No agreement was announced. The Guardian reported on 5 August that Reuters had been told there were no ongoing discussions and that neither company had informed shareholders, The Times reported the same day that a senior source denied the talks, and AstraZeneca's August press-release feed carried only clinical updates.
The market resolves on a regulatory news release from either company carried on the RNS at londonstockexchange.com announcing a firm merger agreement or offer, dated on or before 23:59 BST on 31 August 2026. Press reports do not resolve it. If that source has not published in time, the same announcement republished on astrazeneca.com or investegate.co.uk, and the SEC EDGAR filing of the equivalent Bristol Myers Squibb announcement settle it.
We looked for merger talks involving a UK-listed drugmaker that became public before any deal was signed. Since 1998 this has happened five times. All five ended within six weeks, either with a firm offer or with the talks dead. Two produced an agreed or firm offer, and three collapsed.