Indications for an antidepressive effect of thymosin alpha-1 in a small open-label proof of concept study in common variable immune deficiency patients with depression.
This small open-label proof-of-concept study investigated whether thymosin alpha-1 (Tα1), a thymic peptide hormone, might reduce depressive symptoms in five patients with common variable immunodeficiency (CVID) who also had a comorbid depressive episode. The rationale was that CVID patients share immune abnormalities with major depressive disorder (MDD) patients — notably reduced naïve T cells and premature T-cell senescence — and that Tα1 can stimulate thymic output of naïve T cells, potentially improving mood via immune-limbic system pathways. Patients received Tα1 subcutaneously over eight weeks and were assessed using the Hamilton Depression Rating Scale (HDRS) alongside immune biomarkers. All five CVID patients showed reductions in HDRS scores (average 52%), compared to a 36% average reduction in a non-randomized contrast group of 42 MDD patients receiving treatment as usual. Naïve/memory T-cell ratios improved in all five patients, and IL-6 levels decreased in four of the five. However, depressive and immune improvements were not sustained in a subsequent eight-week wash-out period for the more severely affected patients. Key limitations include the very small sample size (n=5), lack of a placebo control, open-label design, and use of a non-matched contrast group. The authors conclude that larger placebo-controlled trials are warranted.
Why this grade: Open-label design with only five treated participants, no randomization or placebo control, and a non-matched contrast group severely limit causal inference despite being conducted in humans.
Background A considerable proportion (21%) of patients with common variable immunodeficiency (CVID) suffers from depression. These subjects are characterized by reduced naïve T cells and a premature T cell senescence similar to that of patients with major depressive disorder (MDD). It is known that T cells are essential for limbic system development/function. Treatment with thymosin α1 (Tα1) is capable to increase the thymus output of naïve T cells. Objective To treat CVID patients with a comorbid depressive episode with Tα1 to increase naïve T cells and thereby improve mood. Design A small open-label, proof of concept trial. Five depressed CVID patients (Hamilton Depression Rating Scale, HDRS >12) could be treated with Tα1 (8 weeks, 1.6 mg daily subcutaneously, 1st week, thereafter 1.6 mg twice weekly). At the start, at 8 weeks and 8 weeks after the last injection, the HDRS was recorded and blood samples drawn for measuring naïve and memory T cells, Th17 and Treg cells, hsCRP, IL-6 and IL-7. Outcomes were compared to those of a contrast group (42 MDD patients, same severity but treated as usual (TAU)). Results In all 5 depressed CVID patients HDRS decreased during Tα1 treatment (with average 52%, TAU decreased scores with 36% in MDD patients). All 5 CVID patients showed an increase in naïve/memory CD4 + and CD8 + T cell ratios, and in 4 of the 5 patients with detectable IL-6 levels reductions were recorded. TAU did not show such immune improvements. In the 8-week wash-out, depression recurred in the 2 most severe patients, while continued to improve in the others. Immune effects were not sustained in the wash-out. Conclusion This preliminary small study suggests thymus hormone treatment to have antidepressive and related immune correcting effects. Data urge for larger placebo-controlled trials.
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