Extended Data Table 5.

Adverse events with a possible immune-mediated cause and infusion reactions in the as-treated population

	Pembrolizumab group (N=217)		Placebo group (N=216)
Event — no.(%)	Any grade	Grade 3–5	Any grade	Grade 3–5
Infusion-related reactions	39(18.0)	6 (2.8)	28 (13.0)	2 (0.9)
Pneumonitis	11 (5.1)	3(1.4)	3(1.4)	0(0.0)
Colitis	10 (4.6)	6(2.8)	4(1.9)	4(1.9)
Hypothyroidism	10 (4.6)	0 (0.0)	6(2.8)	0 (0.0)
Hyperthyroidism	8 (3.7)	0 (0.0)	7 (3.2)	0 (0.0)
Hypophysitis	3(1.4)	1 (0.5)	0 (0.0)	0 (0.0)
Hepatitis	2 (0.9)	2 (0.9)	2 (0.9)	0 (0.0)
Severe skin reactions	2 (0.9)	2 (0.9)	0 (0.0)	0 (0.0)
Nephritis	1 (0.5)	0 (0.0)	0 (0.0)	0 (0.0)
Thyroiditis	1 (0.5)	0 (0.0)	0 (0.0)	0(0.0)
Type 1 diabetes mellitus	1 (0.5)	1 (0.5)	0 (0.0)	0 (0.0)
Uveitis	1 (0.5)	0 (0.0)	1 (0.5)	0 (0.0)
Myocarditis	0 (0.0)	0 (0.0)	1 (0.5)	1 (0.5)

Adverse events with a possible immune-mediated cause and infusion reactions were considered regardless of attribution to study treatment by the investigator. The specific events are based on a list of terms provided by the sponsor. In addition to the specific terms listed, related terms were also included.