European regulators have expanded the scope of Teva Pharmaceutical's Trisenox, approving its use to treat patients with newly diagnosed Acute Promyelocytic Leukaemia (APL), a rare and aggressive type of blood cancer that can kill within hours or days if left untreated.

Trisenox (arsenic trioxide) was first approved in Europe in 2002 for the treatment of relapsed or refractory APL in patients have not responded to treatment with retinoids and anticancer medicines, or when their disease has come back after this type of treatment.

This latest decision gives patients access to the first chemotherapy-free treatment option for the condition in the first-line setting, which, when used in combination with retinoid acid, has shown a 99 percent overall survival rate (APL0406 study) with almost no relapses after more than four years (50 months) of median follow-up.

APL is caused by a genetic 'translocation' that affects the way the white blood cells grow, and they lack the ability to use retinoic acid (vitamin A). How Trisenox works to treat APL is not completely understood, but it is thought to prevent the production of DNA, which is necessary for leukaemia cells to grow, according to the European Medicines Agency.