ASCO: Merck details Keytruda's second stomach cancer slip

CHICAGO—Last month, Merck revealed that its Keytruda immunotherapy had run into more trouble in stomach cancer, a disease that’s given it difficulty in the past. And it shared the details of that stumble Saturday.

In previously untreated patients with advanced gastric or gastroesophageal junction cancer whose tumors bore biomarker PD-L1, adding Keytruda to chemo failed to improve on chemo alone, both in terms of extending patients’ lives and keeping cancer at bay. And that finding, presented at the American Society of Clinical Oncology annual meeting, held true regardless of patients’ PD-L1 levels.

Merck execs couldn’t explain the flop for Keytruda, which has improved outcomes for patients when added to chemo in other cancers. In lung cancer, for instance, its addition slashed patients’ risk of death by half in a closely watched trial that rolled out last April.

"I think what it highlights is we’re quite early in the total exploration in the place of immuno-oncology therapy, and we continue to learn as we go along," Roy Baynes, M.D., Merck SVP and head of global clinical development, said.

But Scot Ebbinghaus, M.D., vice president of clinical research at Merck Research Laboratories, did characterize the results as a “relatively near miss,” noting the data “were in the right direction, just not quite there” in terms of statistical significance.

RELATED: Merck's Keytruda stumbles again in stomach cancer, this time in new patients

“There was a trend toward improving survival, but it didn’t reach” the threshold, he said.

Meanwhile, though, Keytruda did meet one endpoint in the study, dubbed Keynote-062. It showed it could measure up to chemo when used on its own in PD-L1 expressers. And, in patients with high PD-L1 levels, it recorded a significant survival improvement: 39% of PD-L1-high patients were alive at the two-year mark, versus just 22% of those in the chemo group.

Merck was quick to highlight that success, and Ebbinghaus pointed to Keytruda's potential as a chemo-free option that would help patients avoid the side effects associated with chemotherapy.

RELATED: Merck's Keytruda misses the mark in second-line stomach cancer study

The data build on what’s been a checkered history for Keytruda in gastric cancer. Back in 2017, the superstar drug fell short of its primary endpoint in a second-line study, failing to either keep disease at bay or improve survival for previously treated patients with PD-L1-expressing tumors.

In the wake of that showing, Merck had been looking to Keynote-062 to confirm an accelerated approval it grabbed from the FDA in 2017. That green light cleared it for PD-L1-positive patients who have already received two other therapies. But now, the company will have to turn to other phase 3, frontline studies it has in the works.