Natalizumab for the Treatment of People With Inflammatory Demyelination Suggestive of Multiple Sclerosis, or Definite Multiple Sclerosis, at First Presentation (AttackMS)

This study is testing natalizumab — a medication that reduces inflammation in the brain and spinal cord — in people who have just experienced their first neurological episode that may be multiple sclerosis (MS) or is strongly suggestive of it. The goal is to see if early aggressive treatment can slow or prevent the disease from progressing. **You may be eligible if...** - You are between 18 and 55 years old - You are experiencing your first episode of neurological symptoms that suggest MS or a condition called clinically isolated syndrome (CIS) - You have 2 or more lesions on brain MRI consistent with demyelination (nerve damage) - You are willing to attend regular clinic visits and complete study requirements **You may NOT be eligible if...** - You have a confirmed diagnosis of MS that is not at first presentation - You have already started MS disease-modifying treatment - You are pregnant or breastfeeding - You have significant health conditions that make natalizumab unsafe (e.g., liver disease, active infections) - You have a history of serious allergic reactions to this type of medication Talk to your doctor to see if this trial is right for you.