court in September 1999, and the patent was overturned in November 2000 on the grounds that Pfizer's patent was based on information already in the public domain when the patent was issued. In the United States, Pfizer filed suit against Lilly Icos soon after receiving a broad US patent for PDE5 inhibitors in October 2002. The United States Patent and Trademark Office ordered a reexamination of the patent, and, as in Britain, the examiner found that PDE5 inhibitors were not a new invention by Pfizer, voiding the patent. In Canada, Pfizer moved to block sales of Cialis five months after it was approved there, arguing that there could be consumer backlash against Pfizer should Cialis be pulled from the market months later as a result of an ongoing patent lawsuit. A federal judge refused, saying he could not "imagine demonstrations in the street or storming of the barricades because one impotence medicine is made unavailable". Blindness warning on label In May 2005, the FDA began investigating reports of sudden blindness in users of sildenafil (Viagra). The FDA said it had received reports of the condition, a permanent blindness in one eye known as non-arteritic anterior ischemic optic neuropathy, in 38 users of sildenafil and 5 users of tadalafil or vardenafil (Levitra). Lilly Icos voluntarily amended the Cialis label to warn of the condition. The FDA was criticized for its handling of the matter, as an FDA safety officer had commented on unusual reports of blindness over 13 months before a journal article was published on the issue. United States Senator Chuck Grassley wrote a letter to the FDA detailing his criticism, saying that the FDA's Office of New Drugs (OND) had taken no action "despite OND's knowledge of the blindness risks since January 2004 and general agreement among FDA staff last spring that the label should be updated". Grassley's letter also suggested that Pfizer resisted adding the blindness warning to Viagra's label. In July 2005, the FDA said that Viagra, Levitra, and Cialis labels would all carry warnings on the risk of sudden blindness, though it was unclear whether the drugs were actually causing the blindness. Marketing Lilly Icos hired the Grey Worldwide Agency in New York, part of the Grey Global Group, to run the Cialis advertising campaign. Cialis advertisements were described as being gentler, warmer and with a more relaxed feel than those of its rivals, to reflect