In a small pilot trial, patients with treatment-resistant depression who received a single infusion of tocilizumab — an anti-inflammatory drug already approved for rheumatoid arthritis — were more than twice as likely to reach remission as those given a placebo. Fifty-four percent of participants who received tocilizumab achieved remission, compared with 31% on placebo, over a four-week trial. The study, led by Éimear M. Foley of the University of Bristol’s MRC Integrative Epidemiology Unit, was published May 20, 2026 in JAMA Psychiatry (DOI: 10.1001/jamapsychiatry.2026.1053).
A small, explicitly framed pilot — not a practice-changing trial
The trial enrolled just 30 people with treatment-resistant depression: 14 received a single tocilizumab infusion, 16 received placebo, in a double-blind, parallel-arm, randomized design. Twenty-nine completed the four-week follow-up. The authors describe the study as a “proof-of-concept” trial in the paper’s own title, and the effect size translates to a number needed to treat (NNT) of 5 for remission — meaning roughly one additional person reaches remission for every five treated with tocilizumab instead of placebo. That is a real, moderate effect for such a small sample, but the authors are explicit that a larger confirmatory trial is needed before this becomes anything resembling standard practice. This is a genuine, non-manufactured “needs replication” story: the researchers’ own framing, not outside skepticism, is what puts the caveat front and center. A 30-person trial can generate a promising, statistically real signal and still be too small, on its own, to change how depression is treated.
Why an anti-inflammatory drug for depression at all
Tocilizumab blocks interleukin-6 (IL-6), an inflammatory signaling protein, and is already approved for treating rheumatoid arthritis and related inflammatory conditions. The trial tests a specific hypothesis in psychiatry — sometimes called the inflammatory or immunopsychiatry model of depression — that a subset of treatment-resistant depression is driven or sustained by chronic low-grade inflammation, and that targeting inflammation directly, rather than the brain’s neurotransmitter systems the way most standard antidepressants do, could help patients whose depression hasn’t responded to conventional treatment. Using an already-approved biologic drug for a new, psychiatric indication is known as off-label repurposing, and it carries a real human-subjects-ethics dimension distinct from testing a brand-new experimental compound: participants are receiving a drug with an established general safety profile from its approved use, but for a use it has not been tested or approved for at scale, which is exactly the kind of case an institutional review board has to weigh — established general safety against unknown risk in a new patient population and new dosing context.
A clean, disclosed multi-funder structure
The trial was funded by the Wellcome Trust, the National Institute for Health and Care Research (NIHR) Biomedical Research Centres at Bristol and Cambridge, and the BMA Foundation’s J Moulton grant, with additional support from the UK Medical Research Council. That is a multi-funder public/charitable structure — no pharmaceutical company funding — and each funder is named individually rather than folded into a vague “supported by grants” line, the kind of clean disclosure that makes a funding statement actually useful to a reader trying to judge whether financial interest could have shaped the result.
What comes next
The authors’ own framing sets the bar for what should happen before this changes clinical practice: a larger, adequately powered confirmatory trial, ideally testing whether the effect holds across a broader population of treatment-resistant depression patients and clarifying which patients (for example, those with elevated inflammatory markers) are most likely to benefit. Until then, this remains what it is: a promising, well-disclosed pilot signal for an immunopsychiatry approach to a hard-to-treat condition, not a new treatment recommendation.
Frequently asked questions
Is tocilizumab now a recommended treatment for depression?
No. This is a 30-person pilot trial explicitly framed by its own authors as proof-of-concept, requiring a larger confirmatory trial before any change to clinical practice. Tocilizumab remains approved only for rheumatoid arthritis and related inflammatory conditions; its use for depression here was off-label and experimental.
What does “NNT of 5” mean in this trial?
Number needed to treat (NNT) of 5 means that, based on this trial’s remission rates (54% tocilizumab vs. 31% placebo), roughly one additional person reaches remission for every five people treated with tocilizumab instead of placebo — a way of expressing effect size in terms of how many patients need to be treated to produce one additional good outcome.
Who funded this trial, and were there any conflicts of interest?
The trial was funded by the Wellcome Trust, NIHR Biomedical Research Centres at Bristol and Cambridge, the BMA Foundation’s J Moulton grant, and the UK Medical Research Council — a multi-funder public/charitable structure with no pharmaceutical company funding disclosed.
Sources
Primary source: Foley, E.M. et al., “Interleukin 6 as a Treatment Target for Depression: A Proof-of-Concept Randomized Clinical Trial,” JAMA Psychiatry, published online May 20, 2026. DOI: 10.1001/jamapsychiatry.2026.1053. Secondary coverage: ScienceDaily, May 27, 2026. This article was last checked against the cited sources on August 7, 2026.
