The present invention relates to the treatment of diseases caused by invading organisms in a host by first identifying an enzymatic difference between the host and the invading organism and then administering to the host a pharmaceutically effective amount of a subversive substrate for the differing enzyme of the invading organism, whereby the action of the differing enzyme causes a result counter to the intended result and function of the enzyme that results in its debilitation or death. In particular, treatment of parasitic diseases caused by kinetoplastids including trypanosomes and leishmanias, e.g., African sleeping sickness, Chagas' disease, oriental sore and kala-azar is accomplished by administration of a pharmaceutically effective antiparasitic amount of a competitive toxigenic substrate for trypanothione reductase. Methods of treatment and compositions therefor lcontain a competitive toxigenic substrate for trypanothione reductase. Numerous compounds and corresponding compositions are disclosed.