 Used in treatment of colorectal cancer since 1998, it may also be used in the treatment of malignant mesothelioma.Raltitrexed is approved for use in Canada and some European countries, but is not approved by the US FDA.Raltitrexed is chemically similar to folic acid and is in the class of chemotherapy drugs called folate antimetabolites, which inhibit one or more of three enzymes that use folate and derivatives as substrates