This study is for women in menopause who have moderate to severe hot flashes. It is for women who are unable to use hormone replacement therapy (HRT). Menopause, a normal part of life, is the time after a woman's last period. Hot flashes often occur during menopause. They can disrupt a woman's daily life.

The study medicines (also called investigational products, or IP) are tablets of fezolinetant or placebo. An investigational product means that the product is not yet licensed. In this study, a placebo is a dummy treatment that looks like fezolinetant but does not have any medicine in it. The study will compare fezolinetant with the placebo to learn if fezolinetant reduces the number and severity of hot flashes.

Women that want to take part in the study will be given an electronic handheld device with an app to track their hot flashes. Some women may be able to use the app on their own smartphone. In the last 10 days before their next clinic visit, the women will record information about their hot flashes. They can take part in the study if they have an average of 7 or more moderate to severe hot flashes each day. Women will be picked for 1 of 2 treatments (fezolinetant or placebo) by chance alone.

Women who take part in the study will take 2 tablets every day for 24 weeks. Treatment will be double-blinded. That means that the women in the study and the study doctors will not know who takes which of the study medicines (fezolinetant or placebo). The women will continue recording information about their hot flashes on the electronic device or their phone. They will also use another device to answer questions about how hot flashes affect their daily life.

During the study, the women will visit their study clinic several times for a check-up. This will happen during Weeks 2, 4, 8, 12, 16, 20, 24, and 27. Some women may be able to have home visits instead, from Week 2 to Week 20. At the check-up, they will be asked if they have any medical problems. Other checks will include vital signs (heart rate, temperature and blood pressure) and some blood samples taken for laboratory tests. At some check-ups, the women will have a physical exam. In Week 2 and Week 24, the women will have an ECG to check their heart rhythm. Women who have a uterus will also have a test called a transvaginal ultrasound. A probe is gently placed inside the vagina. Sound waves will create a picture of the organs in the pelvis. This will allow the study doctor to look more closely at the uterus and surrounding organs.

The last check-up (at Week 27) will be 3 weeks after they take their last tablets of study medicine (fezolinetant or placebo).

Inclusion Criteria :

• Participant must be seeking treatment or relief for vasomotor symptoms (VMS) associated with menopause and confirmed as menopausal per one of the following criteria at the screening visit:

  • Spontaneous amenorrhea for >= 12 consecutive months
  • Spontaneous amenorrhea for >= 6 months with biochemical criterion of menopause (follicle-stimulating hormone [FSH] > 40 IU/L)
  • Had bilateral oophorectomy >= 6 weeks prior to the screening visit (with or without hysterectomy)

• Participant has VMS and is unsuitable to receive hormone replacement therapy (HRT) (HRT contraindicated, HRT caution, HRT stoppers and HRT averse participants).

• Participant has a minimum average of 7 moderate to severe hot flash's (HFs) (VMS) per day as recorded in the electronic diary during the last 10 days prior to randomization.

• Participant is in good general health as determined on the basis of medical history, general physical examination, laboratory and other medical assessments.

• Participant has a negative serology panel (including hepatitis B surface antigen, hepatitis C virus antibody and human immunodeficiency virus antibody screens).

• Had hysterectomy without oophorectomy and who meets the biochemical criterion of menopause (FSH > 40 IU/L).

Exclusion Criteria:

• Participant uses a prohibited therapy for VMS (e.g., prescription, over-the-counter or herbal) prior to screening and for the duration of treatment with investigational product (IP).
• Participant has known documented substance abuse or alcohol addiction within 6 months of screening.
• Participant has history of a malignant tumor within the last 5 years, except for basal cell carcinoma.
• Participant has endometrial thickness > 8 mm on the locally read screening transvaginal ultrasound (TVU) or any clinically significant findings that that would make the participant ineligible.
• Participant has history of severe allergy, hypersensitivity or intolerance to the IP and/or any of its excipients.
• Participant has a history of seizures or other convulsive disorders unless well controlled.
• Participant has a medical condition or chronic disease (including history of neurological [including cognitive], renal, cardiovascular, gastrointestinal, pulmonary [e.g., moderate asthma], endocrine or gynecological disease) or malignancy that could confound interpretation of the study outcome.
• Participant has any of the following: active liver disease, jaundice, elevated liver aminotransferases at screening (alanine aminotransferase [ALT] or aspartate aminotransferase [AST]), elevated total bilirubin (TBL) or direct bilirubin (DBL) > 1.5 × upper limit of normal (ULN), elevated International Normalized Ratio (INR) > 1.5 (unless participant is receiving anticoagulant therapy) or elevated alkaline phosphatase (ALP). Participants with mildly elevated ALT or AST up to 1.5 × ULN can be enrolled if TBL and DBL are normal. Participants with mildly elevated ALP (up to 1.5 × ULN) can be enrolled if cholestatic liver disease is excluded and no cause other than fatty liver is diagnosed. Participants with Gilbert's syndrome with elevated TBL may be enrolled as long as DBL, hemoglobin and reticulocytes are normal.
• Participant has creatinine > 1.5 × ULN or estimated glomerular filtration rate using the Modification of Diet in Renal Disease formula <= 59 mL/min per 1.73 m^2 at the screening visit.
• Participant has a history of suicide attempt or suicidal behavior within the last 12 months.
• Participant has participated in another interventional study within the last 30 days prior to screening and for the duration of the study.
• Participant who has been previously enrolled in a clinical study with fezolinetant.
• Participant is unable or unwilling to complete the study procedures.
• Participant has any condition makes the participant unsuitable for study participation.

Access to anonymized individual participant level data collected during the study, in addition to study-related supporting documentation, is planned for studies conducted with approved product indications and formulations, as well as products terminated during development. Studies conducted with product indications or formulations that remain active in development are assessed after study completion to determine if Individual Participant Data can be shared. Further details on Astellas' data sharing policy can be found at https://www.clinicaltrials.astellas.com/transparency/.

Access to participant level data is offered to researchers after publication of the primary manuscript (if applicable) and is available as long as Astellas has legal authority to provide the data.

Researchers must submit a proposal to conduct a scientifically relevant analysis of the study data. The research proposal is reviewed by an Independent Research Panel. If the proposal is approved, access to the study data is provided in a secure data sharing environment after receipt of a signed Data Sharing Agreement.