AstraZeneca invests $2 billion in Summit Therapeutics to pair cancer drugs

AstraZeneca will invest $2 billion in Summit Therapeutics to jointly develop a combination of cancer drugs, the companies announced this week, sending shares of the smaller biotech soaring more than 17% and marking one of the largest single bets yet on Summit's experimental lung cancer treatment.

Under the deal, detailed in AstraZeneca's announcement and in a filing with US securities regulators, AstraZeneca will purchase newly issued preferred stock convertible into roughly 12% of Summit's outstanding shares, or about 10.6% on a fully diluted basis. The preferred shares convert to common stock at a ratio of 1-to-1,000, and the companies expect the investment to close within about a week, pending customary conditions.

The money buys AstraZeneca a stake in ivonescimab, a bispecific antibody that targets both the PD-1 and VEGF pathways, which Summit licensed from the Chinese biotech Akeso and has positioned as a potential successor to Merck's blockbuster immunotherapy Keytruda. In exchange, the two companies will begin testing ivonescimab in combination with sonesitatug vedotin, an AstraZeneca antibody-drug conjugate that targets the protein CLDN18.2, in gastrointestinal cancers, with trials expected to start within weeks. Each company will retain development and commercial rights to its own medicine.

Doubling down on combination therapy

"A core pillar of our oncology strategy is to broaden the reach of our ADC portfolio as the backbone of treatment across tumour types," said Susan Galbraith, AstraZeneca's executive vice president for oncology research and development, in the companies' announcement. Summit's president and co-chief executive, Maky Zanganeh, called the agreement the opening of "an exciting new chapter in the advancement of ivonescimab."

The investment extends a pattern in cancer drug development this year, as large pharmaceutical companies increasingly pair their antibody-drug conjugates — a class of medicines that deliver chemotherapy directly to tumor cells — with immunotherapies developed by smaller rivals, betting that combinations will outperform any single drug. AstraZeneca has built one of the industry's largest ADC pipelines in recent years, including through a long-running development partnership with Japan's Daiichi Sankyo.

For Summit, a company whose stock has climbed sharply over the past year on optimism about ivonescimab's clinical data, the AstraZeneca deal provides both a capital infusion and validation from one of oncology's largest players. Summit and Akeso have reported data suggesting ivonescimab outperformed Keytruda in a head-to-head lung cancer trial conducted in China, results that have not yet been replicated in a US-based study but that have drawn significant investor attention to the drug.

AstraZeneca shares rose nearly 1% on the news, a modest move for a company with a market capitalization above $250 billion, reflecting that the transaction is structured as a minority equity stake rather than an outright acquisition. Under the terms disclosed in the regulatory filing, the deal also includes a memorandum of understanding outlining a broader global development program that could eventually pair ivonescimab with additional AstraZeneca ADCs across other tumor types, though those plans remain preliminary.

The agreement adds to a busy year for cancer drug dealmaking, as major pharmaceutical companies race to secure next-generation combination treatments ahead of patent expirations on some of their existing blockbuster therapies later this decade.