Heart drug double trouble for AZ

The US District Court for the East District of Missouri has ruled that two of AstraZeneca's key patents for its blockbuster angina drug extended-release metoprolol succinate (Toprol-XL) are invalid. The ruling comes after AZ sued generic drugmakers KV Pharmaceutical Co., Andrx Pharmaceuticals and Eon Labs Manufacturing after they filed Abbreviated New Drug Applications (ANDAs) for generic versions of the drug. The judge ruled that AZ's compound patent USP5,081,154 and its composition patent USP5,001,161 were invalid because of double patenting, and unenforceable because of inequitable conduct. Although none of the generic versions of Toprol has yet been approved, the ruling will hit AZ hard — Toprol-XL is its fourth-best-selling drug and brought in US$1.29 billion in revenue in 2005 and had at least 18 months of patent protection left. AZ will appeal the decision.