UPDATE 1-US FDA staff benefits, risk with Bristol drug

* FDA reviewers see heart, other benefits with belatacept

* Risk of death from infection, complications also cited

* Agency's outside advisory panel to meet March 1

WASHINGTON, Feb 25 (Reuters) - Studies of Bristol-Myers Squibb Co's (BMY.N) experimental kidney transplant drug belatacept show improved blood pressure and other benefits in patients, but concerns over the risk of death are still a factor, U.S. regulatory staff said in documents on Thursday.

The company is seeking FDA approval of the injectable biologic drug to prevent organ rejection. On Monday, an FDA advisory panel of experts will meet to discuss whether or not to recommend U.S. approval.

The FDA staff said clinical trial results showed improvements in heart risks, kidney function and other factors. But several cases of post-transplantation complication and rare disorder called Progressive multifocal leukoencephalopathy (PML) are also a concern, they said.

"In summary, careful consideration should be given to whether the data regarding the observed benefits associated with the belatacept regimen ... outweigh the risks of higher mortality and excess morbidity," the staff wrote in documents released ahead of Monday's meeting.

At the meeting, the FDA panel will also discuss risk monitoring plan known as a Risk Evaluation and Mitigation Strategy, or REMS, according to the documents.

While the FDA will weigh its advisory panel's recommendations, the agency will make the final approval decision. (Reporting by Susan Heavey, editing by Gerald E. McCormick)