While Actelion were in negotiations with Johnson & Johnson, Actelion received a higher-priced offer from Sanofi. Actelion and J&J ended discussion on Dececember 14 after J&J said it would not match the Sanofi offer.
When Actelion met with Sanofi on December 19, it had suddenly lowered its proposed asking price. The move caused the Actelion board to restart talks with J&J.
According to the Bloomberg report, while Sanofi sent letters to Actelion on December 21 and January 20 that said it was willing to buy the company according to the prospectus, the Actelion board ultimately finished the deal with J&J, releasing an announcement January 26.