Enoxolone in Major Depression - Biomarker-outcome Relationship

Many different forms of depression exist. It is difficult to predict to what treatment a given patient with depression responds. Studies demonstrate that biomarkers can help to distinguish different forms of depression. Simple markers, like aldosterone/cortisol in body fluids, blood pressure and inflammation markers , have been identified as predictors of therapy resistance in depression. Enoxolone is a molecule derived from the licorice plant and has demonstrated an effect on these biomarkers, which may imply an improved response. The current randomized placebo controlled study is assessing whether the presence of markers of therapy resistance can predict a preferential effect of enoxolone vs. placebo on clinical outcome. Secondarily, it is tested whether these markers change differentially in the treatment groups. Finally, the relationship between the change of the markers and clinical change will be assessed.

The objective of the study is 1. to confirm patient characteristics, which are related to lesser responsivity to antidepressant treatment and 2. to explore the utility of the 11 beta hydroxysteroid-dehydrogenase type 2 (11betaHSD2) inhibitor enoxolone to reverse these markers of refractoriness and, potentially, improve clinical outcome. A broad spectrum of patients is recruited in order to provide the opportunity to compare those with relevant markers of refractoriness vs. those without.

The identified markers are related to the activity of aldosterone, which appears to affect specific CNS areas, which are involved in mood and autonomic regulation. One area of particular relevance is the pontine nucleus of the solitary tract (NTS). Potential primary triggers for an increased aldosterone release under stressful conditions are related to low blood pressure, electrolyte alterations and a dysfunction of the peripheral mineralocorticoid receptor (MR). The resultant aldosterone release evokes activity at the NTS, which may lead to depression and anxiety.

Enoxolone leads to an activation primarily of the peripheral MR by reducing the activity of the 11betaHSD2, therefore allowing cortisol access to the MR and, as a consequence, suppress the release of renin, angiotensin and aldosterone. In addition, it can increase blood pressure slightly.

1. A set of potentially predictive markers for therapy response of enoxolone vs. placebo will be studied, based on this mechanistic pathway, in detail:

   For the primary analysis subjects are grouped into those with higher vs. lower systolic blood pressure values, as determined by the median systolic blood pressure value at baseline.

   For the secondary analysis the ratio of urine aldosterone/cortisol, as collected over night will be used as a differentiating parameter. Split at the median defines the groups.

   Exploratory parameters for a split are the following:
   1. sleep duration
   2. heart rate variability
   3. salt taste sensitivity and salt preference
   4. inflammation markers, in particular C-reactive protein in plasma.
   5. Optional: volumes of lateral ventricles, corpus callosum and choroid plexi.
   6. Optional: white matter integrity, as measured by diffusion tensor imaging
2. Markers of target engagement:

   1. Effect of enoxolone vs. placebo on systolic blood pressure.
   2. Effect of enoxolone vs. placebo on urine aldosterone/cortisol concentration.
   3. Effect of enoxolone vs. placebo on plasma sodium/potassium concentration ratio.
3. The relationship between changes in hormone concentrations and markers of CNS activation of MR, i.e. functional CNS target engagement. These are:

   1. Heart rate variability and heart rate
   2. Systolic blood pressure at rest and nocturnal blood pressure dip
   3. Total sleep time
   4. Salt taste preference and sensitivity
   5. Inflammatory markers
   6. Optional: volumes of lateral ventricles, corpus callosum and choroid plexi.
   7. Optional: white matter integrity, as measured by diffusion tensor imaging

Eligibility Criteria:
Inclusion Criteria:

* Unipolar Depression
* in women: Contraceptive means

Exclusion Criteria:

* Schizophrenic and delusional disorders
* Neurological diseases in which central nervous system involvement is known, such as epilepsies, storage diseases; severe mental retardation
* Internistic diseases of moderate or higher severity, which may make participation in the study risky from a clinical point of view. In particular, multiple systolic blood pressure (measured after at least 5 min supine position) of \> 145 mm Hg as well as hypokalemia (\< 3.5 mmol/l) and clinically relevant ECG changes
* Poorly controlled diabetes mellitus (HbA1c \> 10)
* Pregnancy or active desire for pregnancy for the duration of the study
* Non-consent or inability to consent to the study
* Treatment with the following substances: spironolactone or eplerenone; systemic glucocorticoids
* Treatment with ketamine or electroconvulsive therapy in the last 3 months before randomization
* Acute suicidality
* Intolerance to licorice preparations or licorice contents.