On December 9, 2025 Akeso, Inc. (9926.HK) ("Akeso" or the "Company") reported that data from the Phase II study (COMPASSION-25) for its first-in-class PD-1/CTLA-4 bispecific antibody, cadonilimab, in combination with SOX regimen (oxaliplatin + tegafur/gimeracil/oteracil) as neoadjuvant therapy for resectable gastric or gastroesophageal junction (G/GEJ) adenocarcinoma, was presented at the 2025 ESMO (Free ESMO Whitepaper) Asia Congress.
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Currently, Akeso is running the pivotal Phase III study (AK104-310/COMPASSION-33) investigating cadonilimab combined with the SOX regimen for perioperative treatment of resectable G/GEJ adenocarcinoma. This regimen is expected to further push the efficacy boundaries beyond existing single-target immunotherapies and establish a new standard for perioperative immunotherapy in gastric cancer.
Promising Pathologic Complete Response (pCR) Rate
Among all evaluable patients, the overall pCR rate was 28.6%. Notably, in patients receiving the cadonilimab Q3W dosing regimen, the pCR rate reached 50.0%. pCR, defined as the absence of viable tumor cells in both the primary tumor site and regional lymph nodes upon surgical resection, is considered the "gold standard" surrogate endpoint for evaluating neoadjuvant treatment efficacy and predicting long-term survival benefits.
High Rate of Major Pathologic Response (MPR)
The overall MPR rate (defined as ≤10% residual viable tumor cells) across all evaluable patients was 71.4%. For the cadonilimab Q3W regimen, the MPR rate was as high as 85.7%. This suggests that the cadonilimab-based regimen induces substantial tumor regression in the majority of patients.
100% R0 Resection Rate
All patients who underwent surgery achieved an R0 resection (microscopically margin-negative resection), providing a solid foundation for curative intent and potentially reducing the risk of recurrence.
Significant Tumor Downstaging
Among all evaluable patients, 85.7% achieved downstaging of the primary tumor (ypT), and 75.0% achieved nodal downstaging (ypN). These results confirm the efficacy of the cadonilimab regimen in reducing tumor burden and lowering the pathological stage, thereby improving the conditions for successful surgical intervention.
Manageable Safety Profile with Good Tolerability
Treatment-related adverse events were consistent with the known safety profiles of the SOX regimen and immune checkpoint inhibitors. No new or unexpected safety signals were observed, indicating an overall manageable and favorable safety profile.
In perioperative treatment of resectable G/GEJ adenocarcinoma, chemotherapy remains the standard therapy for locally advanced gastric cancer. However, chemotherapy has limited efficacy. Cadonilimab, the first PD-1/CTLA-4 bispecific antibody, works by synergistically activating the immune system, achieving a dual blockade of the tumor immune suppressive microenvironment. This mechanism provides a stronger anti-tumor effect compared to PD-1/L1 monotherapies.
Currently, cadonilimab’s clinical value in gastric cancer is scientifically well-established. Beyond its ongoing phase III clinical trial in the perioperative setting, cadonilimab combined with chemotherapy as a first-line treatment for advanced gastric cancer (with survival benefits across the PD-L1 expression levels) has been approved for commercialization in China. Additionally, a pivotal phase III trial exploring cadonilimab in combination with pulocimab (VEGFR-2) for immune therapy-resistant advanced gastric cancer is currently ongoing and is expected to offer a new therapeutic option for later-line gastric cancer. Collectively, these pivotal phase III studies will expand the use of cadonilimab, paving the way for a comprehensive gastric cancer treatment options that spans from advanced, unresectable gastric cancer to early-stage, resectable disease.
(Press release, Akeso Biopharma, DEC 9, 2025, View Source [SID1234661331])