Methods are provided for using methotrexate (MTX) active agents in which reduced host toxicity is observed. Aspects of the methods include administering to a subject an effective amount of an MTX active agent in conjunction with a MTX toxicity-reducing adjuvant, such as a 2,2′-anhydropyrimidine, a derivative thereof or a uridine phosphorylase inhibitor. Also provided are compositions and kits that find use in practicing embodiments of the invention. The methods and compositions find use in a variety of applications, including the treatment of a variety of different disease conditions.