Sandoz Launches Tyruko (Natalizumab-Sztn), First Tysabri Biosimilar, in US After JCV Assay Delays on November 18, 2025 Approved Biological Assay Biosimilars JC Virus JCV Leukoencephalopathy, Progressive Multifocal Multiple Sclerosis Polpharma Biologics Progressive Sandoz Tyruko Tysabri United States Food and Drug Administration +