- AstraZeneca shares plunged 8.96% on Monday, wiping more than £17 billion from the company’s market value.
- A merger with Bristol Myers Squibb would create one of the world’s largest pharmaceutical companies.
- Investors question whether AstraZeneca needs a transformational deal while its existing oncology strategy continues to deliver growth.
AstraZeneca shares recovered slightly on Tuesday after suffering a sharp sell-off triggered by reports that the pharmaceutical company has held merger talks with Bristol Myers Squibb.
The AstraZeneca share price rose by about 2.2% to 11,750p in early trading, following Monday’s 8.96% decline to 11,500p. The sell-off wiped more than £17 billion from the company’s market value and marked its steepest one-day decline since April 2025.
The proposed combination would create the world’s fourth-largest pharmaceutical company, with a combined market valuation approaching $400 billion. However, AstraZeneca shareholders have questioned whether acquiring Bristol Myers Squibb would create enough value to justify the financial, regulatory and operational risks.
AstraZeneca Investors Oppose Potential Mega-Merger
Some prominent AstraZeneca shareholders have urged the company to abandon the proposed transaction, arguing that BMS is an industry laggard facing significant commercial challenges.
Evangelos Assimakos, senior investment director at Rathbones, described the talks as surprising because AstraZeneca already has a strong pipeline and remains on track to reach its target of $80 billion in annual revenue by 2030.
AstraZeneca generated $58.7 billion in revenue during 2025 and expects several important clinical trial results covering cancer, obesity and respiratory treatments. Chief executive Sir Pascal Soriot also said recently that the company did not require major acquisitions to achieve its 2030 revenue target.
Markus Manns, a portfolio manager at Union Investment and a shareholder in both companies, said the potential merger made neither strategic nor financial sense. He warned that previous pharmaceutical mega-mergers had frequently destroyed shareholder value and disrupted research and development.
These concerns could become important if negotiations progress. According to MKI Global Partners, AstraZeneca shareholders may have to approve the transaction if the company issues more than one-third of its existing share capital to fund the deal. BMS shareholders would also need to support the proposed combination.
Bristol Myers Squibb Patent Cliff Raises Questions
The biggest concern is the approaching loss of patent protection for several of Bristol Myers Squibb’s leading medicines.
BMS could lose close to half its current revenue as patents expire over the coming years. Its most important products include blood thinner Eliquis and cancer treatment Opdivo, both of which face increasing competition toward the end of the decade.
Once exclusivity expires, cheaper generic or biosimilar alternatives can enter the market and cause revenue from blockbuster medicines to fall rapidly. AstraZeneca would therefore be paying a substantial takeover premium for a company whose existing revenue base is under pressure.
The situation also recalls BMS’s $74 billion purchase of Celgene in 2019. That transaction was designed to strengthen the company’s oncology and immunology operations, but it failed to generate all the growth initially anticipated. Celgene was also facing a major patent cliff when BMS acquired it.
Some investors now fear that AstraZeneca could repeat the same mistake on a much larger scale.
Antitrust Scrutiny Could Complicate the Deal
AstraZeneca and Bristol Myers Squibb have substantial operations in oncology and cardiovascular medicine, creating the possibility of an extended regulatory investigation.
Cancer treatments account for more than two-fifths of revenue at both companies. Their portfolios include competing immunotherapies designed to help the immune system identify and attack cancer cells.
AstraZeneca owns Imfinzi, while BMS owns Opdivo. Both medicines compete in the PD-1 and PD-L1 inhibitor market, which also includes Merck’s blockbuster Keytruda treatment.
Competition regulators could require the companies to sell medicines, clinical-stage assets or business units before approving the merger. Significant divestments would weaken some of the strategic benefits used to justify the transaction.
A lengthy approval process could also distract AstraZeneca’s management and delay important research programmes. Pharmaceutical mega-mergers often require companies to combine laboratories, remove overlapping positions and restructure development priorities.
Could the Merger Still Benefit AstraZeneca?
Despite the opposition, some investors see potential benefits. Combining the two businesses would create one of the world’s most extensive oncology portfolios. It could produce substantial cost savings across research, administration, manufacturing and commercial operations.
The merger would also expand AstraZeneca’s position in the United States, which already accounts for almost half its sales. Greater exposure to the world’s largest pharmaceutical market could support the company’s long-term revenue ambitions. A deal could also strengthen AstraZeneca in blood cancer, immunology, neuroscience and cell therapy. These areas could complement its existing leadership in lung, breast and gastrointestinal cancers.
Some shareholders believe BMS could provide potential internal candidates to succeed Soriot, who turned 67 in May. Speculation has grown that the long-serving chief executive may be considering a legacy-defining deal before eventually stepping down. Soriot took control of AstraZeneca in 2012 and later rejected Pfizer’s nearly £70 billion takeover proposal in 2014. He subsequently rebuilt the drug pipeline and transformed AstraZeneca into one of Europe’s most valuable companies.
Share Price Decline Could Make the Deal More Expensive
The reported talks come at a difficult time for AstraZeneca’s valuation. Before the latest sell-off, BMS shares had gained approximately 20% since the start of 2026, while AstraZeneca shares had declined by about 12%. Monday’s additional 9% drop widened that valuation gap. Because any transaction would probably use a substantial amount of AstraZeneca stock, the lower share price could make it more expensive to acquire BMS.
AstraZeneca may also need to assume additional debt or include a cash component. That could place further pressure on the company’s balance sheet and reduce its capacity for targeted acquisitions and licensing agreements. Neither company has commented on the reports, while the proposed structure and valuation remain unknown. The discussions could still be postponed or abandoned.
For now, the market reaction sends a clear message: AstraZeneca investors remain unconvinced that the potential benefits of a $400 billion pharmaceutical merger outweigh the patent, financing and execution risks.
AstraZeneca shares fell after reports that the company had discussed a potential merger with Bristol Myers Squibb. Investors are concerned about BMS’s patent expirations, the possible acquisition cost and regulatory risks.
No agreement has been announced. AstraZeneca and Bristol Myers Squibb have reportedly held talks, but neither company has confirmed the discussions or disclosed any proposed terms.
Some shareholders believe AstraZeneca can achieve its growth targets independently. They are also concerned that BMS could lose a substantial share of its revenue as patents on major medicines expire.