Who are the largest shareholders of Biogen?

Can you please elaborate on the ownership structure of Biogen and identify the largest shareholders in the company? Are they institutional investors, individuals, or a mix of both? How significant is their stake in the company, and do they have any influence over the company's strategic decisions and operations? It would be helpful to know the top shareholders' backgrounds and investment history to understand their potential motivations and how they might impact Biogen's future growth and performance.