A proof-of-concept randomized clinical trial published online May 20, 2026, in JAMA Psychiatry found signals that tocilizumab—an anti-inflammatory drug used for immune-mediated conditions including rheumatoid arthritis—may improve some symptoms in adults with moderate-to-severe depression who had a poor response to antidepressants and evidence of low-grade inflammation.
Researchers in the UK tested whether blocking interleukin-6 (IL-6) signaling with tocilizumab could help a subgroup of people with depression who also showed signs of systemic inflammation.
The 4-week, double-blind, placebo-controlled trial—known as the Insight Study—randomized 30 participants recruited between 2018 and 2022. Fourteen participants were assigned to a tocilizumab infusion and 16 to a saline placebo infusion; 29 participants ultimately received an infusion. Participants were recruited from primary and secondary care and via self-referral, and the trial was conducted at the University of Cambridge and the University of Bristol.
In the primary analysis, the difference between groups on the study’s main depression measure at the final follow-up was uncertain, with wide confidence intervals. However, the researchers reported a pattern of greater stepwise improvement over time in the tocilizumab group across several measures—particularly fatigue—along with signals of improvement in somatic symptoms, overall depression severity, anxiety, and quality of life. The study also reported that remission and response rates favored tocilizumab at day 28, though estimates were imprecise.
The authors characterized the results as preliminary and said larger trials would be needed to determine whether IL-6 pathway inhibition offers a clinically meaningful treatment option for inflammation-linked, difficult-to-treat depression.
