Objective response rate (per RECIST 1.1 as assessed by blinded independent central review [BICR]) is defined as the number (%) of patients with a confirmed complete response or confirmed partial response and will be based on all treated patients who are PD-L1-positive with measurable disease at baseline per BICR.

Response Evaluation Criteria in Solid Tumors [RECIST] 1.1. criteria are: Complete response [CR] = disappearance of all target lesions since baseline; and partial response [PR] = at least a 30% decrease in the sum of the diameters of target lesions.

Evaluable analysis set - all patients who received at least one dose of study treatment, who had a baseline tumor assessment, and had measurable disease at baseline according to BICR

Best objective response based on BICR assessments according to RECIST v1.1. Response required confirmation after 4 weeks.

Unconfirmed complete (CR) or partial response (PR) refers to CR or PR achieved but either no confirmation assessment was performed or a confirmation assessment was performed but response was not confirmed.

Evaluable analysis set - included all patients who received at least one dose of study treatment who had a baseline tumor assessment and had measurable disease at baseline according to BICR.

Participants remaining in response - based on BICR assessments according to RECIST v1.1.

An ongoing response was defined as a patient who had documented objective response and was still alive and progression-free at the time of the data cut-off.

Evaluable analysis set - included all patients who received at least one dose of study treatment who had a baseline tumor assessment and had measurable disease at baseline according to BICR.

Duration of objective response in patients with objective response based on BICR assessments according to RECIST v1.1.

Duration of response was the time from the first documentation of complete or partial response until the date of progression (which was subsequently confirmed), death, or the last evaluable RECIST assessment for patients that did not progress.

An ongoing response was defined as a patient who had documented objective response and was still alive and progression-free at the time of the data cut-off.

Evaluable analysis set - included all patients who received at least one dose of study treatment who had a baseline tumor assessment and had measurable disease at baseline according to BICR.

Time to onset of response in patients with objective response based on BICR assessments according to RECIST 1.1

Evaluable analysis set - included all patients who received at least one dose of study treatment who had a baseline tumor assessment and had measurable disease at baseline according to BICR.

Disease control (DCR) at 6 months based on BICR assessments according to RECIST v1.1.

DCR at 6 months was evaluated using 2 different approaches to the length of stable disease (SD):

• Method 1: Patients who had a best objective response of complete response (CR) or partial response (PR) within 24 weeks or had demonstrated SD for a minimum interval of 24 weeks following the start of study treatment.
• Method 2: Patients who had a best objective response of CR or PR within 24 weeks or had demonstrated SD for a minimum interval of 16 weeks following the start of study treatment.

Evaluable analysis set - included all patients who received at least one dose of study treatment who had a baseline tumor assessment and had measurable disease at baseline according to BICR.

Progression status based on BICR assessments according to RECIST v1.1 at time of PFS analysis.

Progression was defined as the time from the date of first dose until the date of objective disease progression or death (by any cause in the absence of progression) regardless of whether the patient withdrew from therapy or received another anti-cancer therapy prior to progression.

Full analysis set - included all treated patients who had a baseline tumor assessment and had measurable disease at baseline according to the Investigator site assessment.

Survival status at time of overall survival analysis. 'Still in survival follow-up' includes patients known to be alive at data cut-off. 'Terminated prior to death' includes patients with unknown survival status, or who were lost to follow-up.

Full analysis set - included all treated patients who had a baseline tumor assessment and had measurable disease at baseline according to the Investigator site assessment.

Improvement in quality of life was assessed using European Organisation for Research and Treatment of Cancer (EORTC) questionnaires:

• The impact of treatment on Health-Related Quality of Life, functioning, and symptoms was evaluated using the EORTC QLQ-C30 v3.
• Head and neck cancer-specific symptoms were evaluated using the EORTC QLQ-H&N35.

Function or global health status/quality of life improvement was defined as patients with 2 consecutive assessments at least 14 days apart that showed a clinically meaningful improvement (an increase from baseline score ≥10). Symptom improvement was defined as 2 consecutive assessments at least 14 days apart that showed a clinically meaningful improvement (a decrease from baseline score ≥10).

Scale improvement was defined as patients with 2 consecutive assessments at least 14 days apart that showed a clinically meaningful improvement (a decrease from baseline score ≥10).

Full analysis set - included all treated patients who had a baseline tumor assessment and had measurable disease at baseline according to the Investigator site assessment.