An engineered immunomodulatory IgG1 Fc suppresses autoimmune inflammation through pathways shared with i.v. immunoglobulin
Sunny L. Sneed, … , Pamela B. Conley, Robert M. Anthony
Sunny L. Sneed, … , Pamela B. Conley, Robert M. Anthony
Published February 15, 2024
Citation Information: J Clin Invest. 2024;134(4):e172980. https://doi.org/10.1172/JCI172980.
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An engineered immunomodulatory IgG1 Fc suppresses autoimmune inflammation through pathways shared with i.v. immunoglobulin

Abstract

Immunoglobulin G (IgG) antibodies in the form of high-dose intravenous immunoglobulin (IVIG) exert immunomodulatory activity and are used in this capacity to treat inflammatory and autoimmune diseases. Reductionist approaches have revealed that terminal sialylation of the single asparagine-linked (N-linked) glycan at position 297 of the IgG1 Fc bestows antiinflammatory activity, which can be recapitulated by introduction of an F241A point mutation in the IgG1 Fc (FcF241A). Here, we examined the antiinflammatory activity of CHO-K1 cell–produced FcF241A in vivo in models of autoimmune inflammation and found it to be independent of sialylation. Intriguingly, sialylation markedly improved the half-life and bioavailability of FcF241A via impaired interaction with the asialoglycoprotein receptor ASGPR. Further, FcF241A suppressed inflammation through the same molecular pathways as IVIG and sialylated IgG1 Fc and required the C-type lectin SIGN-R1 in vivo. This contrasted with FcAbdeg (efgartigimod), an engineered IgG1 Fc with enhanced neonatal Fc receptor (FcRn) binding, which reduced total serum IgG concentrations, independent of SIGN-R1. When coadministered, FcF241A and FcAbdeg exhibited combinatorial antiinflammatory activity. Together, these results demonstrated that the antiinflammatory activity of FcF241A requires SIGN-R1, similarly to that of high-dose IVIG and sialylated IgG1, and can be used in combination with other antiinflammatory therapeutics that rely on divergent pathways, including FcAbdeg.

Authors

Sunny L. Sneed, Brian B. Reese, Ana F.S. Laureano, Sneha Ratnapriya, Isabella Fraschilla, Kate L. Jeffrey, Greg P. Coffey, Pamela B. Conley, Robert M. Anthony

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Figure 2

Sialylation of FcF241A is not necessary for antiinflammatory activity but improves half-life and bioavailability in vivo.

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Sialylation of FcF241A is not necessary for antiinflammatory activity bu...
(A) Female WT C57BL/6 mice (n = 5) were given K/BxN serum alongside PBS, IVIG, FcF241A, FcF241A/ST6, FcF241A/B4ST6, or FcF241A/SLC35A1 in a preventative manner, and swelling was scored for 10 days. Day 8 clinical scores, representing maximum separation between PBS and FcF241A-based treatments, are plotted. (B) Female humanized FcRn mice (n = 6) were dosed with 20 mg/kg of FcF241A, FcF241A/ST6, FcF241A/B4ST6, or FcF241A/siSLC. Serum concentration of hIgG Fc was measured via ELISA. Half-life, area under the curve from the time of dosing to the last measurable concentration (AUClast), and clearance rate were calculated. (C) Correlation between sialylation on FcF241A and clinical scores, half-life, AUClast, and clearance. Corresponding R2 and P values are shown. Clinical score correlation was generated from A; other correlations were generated from B. (D) Female WT mice (n = 4) were given control or ASGPR block before FcF241A/B4ST6 or FcF241A/siSLC. Serum concentration of hIgG Fc was measured via ELISA at 1, 3, and 7 days. FcF241A/B4ST6 and FcF241A/siSLC were also analyzed for ASGPR binding on Octet. (E) NTN was induced in female WT mice (n = 3–5) that were given PBS, IVIG, or varying doses of FcF241A. Day 7 serum was used to quantify anti-sheep mIgG via ELISA, represented as absorbance at 450 nm. Day 7 blood urea nitrogen (BUN) levels for NTN mice were also quantified. (F) Female WT C57BL/6 mice (n = 6–10) had EAE induced and were treated with PBS, IVIG, or 100 mg/kg FcF241A on days 5, 10, 15, and 20. EAE clinical scores were recorded daily. Data are plotted as means with SDs in A, B, and D–F. Statistics are ordinary 1-way ANOVA with Tukey’s multiple comparisons (A, B, and D–F) or simple linear regression (C).