EU/3/20/2367: Orphan designation for the treatment of Prader-Willi syndrome

Prader-Willi syndrome is an inherited condition caused by defects in specific regions of chromosome 15. This causes a wide range of symptoms, some of which can appear at birth, such as feeding problems, small size and reduced muscle strength. During childhood further symptoms develop, including increased appetite leading to constant eating and severe obesity, short stature, incomplete sexual development, learning difficulties and behavioural problems, such as aggression and stubbornness.

Prader-Willi syndrome is a life-long debilitating and life-threatening disease because of its serious symptoms, particularly learning difficulties, behavioural problems and obesity.

At the time of designation, Prader-Willi Syndrome affected approximately 0.3 in 10,000 people in the European Union (EU). This was equivalent to a total of around 16,000 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).

At the time of designation, growth hormone was authorised in the EU for treating Prader-Willi syndrome. In addition, symptoms were treated or managed in various ways, including supervised access to food to prevent obesity.

The sponsor has provided sufficient information to show that the medicine might be of significant benefit for patients with Prader-Willi syndrome, with laboratory data showing that it may reduce excessive food intake – a benefit not seen with growth hormone therapy. This assumption will need to be confirmed at the time of marketing authorisation, in order to maintain the orphan status.

Patients affected by Prader-Willi syndrome have high blood levels of a substance named ghrelin, a hormone mainly produced by the stomach wall. By binding to its receptor (target), ghrelin may alter the perception of hunger and promote overeating.

The medicine is expected to bind to the ghrelin receptors and block them, which may result in reduction of the appetite and food intake. 

The effects of the 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 Prader-Willi syndrome had been started.

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

In accordance with Regulation (EC) No 141/2000, the COMP adopted a positive opinion on 5 November 2020, 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.