The states of California, Minnesota and Wisconsin on Thursday joined a Federal Trade Commission lawsuit to stop Amgen's $27.8 billion deal to buy Horizon Therapeutics, according to a court filing.

The FTC said last month it filing suit opposing the deal because it would give Amgen "monopoly positions" for medicines used to treat thyroid eye disease and chronic refractory gout. California Attorney General Rob Bonta said "Amgen’s proposed acquisition of Horizon is dangerous for the future of medicine, dangerous for innovation and research, and most importantly, dangerous for sick people in need of often lifesaving drugs."

(Reporting by David Shepardson)