AstraZeneca, the UK’s largest pharmaceuticals firm, approached its heavyweight US competitor Gilead to discuss a merger, according to Bloomberg.

AstraZeneca contacted Gilead in May but “didn’t specify terms for any transaction,” Bloomberg said, citing sources familiar with the matter.

Discussions with advisers are reportedly underway at Gilead, but the companies aren’t in formal talks, they said.

Gilead is not interested in merging with a rival, Bloomberg said, preferring to focus on smaller acquisitions.

As of Friday, AstraZeneca was worth $141 billion and Gilead $96 billion. If a merger went ahead it would be the largest ever in the industry, and would likely be opposed by UK competition regulators due to the size and power of their combined resources.FILE PHOTO: Gilead Sciences Inc pharmaceutical company is seen after they announced a Phase 3 Trial of the investigational antiviral drug Remdesivir in patients with severe coronavirus disease (COVID-19), during the outbreak of the coronavirus disease (COVID-19), in Oceanside, California, U.S., April 29, 2020. REUTERS/Mike Blake

Foto: FILE PHOTO: Gilead Sciences Inc pharmaceutical company is seen during the outbreak of the coronavirus disease (COVID-19), in California Source: Reuters

AstraZeneca is currently partnering with the Oxford Vaccine Group to help roll out an inoculation against the coronavirus, if a product is approved.

Gilead is not working on a vaccine, but developed remdesivir, a treatment for the coronavirus. The company has a long track record of developing treatments for viruses such as HIV and hepatitis C.

Business Insider contacted both firms for comment but is yet to receive a response.

AstraZeneca told Bloomberg the company doesn't comment on "rumors or speculation."