AstraZeneca Invests $2 Billion in Summit Therapeutics Preferred Equity

AstraZeneca has agreed to invest $2 billion in newly issued equity of Summit Therapeutics (SMMT ) and to enter a clinical collaboration evaluating its antibody drug conjugate sonesitatug vedotin in combination with ivonescimab in gastrointestinal cancers, according to an AstraZeneca announcement published on 28 September 2026. The investment is intended to accelerate the development of ivonescimab, a bispecific antibody targeting PD-1 and VEGF, in combination with antibody drug conjugates (ADCs) across tumour types.

Terms of the Equity Investment

Under the agreement, AstraZeneca will purchase approximately 109 thousand shares of Summit preferred stock convertible into shares of Summit common stock at a 1:1,000 ratio. Summit’s announcement states that, under the Share Purchase Agreement between the companies, AstraZeneca will purchase approximately 108,955 preferred shares, and that at the conversion ratio the investment represents a common stock price of $18.36 per share, the volume weighted-average price (VWAP) for the five trading days from the prior week plus 10%, a premium over the day’s closing price.

Following completion of the investment, AstraZeneca will hold rights equivalent to approximately 12.0% of Summit’s outstanding common stock, and approximately 10.6% on a fully diluted basis. AstraZeneca anticipates closing of the preferred-stock investment within one week and states that any future conversion of the preferred stock into common stock would be subject to customary regulatory clearances. Summit states closing is expected by the end of the week, subject to customary conditions.

Summit also states that the preferred securities have not been registered under the Securities Act of 1933 and that it has agreed to file a registration statement with the Securities and Exchange Commission registering the resale of the shares of common stock following the closing of the securities purchase agreement.

Clinical Collaboration and Planned Combination Programme

Alongside the investment, the companies entered a clinical collaboration agreement to evaluate sonesitatug vedotin (Sone-Ve), a potential global first-in-class CLDN18.2-targeting ADC with a monomethyl auristatin E payload, in combination with ivonescimab, and intend to initiate trials in gastrointestinal cancers imminently. Each company will contribute its respective medicine for the planned combination trials and jointly contribute to trial costs, and each will retain development and commercial rights to its own medicine. Summit states the combination studies are intended to be sponsored by AstraZeneca.

Sone-Ve targets CLDN18.2, a protein found in the stomach lining that AstraZeneca describes as a validated therapeutic target in oncology, particularly for gastrointestinal cancers. The ADC consists of an anti-CLDN18.2 monoclonal antibody, a protease-degradable linker and a cytotoxic small-molecule payload. AstraZeneca (AZN ) entered a global exclusive licence agreement with KYM Biosciences to develop and commercialise Sone-Ve in March 2023.

AstraZeneca recently reported positive high-level results from the CLARITY-Gastric01 trial of Sone-Ve in second-line and later CLDN18.2-positive advanced gastric cancers, demonstrating what the company described as a statistically significant and highly clinically meaningful improvement in overall survival versus investigator’s choice of therapy. The results will be presented at the European Society for Medical Oncology Congress 2026 in a Presidential Symposium. According to Summit, they will appear alongside HARMONi-GI1, an Akeso-sponsored trial from China in which ivonescimab plus chemotherapy demonstrated a statistically significant and clinically meaningful improvement in overall survival versus durvalumab plus chemotherapy in first-line advanced biliary tract cancer.

Sone-Ve is also being evaluated in the Phase III CLARITY-Gastric02 trial in combination with capecitabine, with or without rilvegostomig, as a first-line treatment for advanced or metastatic gastric cancer, GEJ cancer and EAC. In Phase II development, it is being evaluated in patients with advanced solid tumours in multiple combinations across settings, including in CLDN18.2-positive pancreatic and biliary tract cancers.

The companies have also executed a Memorandum of Understanding with the intent to enter an agreement initiating a global development programme combining ivonescimab with AstraZeneca’s cancer medicines, including additional ADCs. Summit states the memorandum is non-binding and mutually non-exclusive, that the companies intend to share clinical development costs of potential future studies, that each company will retain its current development and commercial rights, and that there are no additional financial considerations in the form of milestones, royalties, revenue-sharing or profit-sharing. Summit cautioned there can be no assurance the intended collaboration comes to fruition.

“A core pillar of our oncology strategy is to broaden the reach of our ADC portfolio as the backbone of treatment across tumour types with combinations alongside next-generation immunotherapies,” said Susan Galbraith, Executive Vice President, Oncology Haematology R&D at AstraZeneca. Bispecifics targeting PD-1 and VEGF are rapidly advancing in development and have the potential to improve on current immunotherapies, particularly in lung, breast and gastrointestinal cancers, she said.

Robert W. Duggan, Chairman and Co-Chief Executive Officer of Summit Therapeutics, said: “This significant investment, as well as the collaboration, is a powerful validation of the potential of ivonescimab.” Dr. Maky Zanganeh, President and Co-Chief Executive Officer of Summit, said the developments open a new chapter in the advancement of ivonescimab and that the companies plan trials combining ivonescimab with what she described as promising novel anti-cancer compounds, including ADCs, bringing together complementary approaches to tumour-cell killing, antitumour immunity and the tumour microenvironment.

Ivonescimab is a novel, potential first-in-class bispecific antibody that combines the effects of immunotherapy via a blockade of PD-1 with the anti-angiogenesis effects associated with blocking VEGF in a single molecule. It was engineered by Akeso Inc. Summit holds exclusive rights to develop and commercialise ivonescimab in major territories outside China, while Akeso retains rights in China and other regions.

Ivonescimab is approved to treat certain patients with non-small cell lung cancer (NSCLC) in China, where it was first approved in May 2024, and a Biologics License Application seeking approval in EGFR-mutated NSCLC is under review by the US Food and Drug Administration. Summit states the FDA accepted the application for filing in January 2026, with a Prescription Drug User Fee Act goal date of 14 November 2026.

Summit states that more than 5,000 patients have been treated with ivonescimab in clinical studies globally, and more than 100,000 when including those treated in a commercial setting in China, as noted by Akeso.

According to Summit, 16 Phase III clinical studies of ivonescimab are announced, ongoing or completed: five Summit-sponsored global studies, one multiregional study sponsored by a cooperative group, and ten conducted in China by Akeso. Summit’s own late-stage programme comprises the HARMONi, HARMONi-3, HARMONi-7 and HARMONi-GI3 Phase III trials and the HARMONi-GU1 Phase II/III trial in urothelial carcinoma, and the company states five Phase III trials of ivonescimab have read out positively to date, four in NSCLC and one in biliary tract cancer. AstraZeneca lists ongoing Phase III trials of ivonescimab in NSCLC, small cell lung cancer, biliary tract cancer, bladder cancer, triple-negative breast cancer, head and neck squamous cell carcinoma, colorectal cancer and pancreatic cancer.