A Study of Atezolizumab Plus Tiragolumab and Atezolizumab Plus Placebo as First-Line Treatment in Participants With Recurrent/Metastatic PD-L1 Positive Squamous Cell Carcinoma of the Head and Neck

DOR was defined as the time from the first occurrence of a documented confirmed OR to PD, as determined by the investigator according to RECIST v1.1, or death from any cause, whichever occurred first. Confirmed OR was defined as either a CR or a PR on 2 consecutive occasions ≥ 4 weeks apart. CR was defined as disappearance of all target and non-target lesions \& normalization of tumor marker level. Additionally, any lymph nodes (whether target or non-target) must have a reduction in short axis to < 10 mm. PR was defined as at least a 30% decrease in the SOD of all target lesions, taking as reference the baseline SOD, in the absence of CR. PD was defined as at least a 20% increase in the SOD of target lesions, taking as reference the smallest SOD at prior timepoints (including baseline). Additionally, the SOD must also demonstrate an absolute increase of ≥ 5 mm or unequivocal progression of existing non-target lesions. Kaplan-Meier (K-M) method was used to estimate the median DOR.

PFS was defined as the time from randomization to the first occurrence of PD, as determined by the investigator according to RECIST v1.1, or death from any cause, whichever occurred first. PD was defined as at least a 20% increase in the SOD of target lesions, taking as reference the smallest SOD at prior timepoints (including baseline). Additionally, the SOD must also demonstrate an absolute increase of ≥ 5 mm or unequivocal progression of existing non-target lesions. K-M method was used to estimate the median PFS.

OS was defined as the time from randomization to death from any cause. K-M method was used to estimate the median OS.

PFS rate at 6 months was defined as the percentage of participants who did not experience PD or death from any cause, as determined by the investigator, at Month 6. PFS was defined as the time from randomization to the first occurrence of PD, as determined by the investigator according to RECIST v1.1, or death from any cause, whichever occurred first. PD was defined as at least a 20% increase in the SOD of target lesions, taking as reference the smallest SOD at prior timepoints (including baseline). Additionally, the SOD must also demonstrate an absolute increase of ≥ 5 mm or unequivocal progression of existing non-target lesions. K-M method was used to estimate the PFS rate. Percentages have been rounded off.

OS rate at 6 months and 12 months was defined as percentage of participants who did not experience death from any cause at the specified timepoints. OS was defined as the time from randomization to death from any cause. K-M method was used to estimate OS rate. Percentages have been rounded off.

TTCD=time from the date of randomization to the first confirmed clinically meaningful deterioration (CCMD). PROMIS Item Bank v2.0-PF- Short Form 10b is a 10-item participant-reported questionnaire including 2 types of items to assess PF: 6 ability-based items assessing difficulty in performing activities, scored on a 5-point scale ranging from 1=Unable to do, 2=With much difficulty, 3=With some difficulty, 4=With a little difficulty, 5=Without any difficulty; and 4 limitation-based items assessing the extent to which health limits activities, scored on a 5-point scale ranging from 1=Cannot do, 2=Quite a lot, 3=Somewhat, 4=Very little, 5=Not at all. Item responses were summed to generate a raw score and converted to a PROMIS T-score, with a higher T-score indicating better PF. CCMD=decrease from baseline (≥ 4 points) in T-score, held for at least 2 consecutive assessments. K-M method was used to estimate median TTCD.

An AE was defined as any untoward medical occurrence in a clinical investigation subject administered a pharmaceutical product, regardless of causal attribution. An AE was therefore any of the following: Any unfavorable and unintended sign (including an abnormal laboratory finding), symptom, or disease temporally associated with the use of a medicinal product, whether or not considered related to the medicinal product.

Participants were considered to be ADA positive if they were ADA negative at baseline but developed an ADA response following atezolizumab administration (treatment-induced ADA response), or if they were ADA positive at baseline and the titer of one or more post-baseline samples was greater than the titer of the baseline sample by a scientifically reasonable margin such as at least 0.60 titer unit (t.u.) greater than the baseline titer result (treatment-enhanced ADA response).

Participants were considered to be ADA positive if they were ADA negative at baseline but developed an ADA response following tiragolumab administration (treatment-induced ADA response), or if they were ADA positive at baseline and the titer of one or more post-baseline samples was greater than the titer of the baseline sample by a scientifically reasonable margin such as at least 0.60 t.u. greater than the baseline titer result (treatment-enhanced ADA response).