EU/3/17/1829: Orphan designation for the treatment of Dravet syndrome

Dravet syndrome, also called severe myoclonic epilepsy of infancy (SMEI), is a severe form of epilepsy that affects children and adults. It is caused by defects in genes required for the proper function of brain cells.

In Dravet syndrome, the seizures (fits) begin in the first year of life, and are most often associated with a high temperature (febrile convulsions). Later, other types of seizures typically occur, including status epilepticus (seizure lasting at least 5 minutes and requiring emergency medical care). From the age of 2 years, the child's development begins to decline or reverse, leading to problems such as impaired mental and motor (movement) skills.

Dravet syndrome is debilitating in the long term because of the poor development of mental and motor skills. It is also life threatening particularly because of the occurrence of major seizures.

At the time of designation, Dravet syndrome affected less than 0.5 in 10,000 people in the European Union (EU). This was equivalent to a total of fewer than 26,000 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 28), Norway, Iceland and Liechtenstein. This represents a population of 515,700,000 (Eurostat 2017).

At the time of designation, the medicine Diacomit (stiripentol) was authorised in the EU as add-on treatment for generalised tonic-clonic seizures (major fits, including loss of consciousness) in children with Dravet syndrome. Various epilepsy medicines were used to prevent fits and to treat long-lasting fits.

The sponsor has provided sufficient information to show that the medicine might be of significant benefit for patients with Dravet syndrome because laboratory studies showed that it may improve mental and motor skills and anxiety. This assumption will need to be confirmed at the time of marketing authorisation, in order to maintain the orphan status.

Most patients with Dravet syndrome have defects (mutations) in a gene called SCN1A. This gene is responsible for the production of proteins (voltage-gated sodium channels) that control transmission of electrical impulses within the brain.

This medicine is made of a small strand of synthetic genetic material. When injected into the space that surrounds the spinal cord, the medicine is expected to attach to genetic material inside brain cells and thereby increase the production of voltage-gated sodium channels. This is expected to restore normal electrical activity in the brain and hence improve not only seizures but also other symptoms of Dravet syndrome.

The effects of this medicine have been evaluated in experimental models.

At the time of submission of the application for orphan designation, no clinical trials with the medicine in patients with Dravet syndrome had been started.

At the time of submission, the medicine was not authorised anywhere in the EU for Dravet syndrome or designated as an orphan medicinal product elsewhere for this condition.

In accordance with Regulation (EC) No 141/2000 of 16 December 1999, the COMP adopted a positive opinion on 19 January 2017 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.