When Dr. David R. Gandara presented the ASTRIDE results at ESMO 2026, the figure that drew the most attention was not the median survival but a number that matched an earlier trial: 32% of patients alive at two years, identical to ASTRUM-005.
Extensive-stage small cell lung cancer remains one of the most aggressive thoracic malignancies, and despite the arrival of immunotherapy, durable survival is still difficult to achieve for many patients.
That is why long-term survival signals matter so much in this disease – and why questions of reproducibility matter just as much as efficacy.
The ASTRUM-005 trial had already shown a survival benefit with serplulimab plus chemotherapy in the first-line setting, leading to approvals in multiple countries. But because the study enrolled a predominantly Asian population, U.S. regulators wanted evidence that the results would hold in American patients.
That question led to the development of the ASTRIDE study, presented at ESMO 2026 by Dr. David R. Gandara, Professor Emeritus at the University of California Davis Comprehensive Cancer Center and lead principal investigator of the trial.
Rather than repeat ASTRUM-005, investigators compared serplulimab plus chemotherapy with atezolizumab plus chemotherapy, an established U.S. first-line regimen, to see whether the earlier serplulimab results could be reproduced in a U.S. population.
Why ASTRIDE Was Needed
For Dr. Gandara, the rationale begins with a familiar regulatory issue.
Trials conducted largely outside the United States may generate compelling data, but the FDA can still ask whether the patients treated adequately represent the U.S. population, and therefore whether the same results would have been observed in US patients. In some cases, that means repeating a study. In ASTRIDE, however, the agency allowed a different strategy.
“The FDA said you could do a bridging trial which would show consistency of the data with the prior ASTRUM trial. And that’s what we did.”
ASTRIDE enrolled 201 patients across 63 centers in the United States, with overall survival as the primary endpoint.
The median overall survival was 12.4 months with serplulimab plus chemotherapy, and 10.2 months with atezolizumab plus chemotherapy.
The long-term survival figures drew even more attention.
At two years, around 32% of patients in the serplulimab arm were alive, compared with 18% in the atezolizumab arm.
The 2-year survival data were especially important because ASTRIDE was intended to test whether the earlier signal could be reproduced in U.S. patients.
“These results, 32% of patients being alive at two years in ASTRIDE, are identical with the results in the ASTRUM trial. It was 32% in both of those trials. So I think that tells us that we have consistency of data.”
The atezolizumab arm, importantly, did not underperform. Dr. Gandara said its results were in line with what would be expected from the regimen, while serplulimab continued to show the durable survival signal previously observed.
That makes ASTRIDE less a replacement for ASTRUM-005 than an effort to determine whether its findings could be reproduced in a U.S. population.
A Descriptive Bridging Trial Comparing with Atezolizumab
ASTRIDE is notable because it is the first randomized study to evaluate two immunotherapy-based first-line regimens in a population with extensive-stage small cell lung cancer representative of routine U.S. clinical practice.
That makes the numerical differences between the two arms easy to focus on.
Dr. Gandara, however, was careful about what those numbers can and cannot establish.
“The study was not designed to show that serplulimab was superior or non-inferior. It was designed to show the consistency of the data with the previous ASTRUM-005 trial, and that’s what it did.”
That distinction is important to the way the results should be read.
A superiority trial is built statistically to determine whether one treatment is better than another.
A non-inferiority trial asks whether a new treatment performs no worse than an established standard within a predefined margin.
ASTRIDE did neither.
It was a descriptive bridging study.
The 12-versus-10-month median overall survival and the separation in two-year survival are therefore clinically interesting, but they should not be presented as proof that serplulimab is superior to atezolizumab.
Dr. Gandara’s interpretation was deliberately narrower.
Serplulimab performed very well. Atezolizumab behaved as expected. And, within the limits of the study design, the U.S. data were consistent with the earlier ASTRUM-005 experience.
“Serplulimab is at least equivalent from what we can see in this descriptive study. And some of the long-term data, like the two-year overall survival, suggest that this is clearly a regimen that deserves to be approved worldwide.”
For a trial built primarily to test reproducibility, that is the central result.
What the Two Trials Mean Together
ASTRUM-005 demonstrated an overall survival benefit of serplulimab plus chemotherapy in an international first-line ES-SCLC population and supported approvals across dozens of countries.
ASTRIDE then asked whether those findings held when the regimen was tested in the United States against an active immunotherapy-based comparator.
The answer, in Dr. Gandara’s view, is yes.
“It brings confidence to both patients and to oncologists around the world that the data have now been reproduced in a bridging study in the United States.”
For countries where serplulimab is already available, he sees ASTRIDE largely as confirmatory.
For the United States, the implications are more immediate. The trial adds U.S.-specific clinical evidence to the broader serplulimab data set and places serplulimab alongside a familiar first-line regimen in a population treated across American centers.
Dr. Gandara was clear about what he hopes comes next: regulatory approval that would make serplulimab another first-line option for U.S. patients with extensive-stage disease.
The Next Question May Be Tarlatamab
ASTRIDE answers one question about serplulimab, but the first-line treatment landscape in small cell lung cancer is already moving again.
At ESMO 2026, Dr. Gandara pointed in particular to tarlatamab, another therapy generating considerable interest in small cell lung cancer and now likely moving into first-line treatment strategies.
That raises a different question.
If tarlatamab becomes part of first-line care, where does serplulimab fit?
“(Additional) Studies will need to be done, combining serplulimab with this new drug, tarlatamab.”
The goal is to understand the combination before treatment standards shift again.
“That way, if tarlatamab becomes the standard of care in the first line, investigators and patients will already know how it fits with serplulimab, and we anticipate it will fit very well.”
The next chapter may be less about choosing between regimens and more about how they can be combined.
