Evaluating the Role of IL-17 as an Orchestrator of Peripheral-central Cross Talk in Depressive Symptoms

Approximately 30-40% of patients with immune-mediated inflammatory diseases (IMIDs), such as psoriatic disease, experience depression. These symptoms negatively affect clinical outcomes, quality of life and treatment adherence. There is accumulating evidence that peripheral inflammation may contribute to the origins of depression. In particular, a) stimulation of active phase inflammation results in remitting-relapsing depressive symptoms b) abnormal neural connectivity linked to this depression is correlated with peripheral inflammation and c) biologic therapies targeting specific peripheral inflammation components (cytokines) improve depressive symptoms. In this proposal, psoriatic disease (PsD), encompassing both psoriasis and PsA, will be our IMID exemplar. In this condition, the IL-23/IL-17 cytokine axis is central to pathogenesis, as proven by successful application of inhibitors to this pathway. Moreover, this axis has also recently been implicated in the neurobiology of depression in both preclinical and clinical studies. The investigators aim to uncover the mechanisms that underlie depression in the context of IMIDs, delivered by a focused immune intervention study examining brain circuitry using state of the art imaging in the context of exquisitely specific therapeutic immune interception in human immune disease. The rationale for this study is to use this specific therapeutic immune intervention to leverage mechanistic understanding of brain changes that drive depressive symptoms. Prior animal studies have clearly demonstrated the deleterious effects of proinflammatory cytokines on neural functioning. The investigators will integrate current therapy with innovative neuroimaging technologies to obtain data for the first time in humans that have hitherto only been possible in animal studies. The intervention tools proposed herein (secukinumab, bimekizumab or Ixekizumab) are IL-17 inhibitors licensed for treatment of active PsO and PsA. Secukinumab, bimekizumab and Ixekizumab are widely used in clinical practice globally and across the UK as a first/second-line biologic disease modifying antirheumatic drug (DMARD), in line with national/international NICE (TA350, TA445, TA723, TA916, TA442, TA537) treatment recommendations. Secukinumab is given by self-administered subcutaneous injection weekly for the first five weeks of treatment and thereafter by monthly maintenance injections. Bimekizumab is given by self-administered subcutaneous injection 4 weekly, Ixekizumab is given by self -administered subcutaneous injection either 2 or 4 weekly. Typically, depressive symptoms are attenuated within weeks of therapeutic initiation. Prior study data indicate a beneficial effect of IL17 antagonism on depressive symptoms, but the mechanism of action has not yet been explored.