The disclosure relates generally to gamma polyglutamated methotrexate compositions, including delivery vehicles such as liposomes containing the gamma polyglutamated methotrexate, and methods of making and using the gamma polyglutamated methotrexate compositions to treat hyperproliferative disorders (e.g., cancer) and disorders of the immune system (e.g., inflammation and autoimmune diseases such as rheumatoid arthritis).