Approximately 32 subjects will be enrolled in a panel of 4 cohorts with approximately 8 subjects per cohort. There will be approximately 3 sequential ascending dosing levels of HPN-07, with each cohort administered 1 dose of HPN-07 ranging from 500 mg to 1,500 mg and the fourth cohort administered the highest tolerated dose of HPN-07 plus 1,200 mg NAC.