We propose to test the hypothesis that bezafibrate, a pan-PPAR agonist, may be effective and safe for bipolar depression with the following specific aims: Aim #1. Proof-of-Concept Safety and Tolerability Aim: To assess the safety and tolerability of bezafibrate added to anti-manic medication for bipolar depression, especially with regard to worsening manic symptoms and suicidal ideation. We will conduct a phase IIa, 8-week, open pilot trial of bezafibrate added to FDA-approved anti-manic medication in 30 participants with bipolar depression. We will monitor changes in manic symptoms (Young Mania Rating Scale), suicidal ideation, cognitive functioning specifically in attention and verbal memory, and treatment emergent adverse events (SAFTEE). We will also monitor changes in the Framingham Cardiovascular Risk Score. Aim #2. Preliminary Assessment of Efficacy: To assess the antidepressant efficacy of bezafibrate added to anti-manic medication for acute bipolar I major depressive episodes. Hypothesis: The bezafibrate group will have a statistically significant decrease in the Montgomery Asberg Rating Scale (MADRS) Scores over 8 weeks. The results of this proof-of concept phase IIa study will help us to plan a placebo-controlled randomized trial. In summary, we propose an 8-week, proof-of-concept open pilot trial of an adjunctive pan-PPAR agonist, bezafibrate, for 30 patients with an acute bipolar I major depressive episode. The study may have a profound impact on the development of a novel treatment consistent with the mitochondrial dysregulation hypothesis of bipolar disorder and, to the best of our knowledge, will be the first proof-of-concept trial to assess a pan-PPAR agonist for bipolar disorder.