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.