Merck’s Keytruda may just be on its way to earlier use in head and neck cancer, an area where it once faced some questions.

On Wednesday, the New Jersey drugmaker said that in a phase 3 trial in previously untreated patients, Keytruda topped a standard-of-care regimen that includes Eli Lilly’s Erbitux at extending overall survival in patients with tumors expressing a certain level of biomarker PD-L1. 

The data came from an interim analysis of the trial that also showed Keytruda hadn’t yet met the study’s other primary endpoint, which measures time to cancer progression. But overall survival is often considered the gold standard in cancer trials, and Merck will be taking the win in that department to regulators worldwide.

Right now, Keytruda bears an approval in head and neck cancer but only in patients whose disease has worsened on or after chemo. And after snagging that conditional approval, last July it failed to prove that it could extend the lives of patients in that group.

As analysts pointed out at the time, though, that miss was narrow, coming just shy of statistical significance. The FDA kept the approval in place, and now, Merck has the data to back it up.

If Merck can win a new indication from the FDA, it could gain access to a patient pool that grows by about 63,000 U.S. cases per year. And that's a group Keytruda's rival, Bristol-Myers Squibb’s Opdivo, can't currently treat: Its approval only extends to previously treated patients, at least for now.

Merck isn’t just going the monotherapy route in head and neck cancer, though. The latest results come from a trial dubbed Keynote-048, a study that’s also examining Keytruda as part of a cocktail containing platinum chemo and chemo drug 5-fluorouracil.

The latest win builds on what’s already been a big summer for the immuno-oncology blockbuster. In June, it nabbed approvals on back-to-back days in cervical cancer and a rare type of non-Hodgkin lymphoma.