Table I.

Summary of IgG, albumin, adverse event, and infection data for reported clinical trials of FcRn inhibitors

Indication	N	Intervention and comparator	Duration of follow-up	Mean maximum reduction in IgG (%)	Impact on albumin	TEAEs of interest (%)		Reported infections
Efgartigimod (IV)
MG20 (NCT02965573)	24	•10 mg/kg QW × 4 •Placebo	8 wk	70.7 week 4	Not reported	•Headache •Nausea •Diarrhea •Abdominal pain •Total lymphocyte count decrease •T- and B-lymphocyte decrease •Monocyte count decrease •Neutrophil count increase	33.3 8.3 8.3 8.3 16.7 16.7 16.7 16.7	Herpes zoster: 1 efgartigimod-treated patient (also seen in SoC treatment with prednisone and mycophenolate mofetil)
ITP22 (NCT03102593)	38	•5 mg/kg QW × 4 •10 mg/kg QW × 4 •Placebo	21 wk	60.4 D25 63.7 D25	Similar between groups and within ±10%-15% baseline	•Vomiting (5 mg/kg group only) •Headache (10 mg/kg group only)	15.4 7.7	1 pneumonia (deemed unrelated to efgartigimod treatment); no apparent increased risk of infection
FIH23 (NCT03457649)	MAD: 32	•10 mg/kg Q4D × 6 •10 mg/kg QW × 4 •25 mg/kg QW × 4 •Placebo	58-59 d	78.5 D24 Emax 73.0 D24 Emax 77.7 D24 Emax	No significant decrease	•Headache •Abdominal discomfort •In the SAD part of the study, abnormal differential WBC count was reported by 3 of 4 healthy volunteers receiving 25 mg/kg and 4 of 4 receiving 50 mg/kg	n = 4 n = 1	None
Rozanolixizumab (SC)
MG19 (NCT03052751)	43	Period 1 (D1-29): •7 mg/kg QW × 3 •Placebo Period 2 (D29-43): •4 mg/kg QW × 3 •7 mg/kg QW × 3 •Placebo	55 d	68 D50 in patients receiving 7 mg/kg throughout the study	Not reported	•Headache	57.1	Not reported
ITP21 (NCT02718716)	66	•15 mg/kg × 1 •20 mg/kg × 1 •4 mg/kg × 5 QW •7 mg/kg × 3 QW •10 mg/kg × 2 QW	8 wk	60 D8 for single-dose 20 mg/kg	Not reported	•Headache •Diarrhea •Vomiting	39.4 12.1 9.1	No serious infections
FIH24 (NCT02220153)	SAD SC: 24	•1 mg/kg •4 mg/kg •7 mg/kg •Placebo	79 d	43.4 for 7 mg/kg D10	Modest decrease, not significantly different from placebo	•Headache •Nausea •Diarrhea •Vomiting •Abdominal pain	27.8 0 16.7 11.1 5.6	Incidence of treatment-related infections was lower in the rozanolixizumab total group (13.9%) than in the placebo group (23.1%)
Nipocalimab (IV)
FIH25 (NCT02828046)	MAD: 16	•15 mg/kg QW × 4 •30 mg/kg QW × 4 •Placebo	Up to 14 wk	D20∗: 83 Emax D24∗: 84 Emax	Asymptomatic and transient reduction in total serum protein and albumin	•Headache •Nausea •Gastroenteritis	8.3 8.3 8.3	Incidence of treatment-emergent infections and infestations was similar between nipocalimab (41.7%) and placebo (50%) groups
Orilanolimab (IV)
FIH18 (NCT03643627)	SAD: 31	•1 mg/kg •3 mg/kg •10 mg/kg •30 mg/kg •Placebo	27 d	46.21 median for 30 mg/kg dose group within 5 d	No significant changes	•Headache •Nausea •Diarrhea •Abdominal pain •Decreased appetite	34.8 4.3 4.3 4.3 4.3	Not reported

D, Day; E_max, maximum percentage reduction value; MAD, multiple ascending dose; Q4D, every 4 d; SAD, single ascending dose; SoC, standard of care.

For FIH studies, data are presented for multiple doses if available.

^∗Median time to E_max.