Summit Therapeutics reports survival benefit for cancer drug in trial

Summit Therapeutics (SMMT) on Sunday said its experimental cancer drug ivonescimab helped patients with advanced biliary tract cancer live significantly longer than those receiving an established immunotherapy treatment, according to results from a late-stage clinical trial conducted in China.

The phase 3 HARMONi-GI1 study, conducted by Summit's Chinese partner Akeso (9926.HK), found that patients receiving ivonescimab alongside chemotherapy had a median overall survival of 14.9 months, compared with 12.1 months for those receiving AstraZeneca's (AZN) Imfinzi, also known as durvalumab, plus chemotherapy. The findings were presented at the European Society for Medical Oncology's 2026 congress in Madrid.

The treatment reduced the risk of death during the study by 25% compared with the Imfinzi regimen. The trial enrolled 682 patients, with 340 receiving ivonescimab and 342 receiving durvalumab. The median follow-up period was 14.3 months.

For investors, the results represent an important step in Summit's efforts to establish ivonescimab as a treatment for multiple types of cancer, potentially expanding its commercial opportunities beyond lung cancer. The survival advantage over an established therapy strengthens the case for further development, although the findings come from a study conducted exclusively in China. Summit still must demonstrate sufficient safety and effectiveness to secure regulatory approval in the United States and other markets.

Patients lived longer without cancer worsening

The study also found that patients receiving ivonescimab went a median of 8.4 months before their cancer worsened or they died, compared with 5.8 months for patients receiving durvalumab. This measurement, known as progression-free survival, is commonly used to evaluate whether cancer treatments can delay the advance of a disease.

Ivonescimab reduced the risk of disease progression or death by 39% compared with durvalumab during the study. Tumors shrank by a predefined amount in 53.8% of patients receiving ivonescimab, compared with 32.5% in the comparison group. This measurement is known as the objective response rate.

At 18 months, 44% of patients receiving ivonescimab were alive, compared with 32.5% of those receiving durvalumab.

The survival results were statistically significant, meaning researchers determined that the observed advantage was unlikely to have resulted from chance alone under the trial's statistical assumptions.

Attacking cancer in two ways

Ivonescimab is a bispecific antibody, an engineered protein designed to act on two biological targets simultaneously.

One target, called PD-1, is a protein that can prevent the immune system from attacking cancer cells. Blocking PD-1 helps the body's immune defenses recognize and fight tumors.

The other target, VEGF, is a protein that promotes the growth of blood vessels. Tumors can exploit this process to obtain the oxygen and nutrients they need to grow. Blocking VEGF is intended to interfere with that blood supply.

By combining these two mechanisms in a single drug, ivonescimab is designed to help the immune system attack cancer while limiting the tumor's ability to support its growth.

Biliary tract cancer is a relatively rare but aggressive disease affecting the bile ducts or gallbladder. Because symptoms often appear only after the disease has advanced, many patients are diagnosed when surgery is no longer an option.

Safety findings, U.S. development plans

Summit reported that the drug's safety profile was consistent with earlier clinical studies, with no new safety concerns identified.

Serious adverse events occurring during treatment were reported in 43.4% of patients receiving ivonescimab and 43.7% receiving durvalumab. The most common side effects involved blood abnormalities, including reduced white blood cell counts, lower platelet counts and anemia.

Other potential side effects associated with VEGF inhibition included high blood pressure, protein in the urine and bleeding. Most of these events were classified as mild or moderate.

Summit plans to begin activating U.S. clinical trial sites in the fourth quarter of 2026 for a Phase II/III study conducted in collaboration with the ECOG-ACRIN Cancer Research Group. That trial will compare ivonescimab plus chemotherapy with regimens using either durvalumab or Merck's (MRK) Keytruda, also known as pembrolizumab.

The planned study is intended to generate evidence that could support an application for regulatory approval. Its primary goal will be to determine whether patients receiving ivonescimab live longer than those receiving the comparison treatments.

Ivonescimab is already approved in China for certain forms of non-small cell lung cancer, the most common category of lung cancer. However, the drug remains experimental in the United States and Europe, where Summit holds licensing rights.

According to Summit (SMMT), five phase 3 trials involving ivonescimab have reported positive results, including four involving lung cancer and the latest biliary tract cancer study. The company and its partners are also investigating the drug in colorectal, bladder, breast and other cancers.

The latest findings could help Summit establish ivonescimab as a treatment across several cancer types, although future clinical results, regulatory decisions and competition from existing therapies will determine its commercial potential.