CVS Health is close to clinching a $66bn deal to buy health insurer Aetna.
The acquisition could be announced as early as Monday, according to The Wall Street Journal.
CVS and Aetna shares rose 4.37% and 0.34% respectively on the news in Thursday’s US trading session.
Some institutional investors said the reported figure was less than would have been expected, which would go some way to explaining the relatively muted response from Aetna’s shares.
CVS is one of the largest US pharmacy benefit managers while Aetna is one of the nation’s most established health insurers.
There has been speculation of an imminent tie-up between the two companies for some time as the industry comes under pressure from higher medical costs.