolo[3,4-b]pyridino-3-yl]pyrimidino-5-yl}methyl carbamate — the active ingredient of riociguat, a soluble guanylate cyclase stimulator used to treat pulmonary hypertension.
Yes. A CIPO refusal recommendation from the Patent Appeal Board can be challenged by way of judicial review before the Federal Court of Canada. The applicant must file within the applicable limitation period. The public record as of the case closure date does not confirm whether Adverio Pharma has initiated or intends to initiate such review proceedings.
The refusal means no patent based on CA2807859A1 currently protects Modification II of riociguat in Canada from this application. Generic manufacturers may face reduced risk from this specific application, but should conduct a full freedom-to-operate analysis across the broader riociguat patent family, as other granted Canadian patents may cover related forms, formulations, or uses.
Section 28.3 bars patent protection for subject-matter obvious to a skilled person at the claim date, assessed against prior art and common general knowledge using the four-step Sanofi framework. For polymorphs, where the parent compound is already known, applicants must typically demonstrate that the specific crystalline form has unexpected properties or required non-obvious steps to identify and produce — otherwise the Board is likely to find the form predictable and therefore obvious.
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