KarXT Concentrations in the Breast Milk and Plasma of Lactating Females

Inclusion Criteria: * Participants should have a body mass index (BMI) of 18.0 kg/m2 to 35.0 kg/m2, inclusive, and body weight ≥ 50 kg (110 lb), at screening. * Participants should have well-established lactation (ie, at least 4 weeks postpartum) and can produce stable milk product (ie, approximately 3 oz per 3 hours at screening) using the methods required for the study. * Participants should be willing to exclusively pump breast milk throughout the treatment period and during the 24-hour post last dose period of milk collection during the CRU domincile period. * Participants should agree not to breastfeed or provide milk to infant until after 96 hours post last dose. Exclusion Criteria: * Participants must not have evidence of organ dysfunction or any clinically significant deviation from normal in physical examination, vital signs, 12-lead ECG, or clinical laboratory determinations beyond what is consistent with the target population reference ranges as assessed by the investigator. * Participants must not have history or presence of clinically significant cardiovascular, pulmonary, renal, hematologic, gastrointestinal (eg, obstructive disorders \[including conditions that may decrease GI motility, such as ulcerative colitis, intestinal atony, and myasthenia gravis\]), endocrine, immunologic, dermatologic, neurologic, or oncologic disease or any other condition that, in the opinion of the investigator, would jeopardize the safety of the participant or the validity of the study results. * Other protocol defined inclusion/exclusion criteria apply.