What drug helps MS patients walk?

As someone seeking information on potential treatments for Multiple Sclerosis (MS), I'm curious to know: What specific drug or medication has been shown to assist MS patients in improving their mobility and ability to walk? Is there a medication that is commonly prescribed or one that is currently undergoing clinical trials for this purpose? Additionally, what are the potential side effects and long-term implications of using such a drug, if any? Understanding the benefits and drawbacks of available options is crucial for making informed decisions about one's healthcare.