EU/3/11/921: Orphan designation for the treatment of glycogen storage disease type II (Pompe's disease)

Glycogen storage disease type II is an inherited disorder that is caused by the lack of an enzyme called hydrolase acid alpha glucosidase (GAA). This enzyme is contained in lysosomes (part of the body's cells which break down nutrients and other materials). It breaks down glycogen (carbohydrate stored in the body) into glucose. Without this enzyme, glycogen builds up in the body, typically in muscle cells, causing damage to the cells.

Glycogen storage disease type II is a long-term debilitating and life-threatening disease because it causes breathing and heart problems.

At the time of designation, glycogen storage disease type II affected approximately 0.2 in 10,000 people in the European Union (EU)*. This is equivalent to a total of around 10,000 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 (EU 27), Norway, Iceland and Liechtenstein. This represents a population of 506,300,000 (Eurostat 2011).

At the time of designation, human recombinant alglucosidase alpha enzyme (Myozyme) was authorised for the treatment of glycogen storage disease type II in the EU. Myozyme is an 'enzyme replacement therapy' that works by replacing the missing GAA enzyme.

The sponsor has provided sufficient information to show that GILT-tagged recombinant human acid alpha glucosidase might be of significant benefit for patients with glycogen storage disease type II because early studies show that it may target muscle cells more effectively than the existing treatment. This assumption will need to be confirmed at the time of marketing authorisation, in order to maintain the orphan status.

The medicine is an 'enzyme replacement therapy' which is expected to work by replacing the missing GAA enzyme in glycogen storage disease type II, helping to break down glycogen and stopping it building up in the body. The medicine is produced by a method known as 'recombinant DNA technology': it is made by cells that have received a gene (DNA), which makes them able to produce GAA. The medicine also contains a chemical tag (GILT) designed to enhance its uptake into the lysosomes.

The effects of GILT-tagged recombinant human acid alpha glucosidase have been evaluated in experimental models.

At the time of submission of the application for orphan designation, clinical trials with GILT-tagged recombinant human acid alpha glucosidase in patients with glycogen storage disease type II were ongoing.

At the time of submission, GILT-tagged recombinant human acid alpha glucosidase was not authorised anywhere in the EU for glycogen storage disease type II. Orphan designation of GILT-tagged recombinant human acid alpha glucosidase had been granted in the United States for glycogen storage disease type II.

In accordance with Regulation (EC) No 141/2000 of 16 December 1999, the COMP adopted a positive opinion on 8 September 2011 recommending the granting of this designation.

• the seriousness of the condition;
• the existence of alternative methods of diagnosis, prevention or treatment;
• either the rarity of the condition (affecting not more than 5 in 10,000 people in the EU) or 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 quality, safety and efficacy is necessary before a product can be granted a marketing authorisation.