Table 3.

Safety summary

	Period I (Introduction phase)	Period II (Withdrawal phase)		Period III (Reintroduction phase)
					Period II SC placebo
Patients with event (n (%))	SC abatacept (with intravenous abatacept load) (n=167)	SC abatacept (n=40)	SC placebo (n=80)	Period II SC abatacept (with intravenous placebo load) (n=40)	Intravenous abatacept load (n=35)	Intravenous placebo load (n=44)
AEs	82 (49.1)	13 (32.5)	29 (36.3)	15 (37.5)	17 (48.6)	16 (36.4)
Most common AEs*
URTI	12 (7.2)	1 (2.5)	0	2 (5.0)	1 (2.9)	1 (2.3)
Vaginal infection	0	2 (5.0)	0	0	0	0
Nausea	2 (1.2)	2 (5.0)	0	0	0	0
Flu	5 (3.0)	0	1 (1.3)	0	2 (5.7)	2 (4.5)
UTI	3 (1.8)	1 (2.5)	1 (1.3)	3 (7.5)	0	1 (2.3)
Laryngitis	1 (0.6)	0	0	0	3 (8.6)	0
Discontinuations due to AEs	1 (0.6)	0	0	0	0	0
SAEs	3 (1.8)	0	2 (2.5)	0	0	1 (2.3)
Deaths	1 (0.6)	0	0	0	0	0
Infections and infestations	42 (25.1)	5 (12.5)	7 (8.8)	7 (17.5)	8 (22.9)	7 (15.9)
Serious infections†	1 (0.6)	0	0	0	0	0
Malignancies	0	0	0	0	0	0
Autoimmune events	0	0	0	0	0	0
SC injection site reaction	2 (1.2)	0	0	0	0	0
Acute infusional events	1 (0.6)‡	0	0	0	0	0

^*AEs reported in ≥5% of patients in any group during any treatment period.

^†Serious infections is a subset of SAEs.

^‡Mild non-serious headache, considered probably related to study drug, was reported following intravenous abatacept loading in period I.

AE, adverse event; SAE, serious adverse event; SC, subcutaneous; URTI, upper respiratory tract infection; UTI, urinary tract infection.