After being challenged by another drug company, Teva Pharmaceuticals, Pfizer's successfully defended their patent on sildenafil as a treatment for erectile dysfunction. The patent is set to expire in 2019.Pfizer's original patent on the compound sildenafil will expire next year. Because Pfizer held two different patents for the drug, Teva tried to make the case that the company "double patented". However, the judge ruled in favor of Pfizer's argument, which hinged on the serendipitous circumstances that lead to the discovery that sildenafil could be used treat ED. Pfizer argued that it would not have been apparent to "anyone skilled in the art of drug development" that sildenafil could be used as a treatment for ED.
Its effectiveness as an ED treatment was discovered accidentally during trials of the drug for heart conditions, when men taking the drug experienced spontaneous erections. It seems fair to say that no one would have seen that coming. However, realizing the potential there, Pfizer jumped on it and developed the drug as a treatment for ED. For that bit of foresight, they get to hang onto their patent of the drug - as a treatment for ED - for a few more years.
However, Pfizer's patent Revatio, sildenafil used to treat pulmonary hypertension, is expiring next year. Since this is close to the purpose for which sildenafil was originally developed, we can assume that anyone skilled in the art of drug development could have conceivably figured that out on their own. So Pfizer's probably going to have to let that one go. And when Revatio does become available in a generic form, we can expect that some doctors will prescribe it "off-label" for the treatment of ED.
It will be interesting to see what happens when Revatio goes generic. How will that impact Pfizer's sales of Viagra?
Meanwhile, Pfizer has just filed a suit against Teva Pharmaceuticals to halt sales of their version of generic Viagra in Russia.
Teva has challenged a number of other Pfizer patents, including one for the heartburn drug Protonix. The Viagra victory was a major one for the larger company, and doesn't bode well for Teva in the ongoing legal battle. Teva may be sorry they ever tried to take the pharmaceutical giant down.
