Canada: Pharma In Brief - Canada: Federal Court Dismisses Prohibition Application For Valganciclovir Hydrochloride Tablets [VALCYTE®]

Case: Hoffmann-La Roche Limited v. Apotex Inc. et al.
Drug: Valganciclovir hydrochloride (VALCYTE®)
Nature of case: Prohibition application pursuant to PM(NOC) Regulations
Successful party: Apotex Inc.
Date of decision: July 12, 2013


Hoffmann-La Roche Limited ("Roche") brought an application pursuant to section 6 of the Patented Medicines (Notice of Compliance) Regulations for an order prohibiting the Minister of Health from issuing a Notice of Compliance to Apotex Inc. ("Apotex") in respect of its valganciclovir hydrochloride tablets (the "Apotex Product") until the expiry of Canadian Patent No. 2,154,721 (the "'721 Patent").

The '721 Patent relates to a novel antiviral drug, valganciclovir, described as the mono-L-valine ester of ganciclovir, a leading drug for the treatment of certain herpes viruses, particularly cytomegalovirus.  Ganciclovir itself exhibits low oral bioavailability, requiring slow daily intravenous infusion of the drug.

Apotex alleged that the '721 Patent was invalid on the basis of anticipation, obviousness and overbreadth, and that its Apotex Product would not infringe certain claims of the '721 Patent.  In its analysis, the Court expanded the disclosure component of the anticipation test, departing from the more stringent test set forth by the Supreme Court of Canada in Apotex Inc. v. Sanofi-Synthelabo Canada Inc. (2008 SCC 61) ("Sanofi").  The Court held that Apotex's invalidity allegations with respect to anticipation and obviousness were justified.  The Court also found that Apotex's allegation of non-infringement was justified in respect of one of the '721 Patent's claims.  As such, the Court dismissed Roche's prohibition application.

The inventive concept of the '721 Patent

The parties disagreed as to whether the '721 Patent claims that the mono-L-valine ester of ganciclovir, valganciclovir, has better oral bioavailability than other esters of ganciclovir, including the bis-valine ester, disclosed in EP '329 (European Patent) or whether it only claims that valganciclovir is better than ganciclovir itself.

The Court found that the '721 Patent does not assert that the invention is an improvement over the esters disclosed in a prior application (EP '329), but rather only asserts that the invention is an improvement over the parent compound, ganciclovir.  The Court also rejected Apotex's argument that the invention of the '721 Patent is crystalline valganciclovir and its salts, finding that crystallinity should be construed as an additional advantage rather than the only advantage.

The Court concluded that the inventive concept of the '721 Patent is the invention of valganciclovir, a stable prodrug with low toxicity and improved oral bioavailability over ganciclovir.

Is the '721 Patent a selection patent?

Roche submitted that EP '329 disclosed a class of compounds that encompassed valganciclovir and that the '721 Patent was a selection from that class.  Apotex submitted that the '721 Patent did not meet the criteria of a selection patent as it did not disclose the special advantage(s) of the selected compound, namely the oral bioavailability advantage of valganciclovir  over the esters of ganciclovir encompassed by EP '329.

The Court agreed with Apotex that no such disclosure was made and that the invention of the '721 Patent relates to a formulation of a new prodrug that is an improvement over the previously invented ganciclovir compound.  The Court concluded that the '721 Patent is not a selection patent.


The Court's approach to anticipation, which blended the test set forth by the Supreme Court of Canada in Sanofi with a number of principles set out by Justice Hughes in Abbott Laboratories v. Sandoz Canada Inc. (2008 FC 1359), can be summarized as follows:  (1) the disclosure need not be an "exact description"; (2) the disclosure need only be sufficient to be read and understood without trial and error when read by a person skilled in the art willing to understand; and (3) the disclosure must enable the skilled person to carry out what is disclosed based on their common general knowledge and allowing for a certain amount of trial and error experimentation.

Based on this approach, the Court came to the conclusion that although EP '329 prefers and exemplifies only the bis-esters, the mono-esters were nonetheless disclosed as well and the person skilled in the art would read EP '329 and understand that it was teaching both mono- and bis-esters with improved bioavailability over ganciclovir.  Given this disclosure of EP '329, the skilled person would engage in routine chemistry and no further inventive step would be required.  The Court found that EP '329 anticipated the invention claimed in the '721 Patent, valganciclovir.


The Court applied the four-step test for assessing obviousness as laid out by the Supreme Court of Canada in Sanofi. The analysis ultimately focused on the fourth step: whether the invention of the '721 Patent was obvious to try.

As part of the obvious to try analysis, the Court considered whether it was more or less self-evident that the formation of the mono-L-valine ester of ganciclovir would result in improved bioavailability, stability and low toxicity as compared to ganciclovir.  The Roche experts noted the range of prior art and expressed the view that the prior art taught away from mono-esters, that acyclovir and ganciclovir are different compounds and that improved bioavailability would not be predicted or expected without testing.  The Court agreed with Apotex's experts that both the encouraging results of valaciclovir, a valine ester of acyclovir (an antiviral nucleoside which Apotex argued was structurally and chemically similar to ganciclovir), and the improved bioavailability using mono-esters and bis-esters claimed in EP '329 would have directed the skilled person to follow the acyclovir model which would have led directly to the invention of valganciclovir.

The Court concluded it would have been more or less self-evident that adding the mono-L-valine ester to ganciclovir would also result in increased bioavailability over ganciclovir.  As a result, the Court found the invention of the '721 Patent to be obvious.


The Court rejected Apotex's argument that certain claims of the '721 Patent are overbroad for claiming crystalline and non-crystalline (amorphous) compounds.  The Court found that the inventive concept of the '721 Patent was not crystallinity and the patent discloses both amorphous and crystalline valganciclovir for the treatment of herpes viruses.  As such, the Court held that the '721 Patent does not claim more than the invention made or disclosed.


Apotex alleged in its Notice of Allegation that its valganciclovir hydrochloride tablets are amorphous only.  Since the court construed the claims of the '721 Patent to include both amorphous and crystalline valganciclovir, the court held that there was no dispute that Apotex would infringe all valid claims but one which is directed to crystalline valganciclovir only.

Link to decision

Hoffmann-La Roche Limited v. Apotex Inc., 2013 FC 718

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