40 mg/m^2 IV (may be escalated to 60 mg/m^2 maximum dose) on Days 1, 8, and 15 of each 3-week cycle

75 mg/m^2 IV on Day 1 of each 3- week cycle

400 mg/m^2 IV loading dose on Day 1 and 250 mg/m^2 IV on Days 8 and 15 of Cycle 1, followed by 250 mg/m^2 on Days 1, 8, and 15 of each subsequent 3-week cycle.

PFS was defined as the time from randomization to the first documented disease progression per RECIST 1.1 based on blinded central imaging vendor review or death due to any cause, whichever occurred first. Per RECIST 1.1, progressive disease was defined as at least a 20% increase in the sum of diameters of target lesions. In addition to the relative increase of 20%, the sum must also have demonstrated an absolute increase of at least 5 mm. Note: The appearance of one or more new lesions was also considered progression. The PFS per RECIST 1.1 for all participants is presented. These efficacy results were reported after complete acquisition of all outstanding survival data using a 15-May-2017 data cut-off date with a database update date of 13-Oct-2017.

PFS was defined as the time from randomization to the first documented disease progression per RECIST 1.1 based on blinded central imaging vendor review or death due to any cause, whichever occurred first. Per RECIST 1.1, progressive disease was defined as at least a 20% increase in the sum of diameters of target lesions. In addition to the relative increase of 20%, the sum must also have demonstrated an absolute increase of at least 5 mm. Note: The appearance of one or more new lesions was also considered progression. The PFS per RECIST 1.1 for all participants with PD-L1 expression ≥1% CPS is presented. These efficacy results were reported after complete acquisition of all outstanding survival data using a 15-May-2017 data cut-off date with a database update date of 13-Oct-2017.

ORR was defined as the percentage of the participants in the analysis population who had a Complete Response (CR: Disappearance of all target lesions) or a Partial Response (PR: At least a 30% decrease in the sum of diameters of target lesions) per RECIST 1.1 based on blinded central imaging vendor review with or without confirmation. The ORR per RECIST 1.1 for all participants is presented. These efficacy results were reported after complete acquisition of all outstanding survival data using a 15-May-2017 data cut-off date with a database update date of 13-Oct-2017.

ORR was defined as the percentage of the participants in the analysis population who had a Complete Response (CR: Disappearance of all target lesions) or a Partial Response (PR: At least a 30% decrease in the sum of diameters of target lesions per RECIST 1.1 based on blinded central imaging vendor review with or without confirmation. The ORR per RECIST 1.1 for all participants with PD-L1 expression ≥1% CPS is presented. These efficacy results were reported after complete acquisition of all outstanding survival data using a 15-May-2017 data cut-off date with a database update date of 13-Oct-2017.

For participants who demonstrated a confirmed CR or PR per RECIST 1.1, DOR was defined as the time from first documented evidence of a confirmed CR or PR per RECIST 1.1 until disease progression per RECIST 1.1 or death due to any cause, whichever occurred first. Per RECIST 1.1, progressive disease was defined as at least a 20% increase in the sum of diameters of target lesions. In addition to the relative increase of 20%, the sum must also have demonstrated an absolute increase of at least 5 mm. Note: The appearance of one or more new lesions was also considered progression. DOR assessments were based on blinded central imaging vendor review with confirmation. The DOR per RECIST 1.1 for all participants who experienced a confirmed CR or PR is presented. These efficacy results were reported after complete acquisition of all outstanding survival data using a 15-May-2017 data cut-off date with a database update date of 13-Oct-2017.

For participants who demonstrated a confirmed CR or PR per RECIST 1.1, DOR was defined as the time from first documented evidence of a confirmed CR or PR per RECIST 1.1 until disease progression per RECIST 1.1 or death due to any cause, whichever occurred first. Per RECIST 1.1, progressive disease was defined as at least a 20% increase in the sum of diameters of target lesions. In addition to the relative increase of 20%, the sum must also have demonstrated an absolute increase of at least 5 mm. Note: The appearance of one or more new lesions was also considered progression. DOR assessments were based on blinded central imaging vendor review with confirmation. The DOR per RECIST 1.1 for all participants with PD-L1 ≥1% CPS who experienced a confirmed CR or PR is presented. These efficacy results were reported after complete acquisition of all outstanding survival data using a 15-May-2017 data cut-off date with a database update date of 13-Oct-2017.

TTP was defined as the time from randomization to the first documented disease progression based on assessments by the blinded central imaging vendor review per RECIST 1.1. Per RECIST 1.1, progressive disease was defined as at least a 20% increase in the sum of diameters of target lesions. In addition to the relative increase of 20%, the sum must also have demonstrated an absolute increase of at least 5 mm. Note: The appearance of one or more new lesions was also considered progression. The TTP per RECIST 1.1 for all participants is presented. These efficacy results were reported after complete acquisition of all outstanding survival data using a 15-May-2017 data cut-off date with a database update date of 13-Oct-2017.

TTP was defined as the time from randomization to the first documented disease progression based on assessments by the blinded central imaging vendor review per RECIST 1.1. Per RECIST 1.1, progressive disease was defined as at least a 20% increase in the sum of diameters of target lesions. In addition to the relative increase of 20%, the sum must also have demonstrated an absolute increase of at least 5 mm. Note: The appearance of one or more new lesions was also considered progression. The TTP per RECIST 1.1 for all participants with PD-L1 ≥1% CPS is presented. These efficacy results were reported after complete acquisition of all outstanding survival data using a 15-May-2017 data cut-off date with a database update date of 13-Oct-2017.

PFS was defined as the time from randomization to the first documented progressive disease (PD) per RECIST 1.1 based on blinded central imaging vendor review or death due to any cause, whichever occurred first. Per RECIST 1.1, PD was defined as ≥20% increase in the sum of diameters of target lesions. In addition to the relative increase of 20%, the sum must also have demonstrated an absolute increase of ≥5 mm. Note: The appearance of one or more new lesions was also considered PD. Modified RECIST is similar to RECIST 1.1 with the exception that a confirmation assessment of PD (>4 weeks after the initial PD) is required for participants who remain on treatment following a documented PD per RECIST 1.1. The PFS per modified RECIST for all participants is presented. These efficacy results were reported after complete acquisition of all outstanding survival data using a 15-May-2017 data cut-off date with a database update date of 13-Oct-2017.

PFS was defined as the time from randomization to the first documented progressive disease (PD) per RECIST 1.1 based on blinded central imaging vendor review or death due to any cause, whichever occurred first. Per RECIST 1.1, PD was defined as ≥20% increase in the sum of diameters of target lesions. In addition to the relative increase of 20%, the sum must also have demonstrated an absolute increase of ≥5 mm. Note: The appearance of one or more new lesions was also considered PD. Modified RECIST is similar to RECIST 1.1 with the exception that a confirmation assessment of PD (>4 weeks after the initial PD) is required for participants who remain on treatment following a documented PD per RECIST 1.1. The PFS per modified RECIST for all participants with PD-L1 ≥1% CPS is presented. These efficacy results were reported after complete acquisition of all outstanding survival data using a 15-May-2017 data cut-off date with a database update date of 13-Oct-2017.

An AE was defined as any untoward medical occurrence in a participant administered a study treatment and which does not necessarily have to have a causal relationship with this treatment. An AE can therefore be any unfavorable and unintended sign, symptom, or disease temporally associated with the use of a medicinal product or protocol-specified procedure, whether or not considered related to the study treatment or protocol-specified procedure. Any worsening (i.e., any clinically significant adverse change in frequency and/or intensity) of a pre-existing condition that is temporally associated with the use of study treatment, is also an AE. The number of all participants who experienced at least one AE is presented.

An AE was defined as any untoward medical occurrence in a participant administered a study treatment and which does not necessarily have to have a causal relationship with this treatment. An AE can therefore be any unfavorable and unintended sign, symptom, or disease temporally associated with the use of a medicinal product or protocol-specified procedure, whether or not considered related to the study treatment or protocol-specified procedure. Any worsening (i.e., any clinically significant adverse change in frequency and/or intensity) of a pre-existing condition that is temporally associated with the use of study treatment, is also an AE. The number of all participants with PD-L1 ≥1% CPS who experienced at least one AE is presented.

An AE was defined as any untoward medical occurrence in a participant administered a study treatment and which does not necessarily have to have a causal relationship with this treatment. An AE can therefore be any unfavorable and unintended sign, symptom, or disease temporally associated with the use of a medicinal product or protocol-specified procedure, whether or not considered related to the study treatment or protocol-specified procedure. Any worsening (i.e., any clinically significant adverse change in frequency and/or intensity) of a pre-existing condition that is temporally associated with the use of study treatment, is also an AE. The number of all participants who discontinued study treatment due to an AE is presented.

An AE was defined as any untoward medical occurrence in a participant administered a study treatment and which does not necessarily have to have a causal relationship with this treatment. An AE can therefore be any unfavorable and unintended sign, symptom, or disease temporally associated with the use of a medicinal product or protocol-specified procedure, whether or not considered related to the study treatment or protocol-specified procedure. Any worsening (i.e., any clinically significant adverse change in frequency and/or intensity) of a pre-existing condition that is temporally associated with the use of study treatment, is also an AE. The number of all participants with PD-L1 ≥1% CPS who discontinued study treatment due to an AE is presented.

Participants received standard treatment of either methotrexate 40 mg/m^2 IV (could be escalated to 60 mg/m^2 maximum dose) on Days 1, 8, and 15 of each 3-week cycle; or docetaxel 75 mg/m^2 IV on Day 1 of each 3- week cycle; or cetuximab 400 mg/m^2 IV loading dose on Day 1 and 250 mg/m^2 IV on Days 8 and 15 of Cycle 1, followed by cetuximab 250 mg/m^2 on Days 1, 8, and 15 of each subsequent 3-week cycle.

Total of all reporting groups

The race of participants is presented.

Participants were assessed for their PD-L1 tumor expression level by immunohistochemistry assay using tumor tissue from a newly obtained biopsy. Participants with a TPS ≥50% were classified as PD-L1 strongly positive and participants with a TPS <50% were classified as not strongly positive.

Participants were assessed for ECOG PS: Grade 0: Fully active, able to carry on all pre-disease performance without restriction; Grade 1: Restricted in physically strenuous activity but ambulatory & able to carry out work of a light or sedentary nature; Grade 2: Ambulatory & capable of all selfcare but unable to carry out any work activities, up & about more than 50% of waking hours; Grade 3: Capable of only limited selfcare, confined to bed or chair more than 50% of waking hours; Grade 4: Completely disabled, cannot carry on any selfcare, totally confined to bed or chair or Grade 5: Dead.

Participants were assessed for the presence or absence of HPV in their tumors.

Participants were assessed for their PD-L1 tumor expression level by immunohistochemistry assay using tumor tissue from a newly obtained biopsy. Participants with a CPS ≥1 were classified as PD-L1 positive and participants with a CPS <1 were classified as PD-L1 negative.

Participants received standard treatment of either methotrexate 40 mg/m^2 IV (could be escalated to 60 mg/m^2 maximum dose) on Days 1, 8, and 15 of each 3-week cycle; or docetaxel 75 mg/m^2 IV on Day 1 of each 3- week cycle; or cetuximab 400 mg/m^2 IV loading dose on Day 1 and 250 mg/m^2 IV on Days 8 and 15 of Cycle 1, followed by cetuximab 250 mg/m^2 on Days 1, 8, and 15 of each subsequent 3-week cycle.

OS was defined as the time from randomization to death due to any cause. Participants without documented death at the time of the final analysis were to be censored at the date of the last follow-up. The updated OS for all participants is presented. These OS results were reported after complete acquisition of all outstanding survival data using a 15-May-2017 data cut-off date with a database update date of 13-Oct-2017.

The efficacy population consisted of all randomized participants. Participants are included in the treatment group to which they were randomized.

OS was defined as the time from randomization to death due to any cause. Participants without documented death at the time of the final analysis were censored at the date of the last follow-up. The OS for all participants with PD-L1 expression ≥1% CPS was presented. These efficacy results were reported after complete acquisition of all outstanding survival data using a 15-May-2017 data cut-off date with a database update date of 13-Oct-2017.

The efficacy population consisted of all randomized participants with PD-L1 ≥1% CPS. Participants are included in the treatment group to which they were randomized.

PFS was defined as the time from randomization to the first documented disease progression per RECIST 1.1 based on blinded central imaging vendor review or death due to any cause, whichever occurred first. Per RECIST 1.1, progressive disease was defined as at least a 20% increase in the sum of diameters of target lesions. In addition to the relative increase of 20%, the sum must also have demonstrated an absolute increase of at least 5 mm. Note: The appearance of one or more new lesions was also considered progression. The PFS per RECIST 1.1 for all participants is presented. These efficacy results were reported after complete acquisition of all outstanding survival data using a 15-May-2017 data cut-off date with a database update date of 13-Oct-2017.

The efficacy population consisted of all randomized participants. Participants are included in the treatment group to which they were randomized.

PFS was defined as the time from randomization to the first documented disease progression per RECIST 1.1 based on blinded central imaging vendor review or death due to any cause, whichever occurred first. Per RECIST 1.1, progressive disease was defined as at least a 20% increase in the sum of diameters of target lesions. In addition to the relative increase of 20%, the sum must also have demonstrated an absolute increase of at least 5 mm. Note: The appearance of one or more new lesions was also considered progression. The PFS per RECIST 1.1 for all participants with PD-L1 expression ≥1% CPS is presented. These efficacy results were reported after complete acquisition of all outstanding survival data using a 15-May-2017 data cut-off date with a database update date of 13-Oct-2017.

The efficacy population consisted of all randomized participants with PD-L1 ≥1% CPS. Participants are included in the treatment group to which they were randomized.

ORR was defined as the percentage of the participants in the analysis population who had a Complete Response (CR: Disappearance of all target lesions) or a Partial Response (PR: At least a 30% decrease in the sum of diameters of target lesions) per RECIST 1.1 based on blinded central imaging vendor review with or without confirmation. The ORR per RECIST 1.1 for all participants is presented. These efficacy results were reported after complete acquisition of all outstanding survival data using a 15-May-2017 data cut-off date with a database update date of 13-Oct-2017.

The efficacy population consisted of all randomized participants. Participants are included in the treatment group to which they were randomized.

ORR was defined as the percentage of the participants in the analysis population who had a Complete Response (CR: Disappearance of all target lesions) or a Partial Response (PR: At least a 30% decrease in the sum of diameters of target lesions per RECIST 1.1 based on blinded central imaging vendor review with or without confirmation. The ORR per RECIST 1.1 for all participants with PD-L1 expression ≥1% CPS is presented. These efficacy results were reported after complete acquisition of all outstanding survival data using a 15-May-2017 data cut-off date with a database update date of 13-Oct-2017.

The efficacy population consisted of all randomized participants with PD-L1 ≥1% CPS. Participants are included in the treatment group to which they were randomized.

For participants who demonstrated a confirmed CR or PR per RECIST 1.1, DOR was defined as the time from first documented evidence of a confirmed CR or PR per RECIST 1.1 until disease progression per RECIST 1.1 or death due to any cause, whichever occurred first. Per RECIST 1.1, progressive disease was defined as at least a 20% increase in the sum of diameters of target lesions. In addition to the relative increase of 20%, the sum must also have demonstrated an absolute increase of at least 5 mm. Note: The appearance of one or more new lesions was also considered progression. DOR assessments were based on blinded central imaging vendor review with confirmation. The DOR per RECIST 1.1 for all participants who experienced a confirmed CR or PR is presented. These efficacy results were reported after complete acquisition of all outstanding survival data using a 15-May-2017 data cut-off date with a database update date of 13-Oct-2017.

The efficacy population consisted of all randomized participants who demonstrated a confirmed CR or PR per RECIST 1.1. Participants are included in the treatment group to which they were randomized.

For participants who demonstrated a confirmed CR or PR per RECIST 1.1, DOR was defined as the time from first documented evidence of a confirmed CR or PR per RECIST 1.1 until disease progression per RECIST 1.1 or death due to any cause, whichever occurred first. Per RECIST 1.1, progressive disease was defined as at least a 20% increase in the sum of diameters of target lesions. In addition to the relative increase of 20%, the sum must also have demonstrated an absolute increase of at least 5 mm. Note: The appearance of one or more new lesions was also considered progression. DOR assessments were based on blinded central imaging vendor review with confirmation. The DOR per RECIST 1.1 for all participants with PD-L1 ≥1% CPS who experienced a confirmed CR or PR is presented. These efficacy results were reported after complete acquisition of all outstanding survival data using a 15-May-2017 data cut-off date with a database update date of 13-Oct-2017.

The efficacy population consisted of all randomized participants with PD-L1 ≥1% CPS who demonstrated a confirmed CR or PR per RECIST 1.1. Participants are included in the treatment group to which they were randomized.

TTP was defined as the time from randomization to the first documented disease progression based on assessments by the blinded central imaging vendor review per RECIST 1.1. Per RECIST 1.1, progressive disease was defined as at least a 20% increase in the sum of diameters of target lesions. In addition to the relative increase of 20%, the sum must also have demonstrated an absolute increase of at least 5 mm. Note: The appearance of one or more new lesions was also considered progression. The TTP per RECIST 1.1 for all participants is presented. These efficacy results were reported after complete acquisition of all outstanding survival data using a 15-May-2017 data cut-off date with a database update date of 13-Oct-2017.

The efficacy population consisted of all randomized participants. Participants are included in the treatment group to which they were randomized.

TTP was defined as the time from randomization to the first documented disease progression based on assessments by the blinded central imaging vendor review per RECIST 1.1. Per RECIST 1.1, progressive disease was defined as at least a 20% increase in the sum of diameters of target lesions. In addition to the relative increase of 20%, the sum must also have demonstrated an absolute increase of at least 5 mm. Note: The appearance of one or more new lesions was also considered progression. The TTP per RECIST 1.1 for all participants with PD-L1 ≥1% CPS is presented. These efficacy results were reported after complete acquisition of all outstanding survival data using a 15-May-2017 data cut-off date with a database update date of 13-Oct-2017.

The efficacy population consisted of all randomized participants with PD-L1 ≥1% CPS. Participants are included in the treatment group to which they were randomized.

PFS was defined as the time from randomization to the first documented progressive disease (PD) per RECIST 1.1 based on blinded central imaging vendor review or death due to any cause, whichever occurred first. Per RECIST 1.1, PD was defined as ≥20% increase in the sum of diameters of target lesions. In addition to the relative increase of 20%, the sum must also have demonstrated an absolute increase of ≥5 mm. Note: The appearance of one or more new lesions was also considered PD. Modified RECIST is similar to RECIST 1.1 with the exception that a confirmation assessment of PD (>4 weeks after the initial PD) is required for participants who remain on treatment following a documented PD per RECIST 1.1. The PFS per modified RECIST for all participants is presented. These efficacy results were reported after complete acquisition of all outstanding survival data using a 15-May-2017 data cut-off date with a database update date of 13-Oct-2017.

The efficacy population consisted of all randomized participants. Participants are included in the treatment group to which they were randomized.

PFS was defined as the time from randomization to the first documented progressive disease (PD) per RECIST 1.1 based on blinded central imaging vendor review or death due to any cause, whichever occurred first. Per RECIST 1.1, PD was defined as ≥20% increase in the sum of diameters of target lesions. In addition to the relative increase of 20%, the sum must also have demonstrated an absolute increase of ≥5 mm. Note: The appearance of one or more new lesions was also considered PD. Modified RECIST is similar to RECIST 1.1 with the exception that a confirmation assessment of PD (>4 weeks after the initial PD) is required for participants who remain on treatment following a documented PD per RECIST 1.1. The PFS per modified RECIST for all participants with PD-L1 ≥1% CPS is presented. These efficacy results were reported after complete acquisition of all outstanding survival data using a 15-May-2017 data cut-off date with a database update date of 13-Oct-2017.

The efficacy population consisted of all randomized participants with PD-L1 ≥1% CPS. Participants are included in the treatment group to which they were randomized.

An AE was defined as any untoward medical occurrence in a participant administered a study treatment and which does not necessarily have to have a causal relationship with this treatment. An AE can therefore be any unfavorable and unintended sign, symptom, or disease temporally associated with the use of a medicinal product or protocol-specified procedure, whether or not considered related to the study treatment or protocol-specified procedure. Any worsening (i.e., any clinically significant adverse change in frequency and/or intensity) of a pre-existing condition that is temporally associated with the use of study treatment, is also an AE. The number of all participants who experienced at least one AE is presented.

The safety population consisted of all randomized participants who received at least one dose of study treatment.

An AE was defined as any untoward medical occurrence in a participant administered a study treatment and which does not necessarily have to have a causal relationship with this treatment. An AE can therefore be any unfavorable and unintended sign, symptom, or disease temporally associated with the use of a medicinal product or protocol-specified procedure, whether or not considered related to the study treatment or protocol-specified procedure. Any worsening (i.e., any clinically significant adverse change in frequency and/or intensity) of a pre-existing condition that is temporally associated with the use of study treatment, is also an AE. The number of all participants with PD-L1 ≥1% CPS who experienced at least one AE is presented.

The safety population consisted of all randomized participants with PD-L1 ≥1% CPS who received at least one dose of study treatment.

An AE was defined as any untoward medical occurrence in a participant administered a study treatment and which does not necessarily have to have a causal relationship with this treatment. An AE can therefore be any unfavorable and unintended sign, symptom, or disease temporally associated with the use of a medicinal product or protocol-specified procedure, whether or not considered related to the study treatment or protocol-specified procedure. Any worsening (i.e., any clinically significant adverse change in frequency and/or intensity) of a pre-existing condition that is temporally associated with the use of study treatment, is also an AE. The number of all participants who discontinued study treatment due to an AE is presented.

The safety population consisted of all randomized participants who received at least one dose of study treatment.

An AE was defined as any untoward medical occurrence in a participant administered a study treatment and which does not necessarily have to have a causal relationship with this treatment. An AE can therefore be any unfavorable and unintended sign, symptom, or disease temporally associated with the use of a medicinal product or protocol-specified procedure, whether or not considered related to the study treatment or protocol-specified procedure. Any worsening (i.e., any clinically significant adverse change in frequency and/or intensity) of a pre-existing condition that is temporally associated with the use of study treatment, is also an AE. The number of all participants with PD-L1 ≥1% CPS who discontinued study treatment due to an AE is presented.

The safety population consisted of all randomized participants with PD-L1 ≥1% CPS who received at least one dose of study treatment.

Participants received standard treatment of either methotrexate 40 mg/m^2 IV (could be escalated to 60 mg/m^2 maximum dose) on Days 1, 8, and 15 of each 3-week cycle; or docetaxel 75 mg/m^2 IV on Day 1 of each 3- week cycle; or cetuximab 400 mg/m^2 IV loading dose on Day 1 and 250 mg/m^2 IV on Days 8 and 15 of Cycle 1, followed by cetuximab 250 mg/m^2 on Days 1, 8, and 15 of each subsequent 3-week cycle.

Eligible participants who stopped the initial course of pembrolizumab (200 mg IV Q3W for up to approximately 24 months) with SD or better but progressed after discontinuation initiated a second course of pembrolizumab at the investigator's discretion for up to approximately 1 additional year.