PART 1 The SAD treatment group is comprised of three cohorts where HV will be randomized to either PTI-801 or placebo. Following the conclusion of at least three SAD cohorts, a set of HV will participate in an assigned MAD treatment group. The MAD treatment group is comprised of three cohorts where subjects will be randomized to receive either PTI-801 or placebo once daily (QD) for a total of 7 days. Following the conclusion of at least three SAD cohorts, a set of HV will participate in a FE treatment group. The FE treatment group is comprised of one cohort where subjects will be randomized to receive an initial single dose of PTI-801 either after an overnight fast of at least 10 hours (fasted group) or after an overnight fast of at least 10 hours followed by the consumption of a high fat high and high calorie meal (fed group). After a 10 day washout period, subjects will cross over to the opposite group and receive a second dose of PTI-801. Following the conclusion of at least two MAD cohorts, a set of HV will participate in a DDI treatment group. The DDI treatment group is comprised of one cohort where subjects will receive a 3-drug cocktail consisting of caffeine, bupropion, and midazolam on Day 1. On Day 4, subjects will be randomized to receive either PTI-801 or placebo QD for a total of 12 days. On Day 17, subjects will receive the 3-drug cocktail in combination with PTI-801 or placebo.