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A reappraisal of CTLA-4 checkpoint blockade in cancer immunotherapy
28 April 2018

A reappraisal of CTLA-4 checkpoint blockade in cancer immunotherapy

Authors: Du X, Tang F, Liu M, Su J, Zhang Y, Wu W, Devenport M, Lazarski CA, Zhang P, Wang X, Ye P, Wang C, Hwang E, Zhu T, Xu T, Zheng P, Liu Y.
Citation: Cell Res. 2018 Apr;28(4):416-432. doi: 10.1038/s41422-018-0011-0. Epub 2018 Feb 22.
Products: ONC-392

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It is assumed that anti-CTLA-4 antibodies cause tumor rejection by blocking negative signaling from B7-CTLA-4 interactions. Surprisingly, at concentrations considerably higher than plasma levels achieved by clinically effective dosing, the anti-CTLA-4 antibody Ipilimumab blocks neither B7 trans-endocytosis by CTLA-4 nor CTLA-4 binding to immobilized or cell-associated B7. Consequently, Ipilimumab does not increase B7 on dendritic cells (DCs) from either CTLA4 gene humanized (Ctla4 h/h ) or human CD34+ stem cell-reconstituted NSG™ mice.

In Ctla4 h/m mice expressing both human and mouse CTLA4 genes, anti-CTLA-4 antibodies that bind to human but not mouse CTLA-4 efficiently induce Treg depletion and Fc receptor-dependent tumor rejection. The blocking antibody L3D10 is comparable to the non-blocking Ipilimumab in causing tumor rejection. Remarkably, L3D10 progenies that lose blocking activity during humanization remain fully competent in inducing Treg depletion and tumor rejection. Anti-B7 antibodies that effectively block CD4 T cell activation and de novo CD8 T cell priming in lymphoid organs do not negatively affect the immunotherapeutic effect of Ipilimumab. Thus, clinically effective anti-CTLA-4 mAb causes tumor rejection by mechanisms that are independent of checkpoint blockade but dependent on the host Fc receptor. Our data call for a reappraisal of the CTLA-4 checkpoint blockade hypothesis and provide new insights for the next generation of safe and effective anti-CTLA-4 mAbs.

Last modified on 31 October 2020