EU/3/01/018: Orphan designation for the treatment of glycogen storage disease type II (Pompe's disease)

Patients with glycogen storage disease type II (Pompe's disease) do not have enough of a protein called alpha-glucosidase. This protein is an enzyme, whose function is to break down glycogen (a “storage” carbohydrate) to glucose. If the protein is not present, glycogen builds up in certain tissues, such as the heart and muscle tissue (including the diaphragm, the main breathing muscle under the lungs). The progressive build-up of glycogen causes a wide range of signs and symptoms including progressive weakness of respiratory muscles and enlarged heart and liver. The condition is chronically debilitating and life-threatening.

At the time of designation, glycogen storage disease type II affected approximately 0.137 in 10,000 people in the European Union (EU). This was equivalent to a total of around 5,200 people*, and is below the ceiling for orphan designation, which is 5 people in 10,000. This is based on the information provided by the sponsor and the knowledge of the Committee for Orphan Medicinal Products (COMP).

*Disclaimer: For the purpose of the designation, the number of patients affected by the condition is estimated and assessed on the basis of data from the European Union. At the time of designation, this represented a population of 378,800,000 (Eurostat 2001).

No medicinal products were authorised for the treatment of glycogen storage disease type II (Pompe's disease) in the Community at the time of submission of the application for orphan drug designation. Current management is restricted to symptomatic treatment.

α-Glucosidase is the enzyme (molecule that speeds up chemical reactions in the body) missing in patients with glycogen storage disease type II (Pompe's disease). By replacing the deficient enzyme with a functioning one, recombinant human acid α-glucosidase, this medicine is expected to restore the normal break down of glycogen and ultimately improve the overall outcome of the patients.

The effects of recombinant human acid α-glucosidase were evaluated in experimental models.

At the time of submission of the application for orphan designation, one clinical trial in patients with glycogen storage disease type II (Pompe's disease) was completed.

In accordance with Regulation (EC) No 141/2000 of 16 December 1999, the COMP adopted a positive opinion on 19 December 2000 recommending the granting of this designation.

Update: recombinant human acid α-glucosidase (Myozyme) has been authorised in the EU since 29 March 2006 for long-term enzyme replacement therapy (ERT) in patients with a confirmed diagnosis of Pompe disease (acid α-glucosidase deficiency).

• the seriousness of the condition;
• the existence of alternative methods of diagnosis, prevention or treatment;
• and either the rarity of the condition (affecting not more than five in 10,000 people in the Community) or the insufficient returns on investment.

Designated orphan medicinal products are products that are still under investigation and are considered for orphan designation on the basis of potential activity. An orphan designation is not a marketing authorisation. As a consequence, demonstration of the quality, safety and efficacy is necessary before a product can be granted a marketing authorisation.