U.S. healthcare conglomerate Johnson & Johnson is expected to announce a $21.5 billion deal to buy Swiss medical device maker Synthes on Wednesday, the Wall Street Journal said, citing people familiar with the matter.

The deal is expected to value Synthes at 159 swiss francs ($180.51) a share, the Journal said, citing one person familiar with the matter.

Shares of Synthes closed at 146.50 Swiss francs on Tuesday.

Last week, Synthes confirmed it was in merger talks with J&J about a deal that would be J&J's largest-ever acquisition and reshape the medical devices industry.

The Journal said J&J is expected to pay one-third cash and the remainder in stock as part of the deal.

Synthes declined to comment on the Journal report to Reuters. J&J could not immediately be reached for comment.