Roche Holding AG's acquisition of Spark Therapeutics Inc. received approval in the U.S. after months of delays.

In line with the U.K. Competition and Markets Authority's decision earlier in the day, the U.S. Federal Trade Commission granted the $4.3 billion deal unconditional clearance and termination of the waiting period under the Hart-Scott-Rodino Act.

The transaction has now received all required antitrust approvals.

Swiss drugmaker Roche launched a buyout offer to acquire all outstanding shares of the Philadelphia-based gene-therapy maker for $114.50 apiece in March. Due to investigations by Britain's antitrust regulator and the FTC, the offer was extended 10 times.

The offer was set to expire at 5 p.m. ET on Dec. 16.

The closing of the tender offer is subject to customary closing conditions.

MacKenzie Partners Inc. is the information agent for the tender offer.