Roche has announced plans to enter into a definitive merger agreement to acquire Spark Therapeutics, a leader in discovering, developing and delivering gene therapies with one commercial asset and four programmes currently in clinical trials.

The Swiss drug giant said it plans to fully acquire Spark, the only biotech that has successfully commercialised a gene therapy for a genetic disease in the US, at a price of $114.50 (£87.54) per share, or approximately $4.3 billion (£3.3 billion) overall.

Under the terms of the agreement, Roche will promptly commence a tender offer to acquire all outstanding shares of Spark common stock, and Spark will file a recommendation statement containing the unanimous recommendation of the board that Spark’s shareholders tender their shares to Roche.

“Spark Therapeutics’ proven expertise in the entire gene therapy value chain may offer important new opportunities for the treatment of serious diseases," said Severin Schwan, Roche's chief executive, commenting on the deal.

"In particular, Spark Therapeutics’ haemophilia A programme could become a new therapeutic option for people living with this disease. We are also excited to continue the investments in Spark Therapeutics’ broad product portfolio and commitment to Philadelphia as a centre of excellence.”

Spark’s lead clinical asset is SPK-8011, a novel gene therapy for the treatment of haemophilia A, which is expected to start Phase III in 2019.