Immunotherapy Shows Promise for Treatment-Resistant Depression
Immunotherapy could offer a new treatment avenue for patients with depression who do not respond to standard antidepressants, according to findings from an early clinical trial conducted by UK researchers.
The study investigated tocilizumab, an anti-inflammatory medication commonly prescribed for immune-related conditions such as rheumatoid arthritis, to assess its potential in alleviating symptoms of depression that has proven difficult to treat with conventional methods.
Depression affects a significant portion of the population, with approximately one in six adults in the UK experiencing moderate to severe depressive symptoms during their lifetime. However, about one-third of those diagnosed with depression do not achieve improvement through the primary medical treatments currently available, which primarily target brain chemical imbalances.
Tocilizumab functions by inhibiting the IL-6R receptor, thereby preventing it from binding to cells and blocking inflammatory signals associated with autoimmune diseases.
Trial Design and Results
The clinical trial enrolled 30 participants diagnosed with moderate to severe depression who had shown inadequate responses to standard antidepressant therapies. These individuals were randomly assigned to receive either tocilizumab or a placebo over a four-week treatment period.
While the study's small sample size limited the statistical power to detect significant differences between the groups, participants treated with tocilizumab exhibited greater improvements over time in several measures compared to those receiving placebo. These measures included overall depression severity, fatigue, state anxiety, and quality of life.
Expert Insights
Golam Khandakar, professor of psychiatry and immunology at Bristol Medical School and senior author of the study, described the trial as an
“important milestone”in advancing treatments for particularly challenging cases of depression.
“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,”Khandakar added. He is also an investigator at the MRC Integrative Epidemiology Unit at the University of Bristol.
Remission Rates and Treatment Implications
Participants receiving tocilizumab were more likely to achieve remission from depression than those in the placebo group, with remission rates of 54% versus 31%, respectively. This difference was statistically significant and corresponds to a number needed to treat (NNT) of 5. This means that treating five patients with tocilizumab would result in one additional patient achieving remission compared to placebo.
For comparison, selective serotonin reuptake inhibitors (SSRIs), which are the most commonly prescribed first-line antidepressants for moderate to severe depression, have an NNT of approximately 7. This suggests that immunotherapy with tocilizumab could potentially be more effective in producing remission in certain patients.
Future Directions and Personalized Treatment
The researchers emphasized that despite the small sample size, the trial provides preliminary evidence supporting the potential of immunotherapy to reduce depressive symptoms.
Dr Éimear Foley, senior research associate in immunopsychiatry at the MRC Integrative Epidemiology Unit and co-author of the study, highlighted the broader implications of the findings:
“Depression is estimated to affect around 10-20% 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.”
