A Study to Evaluate the Preliminary Efficacy and Safety of Terfenadine in Patients With Relapsing-Remitting Multiple Sclerosis

The goal of this clinical trial is to evaluate the safety and tolerability of terfenadine when added to standard first-line disease-modifying therapy in adults with multiple sclerosis. The study will also explore whether adding terfenadine may help improve disease-related outcomes. Researchers will compare participants who receive terfenadine plus standard first-line disease-modifying therapy with participants who receive standard first-line disease-modifying therapy alone. Participants will: Be randomly assigned to receive either terfenadine plus standard first-line disease-modifying therapy or standard first-line disease-modifying therapy alone. Take terfenadine 60 mg once daily at bedtime for 1 month if assigned to the terfenadine group. Attend study visits during screening, treatment, and follow-up over 12 months. Have physical examinations, vital sign checks, laboratory tests, electrocardiograms, imaging assessments, neurological evaluations, and collection of blood, stool, and cerebrospinal fluid samples at scheduled visits.