Today's court battle is between Pfizer and two rival drug teams. On Tuesday, Pfizer was issued a US patent relating to Viagra, and that same day they filed lawsuits against Eli Lilly and Icos (one the one hand) along with Bayer and GlaxoSmithKline on the other. Both are developing rivals to Viagra (Cialis and Levitra, respectively.) Both work on exactly the same enzyme, phosphodiesterase-5, and it's the PDE-5 action that Pfizer used as the ground for the suits.
The patent has claims for some chemical matter, and several specific compounds. Their ace, though, is near the end of the list: they claim the treatment of erectile disfunction by administering a PDE-5 inhibitor. Any inhibitor. You can make a compound that hits that enzyme, says Pfizer, but if you treat erectile disfunction with it then you can expect to hear from their lawyers.
This is a pure "method of treatment" patent, and regular readers will know that I don't have a very high opinion of those, on principle. The interesting thing is, Pfizer may not have that high an opinion of their chances here. They've already lost to Lilly and Icos in the UK over just this same issue, and the European Patent Office followed suit last year, citing that decision. The argument was that this mode of action was already known before the patent was applied for, and that'll surely be the defense that Lilly/Icos and Bayer/GSK will use here.
So why is Pfizer even trying? Easy: they'll be trying to tie things up so thoroughly that their competitors will be delayed in getting their drugs to market. When you consider that their legal bills will be perhaps a few weeks worth of Viagra profits (at most,) then it looks pretty cost-effective to make the attempt.
And lest anyone think that I'm just picking on Pfizer, I should add that plenty of other companies in the industry have patents that could allow them to do the same thing in such a situation. And most, probably all, of them would. After all, it makes financial sense. But I have to say, I'd like to live in a world, and work in an industry, where it didn't.