Why is Amgen buying Horizon?

Could you please explain the motivation behind Amgen's decision to acquire Horizon? What strategic advantages does this acquisition offer Amgen in terms of expanding its product portfolio, strengthening its market position, or gaining access to new technologies and research capabilities? Additionally, what challenges or risks might Amgen face as a result of this acquisition, and how does the company plan to mitigate those risks to ensure a successful integration of Horizon into its operations?