Multicenter Study to Evaluate the Efficacy and Safety of Oral ACT-539313 in the Treatment of Adults With Moderate to Severe Binge Eating Disorder

Inclusion Criteria: Criteria assessed at Visit 1: * Signed and dated informed consent form prior to any study-mandated procedure. * Male or female study participants aged 18 to 55 years at the time of signing the informed consent form. * Binge-eating disorder (BED) in accordance with Diagnostic and Statistical Manual of Mental Disorders Fifth Edition (DSM-5) criteria diagnosed using the Structured Clinical Interview for DSM-5 (SCID-5). * Self-reported BED severity of at least moderate level, defined as at least 4 BE episodes per week, on average, for a duration of at least 6 months. * BED in accordance with Eating Disorder Examination Questionnaire (EDE-Q). * Clinical Global Impression of Severity scale (CGI-S) score of ≥ 4. * For women of childbearing potential (WOCBP): Negative serum pregnancy test at Visit 1; agreement to undertake monthly urine or serum pregnancy tests during the study and up to the EOS visit; agreement to use an acceptable contraceptive method. Criteria assessed at Visit 2: * Reporting ≥3 BE days for each of the 2 weeks prior to randomization as documented in the participant's BE diary and with BE diary entries completed for at least 6 days per week during this 2-week period (between Visit 1 and 2). * CGI-S score of ≥ 4. * For WOCBP: negative urine pregnancy test. Exclusion Criteria: Criteria assessed at Visit 1: * BMI \< 18.0 kg/m² or \> 45 kg/m². * Any acute or chronic-persistent psychiatric disorder other than BED diagnosed in the past, including anorexia nervosa, bulimia, psychotic disorders, bipolar disorder, hypomania, or dementia, as defined by the DSM-5 criteria or by the Mini International Neuropsychiatric Interview (MINI©). * Use of any medications for the treatment of BED (including lisdexamfetamine \[Vyvanse®\]), any other eating disorder, obesity, or weight gain, or any other medication that could result in weight gain or weight loss, including over-the-counter and herbal products, within 3 months prior to Screening. * Any clinically unstable medical condition, significant medical disorder or acute illness that, in the investigator's opinion, could interfere with the participants ability to comply with study assessments or abide by study restrictions. Criteria assessed at Visit 1 and Visit 2 * HAMD-17 score ≥ 17 points at Visit 1 and/or Visit 2. * Any of the following conditions related to suicidality: 1. Participant is considered to have a suicide risk in the investigator's opinion or has a previous history of suicide attempt within the past 12 months. 2. Participant answers "yes" to "suicidal ideation" item 4 (active suicidal ideation with some intent to act, without specific plan) or item 5 (active suicidal ideation with specific plan and intent) on the C-SSRS© assessment at Screening (in the past month). Participants who answer "yes" to this question must be referred to the investigator for follow-up evaluation. * Female participants: pregnant, lactating or planning to become pregnant during the projected course of the study.