Shire Pharmaceuticals, the FTSE 100 drugmaker, has put in place another plank in its defence of Adderall, the hyperactivity drug that accounts for almost half its sales but which could lose patent protection within a year.
Shire has written to US regulators demanding that rivals conduct lengthy clinical trials to prove their drugs have the same effect as Adderall, an amphetamine which is given to children suffering from attention deficit hyperactivity disorder (ADHD).
Analysts were uncertain that the regulator, the Food & Drug Administration, will order the trials, but they suspected that its deliberations could delay approval for rival drugs beyond the time - autumn 2006 - when generic versions of Adderall are expected on the market.
Barr Laboratories of the US filed for approval of its version two years ago, raising fears for Shire's medium-term profitability. Despite its attempts to create a portfolio of other blockbuster drugs, the continuing growth of Adderall - which is now sold as Adderall XR, a once-a-day formulation - has eclipsed all other products and increased the pressure on Shire to stall copycat competition. A drug's sales typically crash by three-quarters in the first few months of competition.
Shire says, in a petition to the FDA, that Barr and other rivals should have to prove their versions are metabolised by children in exactly the same way and over the same number of hours. A similar petition by Johnson & Johnson on its ADHD drug Concerta has delayed approval of generic versions for more than a year.
Shire's other tactics for extending the exclusivity of Adderall include suing Barr for patent infringement in a US case that will begin in January.Reuse content