A recent early-stage clinical trial has indicated that immunotherapy could offer a new avenue for treating depression, particularly in patients who have not responded to conventional antidepressant medications. Researchers from the University of Bristol explored whether tocilizumab, an anti-inflammatory drug typically prescribed for autoimmune conditions like rheumatoid arthritis, could alleviate symptoms in individuals with difficult-to-treat depression.
Understanding the Challenge of Treatment-Resistant Depression
Approximately one in three people suffering from depression do not experience improvement with standard medical treatments, which primarily target brain chemicals. In the UK, around one in six adults will encounter moderate to severe depressive symptoms at some point in their lives. Tocilizumab works by blocking the IL-6R receptor, preventing inflammatory signals linked to autoimmune diseases.
The Trial Design and Outcomes
The study involved 30 participants with moderate to severe depression who had shown poor responses to typical antidepressants. They were randomly assigned to receive either tocilizumab or a placebo over four weeks. While the small sample size meant no statistically significant difference was observed between the groups, those receiving tocilizumab showed greater improvements over time in several areas, including overall depression severity, fatigue, anxiety, and quality of life.
Professor Golam Khandakar, senior author and professor of psychiatry and immunology at Bristol Medical School, described the trial as an “important milestone” in developing new treatments for hard-to-treat depression. He noted, “This is one of the first randomised controlled trials to test immunotherapy for depression, the first to target IL-6R, and the first to use a targeted approach selecting patients most likely to benefit.”
Remission Rates and Comparative Effectiveness
Participants treated with tocilizumab were more likely to achieve depression remission compared to the placebo group: 54% versus 31%. This translates to a number needed to treat (NNT) of 5, meaning five patients need treatment for one to benefit. In contrast, the NNT for SSRIs, the most common first-line antidepressants, is about 7, suggesting immunotherapy might be more effective.
Dr. Éimear Foley, co-author and senior research associate in immunopsychiatry at the MRC Integrative Epidemiology Unit, highlighted the broader implications: “Depression affects 10-20% of people worldwide, yet current treatments often fall short. Our study moves us toward more tailored depression care, where treatments match a person’s biology, providing the right treatment at the right time.”
While the trial was small, the researchers believe it offers early evidence that immunotherapy could reduce depressive symptoms, paving the way for larger studies.
