Four studies involving patients at risk of methotrexate toxicity found that Voraxaze was effective at achieving a clinically important reduction (CIR) in the level of methotrexate in the blood (in other words, to a level where methotrexate no longer causes harm). The studies looked at 169 patients in whom the level of methotrexate had been measured using a method called high-performance liquid chromatography (HPLC) at least once after the first dose of Voraxaze. Voraxaze was not compared with other treatments.

The first study involved patients who were at risk of methotrexate toxicity due to reduced kidney function or because they had received too much methotrexate intrathecally (by injection into the fluid surrounding the spinal cord). Treatment with Voraxaze achieved a CIR in the level of methotrexate in the blood in 24 out of 28 (85.7%) patients.

Two studies involved patients who were unable to clear methotrexate from their body because of reduced kidney function. In these studies, treatment with Voraxaze achieved a CIR in the methotrexate blood level in 14 out of 27 (51.9%) and 20 out of 30 (66.7%) patients.

In the last study, patients who were unable to clear methotrexate from their body because of reduced kidney function were given Voraxaze alone or with thymidine (another treatment to lower the level of methotrexate). Of these patients, 46 out of 84 patients (54.8%) achieved a CIR in methotrexate levels in the blood. Of the patients who received Voraxaze and thymidine, 50% achieved a CIR in methotrexate, compared with 59.5% of those receiving Voraxaze alone.

Overall, across the four studies, the average level of methotrexate decreased by between 96.8% and 99.3% within 15 minutes of the first dose of Voraxaze. In addition, the level of methotrexate remained stable for 8 to 15 days.