Drug companies across the world are racing to develop a vaccine for the coronavirus COVID-19 pandemic. Many have entered into profitably appealing corporate mergers to collaborate to meet the urgent global demand for an inoculation against the virus.

AstraZeneca, the largest British pharmaceuticals company, has asked US competitor Gilead to begin talks of entering into a merger, Bloomberg reported on Sunday.

The UK giant first contacted Gilead in May, but terms for a transaction had not yet been specified, Bloomberg said, citing an anonymous source familiar with the communication.

Gilead is reportedly in conversation with advisors, despite the two companies not yet entering into formal talks. The US pharmaceutical giant is not interested in merging with competitors, instead preferring to acquire smaller companies and their patents and intellectual property rights, Bloomberg said.

Following press inquiry, AstraZeneca reportedly told Bloomberg that the mulitnational pharmaceutical giant would not respond to "rumors or speculation." 

If a merger were to take place, it would be the largest in the history of the industry, and would likely see opposition by UK and US regulators due to the sheer size of the eventual synthesis. AstraZeneca is worth an estimated $141 billion and Gilead assets are thought hover at $96 billion, as of Friday.

AstraZeneca is currently in partnership with Oxford Vaccine Group to aid in the development of a serum to help combat COVID-19.

Gilead is not working on a vaccine, but has produced remdesivir, used to treat those struck with the virus and with a long track record of constructing treatments for HIV and hepatitis C.