Merck has unveiled a Phase III data package backing Keytruda’s case as a second-line treatment for the tough indications of esophageal and esophagogastric junction carcinoma, underscoring its earlier confidence that the PD-1 inhibitor represents a significant advance in this field despite only hitting one of three primary endpoints.
The key number the company wants to focus on is 31% — the degree by which Keytruda reduced the risk of death compared to chemotherapy in patients with squamous cell carcinoma or adenocarcinoma, who had progressed after standard therapy and whose tumors expressed PD-L1 (as quantified by a combined positive score, or CPS, of 10 or above).
That subgroup, which constitutes 222 out of 628 total patients in the KEYNOTE-181 study, reached a median OS of 9.3 months versus 6.7 months for the chemo group. They also had a 12-month OS rate of 43% while the chemo arm experienced 20%.
These are patients whose cancer — in the esophagus or the esophagogastric junction — progressed after initial treatment, following a poor prognosis to begin with, researchers added.
For the entire intention-to-treat population, though, the difference in OS between two arms was not statistically significant with a median OS of 7.1 months for both treatment groups. Same goes for the other subgroup analyzed for the study — the 401 patients with squamous cell carcinoma — with the Keytruda group seeing a median OS of 8.2 months compared to 7.1 months in those receiving chemo.
These failures kept investigators from formally testing the secondary endpoints, meaning that we won’t know the progression-free survival and objective response rate.
Meanwhile, a separate Phase III study — dubbed KEYNOTE-590 — is putting the blockbuster checkpoint inhibitor to first-line use in combination with chemotherapy for patients with esophageal carcinoma.
Rivals are lining up their own shots at esophageal and esophagogastric cancers, with late-stage offerings from chief rival Bristol-Myers Squibb. Celgene and BeiGene, which were slated to notch the 7th PD-1 approval in the US, were also in the game, though the program’s fate remains unclear as Bristol-Myers completes its $74 billion acquisition of Celgene.
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