Immunotherapy may help some patients with treatment-resistant depression, early trial results suggest.
The study looked at people with moderate to severe depression who had not responded well to standard antidepressants.
About one in three people with depression do not get better with the main medical treatments available, which are based on targeting chemicals in the brain.
Approximately one in six adults across the UK will experience moderate to severe depressive symptoms during their lifetime.
Researchers at the University of Bristol investigated whether tocilizumab, an anti-inflammatory drug commonly used for immune conditions such as rheumatoid arthritis, could improve symptoms.
Rheumatoid arthritis is an autoimmune condition, where the immune system mistakenly attacks the body’s own tissues.
Tocilizumab works by blocking the IL-6R receptor. This prevents the receptor from binding to cells and blocking inflammatory signals linked to autoimmune conditions.
The trial involved 30 people with moderate to severe depression who had not responded well to standard antidepressants.
Participants were randomly assigned to receive either tocilizumab or a placebo over a four-week period.
A placebo is a dummy treatment used to compare results against an active medicine.
Although the results showed little statistical evidence of a significant difference between the two groups, which researchers said was expected in a small study, people who received tocilizumab appeared to show greater improvements over time.
These included overall depression severity, fatigue, state anxiety and quality of life.
Golam Khandakar, professor of psychiatry and immunology at Bristol medical school and senior author of the study, said the trial represented an “important milestone” in the development of new treatments for depression that was especially difficult to treat.
“This is one of the first randomised controlled trials to test immunotherapy for depression, the first to test IL-6R as the treatment target, and the first to use a targeted approach to select patients most likely to benefit, and to show that it works.”
Participants treated with tocilizumab were also more likely to achieve depression remission than those in the placebo group, at 54 per cent compared with 31 per cent.
The researchers said this equated to a number needed to treat of five, meaning an additional five patients would need to be treated for one extra patient to benefit.
By comparison, they said the number needed to treat for selective serotonin reuptake inhibitors, or SSRIs, is about seven, suggesting immunotherapy could be more likely to help patients feel better.
SSRIs are commonly used antidepressants that work by increasing levels of serotonin, a chemical messenger in the brain linked to mood.
The researchers said the small study provided early evidence that forms of immunotherapy could help reduce depression symptoms.
Dr Éimear Foley, senior research associate in immunopsychiatry at the MRC integrative epidemiology unit and co-author of the study, said: “Depression is estimated to affect around 10-20 per cent of people worldwide during their lifetime, yet for many patients current treatments do not work well enough.
“Our study moves us closer to more tailored depression care, where treatments are chosen to better fit a person’s biology. This will help us to provide the right treatment to the right patients at the right time.”
