Introduction: ACTIMIS (NCT03803007) was a randomized phase 1b/2a clinical trial evaluating glenzocimab, a monoclonal antibody fragment targeting platelet receptor glycoprotein VI, in patients with acute ischemic stroke treated by thrombolysis. The primary analysis demonstrated a reduction in intracranial hemorrhage occurrence and stroke-related mortality. In this sub-analysis, volumetric imaging biomarkers were used to assess the efficacy of glenzocimab.

Methods: In the phase 2a study, patients were randomized (1:1) to receive 1000 mg of glenzocimab or a placebo. CT or MRI was acquired at baseline with CT at 24 hours and MRI at 7 days for safety and efficacy analysis. Baseline and follow-up imaging were processed as a post-hoc analysis using AI core lab software (Brainomix, Oxford, UK). Automated output was reviewed for accuracy by an expert clinician (DC), who was blinded to treatment allocation.

Results and Conclusions: Follow-up imaging data were available from 103/106 patients (51 glenzocimab, 52 placebo) at 24 hours. Of these, 54 underwent mechanical thrombectomy (MT, 27 glenzocimab, 27 placebo). Day-7 imaging was available for 9 fewer placebo patients and 1 glenzocimab patient. All except 2 patients (1 placebo, 1 glenzocimab) with missing data at Day-7 died during the study. Preliminary analysis showed a smaller volume of hemorrhagic transformation (HT) in the glenzocimab group at 24 hours compared to placebo, with a trend toward a smaller volume of ischemic injury. Exploratory analysis also highlighted an interaction effect between the risk of HT following MT and glenzocimab (lower risk in patients treated with glenzocimab). The full results of the imaging sub-analysis of the ACTIMIS study will be presented at the conference and discussed in the context of current literature.