Genzyme has won approval in Europe for Myozyme, its enzyme replacement therapy for the genetic disorder Pompe disease.

Myozyme becomes the first treatment for patients with this potentially fatal muscle condition, caused by an inherited enzyme deficiency, which affects fewer than 10,000 people worldwide.

The US biotechnology company said Myozyme (alglucosidase alfa) had been approved by the European Medicines Agency (EMEA) for the long-term treatment of patients with a confirmed diagnosis of Pompe disease. It was submitted for approval for the same indication in the USA last August, and in January the US Food and Drug Administration (FDA) said it needed more time to review the application.

Genzyme said it would introduce Myozyme in Europe on a country-by-country basis, as pricing and reimbursement approvals are obtained. Analysts have suggested that in time Myozyme could reap in sales of close to $1 billion, despite its tiny target patient population.

Genzyme’s top-selling drug at present is Cerezyme (imiglucerase) for Gaucher disease. The illness affects just 4,500 patients, but Genzyme still earned $932 million from the drug in 2005, 14 years since it first reached the market.