Seattle Genetics says regulators in the USA have granted orphan drug status to the firm's antibody-drug conjugate Adcentris for the treatment of a type of T-cell lymphoma.

Specifically, Adcetris (brentuximab vedotin) has been given orphan drug designation by the US Food and Drug Administration for the treatment of mycosis fungicides, the most common type of cutaneous T-cell lymphoma. Seattle Genetics and partner Takeda are conducting a Phase III trial of Adcetris versus investigator’s choice of methotrexate or bexarotene in patients with CD30-positive CTCL, including MF.

The primary endpoint of the study is overall response rate lasting at least four months and 124 patients will be enrolled. The trial is being conducted under a special protocol assessment agreement from the FDA and has also received scientific advice from the European Medicines Agency.

Getting orphan drug designation "is a part of our Adcetris regulatory strategy”, said Clay Siegall, Seattle Genetics' chief executive. It means the drug will enjoy seven years of market exclusivity upon approval in this indication, as well as grants to defray costs of clinical trials, fee waivers and tax credits.

He added that "the encouraging data from investigator-sponsored trials of Adcetris in CTCL, which will be presented at the American Society of Hematology meeting (starting at the end of next week in Atlanta), provide further support for our activities in this patient population".

Adcetris is already approved for Hodgkin lymphoma  and systemic anaplastic large cell lymphoma in the USA and Europe but sales to date  of the ADC, the technology for which allows an antibody to direct a drug to diseased cells, have caused some concern.

Adcetris, which has been touted as a game-changing blockbuster, brought in just $33.7 million in the third quarter. Seattle Genetics is therefore hoping to add a number of new indications to the label.