South Korean biopharmaceutical firm Celltrion Inc. said Tuesday that its biosimilar drug Truxima began selling in Britain following approval from a European regulator.

Starting earlier this month, Britain-based Napp Pharmaceuticals began distributing Celltrion's biosimilar to Roche's Mabthera at 50 hospitals in the country, Celltrion said.

In February, the European Medicines Agency accepted Celltrion's application to sell the antibody biosimilar which is used in the treatment of a number of diseases, including rheumatoid arthritis and non-Hodgkin's lymphoma, a type of leukemia.

"The first administration of Truxima was completed following the official launch," said a Celltrion official not to be named.

With EMA approval, the biosimilar can also be sold in 28 European Union countries, as well as Norway, Iceland and Lichtenstein, company officials said.

Biosimilars are officially approved copycat medicines developed after patents for the original biopharmaceuticals expire. (Yonhap)