EU/3/02/124: Orphan designation for the treatment of Lambert-Eaton myasthenic syndrome

Lambert-Eaton myasthenic syndrome is characterised by weakness of the muscles. The weakness can be so severe that it becomes difficult to climb the stairs, or even walk. The disease is chronically debilitating, and life-threatening. In some patients the disease occurs in the presence of cancer, often a cancer of the lung.

At the time of designation, Lambert-Eaton myasthenic syndrome affected approximately 0.1 in 10,000 people in the European Union (EU)*. This is equivalent to a total of around 4,000 people, and is below the threshold 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: The number of patients affected by the condition is estimated and assessed for the purpose of the designation, for a European Community population of 377,000,000 (Eurostat 2001) and may differ from the true number of patients affected by the condition. This estimate is based on available information and calculations presented by the sponsor at the time of the application.

Several products have been used to treat this condition, however none of them has been authorised for Lambert-Eaton myasthenic syndrome in the European Union.

Muscles are made up of fibres. The fibres of muscles are connected to the nerves. When activated, nerves release a substance into the space between the nerve and the muscle. This substance is called acetylcholine. It causes the muscle fibres to shrink. As a result, the muscle contracts. The release of acetylcholine occurs through a complex mechanism. The mechanism is based on the different flows of potassium and calcium across the surface of nerve cells. The flow is controlled by certain proteins called potassium channels. 3,4-diaminopyridine phosphate is able to block these proteins. As a result, more calcium is taken up by the cells. This in turn causes release of acetylcholine. This is expected to increase muscle strength.

At the time of submission of the application for orphan designation, clinical trials were ongoing.

Another sponsor has received orphan designation in the United States FDA for Lambert-Eaton myasthenic syndrome in 1990.

The medicinal product was not marketed anywhere worldwide for Lambert-Eaton myasthenic syndrome.

In accordance with Regulation (EC) No 141/2000 of 16 December 1999, the COMP adopted a positive opinion on 15 November 2002 recommending the granting of this designation.

Update: 3,4 Diaminopyridine phosphate (Firdapse) has been authorised in the EU since 23 December 2009 for symptomatic treatment of Lambert-Eaton myasthenic syndrome (LEMS) in adults.

• the seriousness of the condition,
• the existence or not of alternative methods of diagnosis, prevention or treatment and
• either the rarity of the condition (considered to affect not more than five in ten thousand persons in the Community) or the insufficient return of development investments.

Designated orphan medicinal products are still investigational products, which were considered for 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 will be necessary before this product can be granted a marketing authorisation.