CRP and treatment resistant depression: However, it is noteworthy that an ongoing phase 2 clinical trial is testing the efficacy of augmentation with sirukumab, a monoclonal antibody against IL-6, in depressed patients with CRP levels ≥ 3 mg/L (NCT02473289) and in TRD patients who have failed to respond to at least one but no more than three adequate antidepressant treatments during their current episode of depression.