In May, the FTC had opposed the acquisition, arguing that Horizon had a monopoly position with its drugs in the US in the fight against certain diseases. Now, the FTC attaches conditions to its approval: Amgen may not bundle any of its products with Horizon's Tepezza or Krystexxa, nor may it use rebates or contract terms to disadvantage competing products. In addition, Amgen may acquire potential competing products to Horizon drugs only with the FTC's permission.

The transaction is in alignment with Amgen's core strategy of delivering innovative medicines that make a significant difference for patients suffering from serious diseases. Moreover, it is strengthening the Thousand Oaks, California-based biotech company's leading inflammation portfolio by adding first-in-class, early-in-lifecycle medicines, which treat rare inflammatory diseases.

"We have strong momentum in our core business and the addition of Horizon will further position Amgen as a leader across a broader range of diseases," said Robert A. Bradway, Amgen's chairman and chief executive officer. "