Clinical outcomes in the biomarkers of ketamine (Bio-K) study of open-label IV ketamine for refractory depression

Objective: We conducted an open-label clinical trial ("Bio-K") using IV ketamine for treatment-resistant depression to identify biomarkers linked to remission. Here, we report the clinical efficacy and side effect outcomes of Bio-K.

Methods: Across 4 US sites, 75 patients ages 18-65 with treatment-refractory unipolar or bipolar depression received 3 IV ketamine infusions over an 11-day period. Key exclusion criteria were psychotic symptoms, significant substance abuse, unstable medical conditions, and any use of cannabis. Pre-existing antidepressant medication was maintained. Primary outcome was remission as measured by Montgomery-Asberg Depression Rating Scale (MADRS), with secondary outcome of 50 % reduction in Beck Suicide Scale score. Safety monitoring and varying durations of infusions were also key parameters.

Results: Using remission as MADRS score <10, after 3 infusions 52 % achieved remission, with 67 % achieving response. Of those achieving response after a single infusion, 66 % (22 of 33) reached remission after 3 infusions, while 40 % (16 of 40) non-responders after the first infusion went on to achieve remission after 3 infusions. Only 20 % of non-responders after 2 infusions achieved remission. Most (81 %) participants had significant suicidal ideation at baseline; of these, two-thirds (67 %) experienced at least a 50 % reduction in suicidality. Side effects were minimal. Uniquely, we had three different types of infusion categories, with individuals receiving: (1) slow (100-min) infusions only or (2) regular (40-min) infusions only or (3) a mix of infusion durations. These three infusion groups showed comparable safety and efficacy. Exploration of clinical factors revealed no link between BMI, age, or gender to remission.

Conclusions: The consistency of outcomes across 4 clinical sites and across multiple instruments, suggests high acute efficacy and safety of IV ketamine for serious depressive episodes. Duration of infusion did not alter outcomes. Meaningfully, 40 % of non-responders after a single infusion did reach remission subsequently, while only 20 % of non-responders after 2 infusions achieved remission, suggesting early response is suggestive for eventual remission. Our data on varying ketamine infusion duration adds novel insights into the clinical administration of this new treatment for refractory and severe patients. Our limitations included a lack of a control group, necessitating caution about conclusions of efficacy, balanced by the utility of reporting "real-world" outcomes across multiple clinical sites. We could also not separately analyze results for bipolar disorder due to small numbers. Together, the Bio-K clinical results are promising and provide significant sample sizes for forthcoming biological markers analyses.