ONE-YEAR CLINICAL AND IMAGING OUTCOMES OF CYP2C19 PHENOTYPE-GUIDED ANTIPLATELET THERAPY IN PATIENTS WITH ISCHEMIC STROKE AND INTRACRANIAL ARTERIAL STENOSIS OR OCCLUSION

Objective: To describe 12-month clinical and imaging outcomes and explore the association between CYP2C19 metabolizer phenotype and functional outcome in patients with ischemic stroke and intracranial arterial stenosis or occlusion treated using a phenotype-guided antiplatelet strategy. Methods: This singlecenter observational cohort study with 12-month follow-up included 194 patients treated at S.I.S Can Tho International General Hospital between March 2024 and August 2026. CYP2C19 *2 and CYP2C19 *3 were genotyped from peripheral blood using Realgene qualitative IVD kits on a SaCycler-96 real-time PCR system, and patients were classified as normal, intermediate, or poor metabolizers. Antiplatelet treatment comprised aspirin combined with clopidogrel or ticagrelor according to the study protocol. Outcomes included all-cause mortality, recurrent ischemic stroke, modified Rankin Scale (mRS), and follow-up MRI/MRA findings. Imaging analyses were restricted to the 90 patients with repeat imaging. Results: Mean age was 62.06 ± 11.50 years and 67.0% were men. Normal, intermediate, and poor metabolizers accounted for 47.9%, 43.8%, and 8.2%, respectively. At 12 months, 90 patients underwent repeat imaging, 75 had clinical follow-up without repeat imaging, 13 were lost to follow-up, and 16 (8.2%) died. Among the 90 patients with complete clinical and imaging reassessment, 52 (57.8%) had mRS 0–1 and 2 (2.2%) had recurrent ischemic stroke. The proportions with mRS 0–1 were 84.4%, 37.8%, and 0.0% across normal, intermediate, and poor metabolizers, respectively (p<0.001). Follow-up MRI/MRA showed no residual stenosis in 78 (86.7%), severe stenosis in 2 (2.2%), and persistent occlusion in 10 (11.1%). Bleeding outcomes were not systematically available and therefore could not be reliably evaluated. Conclusion: CYP2C19 metabolizer phenotype was significantly associated with 12-month functional outcome in the 90-patient reassessed subgroup in unadjusted analysis. However, the observational design, incomplete follow-up, lack of multivariable adjustment, and sparse recurrent events preclude causal inference or direct comparison of antiplatelet regimens. Larger prospective studies with standardized treatment and complete efficacy and safety ascertainment are warranted.