Amgen is trying to prevent competition to Epogen and its other erythropoietin-based anaemia drug Aranesp (darbepoetin alfa) in the US, which together accounted for $6.6bn or 47 per cent of the company's revenue in 2006. The ruling is the latest in a long-running intellectual property war waged by Amgen in defence of its anaemia franchise. Almost 10 years ago, Amgen fired its first salvo in the US against Transkaryotic Therapies, which was later acquired by Shire Pharmaceuticals. Afer a long battle, Shire won approval to sell Dynepo (epoetin delta), its rival anaemia drug, in Europe back in 2004. The company launched the drug, initially only in Germany, last month. However, for Amgen's competitors it is proving more difficult to break into the US market. Shire has decided not to seek approval to market their product in the US after a court ruled in August 2006 that they had infringed two Amgen patents on Epogen. In fact the Supreme Court decision doesn't really add anything new to Amgen's rivalry with Shire; the latter company has no plans to enter the US anaemia treatment market at the moment. But it could give a boost to another competitor, Switzerland's Roche, which could get marketing approval in the US for its new drug, Mircera/CERA (continuous erythropoietin receptor activator) as early as later this month. Roche claims Mircera is superior to Amgen's products as it can be injected as infrequently as once every four weeks, compared with as often as three times a week for Epogen. Aranesp is currently cleared for dosing every three weeks. The Swiss company says it is confident that its drug does not infringe any American patent, while Amgen insists it will be successful in protecting its intellectual property. So far, Roche has been issued two US patents on Mircera, but in 2005 Amgen filed a patent infringement lawsuit against them. Amgen's original patents on the drugs have already expired in Europe and competition is gaining momentum there to the biotechnology giant's licensing partner Johnson & Johnson, which sells epoetin alfa there as Procrit and Eprex. Roche is already selling an older EPO drug called NeoRecormon (epoetin beta), the leading anaemia treatment in Europe. The entrance of Dynepo to the European market will add another competitor. The Supreme Court's turning down of Amgen's appeal comes just after an FDA committee issued last week an alert informing medical professionals and patients about cases of severe anaemia in patients taking Epogen and Anaresp. This news infers that erythropoietin drugs are actually making patients worse rather than better and that means that they will suffer a restriction in their usage. Amgen shares have dropped 15 per cent to just over $54 since then. Lazard Capital analyst Joel Sendek forecasts a 21 per cent decline in worldwide Aranesp sales in 2007 from 2006. Meanwhile, several companies are planning cheaper 'biosimilar' versions of erythropoietin, which could bring price pressure in Europe where a route to market for these products has been established. Biosimilars - also known as follow-on biologics - are being kept out of the US market at present not only by Amgen's patents but by a lack of regulations for approving copies of biotechnology drugs. Some companies are trying to get around Amgen's patents by avoiding making the drugs in mammalian cells. For example, US firm GlycoFi is producing the drug in yeast. Meanwhile, other companies are hoping to bypass Amgen's intellectual property entirely by developing a new type of active molecule that boosts red cells. For example, Fibrogen has developed a small-molecule drug that can be delivered as a pill rather than by injection, making it potentially more convenient for patients and also less costly.