This is a three-part study. Participants will be enrolled in Part 1 (Effects of Itraconazole), Part 2 (Effects of Phenytoin), or Part 3 (Effects of Paroxetine) on the Pharmacokinetics of Poziotinib. Each part will be an open-label, fixed-sequence, 2-period study and may be conducted concurrently. For each study part, participants will be housed on Day -1 of Treatment Period 1 in the Clinical Research Unit (CRU) and will remain confined in the CRU until after the last scheduled blood draw and/or study procedures in Treatment Period 2. In each part, there will be a washout period of at least 8 days between poziotinib doses.~A total of 75 (25 in each part) healthy, adult male and female participants will be enrolled targeting a female/male ratio greater than or equal to (≥) 1:3 in each study part.~In part 1, CYP2D6 extensive metabolizers will be primarily enrolled with a goal of enrolling at least 2 CYP2D6 poor metabolizers. In Parts 2 and 3, only CYP2D6 extensive metabolizers will be enrolled. In Part 2, CYP2C9 and CYP2C19 poor metabolizers will be excluded.
The purpose of the study is to evaluate the effect of multiple-doses of itraconazole, phenytoin and paroxetine on the single-dose pharmacokinetics (PK) of poziotinib in healthy adult participants.