Credit Suisse First Boston, a regular adviser to Novartis, is working for the other side on a $4.5bn (€3.6bn) US deal. It is joint adviser with Morgan Stanley to Chiron, a biotechnology firm being bought out by the Swiss drugs group.

According to Dealogic, the investment banking research provider, CSFB has advised Novartis on four M&A deals since 2001. This is Morgan Stanley's first M&A deal for Chiron whose legal adviser is Sullivan & Cromwell.