Evaluating tocilizumab in ischemic stroke: Findings from the SPAN multicenter trial

Inflammation, particularly mediated through interleukin-6 (IL-6) signaling, plays a critical role in stroke pathophysiology. High levels of IL-6 are associated with poor outcomes in stroke patients. Therapeutic inhibition of IL-6 signaling may offer a novel strategy to mitigate post-stroke damage and improve recovery. This study evaluated the efficacy of tocilizumab (TCZ), a clinically approved monoclonal antibody that blocks IL-6 receptor signaling, using data from the Stroke Preclinical Assessment Network (SPAN), a multi-center, randomized, blinded, placebo-controlled trial in preclinical stroke models.

We analyzed behavioral and MRI morphometry data from 701 rodents (both males and females; 1:1), including healthy young mice, diet-induced obese mice, aging mice, and spontaneously hypertensive rats (SHR) treated with saline (N = 348) or TCZ (N = 353) at a dose of 100 mg/kg for mice, 10 mg/kg for rats after middle cerebral artery occlusion (MCAO).

In the overall mouse cohort, TCZ did not significantly improve long-term sensorimotor recovery or reduce brain tissue loss measured by MRI. However, aging mice exhibited modest motor function improvements. In SHRs, TCZ treatment resulted in improved sensory-motor function, particularly in male rats, as demonstrated by enhanced corner test scores on days 7 and 28 post-MCAO. While TCZ in SHRs provided early (day 2) cerebroprotection with reduced lesion volume, it did not alter subsequent tissue loss, as measured by tissue atrophy at day 30.

These results suggest that IL-6R blockade with TCZ was associated with functional improvement in aging mice (modest) and hypertensive rats (notably males), without durable effect of brain tissue loss. No benefit was observed in the overall mouse cohort. These findings support IL-6 signaling as a viable therapeutic target and warrant further investigation into IL-6 receptor inhibition as a potential treatment strategy for stroke recovery.