(Reuters) -The U.S. Federal Trade Commission is expected to file a lawsuit as early as Tuesday to block Amgen Inc (NASDAQ:AMGN)'s $27.8 billion deal to buy Horizon Therapeutics (NASDAQ:HZNP) PLC, a person familiar with the matter told Reuters.
Amgen struck a deal last year to buy Horizon to strengthen its rare diseases drugs portfolio. The company has said it hopes to complete the acquisition in the first half of this year.
Amgen said on Monday it wasn't aware of any decision made by the agency. "We will provide any appropriate updates when we have more information," the company said in a statement.
U.S. Senator Elizabeth Warren, an outspoken critic of corporate consolidation, wrote to the FTC earlier this year expressing her concerns about pharmaceutical deals including the Amgen purchase of Horizon.
The Democratic Senator said both Amgen and Horizon Therapeutics "have engaged in brazen price increases," including on Amgen's Enbrel for arthritis and Horizon’s Krystexxa, a gout medication.
Amgen said it disagreed with Warren's analysis of the deal.
It is unusual for the agency to sue to stop a pharmaceutical deal. In recent years, the agency has usually identified ailments where the merging companies made treatments, and required one of the two medicines to be divested.
The deal would give Amgen two fast-growing drugs, the thyroid eye disease treatment Tepezza and Krystexxa. Amgen hopes they can act as a bulwark against competition for its blockbuster arthritis drug Enbrel.
Sales of Amgen's Enbrel tumbled 33% year-over-year in the first quarter of 2023 to $579 million.
Both Tepezza and Krystexxa have an orphan drug designation, a status granted by the U.S. Food and Drug Administration to encourage development of drugs for rare conditions.
Orphan status also means they would likely not be among the drugs for which the U.S. government's Medicare program can negotiate lower drug prices under the Biden Administration's Inflation Reduction Act.
Tepezza, Horizon's largest selling drug, saw sales rise 18% to $1.97 billion in 2022 from a year earlier, but sales in the latest quarter fell 19% to $405 million.
Horizon's Krystexxa brought in sales of $716 million last year. They are forecast to reach $1.58 billion by 2028.