OS was defined as the time from randomization to the date of death due to any cause.

FAS included all randomized participants.

PFS as assessed by blinded IRC per RECIST 1.1 was defined as the time from randomization to the date of the first documented tumor progression, or death due to any cause, whichever occurred earlier.

FAS included all randomized participants.

ORR was defined as the percentage of participants with a best overall response (BOR) of confirmed complete response (CR) or partial response (PR) as assessed by IRC per RECIST 1.1.

FAS included all randomized participants.

BOR was defined as the best overall response as determined by the IRC per RECIST 1.1, between the date of randomization and the date of first documented tumor progression or the date of subsequent anti-cancer therapy, whichever occurred earlier.

FAS included all randomized participants.

DoR was defined as the time from date of first documented response of CR or PR to the date of first documented PD (per RECIST 1.1) or death due to any cause, whichever occurred earlier.

FAS included all randomized participants. Participants with confirmed CR or PR only are reported here.

The EORTC QLQ-C30 is a 30-item questionnaire used to assess the overall QoL in cancer participants. It consists of 15 domains: 1 Global Health Status (GHS)/QoL scale, 5 functional scales (physical, role, cognitive, emotional, social), 9 symptom scales/items (fatigue, nausea and vomiting, pain, dyspnea, sleep disturbance, appetite loss, constipation, diarrhea, financial impact). Reported here are the EORTC QLQ-C30 GHS/QoL scores only. GHS/QoL is derived from two items: "How would you rate your overall health during the past week?" and "How would you rate your overall quality of life during the past week?" Each scored from 1 (very poor) to 7 (excellent). The average of these two items is linearly transformed to a score ranging from 0 to 100; higher scores indicate better overall quality of life, and a positive change from baseline reflects improvement.

FAS included all randomized participants. Overall number of participants analysed = participants evaluable for the outcome measure. Number analyzed = participants evaluable at the specified timepoint.

EORTC QLQ-LC13 is a 13-item questionnaire used in clinical research to assess health-related quality of life in lung cancer patients. The QLQ-LC13 includes questions assessing lung cancer-associated symptoms (coughing, haemoptysis, dyspnoea and site-specific pain), treatment-related side effects (sore mouth, dysphagia, peripheral neuropathy and alopecia). Reported here are the EORTC lung cancer coughing scores only. Scores were calculated and transformed to a range from 0 to 100, with a higher score representing a higher level of symptoms/problems and a negative change from baseline value indicating reduction (i.e. improvement) in symptoms.

FAS included all randomized participants. Overall number of participants analysed = participants evaluable for the outcome measure. Number analyzed = participants evaluable at the specified timepoint.

TEAEs were AEs that developed or worsened during the on-treatment period and any treatment-related AEs that occurred during the post-treatment period but prior to start of another anti-cancer systemic therapy. A summary of all Serious Adverse Events and Other Adverse Events (nonserious) regardless of causality is located in the 'Reported Adverse Events' Section.

The Safety Analysis Set (SAF) included all randomized participants who received any study drug.

Serious TEAEs were defined as medically significant but not immediately life-threatening AEs that developed or worsened during the on-treatment period and any treatment-related AEs that occurred during the post-treatment period but prior to start of another anti-cancer systemic therapy.

SAF included all randomized participants who received any study drug.

The on-treatment period was defined as the day from the first dose of study drug to the day of the last dose of study drug plus 90 days or 1 day before participants receive their first dose of new anti-cancer systemic therapy, whichever is earlier.

SAF included all randomized participants who received any study drug.

Reported here is the number of participants with at least one laboratory abnormality of any grade in measurements for hematology, electrolytes, liver function, chemistry, and coagulation.

SAF included all randomized participants who received any study drug. "Overall number of participants analyzed" includes all participants evaluable for this outcome measure, and "number analyzed" is the number of participants with at least one post-baseline value for that parameter.

The pharmacokinetic analysis set (PKAS) included all randomized participants (SAF) who received cemiplimab and who had at least 1 non-missing cemiplimab concentration following the first dose of cemiplimab up to the end of the study.

The PKAS included all randomized participants (SAF) who received cemiplimab and who had at least 1 non-missing cemiplimab concentration following the first dose of cemiplimab up to the end of the study.

The ADA status of each participant was classified as one of the following:

• Pre-existing - If the baseline sample is positive and all post baseline ADA titers are reported as less than 9-fold the baseline titer value
• Negative - If all samples are found to be negative in the ADA assay
• Treatment-emergent response

The ADA analysis set (AAS) included all participants who received any cemiplimab and who had at least 1 post-dose ADA result.

The NAb status of each participant was categorized as follows:

• Negative - Samples that tested negative in the ADA assay, or samples positive in the ADA assay but tested negative in the NAb assay
• Positive

The NAb analysis set included all treated participants from the AAS who received any amount of study drug, with at least one non-missing NAb result (either assigned or assessed) following the first dose of study drug.