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

This study is testing a new investigational drug called NTX-253 — first in healthy people to check safety and dosing, then in people with stable schizophrenia to assess its effects on symptoms. The goal is to understand how the drug behaves in the body and whether it is tolerated well. **You may be eligible if...** - You are 18–55 years old - You are generally in good health (or, for the schizophrenia portion, have stable schizophrenia) - You are not pregnant or breastfeeding and agree to use birth control if needed - If in the schizophrenia group, your symptom score (PANSS) is below 80 **You may NOT be eligible if...** - You have a significant medical illness or mental health condition (healthy participants only) - You have been diagnosed with or treated for cancer in the past 7 years - You have serious digestive problems that could affect how the drug is absorbed - You have a significant abnormality on your heart tracing (ECG) - You have a primary psychiatric diagnosis other than schizophrenia (schizophrenia group) or have treatment-resistant schizophrenia or a history of clozapine use Talk to your doctor to see if this trial is right for you.