 Part B is a randomized, open-label, unbalanced, 3-period, cross-over design; subjects will be randomized 1:1 to each sequence. The relative bioavailability of single 100mg doses of powder in a bottle PIB active pharmaceutical ingredient API of GSK2838232 versus PIB spray-dried dispersion SDD will be assessed. A single dose of GSK2838232 will co-administered on the 10th day of RTV dosing; RTV dosing will continue for an additional 4 days total of 14 days. Subjects will have a screening visit within 30 days prior to first dose and a follow-up visit 7-14 days after the last dose. 