Inclusion Criteria:  PTSD (DSM-5 criteria) Stable allowed medications with no planned changes from 30 days prior to screening through study participation Willing to use highly effective birth control Willing to comply with protocol visits and procedures  Exclusion Criteria:  Moderate to severe traumatic brain injury Other psychiatric disorders (based on SCID-5-CT) or neurodegenerative disorders Substance use disorder or alcohol use disorder within 6 months prior to screening Psychotherapy or cognitive based therapy within 30 days prior to screening Use of investigational drug within 30 days prior to screening Prior participation in study of NYX-783, NYX-2925 or NYX-458.