Pfizer to sue four rivals in Viagra patent row

Pfizer, manufacturer of Viagra, is suing four rival manufacturers alleging that their proposed erectile dysfunction drugs infringe its intellectual property. Eli Lilly and Icos are planning an impotence remedy known as Cialis, while GlaxoSmithKline and Bayer are to introduce Levitra into the same market. Both the new drugs are half way through the US FDA approval process and were due to be launched next year.

Bayer, which is currently examining the content of the statement of claim, has said it will 'defend itself appropriately' against the legal claim and is confident that it will succeed in protecting its interests.

Earlier this year, a court of appeal in the UK refused to grant the US pharmaceutical company patent protection for the principle of action of the class of substances known as PDE 5 inhibitors. This decision was recently affirmed by the House of Lords, which refused to accept the case. The legal action instigated by Pfizer in the US is based on similar claims, said Bayer, and relates to Pfizer's newly issued 'method of use' US patent (No. 6,469,012).

Lilly ICOS, Eli Lilly and Company, and ICOS Corporation will also vigorously defend the lawsuit and are confident they will prevail.

The value of the market for erectile dysfunction drugs is estimated at around US$1.6bn currently, and could reach $3-4bn a year by 2006.