Finnish drug maker Orion says that it is weighing up its legal options to protect the patent on its best-selling treatment after it discovered that a rival unnamed firm seeks authorisation to produce a generic version.

Orion's two best-selling drugs are for Parkinson's disease, Stalevo (carbidopa, levodopa and entacapone) and Comtess/Comtan (entacapone) and it is the firm’s patents on entacapone that are under threat.

The Espoo-based company said in a statement that an Abbreviated New Drug Application has been filed for Comtan but “at this point, the ANDA review process is just beginning and the realisation of generic competition is neither certain nor imminent,” it said.

The firm said it is currently evaluating its legal options to protect its rights, noting that under the US system, if a patent owner brings a lawsuit against an ANDA applicant within a certain time limit, there will be a 30-month stay of final FDA approval. During that time, the FDA can give only a tentative approval to the ANDA applicant unless the applicant obtains a favourable decision on all challenged patents in the lawsuit.

Orion also said that two of its patents on entacapone will run out in the USA in 2009.