Roche Holding AG has completed the $4.3 billion acquisition of gene therapy developer Spark Therapeutics Inc. after securing all required regulatory approvals.

The Switzerland-based pharmaceutical giant on Dec. 16 concluded a tender offer, which was started in March, to acquire all outstanding shares of Philadelphia-based Spark for $114.50 apiece. Roche also managed to secure approvals from regulators in the U.S. and U.K., after the tender offer had been extended several times in the past months to allow the agencies to look further into the deal.

Spark's shares will no longer trade on the Nasdaq Stock Market, and the company will become a wholly owned unit of Roche. The unit will continue to operate independently within the Roche Group, according to a Dec. 17 press release.

Roche initially offered to buy Spark in February, with closing originally expected in the second quarter.