This clinical trial is focused on studying a treatment for Primary and Secondary Progressive Multiple Sclerosis, a condition where the immune system mistakenly attacks the protective covering of nerves, leading to worsening physical disability. The treatment being tested is called KYV-101, which is a type of therapy that uses the patient’s own immune cells, specifically T-cells, that are modified to better target and fight the disease. This therapy is known as Anti-CD19 CAR T-cell Therapy, where CAR stands for Chimeric Antigen Receptor, a special receptor added to the T-cells to help them recognize and attack the disease more effectively.

The purpose of the study is to evaluate how effective KYV-101 is in treating this form of multiple sclerosis. Participants in the study will receive the treatment and be monitored over a period of time to see how their condition changes. The study will look at various aspects, such as changes in physical disability, the number of relapses, and any changes observed in brain scans using MRI (Magnetic Resonance Imaging). The study will also monitor the presence of specific cells and proteins in the body to understand how the treatment is working.

Throughout the study, participants will receive either the KYV-101 treatment or a placebo, and their progress will be tracked to assess the treatment’s impact. The study aims to provide valuable information on whether this new therapy can help manage or slow down the progression of Primary and Secondary Progressive Multiple Sclerosis. The study is expected to continue until 2028, with recruitment starting in 2024.