A Phase 3 trial of Amgen Inc's Kyprolis drug failed to show it could extend survival compared to standard care for patients with advanced multiple myeloma, a type of blood cancer that develops in the bone marrow.

Shares of Amgen were down 2.3 percent at $124.41 in after-hours trading on Wednesday.

Amgen said the 315-patient trial also showed an increase in adverse kidney events for patients given Kyprolis when compared to the control group and to the risks described on the drug's current label.

Kyprolis, acquired by Amgen in its $10 billion takeover of Onyx Pharmaceuticals, was approved in the United States for treating advanced multiple myeloma based on data showing that patients responded to the drug.

This latest trial, known as FOCUS, was intended to show that the drug helped patients live longer, something that European regulators generally require before approving a drug.

Amgen said in a statement that it believes positive results announced earlier this month from a separate study of Kyprolis in patients with earlier-stage disease "will be sufficient to support regulatory submissions around the world."