Johnson & Johnson dealt what could be a heavy blow to Merck’s $41bn takeover of Schering-Plough by threatening legal action to seize full control of two pivotal drugs claimed by the merged company.

In a regulatory filing ahead of a shareholder vote on the acquisition, Schering-Plough said it had been notified of an “intention to arbitrate” over its rights to sell J&J’s Remicade, the anti-inflammatory blockbuster medicine, outside the US, and its experimental improved version Simponi.