Merck (MRK) said Sunday its immunotherapy drug Keytruda improved by event-free survival by 34% in a phase 3 trial evaluating it as a perioperative treatment for patients with stage III or IVA resected locally advanced head and neck squamous cell carcinoma.

Median event-free survival in the study was 51.8 months to 59.7 months among patients treated with Keytruda in combination with radiotherapy compared 29.6 months to 30.4 months for those treated with radiotherapy alone, the biotech giant said.

Merck said it has a supplemental biologics license application for Keytruda based on the study under priority review with the US Food and Drug Administration with a target action date of June 23.