Single and Multiple Ascending Doses of NTX-253 in Healthy Participants and Participants With Stable Schizophrenia

Primary Inclusion Criteria: * Male or non-pregnant, non-lactating female participants, ages 18-55 who are not of childbearing potential, with a truly abstinent lifestyle, or agrees to use medically acceptable forms of birth control * Part 1 a/b, Part 2 Cohort 7 only: Body mass index (BMI) within the range ≥18.0 to ≤30.0 kg/m2 * Participants in the food effect cohort must be willing to eat a single high fat breakfast * (Part 2 only): Stable schizophrenia participants (schizophrenia cohorts only) * Body mass index (BMI) within the range ≥17.5 to ≤36.0 kg/m2 * Positive and Negative Syndrome Scale (PANSS) total score \<80 at screening Primary Exclusion Criteria: * (Part 1a/b, Part 2 Healthy): History of or current clinically significant medical or mental illness * Cancer diagnosis/treatment in the past 7 years * Acute or chronic gastrointestinal conditions that would interfere with drug tolerance or absorption * Any clinically significant, abnormal 12 lead ECG * Part 2: Any primary DSM-5TR disorder other than schizophrenia * Participants with schizophrenia who are considered resistant/refractory to antipsychotic treatment by history; history of clozapine use.