Amgen Inc. will end a partnership to develop a drug for psoriasis because it could face restrictive labeling due to concerns from regulatory agencies that it might lead to suicidal thoughts.

In 2012, the Thousand Oaks biotech signed an agreement with London-based AstraZeneca to develop and commercialize the skin treatment called brodalumab. But during clinical studies, patients reported thoughts of suicide, and Amgen concluded that will prompt warning labels limiting the marketability of the drug.

"During our preparation process for regulatory submissions, we came to believe that labeling requirements likely would limit the appropriate patient population for brodalumab," said Dr. Sean Harper, executive vice president of research and development at Amgen, in a statement.

While the announcement surprised analysts, the news hurt AstraZeneca more than Amgen. Alexandra Hauber, an analyst at UBS AG, lowered her sales projections for AstraZeneca by 3 to 9 percent for 2017-2020.

In a statement, Amgen said the company “continues to make progress against its strategic and financial commitments and does not expect any meaningful impact from this decision on its ability to meet them.”

Amgen announced termination of the partnership late Friday before the Memorial Day weekend.

Shares closed Tuesday down $4.57, or 2.8 percent, to $159.01 on the Nasdaq.