@article{dc535090da6e4edbbdbbf697d05f92b5,
title = "Anti-CTLA-4 therapy requires an Fc domain for efficacy",
abstract = "Ipilimumab, a monoclonal antibody that recognizes cytotoxic T lymphocyte antigen (CTLA)-4, was the first approved “checkpoint”-blocking anticancer therapy. In mouse tumor models, the response to antibodies against CTLA-4 depends entirely on expression of the Fcγ receptor (FcγR), which may facilitate antibody-dependent cellular phagocytosis, but the contribution of simple CTLA-4 blockade remains unknown. To understand the role of CTLA-4 blockade in the complete absence of Fc-dependent functions, we developed H11, a high-affinity alpaca heavy chain-only antibody fragment (VHH) against CTLA-4. The VHH H11 lacks an Fc portion, binds monovalently to CTLA-4, and inhibits interactions between CTLA-4 and its ligand by occluding the ligand-binding motif on CTLA-4 as shown crystallographically. We used H11 to visualize CTLA-4 expression in vivo using whole-animal immuno-PET, finding that surface-accessible CTLA-4 is largely confined to the tumor microenvironment. Despite this, H11-mediated CTLA-4 blockade has minimal effects on antitumor responses. Installation of the murine IgG2a constant region on H11 dramatically enhances its antitumor response. Coadministration of the monovalent H11 VHH blocks the efficacy of a full-sized therapeutic antibody. We were thus able to demonstrate that CTLA-4-binding antibodies require an Fc domain for antitumor effect.",
keywords = "CTLA-4, Cancer, Checkpoint blockade, Immunotherapy, Single-domain antibody",
author = "Ingram, {Jessica R.} and Blomberg, {Olga S.} and Mohammad Rashidian and Lestat Ali and Scott Garforth and Elena Fedorov and Fedorov, {Alexander A.} and Bonanno, {Jeffrey B.} and {Le Gall}, Camille and Stephanie Crowley and Camilo Espinosa and Tamara Biary and Keliher, {Edmund J.} and Ralph Weissleder and Almo, {Steven C.} and Dougan, {Stephanie K.} and Ploegh, {Hidde L.} and Michael Dougan",
note = "Funding Information: We thank Charles Shoemaker, Jean Mukherjee, and Jacqueline Tremblay (Tufts Cummings Veterinary School) for their assistance with alpaca immunizations; Peter Sage and Arlene Sharpe (Harvard Medical School, Boston, MA) for providing CTLA-4 conditional KO mice; Alica Linnebacher, Christina Martone, Nora Kory, Patti Wisniewski and the Whitehead Flow Cytometry Core (Whitehead Institute for Biomedical Research, Cambridge, MA), and Howard Mak and Scott Malstrom (Koch Institute Animal Imaging and Preclinical Testing, MIT) for technical assistance. Funding was provided by a Ludwig Cancer Research Postdoctoral Fellowship (to J.R.I.); the Claudia Adams Barr Program for Innovative Cancer Research (J.R.I.); De Maag Lever Darm Stichting (O.S.B.); Stichting Bekker-La Bastide-Fonds (O.S.B.); a Cancer Research Institute Postdoctoral Fellowship (to M.R.); the Melanoma Research Alliance (S.K.D.); the Pew Foundation (S.K.D.); National Institutes of Health (NIH) Grants HG008325 (to S.C.A.), GM094662 (to S.C.A.), GM094665 (to S.C.A.), DP1-GM106409-03 (to H.L.P.), and R01-GM100518-04 (to H.L.P.); Albert Einstein Cancer Center Grant P30CA013330 (to S.C.A.); the Lustgarten Foundation (H.L.P.); Mentored Clinical Scientist Development Award 1K08DK114563-01 (to M.D.); NIH Training Grant 1F32CA210568-01 (to M.D.); Center for the Study of Inflammatory Bowel Disease Grant DK043351 (to M.D.); and an American Gastroentero-logical Association Research Scholars Award (to M.D.). Funding Information: ACKNOWLEDGMENTS. We thank Charles Shoemaker, Jean Mukherjee, and Jacqueline Tremblay (Tufts Cummings Veterinary School) for their assistance with alpaca immunizations; Peter Sage and Arlene Sharpe (Harvard Medical School, Boston, MA) for providing CTLA-4 conditional KO mice; Alica Linnebacher, Christina Martone, Nora Kory, Patti Wisniewski and the Whitehead Flow Cytometry Core (Whitehead Institute for Biomedical Research, Cambridge, MA), and Howard Mak and Scott Malstrom (Koch Institute Animal Imaging and Preclinical Testing, MIT) for technical assistance. Funding was provided by a Ludwig Cancer Research Postdoctoral Fellowship (to J.R.I.); the Claudia Adams Barr Program for Innovative Cancer Research (J.R.I.); De Maag Lever Darm Stichting (O.S.B.); Stichting Bekker-La Bastide-Fonds (O.S.B.); a Cancer Research Institute Postdoctoral Fellowship (to M.R.); the Melanoma Research Alliance (S.K.D.); the Pew Foundation (S.K.D.); National Institutes of Health (NIH) Grants HG008325 (to S.C.A.), GM094662 (to S.C.A.), GM094665 (to S.C.A.), DP1-GM106409-03 (to H.L.P.), and R01-GM100518-04 (to H.L.P.); Albert Einstein Cancer Center Grant P30CA013330 (to S.C.A.); the Lustgarten Foundation (H.L.P.); Mentored Clinical Scientist Development Award 1K08DK114563-01 (to M.D.); NIH Training Grant 1F32CA210568-01 (to M.D.); Center for the Study of Inflammatory Bowel Disease Grant DK043351 (to M.D.); and an American Gastroenterological Association Research Scholars Award (to M.D.). Publisher Copyright: {\textcopyright} 2018 National Academy of Sciences. All Rights Reserved.",
year = "2018",
doi = "10.1073/pnas.1801524115",
language = "English (US)",
volume = "115",
pages = "3912--3917",
journal = "Proceedings of the National Academy of Sciences of the United States of America",
issn = "0027-8424",
publisher = "National Academy of Sciences",
number = "15",
}
