Table 1.

Timing and characteristics of severe infusion-related events.

Severe infusion-related adverse effect	Timing	Infusion number	Withdrawal	Anti-NTZ antibody concentration (AU/ml)a
Case 1
Generalised rash	During	2	Yes	740b
Case 2
Pruritic rash	During	2	Yes	26c
Case 3
Pruritic rash	During	2	Yes	890c
Case 4
1. Chest discomfort, headache, sweating, facial erythema	During	2	Yes	580b
2. Chest discomfort, headache, sweating, facial erythema	During	3
Case 5
Generalised erythema	During	3	No	80c
Case 6
Pruritic erythema	During	6	Yes	< 12d
Case 7
Generalised rash	Unknown	1e	No	13c
Case 8
1. Pruritic erythema	During	28	Yes	< 12c
2. Pruritic erythema	During	29
Case 9
Generalised urticaria	During	58	Yes	< 12b

Except for case 2 and case 8, all patients received oral or IV clemastine.

NTZ: natalizumab; IV: intravenous; IAE: infusion-related adverse event.

^aHigh concentration > 100 AU/ml, low concentration ⩾ 12–100 AU/ml, negative concentration < 12 AU/ml.

^b3–12 months between serum sample and IAE.

^c< 3 months between serum sample and IAE.

^d> 1 year between serum sample and IAE.

^eThe first infusion after NTZ discontinuation, that is, the second therapy course.