Patent cliff: the real driver behind pharma mega-mergers
Two drug giants reportedly discussed a $400 billion merger. The move makes little sense as industrial strategy and a great deal of sense as a calendar. At both companies, half of all sales rest on molecules whose US protection runs out in 2028.
The fact
Britain's AstraZeneca opened merger talks with US rival Bristol Myers Squibb, according to the Financial Times on 2 August. The combination would create a group worth close to $400 billion on the stock market, the fourth largest drugmaker in the world by market value. A source close to the groups has since denied any talks.
Why this deal is really about a calendar
A drugmaker does not simply sell a molecule: it sells a legal monopoly with an expiry date. A patent protects a medicine for twenty years from filing, and extensions can add up to five more. Once clinical trials are deducted, a chemical molecule keeps twelve to fifteen years of exclusive sales. When protection lapses, far cheaper copies arrive: generics for chemical molecules, biosimilars for those derived from living cells. Against a generic the fall is brutal: roughly three quarters of the market lost within a year. Against a biosimilar, much harder to manufacture, the erosion is slower and often only partial.
That calendar explains the move. Two medicines, the anticoagulant Eliquis and the immunotherapy Opdivo, brought in $24.5 billion in 2025, half of all Bristol Myers Squibb sales. Their US exclusivity runs out in 2028, and Eliquis loses its European protection as early as November 2026. The pattern is not confined to one company: at Merck, Keytruda alone accounted for $31.7 billion, close to half the group, on the same US timetable. Since research cannot be accelerated on demand, buying a rival amounts to buying younger molecules and, with them, time.
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