Reports that AstraZeneca and Bristol Myers Squibb held merger discussions pushed AstraZeneca shares lower as investors weighed the likelihood of regulatory and business-overlap hurdles. Separate coverage highlighted potential scale—analysts said even a deal framed as unlikely could still “reset” the deal environment if it advanced. The companies compete in overlapping oncology areas, including non-small cell lung cancer, where BMS markets Opdivo and AstraZeneca markets Imfinzi. Analysts cited antitrust scrutiny across both the US and Europe as a central obstacle, given commercial portfolio overlap. Neither company confirmed terms. The reporting also noted AstraZeneca’s recent messaging around achieving growth targets without major acquisitions, increasing attention on whether any talks could survive competition review.