AstraZeneca PLC’s (LON:AZN) proposed US$39bn (£27.5bn) acquisition of Alexion Pharmaceuticals, Inc. is now under investigation by the Competition and Markets Authority (CMA).
The watchdog said it is considering whether it is or may be the case that this transaction will become a merger. If so, it may result in a substantial lessening of competition across the relevant markets, it added.
READ: AstraZeneca receives green light from US regulators for Alexion acquisition
The CMA has opened an invitation to comment until 3 June for parties involved.
The FTSE 100 pharma giant has received approval in the US, Canada, Brazil, Russia but was still waiting for the green light from the UK, the EU and Japan.
The megadeal, announced in December, would allow the Anglo-Swedish group to boost its growing presence in immunology.
The deal will see Alexion shareholders paid US$175 for each share, made up of US$60 in cash and 2.1243 American depositary shares (ADSs), which each represent one-half of one ordinary AstraZeneca share.
Shares in the firm were flat at 8,111p on Tuesday morning.