This 2-part study will assess the effect of formulation and food on the pharmacokinetics of Indoximod in healthy volunteers. Part 1 is an open-label, 3-period, 6-sequence study. Participants will receive single doses of Indoximod base or salt formulation, in the fasted or fed state. Part 2 is a randomized single ascending dose study of indoximod salt formulation to characterize the PK profile and determine the safety and tolerability of each dose in healthy male volunteers.