The UK's BTG is celebrating after the US Food and Drug Administration approved Voraxaze to treat patients with toxic levels of the chemotherapy methotrexate in their blood due to kidney failure.

The approval of Voraxaze (glucarpidase), which was granted under priority review, was primarily based on a study of 22 patients which looked to see if the methotrexate level fell below a critical level within 15 minutes and stayed below for eight days. The FDA noted that ten of the 22 patients achieved this standard and although not all patients experienced this result, Voraxaze eliminated 95% of the methotrexate in all patients.

A separate clinical study evaluated the safety of Voraxaze in 290 patients experiencing problems clearing methotrexate from their blood. The drug works by breaking down methotrexate into its inactive metabolites which are then eliminated from the body by routes other than the kidney, primarily the liver.

Richard Pazdur, director of the Office of Hematology and Oncology Drug Products in the FDA’s Center for Drug Evaluation and Research, said that prolonged exposure to high levels of methotrexate "can result in kidney and liver damage, severe mouth sores, damage to the lining of the intestine, skin rashes, and death due to low blood counts”. Voraxaze is, therefore, "an important new treatment option for cancer patients aimed at preventing these toxicities".

BTG chief executive Louise Makin noted that Voraxaze, which the firm acquired though its £218-million merger with Protherics in 2008, is the first product the firm has taken through to approval in the USA. It will be launched over coming months and "sold by our existing specialty pharmaceuticals sales force, with the addition of a few extra personnel", she said, alongside "our established emergency room medicines", rattlesnake antivenom CroFab (crotalidae polyvalent immune fab) and toxicity drug DigiFab (digoxin immune fab).