A 41-year-old woman with obsessive-compulsive disorder presents for re-evaluation after inadequate response to two sequential SSRI trials. She completed 14 weeks of fluvoxamine titrated to 300 mg daily and 12 weeks of sertraline titrated to 200 mg daily, both at maximum tolerated doses with confirmed adherence, and reports less than 25% improvement on the Yale-Brown Obsessive Compulsive Scale (Y-BOCS). She also completed 16 sessions of exposure and response prevention (ERP) therapy with a trained cognitive-behavioral therapist. Her current Y-BOCS score is 28, indicating severe symptoms. She has no comorbid psychotic features, tic disorder, or bipolar disorder. The PMHNP is formulating the next step in the treatment plan. Which of the following is the most appropriate treatment planning strategy?