The bidding war for Spark Therapeutics

A new financial filing from Spark Therapeutics reveals that Roche low-balled its first offer to buy Spark for $70 a share, and then outbid three other pharmaceutical companies over several months before Spark agreed to Roche's offer of $114.50 per share — 64% higher than the original that resulted in the nearly $5 billion deal.

Between the lines: Spark's work centers around gene therapy, where mutated genes are replaced with new ones, and the filing shows its hemophilia research was the crown jewel that had everyone interested.