When does the patent on Tysabri expire?

The patent for Tysabri (natalizumab) was initially set to expire in 2019, but additional patents related to the drug have been filed and granted, potentially extending its exclusivity. The exact expiration date can vary based on these additional patents and any ongoing litigation. For the most accurate and up-to-date information, checking the latest patent filings or announcements from the manufacturer, Biogen, would be advisable.