Roche Holding AG said the European Commission approved its drug Hemlibra for preventing bleeding episodes in certain patients with hemophilia A, a bleeding disorder.

The approval is for use of Hemlibra to treat people with severe hemophilia A without factor VIII inhibitors. Factor VIII is an essential blood-clotting protein and people with hemophilia A either lack or do not have enough of it.

A serious complication to treatment occurs when patients become resistant by developing antibodies, or inhibitors, which block the replacement factor VIII, making it difficult to control bleeding.

The approval is based on two phase 3 studies called Haven 3 and Haven 4. Haven 3 showed that Hemlibra produced statistically significant reductions in treating bleeds when compared to an absence of a preventive treatment while in Haven 4, Hemlibra, given every four weeks, produced clinically meaningful control of bleeding in previously treated patients.

Hemlibra, or emicizumab, is already approved in the EU for treating patients with hemophilia A with factor VIII inhibitors. The therapy has also received nods in the U.S. and Japan.

Hemlibra is being co-developed globally by Basel, Switzerland-based Roche and its majority-owned Japanese unit Chugai Pharmaceutical Co. Ltd. The medicine has been evaluated in multiple phase 3 studies.