This protocol provides an early evaluation of an entirely new class of small molecule agents directed at disruption or elimination of tumor tolerance, a phenomenon now demonstrated to be involved in the growth of many solid tumors. D-1MT, or any other substance targeting this enzymatic pathway indoleamine-(2,3)-dioxygenase (IDO), has not been used previously in humans. Although pre-clinical toxicology in rats and dogs shows an extremely encouraging toxicity profile, the study needs to carefully evaluate the toxicities and pharmacokinetics to provide the basis for assigning a safe and biologically effective dosing regimen for later trials determining its contribution to tumor responses in phase II and III clinical trials.