Each participant will participate in 2 study periods separated by a washout of at least 5 days between investigational product (IP) administrations. Participants will be randomized to 1 of 2 sequences: either fezolinetant test formulation followed by fezolinetant reference formulation or fezolinetant reference formulation followed by fezolinetant test formulation. Participants will be admitted to the clinical unit on day -1 and will be residential for 2 study periods for a total of 10 days/9 nights. Premenopausal female participants will be admitted to the clinical unit during days 1 to 3 of their menstrual cycle. Participants will receive a single dose of test formulation or reference formulation under fasting conditions on day 1 of each period i.e., days 2 to 4 (period 1) and days 7 to 9 (period 2) of their menstrual cycle for premenopausal female participants. Participants are to remain semirecumbent and avoid lying on either the left or right side for 4 hours postdose. Pharmacokinetic samples will be collected predose on day 1 of each period and at multiple time points postdose. Standard safety and tolerability assessments will be conducted. Participants will be discharged from the clinical unit on day 4 of period 2 on the condition that all required assessments have been performed and that there are no medical reasons for a longer stay in the clinical unit.~The study will be completed with an end-of-study visit (ESV). The ESV will take place 5 to 9 days after discharge from period 2 or at early discontinuation from the study.
The purpose of this study is to assess the bioequivalence of a single dose of fezolinetant test formulation compared to a single dose of fezolinetant reference formulation under fasting conditions. This study will also evaluate the safety and tolerability of a single dose of fezolinetant test formulation and a single dose of fezolinetant reference formulation.