SUMMARY: The American Cancer Society estimates that in the US about 26,890 new gastric cancer cases will be diagnosed in 2024 and about 10,880 people will die of the disease. It is one of the leading causes of cancer-related deaths in the world. Several hereditary syndromes such as Hereditary Diffuse Gastric Cancer (HDGC), Lynch syndrome (Hereditary Nonpolyposis Colorectal Cancer) and Familial Adenomatous Polyposis (FAP) have been associated with a predisposition for gastric cancer. Additionally, one of the strongest risk factor for gastric adenocarcinoma is infection with Helicobacter pylori (H.pylori), which is a gram-negative, spiral-shaped microaerophilic bacterium.
Patients with localized disease (Stage II and Stage III) are often treated with multimodality therapy and 40% of the patients may survive for 5 years or more. However, majority of the patients with gastric and gastroesophageal junction (GEJ) adenocarcinoma have advanced disease at the time of initial presentation and have limited therapeutic options with little or no chance for cure. The five-year relative survival rate for patients at the metastatic stage is approximately 15%. These patients frequently are treated with platinum containing chemotherapy along with a Fluoropyrimidine such as modified FOLFOX6 or CAPOX. Patients with HER2-positive disease are usually treated with chemotherapy plus Trastuzumab, and for those patients with HER2-negative disease, patients receive chemotherapy along with a checkpoint inhibitor, or checkpoint inhibitor alone, if the tumors express PD-L1.
Cadonilimab (AK104) is a human, bispecific IgG1 antibody with high binding avidity especially to high density of PD-1 and CTLA-4 due to its tetravalent design, and could simultaneously bind different cells expressing PD-1 and CTLA-4, respectively. By effective blocking both PD-1 and CTLA-4 pathways, Cadonilimab activates T cells by increasing interleukin-2 (IL-2) and interferon-gamma secretion to similar extent, as compared with anti-PD-1 and anti-CTLA-4 combination.
COMPASSION-15 is a double-blind, randomized, multicenter, Phase III trial that enrolled 610 patients diagnosed with locally advanced unresectable or metastatic gastric or gastroesophageal junction (GEJ) cancer. They were randomly assigned 1:1 to receive either Cadonilimab in combination with Oxaliplatin and Capecitabine chemotherapy, or placebo plus the same chemotherapy. Chemotherapy with Oxaliplatin and Capecitabine was given every 3 weeks for up to six cycles. Capecitabine was administered at 1000 mg/m2 orally twice daily on days 1 through 14 every 3 weeks and Oxaliplatin IV at 130 mg/m2 every 3 weeks. Cadonilimab 10 mg/kg IV or placebo was given on day 1 of each cycle every 3 weeks. Following the 6 cycles, patients then received Cadonilimab 10 mg/kg IV monotherapy or placebo every 3 weeks. Stratification factors included ECOG performance status (0 versus 1), PD-L1 expression (CPS 5% or more, or less than 5%), and the presence or absence of liver metastasis. The Primary endpoint was Overall Survival (OS) in the Intent to Treat (ITT) population.
The researchers herein presented the interim analysis data of COMPASSION-15 trial. The results revealed a significant improvement in Overall Survival with Cadonilimab combination therapy compared to placebo. The median OS was 15.0 months with Cadonilimab combination, compared with 10.8 months for those in the placebo arm (HR=0.60; P<0.001). The 18-month Overall Survival rate was 45.8% in the Cadonilimab group versus 25.5% in the placebo group.
Subgroup analysis based on PD-L1 expression levels (CPS 5% or more, or less than 5%) also demonstrated favorable outcomes with Cadonilimab across all strata. Among patients with a PD-L1 CPS of less than 5%, Cadonilimab combination achieved a median OS of 14.8 months, compared with 11.1 months in the placebo group. The 18-month OS rates were 44.1% compared with 27.5%, respectively.
Progression-Free Survival (PFS), another critical measure of treatment efficacy, showed consistent benefits with Cadonilimab combination compared to placebo plus chemotherapy, irrespective of PD-L1 expression. Median PFS was 7 months versus 5.3 months in the ITT population, with similar trends observed in CPS 5% or more, and less than 5% subgroups.
The safety analysis revealed no new safety signals. However, Grade 3 or higher treatment-related adverse events were more commonly reported in the combination therapy group compared to the placebo group. Treatment-related adverse events leading to therapy discontinuation were also more frequent in the Cadonilimab group.
It was concluded from this study that Cadonilimab is the first PD-1/CTLA-4 bispecific antibody to demonstrate substantial improvements in Overall Survival and Progression-Free Survival benefit in combination with chemotherapy, offering a potential new standard of care for patients diagnosed with locally advanced unresectable or metastatic gastric or gastroesophageal junction (GEJ) cancer. This study represents a significant milestone in the quest for improved first-line treatments for gastric and GEJ cancers, even for patients with low PD-L1 expression tumors.
Cadonilimab plus chemotherapy versus chemotherapy as first-line treatment for unresectable locally advanced or metastatic gastric or gastroesophageal junction (G/GEJ) adenocarcinoma (COMPASSION-15): A randomized, double-blind, phase 3 trial. Ji J, Shen L, Li Z, et al. Presented at: 2024 AACR Annual Meeting; April 5-10, 2024; San Diego, CA.
