This study is testing a new medicine, called KYN-5356, for adults with thinking problems related to schizophrenia, a mental disorder affecting how a person thinks, feels, and behaves. The study is "double-blind," meaning neither the doctors nor the participants know who is getting the real medicine or a fake one (a placebo). It lasts for 32 days, with participants staying at the clinic the whole time. They will take the medicine every day for 28 days, with doctors checking safety and how well it works throughout the study.

Participants need to have had schizophrenia for at least a year, be on a stable medication plan for at least two months, and be between 18 and 55 years old. They should not have other serious health problems or rely on more than one antipsychotic medicine.

• Length of the study: 32 days at the clinic.
• Treatment: Daily doses of KYN-5356 or placebo.
• Eligibility: Must have stable schizophrenia and be on a stable medication plan.