This study will assess the safety, tolerability, and pharmacokinetics of NTX-253 following oral administration in both healthy adult participants as well as adult participants with stable schizophrenia. NTX-253 is an investigational drug being developed for the treatment of schizophrenia. The study will consist of a single ascending dose (SAD - Part 1a) phase which will include a food effect cohort, and a cerebrospinal fluid (CSF - Part 1b) cohort in healthy volunteers. Participants will receive a single dose of either oral NTX-253 or placebo. The multiple ascending dose (MAD - Part 2) phase will follow. In Part 2, participants will be dosed for 10 consecutive days with either NTX-253 or placebo. Each phase will include sequential escalating doses in healthy volunteers. Two cohorts in the MAD phase will include stable schizophrenic adult participants who have had antipsychotic medication withdrawn for up to 8 days prior to dosing with NTX-253.
