Amgen (AMGN) said its multiple myeloma Kyprolis drug met its primary endpoint in an interim analysis, showing progression-free survival for patients treated with relapsed multiple myeloma.

Kyprolis, in combination with two other drugs, helped patients live 8.7 months longer without their disease worsening than another treatment combination, the company said.

Shares rose 4% in recent premarket trading.

Multiple myeloma is the second most common hematologic cancer. In the U.S., about 70,000 people are living with the disease and about 24,000 new cases are diagnosed annually, the company said.

Amgen and unit Onyx Pharmaceuticals Inc. said data weren't yet mature for the drug's secondary endpoint of overall survival.

Last year, the company bought Onyx Pharmaceuticals for $10.4 billion.

Amgen said it sees worldwide regulatory submissions beginning next year.

The announcement follow news last week that Amgen plans to reduce its global workforce by 12% to 15% and close facilities in two states, a restructuring move it said was part of a focus on developing new drugs.

"Kyprolis is an important building block in our robust, differentiated pipeline," said Chairman and Chief Executive Robert A. Bradway, adding the company's pipeline "continues to show notable progress."

Amgen was a biotechnology pioneer and is the largest biotech by sales.

Write to Joshua Jamerson at joshua.jamerson@dowjones.com