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Serplulimab Combined With SOX Chemotherapy Improves Event Free Survival in Gastric CancerTrial shows serplulimab improves outcomes for gastric cancer patients

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Key Takeaway
Serplulimab plus SOX chemotherapy significantly improves event-free survival and safety in PD-L1-positive gastric cancer.

This Phase 3 multicenter randomized controlled trial evaluated the efficacy and safety of neoadjuvant serplulimab combined with S-1 and oxaliplatin (SOX) chemotherapy followed by adjuvant serplulimab in patients with PD-L1-positive, locally advanced, resectable gastric or gastro-oesophageal junction adenocarcinoma. The study enrolled 588 participants across sites in China and Thailand, specifically targeting those with a CPS score of at least 5. The primary endpoint was investigator-assessed event-free survival (EFS), which provides a critical metric for assessing the durability of response in this patient population.

The trial compared the serplulimab plus SOX regimen against a control arm receiving placebo plus SOX chemotherapy. In the intention-to-treat population (CPS ≥5), patients receiving serplulimab demonstrated significantly longer event-free survival compared to those receiving the placebo. The hazard ratio was 0.73 (95% CI, 0.56–0.94; p=0.015). Furthermore, in the subset of patients with a higher PD-L1 expression (CPS ≥10), the benefit was even more pronounced, with a hazard ratio of 0.65 (95% CI, 0.47–0.90; p=0.0082) and a median EFS not yet reached in the treatment arm versus 42.0 months in the control group.

Safety profiles were a key secondary outcome for clinical implementation. The data indicated that patients receiving serplulimab experienced fewer grade 3 or higher treatment-related adverse events (47%) than those in the placebo group (59%). Additionally, the rate of treatment-related discontinuations was notably lower in the serplulimab cohort (7% versus 11% for placebo). These findings suggest that the addition of serplulimab may improve the tolerability of the intensive SOX chemotherapy regimen while enhancing clinical outcomes.

The study design provides high internal validity due to its randomized, multicenter nature. The inclusion of both gastric and gastro-oesophageal junction adenocarcinoma ensures broader applicability across common histological presentations in this region. However, because the trial is ongoing, long-term overall survival data remains pending. Clinicians should interpret these results as a strong signal for neoadjuvant and adjuvant serplulimab integration into standard protocols for high-risk patients. In conclusion, the addition of serplulimab to SOX chemotherapy provides a statistically significant improvement in event-free survival for PD-L1-positive gastric cancer. The combination appears manageable from a toxicity standpoint, potentially offering a more tolerable treatment pathway for patients with locally advanced disease. Further follow-up is necessary to confirm overall survival benefits and long-term durability of the response.

How this fits prior evidence

How this fits prior evidence: This study addresses a gap in the management of gastric cancer by evaluating serplulimab as an immunotherapeutic addition to chemotherapy. While previous findings established that serplulimab plus chemotherapy improves overall survival in nsq-NSCLC, this trial specifically targets the gastric and gastro-oesophageal junction adenocarcinoma population. It provides new data on event-free survival and safety profiles for these specific indications.

For people living with advanced gastric cancer or cancers at the junction of the esophagus and stomach, finding effective treatments is a constant priority. These cancers are often difficult to treat, and patients need options that not only work effectively but are also manageable in terms of side effects. This recent study looks at a new approach involving a drug called serplulimab combined with standard chemotherapy.

Researchers conducted a large-scale Phase 3 clinical trial involving 588 patients across multiple hospitals in China and Thailand. The participants had specific types of advanced, resectable stomach cancers that tested positive for a protein called PD-L1. The study was designed to see if adding serplulimab to a standard chemotherapy regimen (known as SOX) would improve outcomes compared to using the chemotherapy alone.

The results showed a significant improvement in event-free survival for patients who received serplulimab along with their chemotherapy. In the group of patients with higher levels of PD-L1, those treated with serplulimab had a much longer period of time without disease progression or death compared to those who received only the standard treatment. Specifically, the study found that adding serplulimab significantly extended the time patients remained free from events. Furthermore, the data suggested that the combination was better tolerated by patients than the chemotherapy alone, with fewer severe side effects and fewer people needing to stop treatment due to complications.

While these results are promising, it is important to keep a few things in mind. This study specifically looked at 'event-free survival,' which means the time patients lived without their cancer getting worse or returning. While this is a very important measure of success, the trial is still ongoing. Because of this, long-term data on 'overall survival'—the total length of time patients live with the disease—is not yet fully established and will require more time to confirm.

For patients today, these findings suggest that serplulimab could become a valuable new tool in the fight against specific types of gastric cancer. It offers a potential way to improve both the effectiveness of treatment and the quality of life during therapy. However, because this is one specific study, doctors will need more time to see how it performs across broader populations before it becomes a standard recommendation for everyone. For now, it represents a significant step forward in targeted cancer care.

What this means for you:
Adding serplulimab to chemotherapy improved survival times and safety for certain types of stomach cancer.

Study Details

Study typeRct
Sample sizen = 292
EvidenceLevel 2
Follow-up840.0 mo
PublishedJun 2026
View Original Abstract ↓
BACKGROUND: Perioperative chemo-immunotherapy shows variable outcomes in resectable gastric or gastro-oesophageal junction adenocarcinoma. We evaluated the efficacy and safety of neoadjuvant serplulimab with S-1 plus oxaliplatin (SOX) chemotherapy followed by adjuvant serplulimab versus neoadjuvant placebo plus SOX followed by adjuvant SOX in patients with PD-L1-positive, locally advanced, resectable gastric or gastro-oesophageal junction adenocarcinoma. METHODS: In this randomised, double-blind, multicentre phase 3 ASTRUM-006 study, patients were screened at 75 hospitals in China and Thailand. Eligible patients aged 18-70 years with PD-L1 combined positive score (CPS) ≥5, resectable gastric or gastro-oesophageal junction adenocarcinoma were randomly assigned 1:1 to neoadjuvant serplulimab or placebo (intravenous; 4·5 mg/kg) plus SOX chemotherapy (intravenous oxaliplatin 130 mg/m on day 1, and oral S1 40-60 mg twice daily on days 1-14) for three cycles (cycle length 21 days), followed by adjuvant serplulimab (up to 17 cycles; serplulimab group) or SOX (five cycles; placebo group). The primary endpoint was investigator-assessed event-free survival (defined as the time from randomisation to the occurrence of progressive disease or local or distant recurrence, other new malignancies, or death), with efficacy first evaluated in PD-L1 CPS ≥10, then in the intention-to-treat (CPS ≥5) population. This study is registered with ClinicalTrials.gov, NCT04139135, and is ongoing. FINDINGS: Between Nov 26, 2019, and April 19, 2024, 1646 patients were screened, of whom 588 patients (median age 61·0 years [IQR 55-66]; 124 [21%] female and 464 [79%] male) at 57 hospitals in China were randomly assigned to the serplulimab group (n=292) or placebo group (n=296). With a median follow-up duration of 42·7 months (IQR 24·3-53·6), median event-free survival was significantly longer with serplulimab than with placebo in the PD-L1 CPS ≥10 population (not reached [NR] vs 42·0 months; hazard ratio 0·65 [95% CI 0·47-0·90]; p=0·0082). With a median follow-up of 35·9 months (IQR 23·5-49·4), median event-free survival was also significantly longer with serplulimab than with placebo in the intention-to-treat population (NR vs 35·9 months; 0·73 [95% CI 0·56-0·94]; p=0·015). Grade 3 or worse treatment-related adverse events occurred in 136 (47%) patients in the serplulimab group and 172 (59%) patients in the placebo group; 19 (7%) and 31 (11%) patients in the respective groups discontinued treatment due to treatment-related adverse events. INTERPRETATION: Neoadjuvant serplulimab plus SOX followed by adjuvant serplulimab significantly improved event-free survival and demonstrated a better safety profile compared with neoadjuvant and adjuvant SOX in PD-L1-positive, resectable gastric or gastro-oesophageal junction adenocarcinoma. Extended follow-up for the overall survival data is warranted to confirm a survival advantage of this perioperative strategy with a chemotherapy-sparing adjuvant component for this indication. FUNDING: Shanghai Henlius Biotech.
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