Antibodies targeting sialyl Lewis A mediate tumor clearance through distinct effector pathways
Polina Weitzenfeld, … , Stylianos Bournazos, Jeffrey V. Ravetch
Polina Weitzenfeld, … , Stylianos Bournazos, Jeffrey V. Ravetch
Published August 19, 2019
Citation Information: J Clin Invest. 2019;129(9):3952-3962. https://doi.org/10.1172/JCI128437.
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Research Article Immunology

Antibodies targeting sialyl Lewis A mediate tumor clearance through distinct effector pathways

Abstract

Sialyl Lewis A (sLeA, also known as CA19-9), a tetrasaccharide selectively and highly expressed on advanced adenocarcinomas including colon, stomach, and pancreatic cancers, has long been considered as an attractive target for active and passive vaccination. While progress in antibodies targeting tumor-associated protein antigens resulted in an impressive array of therapeutics for cancer treatment, similar progress in exploiting tumor-associated carbohydrate antigens, such as sLeA, has been hampered by the lack of a detailed understanding of the singular characteristics of these antigens. We have addressed this issue by analyzing antibodies derived from patients immunized with an sLeA/KLH vaccine. These antibodies were engineered to mediate tumor clearance in vivo in preclinical models through Fc-FcγR interactions. However, in contrast to protein antigens in which hFcγRIIIA engagement was both necessary and sufficient to mediate tumor clearance in both preclinical and clinical settings, a similar selective dependence was not seen for anti-sLeA antibodies. Thus, re-engineering the Fc portion of sLeA-targeting antibodies to broadly enhance their affinity for activating FcγRs led to an enhanced therapeutic effect. These findings will facilitate the development of more efficient anticancer therapies and further advance this promising class of therapeutic antibodies into clinical use.

Authors

Polina Weitzenfeld, Stylianos Bournazos, Jeffrey V. Ravetch

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Figure 4

Engagement of either hFcγRIIA or hFcγRIIIA is necessary and sufficient for tumor clearance, mediated by sLeA-targeting Abs with an hIgG1 Fc.

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Engagement of either hFcγRIIA or hFcγRIIIA is necessary and sufficient f...
Mice were inoculated i.v. with 5 × 105 B16-FUT3 tumor cells. One hundred micrograms of anti-sLeA Abs or isotype-matched control Abs was administered i.p. on days 1, 4, 7, and 11. Fourteen days after inoculation, mice were euthanized, lungs were excised and fixed, and metastatic foci were counted. *P < 0.05, **P < 0.01, ***P < 0.001, ****P < 0.0001 (1-way ANOVA with Bonferroni’s post hoc test). For all panels, the box extends from the 25th to 75th percentile, the line within the box represents the median value, and the whiskers correspond to the 5th to 95th percentile. (A) Fc-engineered anti-sLeA Ab variants demonstrate superior antitumor efficacy. FcγR-humanized mice were treated with clones 5B1 or 7E3, hIgG1 or hIgG1-GAALIE with G236A/A330L/I332E mutations. Data were pooled from n = 2–3 experiments, n ≥ 13/group, except for 7E3-hIgG1-GAALIE (n = 7). (B) 5B1-hIgG1 Abs with enhanced binding affinity for hFcγRIIA, or hFcγRIIIA, or both demonstrate a superior antitumor effect. FcγR-humanized mice were treated with Fc variants 5B1-hIgG1, 5B1-hIgG1-GA with a G236A mutation, 5B1-hIgG1-ALIE with A330L/I332E mutations, or 5B1-hIgG1-GAALIE with G236A/A330L/I332E mutations. Data were pooled from n = 2–4 experiments. n ≥ 12/group. (C) hFcγRIIA or hFcγRIIIA engagement is essential for efficient tumor clearance of sLeA+ tumors. Activating FcγR-null (aFcγR-null, γ chain–KO), FcγR-humanized, hFcγRIIA/IIB–transgenic, and hFcγRIIIA/IIIB–transgenic mice were treated with the Ab 5B1-hIgG1-GAALIE with G236A/A330L/I332E mutations. Data were pooled from n ≥ 2 experiments for aFcγR-null and FcγR-humanized mice, n ≥ 12/group. For hFcγRIIA/IIB–transgenic and hFcγRIIIA/IIIB–transgenic, n = 5–8/group.