The primary objectives of this application are to determine if the selective ERβ agonist LY500307, when added to antipsychotic medications, improves negative and/or cognitive symptoms in patients with schizophrenia. The specific hypotheses to be tested are to determine if LY500307 is safe and well tolerated in this population and whether it elicits a sufficient efficacy signal to be advanced for further testing in schizophrenia. A two-stage Phase 1b/Phase 2a adaptive ("drop the inferior dose") experimental design is ongoing that combines three studies (clinical dose optimization, cortical target engagement confirmation and efficacy and safety assessment) into a single clinical trial.