Combo Therapy Prolongs Survival in Gastric Cancer Patients

SAN DIEGO — First-line treatment with a combination of cadonilimab, a PD-1/CTLA-4 bispecific immune checkpoint inhibitor, and standard chemotherapy provides a survival advantage over placebo plus chemotherapy in patients with locally advanced or metastatic gastric or gastroesophageal junction (G/GEJ) adenocarcinoma,, according to a new study.

Jiafu Ji, MD, PhD, presented this and other findings of the randomized, double-blind, placebo-controlled phase 3 COMPASSION-15 trial at the annual meeting of the American Association for Cancer Research (AACR).

“The consistent survival benefits across all prespecified PD-L1 expression cutoffs, particularly in patients with low PD-L1 expression, have significant implications for clinical practice by expanding treatment options, improving outcomes for patients with PD-L1–low tumors, influencing guidelines, and stimulating further research in advanced G/GEJ adenocarcinoma treatment,” said Dr. Ji, a principal investigator of this trial, in an interview.

Unmet Need

The incidence of gastric cancer is particularly high in China, but as Dr. Ji discussed in his talk, the treatment options for patients with advanced disease remain limited. Although the Food and Drug Administration (FDA) has approved the combination of PD-L1 inhibitors with chemotherapy for the first-line treatment of advanced gastric cancer, not all patients respond to the treatment, explained Dr. Ji, who is a professor of gastrointestinal surgery and president of Peking University Cancer Hospital and Beijing Institute for Cancer Research in China.

He added that the combination of PD-L1 inhibitors and chemotherapy has not yet been approved for the treatment of advanced gastric cancer in China, leaving chemotherapy as the only treatment option for Chinese patients.

Study Design

To evaluate the efficacy and safety of first-line cadonilimab plus standard chemotherapy in patients with advanced or metastatic gastric cancer, the authors of the COMPASSION-15 trial enrolled 610 patients with unresectable, locally advanced, or metastatic G/GEJ adenocarcinoma who had not received any prior treatments. PD-L1 expression status was not used to exclude patients from the trial.

In a press conference held at AACR 2024, Dr. Ji explained the study rationale, design, and endpoints. He said that patients with tumors without PD-L1 expression typically show little to no benefit from anti–PD-1/PD-L1 inhibitors, and their treatment options are limited to chemotherapy.

“Testing the efficacy of this bispecific antibody in this patient population could provide an alternative treatment approach for them,” he added.

Patients were randomized 1:1 to receive either cadonilimab (10 mg/kg every 3 weeks) plus chemotherapy or placebo plus chemotherapy. The primary endpoint of the study was overall survival (OS) in the intent-to-treat (ITT) population, and secondary efficacy endpoints included OS, progression-free survival (PFS), and objective response rate (ORR) in the ITT population, as well as in patients stratified by PD-L1 expression.

Cadonilimab Plus Standard Chemotherapy Improves OS

Interim analysis, conducted with a median follow-up of 18.69 months, showed a significant improvement in OS for the cadonilimab plus chemotherapy group compared with the chemotherapy-alone group, according to data presented at the press conference. The median OS was 15.0 months in the cadonilimab group versus 10.8 months in the placebo group, representing a 38% reduction in the risk of death (hazard ratio [HR], 0.62; 95% CI, 0.50-0.78, P <.001>

Yelena Y. Janjigian, MD, who not involved in COMPASSION-15, provided critique of the study, during another session at the meeting, in which she discussed the CheckMate 649 trial. She noted that, although the median OS of 15 months in the COMPASSION-15 study was slightly higher than the OS in the CheckMate 649 trial (approximately 14 months), comparing the results of two studies is challenging.

“In the COMPASSION-15 trial, chemotherapy was stopped after [4.5 months], and only 50% of patients received chemotherapy with subsequent treatment — this is not standard and may limit the comparison with other immunotherapy trials,” explained Dr. Janjigian, who is a gastrointestinal oncologist and was a principal investigator in the phase 3 CheckMate 649 immunotherapy trial for advanced gastric cancer.

Importantly, survival benefit with cadonilimab plus chemotherapy was observed across all prespecified PD-L1 expression levels, including in patients with low PD-L1 expression (PD-L1 combined positive score [CPS] less than 5%). In the low PD-L1 expression group (CPS less than 5%), the median OS was 14.8 months in the cadonilimab group compared with 11.8 months in the placebo group (HR, 0.70; 95% CI, 0.51-0.95; P=.011).

“These positive survival outcomes when cadonilimab was combined with chemotherapy may be attributed to synergistic mechanisms of action, enhanced immune responses, modulation of the tumor microenvironment, and careful patient selection based on biomarker assessments,” noted Dr. Ji, during an interview. “Targeting multiple pathways using bispecific antibodies provides potential synergistic effects, enhancing anti-tumor activity and improving treatment outcomes.”

Cadonilimab Plus Standard Chemotherapy Reduces the Risk of Tumor Progression

In addition to prolonging OS, cadonilimab plus chemotherapy also provided superior PFS and ORR compared to placebo plus chemotherapy.

The median PFS was 7.0 months in the cadonilimab plus chemotherapy group, versus 5.3 months in the chemotherapy-only group (HR, 0.53; 95% CI, 0.44-0.65, P <.001 and the orr was versus respectively. furthermore duration of response longer with cadonilimab plus chemotherapy than placebo months respectively>

Toxicities Associated With Cadonilimab Plus Standard Chemotherapy Are Manageable

The safety profile of the cadonilimab plus chemotherapy regimen was manageable, with grade 3 or higher treatment-related adverse events occurring in 71.8% of patients in the cadonilimab group and 60.5% of patients in the placebo group. No new safety signals were observed.

During an interview, Dr. Ji said that the most common adverse events were endocrine toxicity, skin toxicity, and lung toxicity. “These adverse events were managed through close monitoring, symptom management, and appropriate interventions based on the severity and nature of the toxicity experienced by patients,” he explained. He added that this toxicity profile of cadonilimab is similar to the toxicity profiles of approved PD-1 and CTLA-4 inhibitors.

Implications — A New Treatment Paradigm for Advanced Gastric Cancer?

According to Dr. Ji, the interim results from the cadonilimab study suggest that this novel PD-1/CTLA-4 bispecific antibody, in combination with chemotherapy, could become a new standard first-line treatment option for patients with advanced G/GEJ adenocarcinoma, offering a significant survival advantage over chemotherapy alone, regardless of PD-L1 status.

“The ability of cadonilimab to improve survival outcomes, regardless of PD-L1 status, is a significant advancement, as we have struggled to find effective treatments for patients with low PD-L1 expression in this setting,” he said, during the interview.

Despite these promising findings, Dr. Janjigian highlighted that patient stratification in the COMPASSION-15 study is currently lacking. She explained that biomarkers such as MSI status, T-reg signatures, and HER-2 are important to consider according to data from the CheckMate 649 trial.

“Hazard ratios for patients with T-reg–high tumors were almost 0.6, independent of inflammatory status. These data suggest that we can maybe even cure some patients with PD-1/CTLA-4 inhibitors,” she noted.

She added that knowing the status of MSI and HER-2 is clinically important as it can inform clinicians whether they can avoid chemotherapy or add trastuzumab.

“Despite the suboptimal comparator arm, the study is very important and offers a rationale for dual PD-1/CTLA-4 blockade,” Dr. Janjigian concluded.

COMPASSION-15 was funded by Akeso Biopharma, Inc. Dr. Ji reported no relationships with entities whose primary business is producing, marketing, selling, reselling, or distributing healthcare products used by or on patients. Dr. Janjigian lists relationships with AbbVie, AmerisourceBergen Drug Corporation, Arcus Biosciences, Ask-Gene Pharma, Inc., Astellas Pharma, AstraZeneca, Basilea Pharmaceutica Ltd., Bayer, Bristol Myers, Squibb, Eli Lilly and Company, GlaxoSmithKline, Merck, Pfizer, and many other companies, as well as the U.S. Department of Defense, National Cancer Institute, and others.

This article originally appeared on MDedge.com, part of the Medscape Professional Network.

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