Bispecific Antibody Cadonilimab Shows Survival Edge Over PD-1 Drugs in Gastric Cancer

Gastric cancer and gastroesophageal junction cancer together rank among the fifth most common malignancies worldwide and remain leading causes of global cancer mortality, with an especially heavy burden in Eastern Asia. Because early-stage disease rarely produces symptoms, many patients are diagnosed only after the cancer has advanced or spread, leaving first-line systemic therapy as the mainstay of care. Over the past several years, immune checkpoint inhibitors added to platinum and fluoropyrimidine chemotherapy have transformed outcomes in this setting, and multiple regimens combining PD-1 or PD-L1 antibodies with chemotherapy have been approved in China for HER2-negative advanced disease. Yet a persistent and clinically uncomfortable question has shadowed these approvals: do all patients benefit equally, or does the benefit of PD-(L)1 blockade collapse in certain subgroups?

That question took on renewed urgency at the 2024 meeting of the FDA Oncologic Drugs Advisory Committee, which re-examined the comparative efficacy of PD-1 inhibitors plus chemotherapy across PD-L1 expression levels. The committee concluded that patients whose tumors express PD-L1 at a combined positive score or tumor area positivity score of 10 or higher derive the clearest benefit from PD-1 inhibitors, while those scoring below 1 show no meaningful improvement over chemotherapy alone. The large intermediate zone between those thresholds remains contested, and even in higher-expression groups certain populations, notably patients with liver metastases, appear relatively resistant to single-target immunotherapy. Against this backdrop, a new network meta-analysis published in Cancer Reports offers the first systematic indirect comparison of a different immunotherapy architecture: cadonilimab, a tetravalent bispecific antibody that blocks both PD-1 and CTLA-4 within a single molecule.

The research team, registered in the PROSPERO repository and conducted under PRISMA guidelines, searched PubMed, Web of Science, Embase and the Cochrane Library from inception through December 31, 2024, supplementing the database results with conference abstracts from ASCO, ESMO and AACR and with FDA advisory committee documents. Their inclusion criteria were deliberately strict: only Phase III randomized controlled trials in pathologically confirmed, previously untreated, HER2-negative gastric or gastroesophageal junction cancer qualified, and every experimental arm had to combine chemotherapy with either a single-agent anti-PD-(L)1 antibody or the anti-PD-1/CTLA-4 bispecific antibody cadonilimab. From an initial pool of 4,089 publications, screening narrowed the field to eight trials that met all criteria: KEYNOTE-062, ATTRACTION-4, CheckMate-649, KEYNOTE-859, GEMSTONE-303, ORIENT-16, COMPASSION-15 and RATIONALE 305. Together these trials enrolled 7,127 patients, of whom 3,572 received chemotherapy plus an immune checkpoint inhibitor and 3,555 received chemotherapy with placebo.

Because no head-to-head trial has ever compared cadonilimab with a PD-(L)1 antibody, the investigators used a frequentist network meta-analysis, treating all platinum-fluoropyrimidine doublet backbones—XELOX, FOLFOX, SOX and fluorouracil-platinum—as a common chemotherapy comparator node, an approach supported by prior noninferiority trials and systematic reviews showing these regimens are clinically interchangeable. Overall survival, defined as time from randomization to death from any cause, served as the primary endpoint, with progression-free survival and Grade 3 to 5 treatment-related and serious adverse events as secondary measures. Risk of bias was low across the included studies when assessed with the Cochrane RoB 2 tool, and all trials were analyzed on an intention-to-treat basis. Because the network was star-shaped, with cadonilimab connected to the PD-(L)1 inhibitors only through the shared chemotherapy node, formal inconsistency testing was not possible, a structural limitation the authors acknowledge openly.

The headline finding is striking. In the intention-to-treat population, every immunotherapy regimen outperformed chemotherapy alone, but cadonilimab plus chemotherapy delivered the largest survival gain, with a hazard ratio for overall survival of 0.62 (95 percent confidence interval 0.50 to 0.77), compared with hazard ratios of 0.75 to 0.82 for the five PD-(L)1 antibodies: sugemalimab, sintilimab, pembrolizumab, tislelizumab and nivolumab. In the indirect comparison against the pooled PD-(L)1 class, cadonilimab was associated with a statistically significant 22 percent reduction in the hazard of death (hazard ratio 0.78, 95 percent confidence interval 0.62 to 0.98), with essentially no heterogeneity among trials. Treatment ranking by P-score placed cadonilimab first with a probability score of 0.9586, well ahead of the rest of the field, and progression-free survival followed the same pattern, with a hazard ratio of 0.70 (95 percent confidence interval 0.57 to 0.86) favoring the bispecific approach.

The mechanistic rationale for this advantage lies in cadonilimab’s unusual tetravalent design. Gastric adenocarcinomas commonly express the immune checkpoints PD-1 and CTLA-4, which tumors exploit to suppress T-cell responses, and preclinical work has long shown that blocking both pathways synergistically enhances antitumor immunity. Conventional combination immunotherapy with separate PD-1 and CTLA-4 antibodies, tested in the CheckMate 649 trial, was hampered by dose-limiting toxicity and failed to improve survival. Cadonilimab instead packs both binding specificities into one antibody that preferentially accumulates in tumor tissue where PD-1 and CTLA-4 are co-expressed, concentrating dual blockade at the tumor site while sparing normal tissue. That design, the authors argue, explains both the improved efficacy and the tolerability profile observed in COMPASSION-15.

Safety data appear to support that interpretation. Across the included trials, no statistically significant differences emerged between cadonilimab and PD-(L)1 inhibitors in Grade 3 or higher treatment-related adverse events (odds ratio 0.83, 95 percent confidence interval 0.54 to 1.28) or serious adverse events (odds ratio 0.89, 95 percent confidence interval 0.56 to 1.42). Egger’s tests for publication bias were non-significant across all endpoints, and leave-one-out sensitivity analyses left the direction and significance of every primary result unchanged. Still, the authors caution that the confidence intervals around the safety comparisons are wide and rest on a limited number of trials, so a clinically meaningful difference in toxicity cannot be definitively excluded.

The most consequential findings emerge from exploratory subgroup analyses. In patients with low PD-L1 expression—combined positive scores below 10—the hazard ratio for overall survival favored cadonilimab over PD-(L)1 therapy with a point estimate of 0.77 (95 percent confidence interval 0.58 to 1.01), consistent across the CPS below 1 and below 5 cutoffs, while the single-target antibodies showed little or no benefit versus chemotherapy in the same strata. Even more pronounced was the liver metastasis subgroup, where cadonilimab reduced the hazard of death by 33 percent relative to PD-(L)1 inhibitors (hazard ratio 0.67, 95 percent confidence interval 0.49 to 0.93) and halved it relative to chemotherapy alone. This matters because liver metastases deplete peripheral T cells, erode intratumoral T-cell diversity and enrich immunosuppressive regulatory T cells and macrophages, creating a microenvironment that single-agent PD-1 blockade struggles to overcome; the authors propose that simultaneous CTLA-4 inhibition, which suppresses regulatory T cells, counters this biology more effectively. Statistically significant advantages for cadonilimab also appeared in male patients and those with an ECOG performance status of 1, subgroups in which androgen-receptor signaling and heightened systemic inflammation respectively promote T-cell exhaustion that dual checkpoint blockade may more fully reverse.

The authors are careful to frame these subgroup results as hypothesis-generating. All subgroup estimates derive from study-level aggregate data rather than individual patient information, which introduces the risk of ecological bias and limits control of within-trial confounding, and the PD-L1 analyses relied on different immunohistochemistry platforms, albeit assays with demonstrated substantial to excellent concordance in gastric cancer. Ranking analyses are sensitive to network structure and cannot by themselves establish superiority. Nevertheless, the overall picture is internally consistent: for patients whose tumors express high levels of PD-L1, all immunotherapy regimens deliver clear survival benefits over chemotherapy, but for the large populations left in clinical limbo—those with low PD-L1 expression, liver metastases, or intermediate expression where regulatory debate continues—this analysis suggests that a bispecific antibody harnessing two immune escape pathways simultaneously may be the preferable first-line partner for chemotherapy. The findings stop short of Level 1 evidence, and the authors call explicitly for prospective head-to-head trials, but they mark the first quantitative indication that bispecific checkpoint engineering could redraw the treatment algorithm for advanced gastric and gastroesophageal junction cancer.

Subject of Research: Indirect comparison of cadonilimab, a PD-1/CTLA-4 bispecific antibody, versus PD-(L)1 inhibitors as first-line therapy for advanced gastric and gastroesophageal junction cancer

Article Title: Survival Outcomes With Cadonilimab Versus PD‐(L)1 Therapy in Front‐Line Gastric Cancer: A Network Meta‐Analysis

Article References: Yu, Z.-K., Yi, J.-H., Xue, J., Huang, Y.-C., Zhao, Y., Jiang, C., Yin, C.-X., Xia, B., Zhou, Y.-X., He, W.-Z., & Xia, L.-P. (2026). Survival Outcomes With Cadonilimab Versus PD ‐(L)1 Therapy in Front‐Line Gastric Cancer: A Network Meta‐Analysis. Cancer Reports, 9(9), Article e70672. https://doi.org/10.1002/cnr2.70672

Image Credits: AI Generated

DOI: 10.1002/cnr2.70672

Keywords: cadonilimab, gastric cancer, gastroesophageal junction cancer, network meta-analysis, immune checkpoint inhibitors, PD-1, CTLA-4, bispecific antibody, PD-L1 expression, liver metastasis, overall survival, COMPASSION-15