Refusal of orphan designation for the treatment of P-gp positive breast cancer


Table of contents


On 21 March 2012, the Committee for Orphan Medicinal Products (COMP) adopted a negative opinion on the orphan designation application for tariquidar for the treatment of P-gp positive breast cancer. A negative decision was issued by the European Commission on 27 July 2012.

The sponsor applied for orphan designation on the basis of the seriousness and the rarity of the condition, as well as an assumption of potential benefit over currently available methods of treatment.

The negative opinion was based on the following reasons:

  • the orphan condition applied for is the 'treatment of P-gp positive breast cancer'. With this condition the sponsor was specifically targeting breast cancer that is multidrug resistant due to high levels of P-gp. P-gp (or P-glycoprotein) is a protein used to transport a variety of substances in and out of cells. In breast cancer, P-gp is known to transport cytotoxic (cell-killing) medicines out of cancer cells before they can have their effect, thereby making the cancer resistant to treatment. The proposed orphan condition refers to a subset of a broader medical condition, namely breast cancer, which is not rare. The sponsor claimed that the proposed condition covers only 25% of P-gp positive breast cancers as this is the proportion they expect to be multidrug resistant. However, the COMP noted that P-gp may be found in close to 100% of breast cancer patients, and that tariquidar could therefore have an effect in a much larger population group than the subset proposed by the sponsor;
  • the COMP considered the 25% cut-off point to be arbitrary and unsupported by evidence, and concluded that the condition applied for (treatment of P-gp positive breast cancer) is not a valid subset for orphan designation. Therefore, the prevalence of the broader medical condition (breast cancer) should have been taken into account. This is more than 5 in 10,000 people in the European Union and therefore above the ceiling for orphan designation.

Requests for designation as an orphan medicinal product are made for investigational products. Absence of orphan designation does not preclude the development of this product, including its use in clinical trials. A marketing authorisation can still be obtained if quality, safety and efficacy are demonstrated.

Key facts

Active substance
Intended use
treatment of P-gp positive breast cancer
Orphan designation status
EU designation number
Date of refusal of designation
Avaant Holdings Ltd
Studio 1
Dorset House
Gloucester Place
United Kingdom
Telephone: +44 7771 77 80 84

Documents related to this orphan designation evaluation

Patients' organisations

For contact details of patients’ organisations whose activities are targeted at rare diseases, see:

  • European Organisation for Rare Diseases (EURORDIS), a non-governmental alliance of patient organisations and individuals active in the field of rare diseases.

  • Orphanet, a database containing information on rare diseases, which includes a directory of patients’ organisations registered in Europe.

EU register of orphan medicines

The list of medicines that have received an orphan designation in the EU is available on the European Commission's website:

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