Intracranial Atherosclerotic Disease (ICAD)

Intracranial atherosclerotic disease is an important cause of ischemic stroke, and intracranial stent implantation is increasingly used for patients with severe stenotic lesions. Evaluation of stent patency and detection of in-stent restenosis are essential during follow-up. Digital subtraction angiography (DSA) remains the reference standard for intracranial stent assessment; however, it is an invasive procedure associated with potential complications and radiation exposure. Conventional CT angiography may be limited by stent-related artifacts, including blooming artifact and beam-hardening effects, which can impair accurate evaluation of the stent lumen.

The goal of this clinical trial is to learn whether pemafibrate can help prevent worsening of intracranial arterial stenosis (ICAS) in patients who have symptomatic ICAS and high triglycerides (TG) levels after ischemic stroke or transient ischemic attack (TIA). The main questions this study aims to answer are: 1. Does pemafibrate lower the chance that ICAS gets worse over 12 months? 2. Does pemafibrate improve TG levels and other vascular risk markers? 3. What are the effects of pemafibrate on vascular events, functional outcomes, and safety over 12 months? Researchers will compare a pemafibrate group with a non-pemafibrate group to see whether pemafibrate helps prevent progression of ICAS. This is an open-label, randomized, parallel-group trial. That means participants are assigned by chance to 1 of 2 groups, and both the researchers and participants know which group was assigned. Participants in both groups will continue to receive standard stroke care, including antithrombotic therapy and management of vascular risk factors such as blood pressure, low-density lipoprotein cholesterol, diabetes, and smoking. Participants may be eligible if they are 18 years or older, have clinically stable ischemic stroke or TIA, have 50% to 99% stenosis in a symptomatic intracranial artery on contrast-enhanced CT angiography (CTA), and have elevated fasting (\>=150 mg/dL) or non-fasting (\>=175 mg/dL) TG levels. Some people will not be eligible, such as those with ICAS due to non-atherosclerotic arterial disease, severe extracranial carotid stenosis, recent intravenous thrombolysis or mechanical thrombectomy, planned revascularization, contraindications to pemafibrate or iodinated contrast media, dialysis, or pregnancy. Participants will: * Be randomly assigned to a pemafibrate group or a non-pemafibrate group * Take pemafibrate for 12 months if assigned to the pemafibrate group, with possible dose adjustment based on TG levels and kidney function * Have blood tests and clinical assessments at baseline and during follow-up * Undergo brain CTA at study entry and again at 12 months * Undergo brain MRI/MRA and vascular tests such as ankle brachial index, cardio ankle vascular index, and pulse wave velocity according to the study schedule * Be followed for vascular events, functional outcome, and adverse events for 1 year