DOW JONES NEWSWIRES Amgen Inc. (AMGN) has agreed to acquire privately held company KAI Pharmaceuticals for $315 million in cash, giving the drug maker rights to an experimental drug to treat chronic kidney disease. In connection with the deal, Amgen is providing a loan prior to closing for Phase 3 clinical testing of KAI-4169, a drug that is being studied for the treatment of secondary hyperparathyroidism, a common complication for patients who are on dialysis. The deal will give Amgen rights to KAI-4169, outside of Japan. "KAI has demonstrated encouraging results in the clinic. We are excited about acquiring KAI, as well as the opportunity to potentially deliver a novel therapy for chronic kidney disease patients on dialysis suffering from secondary hyperparathyroidism," said Sean E. Harper, executive vice president of research and development at Amgen. Amgen, the biggest stand-alone biotechnology company, has been making acquisitions in a bid to bolster its research-and-development pipeline as sales growth for older drugs has slowed. The transaction, which has been approved by KAI stockholders and both companies' boards, is subject to regulatory approvals. After the deal is completed, KAI will become a wholly owned unit of Amgen. Amgen shares closed at $67.02 on Monday and were inactive in premarket trading. The stock is up 4.4% so far this year. ---By Kristin Jones, Dow Jones Newswires; 212-416-2208; kristin.jones@dowjones.com