|
On November 8 2000, the
United Kingdom's High Court ruled that Pfizer's European
patent designated in the UK and covering the method of use
of sildenafil, the active ingredient in Viagra, was invalid.
However, this patent only covers the use of phosphodiesterase
V (PDE V) inhibitors in the treatment of impotence i.e.
the way in which sildenafil works, not the drug itself.
The UK court action was brought by Eli Lilly and ICOS Corp,
who are co-developing Cialis (IC 351), a rival impotence
treatment also based on a PDE V inhibitor. Cialis is currently
in Phase III trials and scheduled for filing in 2001.
Lilly and ICOS argued that sildenafil's mode of action was
obvious - it was well known before Pfizer filed its patent
application that the inhibition of PDE V affected impotence.
Mr Justice Hugh Laddie, the judge in this case, agreed.
Viagra is still immune to generic rivals. IMS HEALTH's Patents
International, states that the sildenafil product patent
is protected by European patent 463756 until 7 June 2011.
Supplementary Protection Certificate applications for
Viagra have been filed in Denmark, France, Germany, Italy
and the UK, and granted in Belgium, Greece, Luxembourg,
the Netherlands, Sweden, and Switzerland - all expiring
in June 2013. If the application is granted in the UK, the
SPC should also expire in June 2013.
However, because of this ruling Viagra may face stiffer
competition if newer products enter the market at competitive
prices. Lilly and ICOS are not the only companies researching
ED - according to R&Dfocus,
there are more than 10 products in late-stage development
within the G4B3 ED Products therapy class, including drugs
from pharmaceutical giants like Bayer and Pharmacia Corp.
That said, Pfizer, now the largest pharmaceutical company
in the world since its acquisition of Warner-Lambert in
June 2000, has its own follow-up compounds to Viagra in
early-mid stages of development. The company also points
out that the licensing authority would want new products
to be more or at least as effective as Viagra.
|
