UPDATE 1-US FDA declines to approve expanded use of Dynavax's hepatitis B vaccine

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May 14 (Reuters) - Dynavax Technologies said on Tuesday the U.S. Food and Drug Administration (FDA) has declined to approve the expanded use of its hepatitis B vaccine in patients undergoing hemodialysis, citing insufficient safety and effectiveness data.

The FDA, in its so-called "complete response letter", stated that the data was insufficient as a third-party clinical trial site operator had destroyed data source documents for about half of the subjects enrolled in the vaccine's trial, according to the company.

Shares of the California-based company fell more than 7% in premarket trading.

Dynavax's vaccine, Heplisav-B, was first approved by the FDA in 2017, having been rejected twice before in 2013 and 2016 over unresolved safety concerns.

The agency's latest decision will make it harder for the company to implement its plans to expand the total addressable market for its lead commercial asset.

(Reporting by Christy Santhosh and Pratik Jain in Bengaluru; Editing by Tasim Zahid and Shilpi Majumdar)