FILE PHOTO: The logo of Swiss drugmaker Roche is seen at its headquarters in Basel, Switzerland February 1, 2018. REUTERS/Arnd Wiegmann/File Photo GLOBAL BUSINESS WEEK AHEAD

ZURICH (Reuters) - Roche ROG.S and Spark Therapeutics ONCE.O announced another extension of the Swiss drugmaker's $4.3 billion takeover offer for the U.S. gene therapy specialist as regulatory reviews in the United States and Britain continue.

The offer for Spark shares now runs to Sept. 3, Roche said, adding terms and conditions are unchanged. “The parties remain committed to the transaction and are working cooperatively and expeditiously with the Federal Trade Commission and UK Competition and Markets Authority,” Roche said.