Retlirafusp Alfa Extends Survival in First-Line HER2-Negative Gastric Cancer
A dual-checkpoint strategy is moving into the front line for HER2-negative gastric or gastroesophageal junction adenocarcinoma. In the phase III RELIGHT study, retlirafusp alfa combined with CAPOX produced a clear survival gain over chemotherapy alone, with the strongest effect seen in patients whose tumors carried a PD-L1 combined positive score of at least 5.
The regimen paired standard cytotoxic treatment with an anti-PD-L1/transforming growth factor-β bispecific antibody, a design meant to attack two immune escape pathways at once. PD-L1 blockade can release exhausted antitumor T-cell activity, while interference with TGF-β signaling may blunt immune suppression in the tumor microenvironment and reduce the fibrotic, immune-excluding biology that often makes gastric cancers difficult to treat. In a disease where early systemic spread is common and chemotherapy responses are often transient, the mechanism fits the clinical need.
Survival Gains Emerged Across the Full Study Population
RELIGHT enrolled 731 previously untreated patients with unresectable, locally advanced, or metastatic disease and assigned them in a 1:1 ratio to receive retlirafusp alfa or placebo, each given intravenously every 3 weeks with capecitabine and oxaliplatin. The trial was double-blind, and overall survival served as the primary end point in both the PD-L1 CPS ≥5 subgroup and the intention-to-treat population.
The survival curve separated in both prespecified analyses. Among patients with PD-L1 CPS ≥5, median overall survival reached 16.8 months with retlirafusp alfa plus CAPOX versus 10.4 months with placebo plus CAPOX, translating to a stratified hazard ratio of 0.53. In the full intention-to-treat cohort, median overall survival was 15.8 months versus 11.2 months, with a stratified hazard ratio of 0.66. Both comparisons crossed a highly significant threshold, with one-sided P values below .0001.
The magnitude of benefit is difficult to dismiss. A difference of more than six months in median overall survival in the biomarker-positive group is clinically meaningful in a disease setting where treatment lines are often limited by declining performance status, nutritional compromise, and cumulative metastatic burden.
Progression Slowed Before Patients Reached Later Lines of Therapy
Progression-free survival followed the same pattern. In the PD-L1 CPS ≥5 cohort, median progression-free survival was 7.6 months with the bispecific antibody combination and 5.5 months with chemotherapy alone, with a stratified hazard ratio of 0.52. In the intention-to-treat population, median progression-free survival was 7.0 months versus 5.5 months, with a stratified hazard ratio of 0.57.
That earlier disease control matters at the bedside because first-line therapy often determines whether patients remain fit enough for second-line treatment. Gastric and gastroesophageal junction adenocarcinoma can deteriorate quickly once progression begins, especially when primary tumors or peritoneal disease interfere with oral intake, weight maintenance, or organ function. A regimen that slows progression at the start can preserve treatment options later, even before overall survival differences fully mature.
The benefit was not confined to a narrow biomarker subset, although the effect was more pronounced in PD-L1 CPS ≥5 disease. This pattern is biologically plausible. Tumors with measurable PD-L1 expression may be more dependent on immune evasion through the PD-1/PD-L1 axis, while TGF-β inhibition may further open the tumor microenvironment to immune attack. The combination appears designed to work where the immune system is already partially engaged but held in check.
Toxicity Stayed in the Same Range as Chemotherapy Alone
Safety data did not reveal a major penalty for adding retlirafusp alfa. Grade 3 or higher treatment-related adverse events occurred in 62.6% of patients receiving retlirafusp alfa plus CAPOX and in 59.0% of those receiving placebo plus CAPOX. In other words, intensifying the immune component of treatment did not produce a large jump in severe treatment-related toxicity.
That balance is important in first-line gastric cancer, where clinicians are often choosing between efficacy and tolerability in patients who may already be frail, anemic, or undernourished. A regimen can produce a striking survival signal and still fail in practice if the adverse-event burden forces dose reductions, early discontinuation, or hospitalization. RELIGHT did not show that kind of toxicity escalation in the headline safety readout.
The trial’s double-blind structure also strengthens confidence in the efficacy signal. When both investigators and patients remain unaware of assignment, bias from treatment expectations is reduced, and progression and survival assessments carry more weight. The fact that both overall survival and progression-free survival moved in the same direction across both analysis sets adds internal consistency to the findings.
CAPOX Alone as the Comparator Limits Direct Comparison With Current Standards
One caveat shapes how these results should be placed into practice. CAPOX alone served as the control arm because the study protocol was finalized before PD-1 inhibitor plus chemotherapy became the approved standard-of-care regimen in China. As a result, RELIGHT does not directly answer whether retlirafusp alfa should replace or be layered onto contemporary immunotherapy-based first-line regimens.
That limitation is not academic. Clinical decision-making now depends on how a new option performs against the most effective available standard, not against an older benchmark that has already been displaced in many settings. The trial nevertheless establishes that retlirafusp alfa has true activity on top of platinum-based chemotherapy and that the mechanism can translate into a survival advantage without an obvious safety collapse.
For now, the data define retlirafusp alfa plus CAPOX as a credible first-line option for unresectable, locally advanced, or metastatic HER2-negative gastric or gastroesophageal junction adenocarcinoma. The remaining question is where it fits relative to PD-1 inhibitor-based combinations and whether the signal will persist when tested against the modern immunotherapy backbone now used in routine care.