AstraZeneca shares fell 8.9% on Monday, erasing more than £17bn from its market value after reports that the company was in discussions to acquire Bristol Myers Squibb, a deal that could create a near $400bn pharmaceutical group. The potential merger would rank among the largest in the pharmaceutical industry and could position the combined company as the world’s fourth‑largest drugmaker by market capitalisation. AstraZeneca, headquartered in Cambridge, had a market value of about £196bn before the news, while Bristol Myers Squibb was valued at $133bn (£98bn). Investors reacted to the Financial Times report, which said the talks were ongoing but not certain to result in a transaction. AstraZeneca’s FTSE 100‑listed shares closed at £115, down from a pre‑news level of nearly £196bn, pushing the company’s valuation to roughly £178bn and displacing it from the second‑largest UK listed firm behind Shell. Bristol Myers Squibb shares rose 1.7% in early New York trading before paring gains. Analysts expressed mixed views. Jefferies analysts, led by Michael Leuchten, said the rationale for a combination was unclear, noting that the merged oncology portfolio could become the broadest in the industry, but that pipeline assets could be sourced elsewhere. Chris Beauchamp of IG noted that while a UK firm acquiring a US peer is rare, the deal could accelerate AstraZeneca’s US footprint and raise concerns about the loss of a national champion; he also highlighted shareholder scepticism over the need for expensive M&A when the stock was performing well. Shareholder statements included Lucy Coutts, investment director at JM Finn, who said the primary benefit would be to strengthen AstraZeneca’s US presence, adding that Bristol Myers shareholders would likely gain while AstraZeneca investors might view the news negatively. A major shareholder told the Guardian that the move was bold but lacked concrete details. Lukas Leu of ATG Healthcare Investments suggested the deal could improve margins through cost synergies and expand reach into neuroscience and cell therapy, though he warned that mega‑mergers could hinder innovation and agility. John Murphy of Bloomberg Intelligence said the merger made limited strategic sense, citing divergent earnings growth forecasts and differing pipeline prospects, and warned that integrating large oncology divisions could impede pipeline progress. AstraZeneca declined to comment, and Bristol Myers was also contacted for comment. The talks come as AstraZeneca aims to reach $80bn in annual sales by 2030, up from $59bn in the previous year, after a recent setback with its heart disease candidate Wainua. Bristol Myers reported second‑quarter revenues of $12.97bn, a 5% increase year‑over‑year, and raised its 2026 outlook. The potential transaction would also expand BMS’s UK workforce of about 800 employees, including a research team of 250 at its Moreton site.