ESMO: Merck's Keytruda-chemo combo spurs big response in new stomach cancer patients across the PD-L1 board

MADRID, Spain—Merck immuno-oncology star Keytruda has posted updated, longer-term positive data in previously untreated stomach cancer patientsand some new data showing it could be effective for some patients much later in therapy, too.

Friday at the European Society of Medical Oncology (ESMO) annual meeting in Madrid, the New Jersey drugmaker presented data from all three cohorts of a phase 2 trial. Two of them, made up of previously untreated patients, build on data the pharma giant rolled out at ASCO, adding three months of additional follow-up that demonstrated “durability of clinical benefit,” a spokesperson said by email.

In PD-L1 patients new to therapy, Keytruda provoked a response rate of 26%but that number went more than twice as high for patients who had chemo added into the mix. About 69% of PD-L1 positive patients receiving a Keytruda-chemo combo responded to the regimen, as did 60% of patients in the overall Keytruda-chemo group.

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The med also posted modest numbers in patients who had already received two or more lines of therapy. Twelve percent of the overall population—not segmented by PD-L1 status—responded to treatment with solo Keytruda, Merck said, with 3% achieving complete responses. Among PD-L1 positive patients, 16% responded.

While the numbers are low, they’re still ones that Merck cheered. Within the cohort, nearly half of patients48%, to be exactwere fourth- or fifth-line patients, and right now, there “is no approved or even a recommended therapy,” according to the company spokesperson.

"In essence, these folks are without options at that point," Merck SVP of global clinical development Roy Baynes said in an interview, adding that "if you look at the response rate, while it is on the low side, it is certainly better than anything that's available, at least in the single-arm experience."

Responses investigators did see where "very durable," too. "This is a group of patients with very short life expectancy ... if that response is of many months' duration, that is clearly a value add to the patient," Baynes said. "Some of these are getting up beyond a year, so it's pretty significant."

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Merck is currently waiting for an FDA decision in stomach cancer after U.S. regulators granted Keytruda their “priority” distinction in May. If approved, Merck will be able to market the med for treatment of gastric or gastroesophageal junction adenocarcinoma patients who have received at least two rounds of chemo; the company will have its verdict by Sept. 22.

Leading rival Opdivo from Bristol-Myers Squibb, meanwhile, has posted its own successes in the gastric cancer space. Last November, partner Ono Pharmaceutical said Opdivo had topped placebo at extending overall survival among chemo-intolerant patients or those who failed to respond to chemo.