AstraZeneca is investing $2 billion in Summit Therapeutics to accelerate the development of PD-1xVEGF bispecific ivonescimab in combination with antibody-drug conjugates (ADCs).
The newly minted partners will start by testing ivonescimab—which is already approved in China for multiple non-small cell lung cancer indications—with AstraZeneca’s CLDN18.2-directed ADC in gastrointestinal cancers.
There are three parts to the deal. First, AstraZeneca is buying a 12% stake in Summit at an 18% premium to the biotech’s closing price Monday. Second, AstraZeneca and Summit will jointly fund clinical trials of ivonescimab with sonesitatug vedotin (sone-ve), a CLDN18.2-directed ADC. Third, the companies formed a nonbinding agreement to test ivonescimab with other AstraZeneca medicines, including ADCs.
The deal is “a win on multiple fronts,” Evercore ISI analysts said in a note to investors about Summit. The multipart agreement is a “validating buy-in from a global oncology leader, a major show of faith ahead of an imminent binary event, offers a much-needed and sizable cash infusion and completely retains [Summit’s] strategic optionality,” the analysts said.
Citing AstraZeneca’s “broad ADC pipeline and overall oncology know-how,” the analysts began touting the Anglo-Swedish drugmaker as a preferred partner for Summit before reports of a mooted $15 billion deal emerged in 2025.
Shares in Summit jumped 18% to $18.23 in after-hours trading Monday following the announcement of the deal.
According to the analysts, Summit management had told them that AstraZeneca has no right of first refusal on future deals. Summit leaders highlighted AstraZeneca’s “unique understanding of data generated in China” as a positive, the analysts said.
Questions about whether global studies will replicate Chinese trial data have hung over ivonescimab. The analysts said they took “incremental confidence” from AstraZeneca’s willingness to invest before the readout of HARMONi-3, Summit’s global phase 3 lung cancer trial. AstraZeneca has no visibility into the ongoing study, Summit told the analysts.
Susan Galbraith, Ph.D., executive vice president of oncology R&D at AstraZeneca, commented on another ivonescimab lung cancer trial, HARMONi-6, at an event in June.
“HARMONi-6 is obviously a positive study,” Galbraith said at the time. “What we've previously known is that both VEGF and PD-1 are clearly active mechanisms in this disease. Whether there’s a further benefit from it being in a bispecific remains a question. But it’s clearly an active drug and it's going to be exciting to see the data that come out of the global study.”
Galbraith added that “one advantage of having a bispecific is it’s easier to combine with the other drugs that are active in that space because you’ve got one drug rather than a doublet comparison.” The deal positions AstraZeneca to explore how ivonescimab combines with other assets, starting with trials of the bispecific with sone-ve, for which AstraZeneca paid KYM Biosciences $63 million upfront back in 2023.
Summit and AstraZeneca will retain development and commercial rights to their respective molecules. The partners are considering applying the same split-cost, retained-ownership model to other pairings of AstraZeneca molecules with ivonescimab. But that part of the deal is nonbinding and it is possible that the partners will opt against advancing a combination beyond the ivonescimab-sone-ve cocktail.