Canada's Supreme Court Tosses Viagra Patent For Vagueness

Freshly Exhumed writes "In a 7-to-0 decision, the Supreme Court Of Canada has ruled that Pfizer Canada Inc.'s patent on well-known erectile dysfunction remedy Viagra is now invalid due to insufficient information in Pfizer's patent application. The upshot is that competitors can now manufacture cheaper, generic versions of Viagra for sale in Canada."

Comments

Generics and Legal Challenges

[reverseengineer]

This particular patent fight is also occurring in other places. In the US, there was a decision last year between Pfizer and Teva that was ruled the opposite way, and if no other challenge is successful, I believe Viagra will continue to exist under patent for Pfizer until 2019. At issue is that Viagra really has two patents- one for sildenafil and its formulation into a drug and one for the use of sildenafil to treat erectile dysfunction. Sildenafil was originally developed for blood pressure and cardiovascular disease, so the application for the ED indication patent trailed the formulation patent by several years. The formulation patent expired this year, but the indication patent lasts until 2019. In the US, a regulatory framework known as a Paragraph IV challenge exists for generic drug manufacturers to either argue that their proposed generic does not violate the existing patents, or that the patents themselves are invalid. This potentially allows them to open up the generic market years before the patent was originally set to expire, so this sort of legal action is not uncommon, particularly for blockbuster drugs.

Re:Generics and Legal Challenges

[reverseengineer]

Just to follow on, the Canadian Supreme Court decision is here and the invalidated patent is here. What caused the patent to be invalidated was that the patent is basically written to cover a wide array of similar molecules, all derivatives of a central molecular skeleton. Often, minor alterations to a molecule can be made that do not change the behavior of the molecule as a drug. What it appears Pfizer was looking to do here was prevent competitors from developing ED drugs that were simple derivatives of sildenafil (Viagra) (like adding a methyl group or a fluorine atom somewhere it would have no significant effect). That's considered acceptable strategy, and as a result, other ED drugs like vardenafil (Levitra) and tadalafil (Cialis) have differences in their core structures that keep them from infringing.

However, the Canadian court found that Pfizer had failed to essentially zero in on sildenafil with their claims. When it came down to actually stating that this molecule is the one that lab studies have found treats ED, Pfizer only ever mentions the core skeleton (known as "formula I") and never uniquely identifies sildenafil. It mentions sildenafil (not even by name, only by its R groups) in one claim, but never connects it and only it to ED. The court judgement notes that "formula I" represents 260 quintillion possible compounds, and therefore rejected the patent for vagueness.

Re:Generics and Legal Challenges

[reverseengineer]

That's not necessarily true of pharmaceuticals, and in fact, quite a few other blockbuster drugs have come about as re-purposed molecules: Merck originally developed Proscar (finasteride) as a prostate enlargement treatment. Then it submitted finasteride to the FDA again as Propecia for male pattern baldness. Wikipedia tells me, "Merck's patent on finasteride for the treatment of BPH expired on June 19, 2006. Merck was awarded a separate patent for the use of finasteride to treat MPB. This patent is set to expire in November 2013." Bupropion was developed as an antidepressant (Wellbutrin), but there's a separate patent covering Zyban, which is the same molecule when prescribed for smoking cessation. Latisse is the glaucoma drug Lumigan, repurposed when they found it makes your eyelashes grow.
For that matter, Viagra itself is also sold in a different dose as Revatio for pulmonary hypertension- I'm pretty sure that Pfizer's "treatment of erectile dysfunction" patent expiring in 2019 does not apply to that product. I will note that these "use patents" are much more likely to be invalidated in court challenges compared to the "composition of matter" patent (it was considered surprising by many observers when Pfizer won their case with Teva in the US last year), but they are out there.

Re:Insufficient information

[Maow]

So the Supreme Court Of Canada found the patent hard to understand.

You can believe that if it makes you feel good, but reality says otherwise, that the patent was purposefully obfuscated:

"Pfizer gained a benefit from the act -- exclusive monopoly rights -- while withholding disclosure in spite of its disclosure obligations under the act," Justice Louis LeBel wrote on behalf of the court.

"As a matter of policy and sound statutory interpretation, patentees cannot be allowed to 'game' the system in this way. This, in my view, is the key issue in this appeal.

"Pfizer had the information needed to disclose the useful compound and chose not to release it."

So, no one could "understand" it because they didn't disclose proper information - enough for someone skilled in the profession to create a copy of the drug.

It's a remarkably sensible decision and one that should be applied in US courts - particularly in the current mobile patent war (the part about not being allowed to "game the system").

Re:Insufficient information

[reverseengineer]

Yes, Teva's central argument in the challenge was that in the patent in question, Pfizer never specifically establishes the relationship between sildenafil and the treatment of ED. From the judgement:

As required by s. 2 of the Act, an invention must be novel. In the instant case, the invention is not sildenafil, per se, because this compound was already known. In fact, Pfizer had been investigating sildenafil as a cardiovascular drug when it first suspected that the compound would be useful in treating ED (R.F., at para. 13). The invention is therefore not sildenafil, but the use of sildenafil to treat ED.(italics theirs)

The court ruled that the patent never concretely established this relationship:

Although Patent ’446 includes the statement that “one of the especially preferred compounds induces penile erection in impotent males” (A.R., vol. X, at p. 173), the specification does not indicate that sildenafil is the effective compound, that Claim 7 contains the compound that works, or that the remaining compounds in the patent had been found not to be effective in treating ED. The claims were structured as “cascading claims”, with Claim 1 involving over 260 quintillion compounds, Claims 2 to 5 concerning progressively smaller groups of compounds, and Claims 6 and 7 each relating to an individual compound.

The disclosure in the specification would not have enabled the public “to make the same successful use of the invention as the inventor could at the time of his application”, because even if a skilled reader could have narrowed the effective compound down to the ones in Claim 6 and Claim 7, further testing would have been required to determine which of those two compounds was actually effective in treating ED. As the trial judge stated, at para. 146, “[a] skilled reader would then conduct tests on those two compounds and determine which of those compounds worked.” And as he also stated, at para. 135, “the skilled reader must undertake a minor research project to determine which claim is the true invention”.

Pfizer had the information needed to disclose the useful compound and chose not to release it. Even though Pfizer knew that the effective compound was sildenafil at the time it filed the application, it limited its description to the following statement: In man, certain especially preferred compounds have been tested orally in both single dose and multiple dose volunteer studies. Moreover, patient studies conducted thus far have confirmed that one of the especially preferred compounds induces penile erection in impotent males. [Emphasis added; A.R., vol. X, at p. 173.] It chose a method of drafting that failed to clearly set out what the invention was. Even now, in its factum to this Court, Pfizer offers no explanation as to why — knowing that Claim 7 contained the tested and thus, the useful, compound — it elected to withhold that information.

Re:Maybe they require photos?

[Samantha Wright]

No, a chemical patent has to be very specific about the range of structures that are patented. A good chemical patent may contain sentences that are over a hundred words in length, just listing out alternative functional groups that could be at a given spot on the backbone. They're very technical and extremely detailed; you can't just patent a cause-and-effect relationship like that. In software, maybe, but not in pharmacology.