Lumizyme is supposed to be the same therapeutic as Myozyme but in scaling up from 160L reactors to 2000L the product became considerably different, according to the US Food and Drug Administration (FDA).

Genzyme had thought it was on the verge of gaining approval for the 2000L version but in a complete response letter the FDA has said more work is needed. This has delayed Lumizyme’s release by six months, according to Genzyme, and cut sales forecasts by around $65m.