Research Perspectives:

Targeting GITR in cancer immunotherapy – there is no perfect knowledge

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Oncotarget. 2023; 14:614-621. https://doi.org/10.18632/oncotarget.28461

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Diwakar Davar _ and Roberta Zappasodi


Diwakar Davar1,2 and Roberta Zappasodi3,4

1 Hillman Cancer Center, University of Pittsburgh Medical Center (UPMC), Pittsburgh, PA 15232, USA

2 University of Pittsburgh, Pittsburgh, PA 15232, USA

3 Division of Hematology and Medical Oncology, Department of Medicine, Weill Cornell Medical College, NY 10065, USA

4 Immunology and Microbial Pathogenesis Program, Weill Cornell Graduate School of Medical Sciences, NY 10065, USA

Correspondence to:

Diwakar Davar, email: [email protected]

Keywords: cancer; immunotherapy; programmed death-1 (PD-1); cytotoxic T-lymphocyte Antigen-4 (CTLA-4); glucocorticoid-induced TNFR-related protein (GITR)

Received: April 19, 2023     Accepted: June 05, 2023     Published: June 19, 2023

Copyright: © 2023 Davar and Zappasodi. This is an open access article distributed under the terms of the Creative Commons Attribution License (CC BY 3.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.


Glucocorticoid-induced TNFR-related protein (GITR) belongs to the TNFR superfamily (TNFRSF) and stimulates both the acquired and innate immunity. GITR is broadly expressed on immune cells, particularly regulatory T cells (Tregs) and natural killer (NK) cells. Given its potential to promote T effector function and impede Treg immune suppression, GITR is an attractive target for cancer immunotherapy. Preclinically, GITR agonists have demonstrated potent anti-tumor efficacy singly and in combination with a variety of agents, including PD-1 blockade. Multiple GITR agonists have been advanced into the clinic, although the experience with these agents has been disappointing. Recent mechanistic insights into the roles of antibody structure, valency, and Fc functionality in mediating anti-tumor efficacy may explain some of the apparent inconsistency or discordance between preclinical data and observed clinical efficacy.


The glucocorticoid-induced tumor-necrosis factor receptor related protein (GITR, also known as TNFRSF18, AITR, and CD357) belongs to the TNF superfamily, which comprises 19 ligands and 29 receptors [1]. TNF superfamily (TNFSF) ligands and TNF receptor superfamily (TNFRSF) receptors are expressed by a wide variety of immune cells including T cells, antigen-presenting cells (APC), and tumor cells [2, 3]. The diverse expression pattern of TNFSF/TNFRSF proteins explains the critical role they play in coordinating immune responses. In humans, GITR is constitutively expressed on Foxp3+ regulatory T cells (Treg) at high levels and at lower levels on CD56+ natural killer cells, B cells, naïve, and memory T cells [46]. Upon T cell activation, GITR expression is upregulated on both Tregs and CD4+ and CD8+ effector T (Teff) cells [46].

TNFSF ligands are type II membrane proteins comprising a C-terminal TNF homology domain (THD) separated from the cytoplasmic domain by a stalk region of variable length [7, 8]. TNFSF ligands are typically membrane bound, although soluble moieties occur naturally due to proteolytic processing in the stalk region separating the THD from the transmembrane domain [9]. Human TNFRSF receptor activation requires trimerization and membrane-bound ligand trimers trigger receptor signaling more efficiently compared to the soluble, cleaved moieties. TNFRSF receptors are type I transmembrane proteins that contain between 1 and 6 pseudorepeats of cysteine-rich domains (CRDs) in their ectodomains, which are involved in ligand binding but can also promote receptor self-assembly [10, 11]. The natural GITR ligand (GITRL, TNFSF18) is predominantly expressed by activated APCs, including dendritic cells, macrophages, and activated B cells [12, 13]. GITRL expression can also be induced in endothelial cells following type I interferon (IFN) exposure [4] and has been observed in certain tumor types (e.g. gastrointestinal cancers and myeloid cell neoplasms) [14, 15].

TNFRSF members possess a domain that mediates self-assembly of two (or three) receptor molecules creating a single high affinity site for non-covalent binding of TNFSF ligand trimers [16, 17]. From a signaling perspective, the majority of TNFRSF members – including GITR – contain motifs that bind to TNF receptor-associated factor (TRAF) that links these receptors to intracellular signaling pathways including nuclear factor-κB (NF-κB), JUN N-terminal kinase, and mitogen-activated protein kinase (MAPK) pathways [18, 19]. Like other TNFRSF members, GITR lacks intrinsic enzymatic activity, and upon ligation through GITRL, GITR signaling is mediated by TRAF5 and TRAF2 protein adaptors to induce the NF-κB and MAPK pathways, which leads to the upregulation of critical cytokines for T cell activation and proliferation (IL-2 and IFN-γ) [20, 21]. In contrast, the GITRL reverse signaling in APCs and tumor cells was reported to promote some tolerogenic effects, including the release of TGF-beta, IL-10, and induction of indoleamine 2,3-dioxygenase (IDO) for tryptophan catabolism [14, 15, 22].

Because of the overall and multiple positive effects on T cell responses, GITR has emerged as a promising immunotherapeutic target, similar to other TNFRSF members, including in particular 4-1BB (CD137/TNFRSF9), and OX40 (CD134/TNFRSF4) [23, 24]. Several preclinical studies have demonstrated strong anti-tumor activity of GITR stimulation using either agonist antibodies (Abs) or multimeric GITRLs as monotherapy or in combination with other types of immunotherapy, including vaccines and immune checkpoint inhibitors (ICI), against multiple syngeneic tumor models. This led to the clinical development of human GITR agonist agents. Since the first anti-human GITR agonist Ab (TRX518) entered the clinical evaluation in 2010, 11 additional human GITR agonist agents have been tested in the clinic. Despite the huge expectation based on the extremely supportive preclinical data, the efficacy of human GITR agonists has been limited in patients. This may reflect the clinical scenario in which historically these agents have entered the clinical evaluation for therapeutic efficacy – mainly in patients with immunotherapy-refractory advanced tumors. Alternatively, this outcome may be due to fundamental biologic differences of the GITR pathway in the human and mouse systems. Here, we discuss these aspects, with a focus on the clinical landscape of GITR agonists and how the field has evolved to guide the development of clever modalities to engage the GITR pathway for the treatment of cancer in patients.

Rationale for targeting GITR in cancer

The rationale for targeting GITR can be separately considered through its effects upon either the Teff or Treg cell compartments [25, 26]. In the context of Teff cells, GITR activation increases Teff cell cytotoxic function [27], and activation by inducing IL-2 and IFN-γ, enhancing CD25 expression, in turn stimulating cell proliferation [28, 29]. In addition, GITR ligation promotes T cell survival for example of bone marrow-derived CD8+ memory T cells, at least partially by upregulating expression of Bcl-xL and separately by reducing T cell apoptosis [21, 30]. The effects of GITR signaling upon Tregs are more complex. In vitro studies demonstrated that GITR stimulation can reduce Treg immunosuppression via two main mechanisms, (1) by protecting Teff from Treg-mediated inhibition [31], and (2) by directly reducing Treg suppression activity [32, 33]. In vivo, agonistic anti-GITR monoclonal Abs (mAbs), such as the anti-mouse GITR DTA-1 and the anti-human GITR MK-4166, were found to transiently increase intratumoral Treg proliferation and activation, although these cells eventually became unstable and were preferentially targeted for elimination [34, 35]. In fact, GITR can be exploited as a target to deplete Tregs using Abs that are able to bind with high affinity to Fc receptors, as DTA-1 and MK-4166. Intratumoral Tregs express GITR at relatively high level, making GITR a suitable marker for preferential intratumoral Treg targeting, which is highly desired to avoid systemic autoimmune toxicity. Preclinical in vivo studies have shown that the anti-tumor activity of GITR agonist Abs is largely dependent on this mechanism of Treg depletion [36], although functional Treg modulation can also contribute to the anti-tumor immune responses [37]. The extensive perturbation of the Treg compartment in the tumor microenvironment with GITR agonist mAbs has shown to in turn promote functional reinvigoration of CD8+ T cells [35]. In addition, it was reported that direct GITR stimulation in CD8+ T cells induces extensive metabolic changes supporting CD8 T cell proliferation and effector function [38]. These multiple positive effects in T cell responses may explain the potent T cell costimulatory activity and antitumor efficacy observed with the anti-GITR DTA-1 Ab in several mouse syngeneic tumor models, including CT26 and MC38 colorectal cancer [35, 39], B16 melanoma [40], C3 cervical cancer [41], and multiple models of glioblastoma [34]. In preclinical models, the antitumor efficacy of DTA-1 was found to be synergistic with anti-CTLA-4 and PD-1 [32, 38, 4244], but not with anti-CD25, likely secondary to anti-CD25-mediated depletion of Tregs and Teff cells, both of which express CD25 [39].

Taken collectively, these preclinical findings in mouse syngeneic models indicate the GITR targeting results in enhanced Teff function, and induces potent anti-tumor efficacy – dependent upon both agonistic GITR signaling and Treg modulation – as neither mechanism singly fully rescues anti-tumor T cell responses [34, 35, 40]. Overall, the above observations provided compelling rationale to evaluate GITR agonists in cancer patients.

Clinical development of GITR targeting mAb: form meets function

GITR therapeutic targeting requires careful consideration of the complex structural and mechanistic features of GITR:GITRL interactions. Given the observed preclinical efficacy of DTA-1, the initial clinical development of GITR agonists focused on monospecific agonistic mAbs, although more recently bispecific agonistic mAbs, and co-stimulatory GITR ligands have been developed.

Nine GITR monospecific agonistic mAbs – AMG-228, ASP1951, BMS-986156, GWN323, INCAGN1876, MK-1248, MK-4166, REGN6569, and TRX518 – have been publicly disclosed, and the structure, isotype, predicted antibody-dependent cellular cytotoxicity (ADCC) and valency of these mAbs are summarized in Table 1. Generally, regardless of structure, the 7 GITR agonists (AMG-228, BMS-986156, GWN323, MEDI1873, MK-4166, MK-1248, and TRX518) studied as a monotherapy or in combination with PD-1 inhibitors or chemotherapeutic agents in patients with advanced solid tumors demonstrated no unusual safety signals [4551]. Of these, only TRX518 reported single agent activity (1 responder with PD-1 and CTLA-4 refractory hepatocellular carcinoma) [46]. Of note, TRX518 is the only agent that is known to block the interaction between GITR and GITRL thus abrogating the potential GITRL reverse tolerogenic signaling while triggering GITR co-stimulation. Combinations of GITR with anti-PD-1 immunotherapy resulted in clinical responses, although without additive toxicity, and chemotherapy combinations were uninformative. Pharmacodynamic effects observed in these studies included extensive modulation of peripheral Tregs, with reductions in GITR+ Tregs and effector Treg subsets, and trends toward increased proliferating CD8 Teffs and NK cells with combination therapy [32, 52]. Interestingly, Treg reductions were observed also with Fc-inert GITR agonist mAbs (such as TRX518), indicating that functional modulation of Tregs through GITR signaling can take place in humans. Despite the poor efficacy outcome with agonist GITR agents, three of them (ASP1951, INCAGN1876 and REGN6569) remain in clinical development, of which only REGN6569 has been reported on publicly [53]. The clinical efficacy is summarized in Table 2.

Table 1: Structure of GITR agonists being evaluated in ongoing or completed clinical trials

Agent (Sponsor)SponsorStructureIsotypePredicted ADCCValency
AMG-228AmgenMonospecific agonistic antibodyHumanized IgG4NoTetravalent
ASP1951AstellasHinge-stabilized monospecific agonistic antibodyFully human IgG4NoTetravalent
BMS-986156Bristol-Myers SquibbMonospecific agonistic antibodyFully human IgG1YesNot reported
GWN323NovartisMonospecific agonistic antibodyHumanized IgG1YesBivalent
INCAGN1876IncyteMonospecific agonistic antibodyHumanized IgG1YesNot reported
MK-1248MerckMonospecific agonistic antibodyHumanized IgG4NoBivalent
MK-4166MerckMonospecific agonistic antibodyHumanized IgG1YesBivalent
REGN6569RegeneronMonospecific agonistic antibodyFully human IgG1YesNot reported
TRX518Leap TherapeuticsMonospecific agonistic antibodyFully humanized aglycosylated IgG1κ agonisticNoBivalent
UndisclosedAbbvieAnti-PD-1–GITR-L bispecific agonistic antibodyHumanized IgG1 with inert FcNoTrivalent
Co-stimulatory GITR ligand
MEDI1873AstraZenecaHexameric GITRL fusion protein (GITRL FP) comprising 2 GITRL ECD trimers and IgG1 Fc linked by isoleucine zipper trimerization domainFully human IgG1YesHexavalent
HERA-GITRLApogenixTwo trivalent single-chain GITRL binding domain (scGITRL-RBD) fused to IgG1 (Fc inert) dimerization scaffoldHumanized IgG1 with inert FcNoHexavalent

Table 2: Reported clinical activity of GITR agonists being evaluated in ongoing or completed clinical trials

Agent (Sponsor)Tumor typeCombinationPhaseStatusNCT.GOV IDSingle-agent activityCombination activityPrimary publication
Monospecific agonistic antibody
AMG-228 (Amgen)All solid tumorsNot observedI/IICompletedNCT02437916Not reportedNot applicableTran et al. [50]
ASP1951 (Astellas)All solid tumorsPembrolizumabI/IIActive, not recruitingNCT03799003Not reportedNot reportedNot reported
BMS-986156 (Bristol-Myers Squibb)All solid tumorsNivolumabI/IICompletedNCT02598960Not reportedReportedHeinhuis et al. [47]
Metastatic tumors in the liver or lungIpilimumab/nivolumab +/− SBRTI/IIActive, not recruitingNCT04021043Not reportedNot reportedNot reported
GWN323 (Novartis)All solid tumors and lymphomasSpartalizumabI/IICompletedNCT02740270Not reportedReportedPiha-Paul et al. [49]
INCAGN1876 (Incyte)All solid tumorsN/AI/IICompletedNCT02697591Not reportedNot reportedNot reported
All solid tumorsIpilimumab or nivolumabI/IICompletedNCT03126110Not reportedNot reportedNot reported
Recurrent glioblastomaRetifanlimabIIActive, not recruitingNCT04225039Not reportedNot reportedNot reported
MK-1248 (Merck)All solid tumorsNot observedI/IICompletedNCT02553499Not reportedReportedGeva et al. [46]
MK-4166 (Merck)All solid tumorsPembrolizumabICompletedNCT02132754Not reportedReportedPapadopoulos et al. [48]
REGN6569 (Regeneron)All solid tumorsCemiplimabIActive, recruitingNCT04465487Not reportedNot reportedNot reported
TRX518 (Leap Therapeutics)All solid tumorsAnti-PD-1 nivolumab, pembrolizumab and chemotherapyI/IICompletedNCT02628574ReportedReportedDavar et al. [45]
Co-stimulatory GITR ligand
MEDI1873 (AstraZeneca)All solid tumorsNot studiedICompletedNCT02583165No objective responses (prolonged stable disease)N/ABalmanoukian et al. [44]

TNFRSF receptors such as GITR may also be activated by recombinant forms of their ligands. Fc-GITRL (MEDI1873) is one such example, and comprises 2 trimers of humanized GITRL extracellular domain (ECD) linked to two human IgG1 Fc domains by an isoleucine zipper trimerization domain that enforces ligand trimerization [54]. MEDI1873 demonstrated Fc/FcγR-mediated co-stimulatory activity and inhibition of Treg suppression in both in vitro and in vivo studies preclinically [54]. When evaluated in human cancer patients, MEDI1873 demonstrated an overall acceptable safety profile, reduced GITR+ Tregs within the tumor and dose-dependent GITR engagement on circulating memory T cells [45]. Despite its hexameric design and Fc receptor engagement, MEDI1873 produced only prolonged disease stabilization in patients and the lack of objective responses truncated its further clinical development [45].

To overcome the limitations of antibody based GITR agonists, Apogenix developed a novel hexavalent GITR agonist comprising two trivalent single-chain GITRL-receptor-binding-domain (scGITRL-RBD) units bound to an IgG1-derived silenced Fc-domain that serves as a dimerization scaffold (HERA-GITRL) [55]. Despite having no discernable effects upon Treg cell survival or proliferation, HERA-GITRL improved Teff function following stimulation in vitro. In syngeneic mouse tumor models, HERA-GITRL increased antigen-specific CD4+ and CD8+ T cell responses independent of FcγR-binding [55]. Clinical development plans of this agent have not been publicly reported.

Bispecific Abs targeting a co-stimulatory receptor and either an inhibitory immune receptor or a tumor-associated antigen (TAA) have the potential to localize the agonistic activity to immune cells or the tumor site, respectively. PD-1 and GITR are co-expressed on antigen-experienced T cells and memory T cells [44, 56]. In preclinical models, co-targeting PD-1 and GITR improves anti-tumor efficacy [43], possibly by restoring TIGIT/CD226 balance and preventing SHP2-mediated dephosphophorylation of the CD226 intracellular domain [44]. This has been explored with GITR in the context of an antibody-fusion protein composed of anti-PD-1 IgG1 antibody fused at the C-terminus of the silenced Fc to scGITRL [56]. The bispecific mAb induces FcγR-independent but PD-1 dependent GITR clustering in cis, resulting in enhanced activation, proliferation and memory differentiation of primed antigen-specific GITR+PD-1+ T cells along with consequent anti-tumor activity in syngeneic, genetically engineered and xenograft humanized mouse tumor models [56]. Compared to combination therapy with anti-PD-1 and anti-GITR (murine IgG2a with effector function), the bispecific mAb induces expansion of TAA-specific memory T cells with consequent rejection of tumor in challenge/rechallenge experiments [56]. However, it remains unclear whether this agent will be evaluated in human patients.

Future directions

There is no perfect knowledge which can be entitled ours, that is innate; none but what has been obtained from experience, or derived in some way from our senses.” – William Harvey. Lumleian Lecturer, and author, “De Motu Cordis”.

Overall, the clinical results obtained so far with GITR agonist agents have demonstrated specific immune effects in the expected immune cell populations based on preclinical studies. However, these effects have not produced substantial therapeutic activity in cancer patients. Our maturing understanding of the immune responses to GITR agonism in human cancers have clarified novel issues specific to drug development in this space including Ab structure (monospecific and bispecific mAbs and co-stimulatory GITR ligands), Ab valency, and Fc functionality. This improved understanding of the immune responses to GITR agonism in patients should be kept in consideration for the design of novel rational combinations or treatment regimens in earlier disease settings where immunotherapy is gradually becoming the treatment of choice. Considering the multiple mechanisms by which cancer cells can evade immune surveillance, having agents to modulate multiple immune targets concurrently may facilitate the design of therapeutic strategies that limit the development of resistance. In this direction, the experience with GITR targeting in patients may inform the development of next-generation immunotherapy approaches. Furthermore, these results underscore the mechanistic differences of critical immunotherapeutic pathways between preclinical animal models and humans. This suggests that advancing translational science for transformational impact in patients requires dedicated reverse translational efforts and the use of improved preclinical models.


Authors have no conflicts of interest to declare.


D.D. is supported by grants from Melanoma Research Foundation Breakthrough Consortium (MRFBC); Gateway Fund for Cancer Research (GFCR); NCI/NIH including R01 CA257265, R01 CA257265, U01 CA271407. R.Z. is supported by research grants from the Breast Cancer Alliance, Leukemia and Lymphoma Society, AstraZeneca, and Bristol Myers Squibb.


1. Aggarwal BB. Signalling pathways of the TNF superfamily: a double-edged sword. Nat Rev Immunol. 2003; 3:745–56. https://doi.org/10.1038/nri1184. [PubMed].

2. Chen L, Flies DB. Molecular mechanisms of T cell co-stimulation and co-inhibition. Nat Rev Immunol. 2013; 13:227–42. https://doi.org/10.1038/nri3405. [PubMed].

3. Watts TH. TNF/TNFR family members in costimulation of T cell responses. Annu Rev Immunol. 2005; 23:23–68. https://doi.org/10.1146/annurev.immunol.23.021704.115839. [PubMed].

4. Nocentini G, Riccardi C. GITR: a modulator of immune response and inflammation. Adv Exp Med Biol. 2009; 647:156–73. https://doi.org/10.1007/978-0-387-89520-8_11. [PubMed].

5. Shimizu J, Yamazaki S, Takahashi T, Ishida Y, Sakaguchi S. Stimulation of CD25(+)CD4(+) regulatory T cells through GITR breaks immunological self-tolerance. Nat Immunol. 2002; 3:135–42. https://doi.org/10.1038/ni759. [PubMed].

6. McHugh RS, Whitters MJ, Piccirillo CA, Young DA, Shevach EM, Collins M, Byrne MC. CD4(+)CD25(+) immunoregulatory T cells: gene expression analysis reveals a functional role for the glucocorticoid-induced TNF receptor. Immunity. 2002; 16:311–23. https://doi.org/10.1016/s1074-7613(02)00280-7. [PubMed].

7. Eck MJ, Sprang SR. The structure of tumor necrosis factor-alpha at 2.6 A resolution. Implications for receptor binding. J Biol Chem. 1989; 264:17595–605. https://doi.org/10.2210/pdb1tnf/pdb. [PubMed].

8. Hymowitz SG, Christinger HW, Fuh G, Ultsch M, O’Connell M, Kelley RF, Ashkenazi A, de Vos AM. Triggering cell death: the crystal structure of Apo2L/TRAIL in a complex with death receptor 5. Mol Cell. 1999; 4:563–71. https://doi.org/10.1016/s1097-2765(00)80207-5. [PubMed].

9. Wajant H, Gerspach J, Pfizenmaier K. Engineering death receptor ligands for cancer therapy. Cancer Lett. 2013; 332:163–74. https://doi.org/10.1016/j.canlet.2010.12.019. [PubMed].

10. Locksley RM, Killeen N, Lenardo MJ. The TNF and TNF receptor superfamilies: integrating mammalian biology. Cell. 2001; 104:487–501. https://doi.org/10.1016/s0092-8674(01)00237-9. [PubMed].

11. Smith CA, Farrah T, Goodwin RG. The TNF receptor superfamily of cellular and viral proteins: activation, costimulation, and death. Cell. 1994; 76:959–62. https://doi.org/10.1016/0092-8674(94)90372-7. [PubMed].

12. Hanabuchi S, Watanabe N, Wang YH, Wang YH, Ito T, Shaw J, Cao W, Qin FX, Liu YJ. Human plasmacytoid predendritic cells activate NK cells through glucocorticoid-induced tumor necrosis factor receptor-ligand (GITRL). Blood. 2006; 107:3617–23. https://doi.org/10.1182/blood-2005-08-3419. [PubMed].

13. Krausz LT, Bianchini R, Ronchetti S, Fettucciari K, Nocentini G, Riccardi C. GITR-GITRL system, a novel player in shock and inflammation. ScientificWorldJournal. 2007; 7:533–66. https://doi.org/10.1100/tsw.2007.106. [PubMed].

14. Baessler T, Krusch M, Schmiedel BJ, Kloss M, Baltz KM, Wacker A, Schmetzer HM, Salih HR. Glucocorticoid-induced tumor necrosis factor receptor-related protein ligand subverts immunosurveillance of acute myeloid leukemia in humans. Cancer Res. 2009; 69:1037–45. https://doi.org/10.1158/0008-5472.CAN-08-2650. [PubMed].

15. Baltz KM, Krusch M, Bringmann A, Brossart P, Mayer F, Kloss M, Baessler T, Kumbier I, Peterfi A, Kupka S, Kroeber S, Menzel D, Radsak MP, et al. Cancer immunoediting by GITR (glucocorticoid-induced TNF-related protein) ligand in humans: NK cell/tumor cell interactions. FASEB J. 2007; 21:2442–54. https://doi.org/10.1096/fj.06-7724com. [PubMed].

16. Chan FK, Chun HJ, Zheng L, Siegel RM, Bui KL, Lenardo MJ. A domain in TNF receptors that mediates ligand-independent receptor assembly and signaling. Science. 2000; 288:2351–54. https://doi.org/10.1126/science.288.5475.2351. [PubMed].

17. Papoff G, Hausler P, Eramo A, Pagano MG, Di Leve G, Signore A, Ruberti G. Identification and characterization of a ligand-independent oligomerization domain in the extracellular region of the CD95 death receptor. J Biol Chem. 1999; 274:38241–50. https://doi.org/10.1074/jbc.274.53.38241. [PubMed].

18. Park HH. Structure of TRAF Family: Current Understanding of Receptor Recognition. Front Immunol. 2018; 9:1999. https://doi.org/10.3389/fimmu.2018.01999. [PubMed].

19. Xie P. TRAF molecules in cell signaling and in human diseases. J Mol Signal. 2013; 8:7. https://doi.org/10.1186/1750-2187-8-7. [PubMed].

20. Esparza EM, Lindsten T, Stockhausen JM, Arch RH. Tumor necrosis factor receptor (TNFR)-associated factor 5 is a critical intermediate of costimulatory signaling pathways triggered by glucocorticoid-induced TNFR in T cells. J Biol Chem. 2006; 281:8559–64. https://doi.org/10.1074/jbc.M512915200. [PubMed].

21. Snell LM, Lin GH, McPherson AJ, Moraes TJ, Watts TH. T-cell intrinsic effects of GITR and 4-1BB during viral infection and cancer immunotherapy. Immunol Rev. 2011; 244:197–217. https://doi.org/10.1111/j.1600-065X.2011.01063.x. [PubMed].

22. Grohmann U, Volpi C, Fallarino F, Bozza S, Bianchi R, Vacca C, Orabona C, Belladonna ML, Ayroldi E, Nocentini G, Boon L, Bistoni F, Fioretti MC, et al. Reverse signaling through GITR ligand enables dexamethasone to activate IDO in allergy. Nat Med. 2007; 13:579–86. https://doi.org/10.1038/nm1563. [PubMed].

23. Croft M. The role of TNF superfamily members in T-cell function and diseases. Nat Rev Immunol. 2009; 9:271–85. https://doi.org/10.1038/nri2526. [PubMed].

24. Croft M. The TNF family in T cell differentiation and function--unanswered questions and future directions. Semin Immunol. 2014; 26:183–90. https://doi.org/10.1016/j.smim.2014.02.005. [PubMed].

25. Knee DA, Hewes B, Brogdon JL. Rationale for anti-GITR cancer immunotherapy. Eur J Cancer. 2016; 67:1–10. https://doi.org/10.1016/j.ejca.2016.06.028. [PubMed].

26. Riccardi C, Ronchetti S, Nocentini G. Glucocorticoid-induced TNFR-related gene (GITR) as a therapeutic target for immunotherapy. Expert Opin Ther Targets. 2018; 22:783–97. https://doi.org/10.1080/14728222.2018.1512588. [PubMed].

27. Snell LM, Lin GH, Watts TH. IL-15-dependent upregulation of GITR on CD8 memory phenotype T cells in the bone marrow relative to spleen and lymph node suggests the bone marrow as a site of superior bioavailability of IL-15. J Immunol. 2012; 188:5915–23. https://doi.org/10.4049/jimmunol.1103270. [PubMed].

28. Cohen AD, Diab A, Perales MA, Wolchok JD, Rizzuto G, Merghoub T, Huggins D, Liu C, Turk MJ, Restifo NP, Sakaguchi S, Houghton AN. Agonist anti-GITR antibody enhances vaccine-induced CD8(+) T-cell responses and tumor immunity. Cancer Res. 2006; 66:4904–12. https://doi.org/10.1158/0008-5472.CAN-05-2813. [PubMed].

29. Nishikawa H, Kato T, Hirayama M, Orito Y, Sato E, Harada N, Gnjatic S, Old LJ, Shiku H. Regulatory T cell-resistant CD8+ T cells induced by glucocorticoid-induced tumor necrosis factor receptor signaling. Cancer Res. 2008; 68:5948–54. https://doi.org/10.1158/0008-5472.CAN-07-5839. [PubMed].

30. Snell LM, McPherson AJ, Lin GH, Sakaguchi S, Pandolfi PP, Riccardi C, Watts TH. CD8 T cell-intrinsic GITR is required for T cell clonal expansion and mouse survival following severe influenza infection. J Immunol. 2010; 185:7223–34. https://doi.org/10.4049/jimmunol.1001912. [PubMed].

31. Stephens GL, McHugh RS, Whitters MJ, Young DA, Luxenberg D, Carreno BM, Collins M, Shevach EM. Engagement of glucocorticoid-induced TNFR family-related receptor on effector T cells by its ligand mediates resistance to suppression by CD4+CD25+ T cells. J Immunol. 2004; 173:5008–20. https://doi.org/10.4049/jimmunol.173.8.5008. [PubMed].

32. Zappasodi R, Sirard C, Li Y, Budhu S, Abu-Akeel M, Liu C, Yang X, Zhong H, Newman W, Qi J, Wong P, Schaer D, Koon H, et al. Rational design of anti-GITR-based combination immunotherapy. Nat Med. 2019; 25:759–66. https://doi.org/10.1038/s41591-019-0420-8. [PubMed].

33. Valzasina B, Guiducci C, Dislich H, Killeen N, Weinberg AD, Colombo MP. Triggering of OX40 (CD134) on CD4(+)CD25+ T cells blocks their inhibitory activity: a novel regulatory role for OX40 and its comparison with GITR. Blood. 2005; 105:2845–51. https://doi.org/10.1182/blood-2004-07-2959. [PubMed].

34. Amoozgar Z, Kloepper J, Ren J, Tay RE, Kazer SW, Kiner E, Krishnan S, Posada JM, Ghosh M, Mamessier E, Wong C, Ferraro GB, Batista A, et al. Targeting Treg cells with GITR activation alleviates resistance to immunotherapy in murine glioblastomas. Nat Commun. 2021; 12:2582. https://doi.org/10.1038/s41467-021-22885-8. [PubMed].

35. Mahne AE, Mauze S, Joyce-Shaikh B, Xia J, Bowman EP, Beebe AM, Cua DJ, Jain R. Dual Roles for Regulatory T-cell Depletion and Costimulatory Signaling in Agonistic GITR Targeting for Tumor Immunotherapy. Cancer Res. 2017; 77:1108–18. https://doi.org/10.1158/0008-5472.CAN-16-0797. [PubMed].

36. Bulliard Y, Jolicoeur R, Windman M, Rue SM, Ettenberg S, Knee DA, Wilson NS, Dranoff G, Brogdon JL. Activating Fc γ receptors contribute to the antitumor activities of immunoregulatory receptor-targeting antibodies. J Exp Med. 2013; 210:1685–93. https://doi.org/10.1084/jem.20130573. [PubMed].

37. Schaer DA, Budhu S, Liu C, Bryson C, Malandro N, Cohen A, Zhong H, Yang X, Houghton AN, Merghoub T, Wolchok JD. GITR pathway activation abrogates tumor immune suppression through loss of regulatory T cell lineage stability. Cancer Immunol Res. 2013; 1:320–31. https://doi.org/10.1158/2326-6066.CIR-13-0086. [PubMed].

38. Sabharwal SS, Rosen DB, Grein J, Tedesco D, Joyce-Shaikh B, Ueda R, Semana M, Bauer M, Bang K, Stevenson C, Cua DJ, Zúñiga LA. GITR Agonism Enhances Cellular Metabolism to Support CD8(+) T-cell Proliferation and Effector Cytokine Production in a Mouse Tumor Model. Cancer Immunol Res. 2018; 6:1199–211. https://doi.org/10.1158/2326-6066.CIR-17-0632. [PubMed].

39. Ko K, Yamazaki S, Nakamura K, Nishioka T, Hirota K, Yamaguchi T, Shimizu J, Nomura T, Chiba T, Sakaguchi S. Treatment of advanced tumors with agonistic anti-GITR mAb and its effects on tumor-infiltrating Foxp3+CD25+CD4+ regulatory T cells. J Exp Med. 2005; 202:885–91. https://doi.org/10.1084/jem.20050940. [PubMed].

40. Cohen AD, Schaer DA, Liu C, Li Y, Hirschhorn-Cymmerman D, Kim SC, Diab A, Rizzuto G, Duan F, Perales MA, Merghoub T, Houghton AN, Wolchok JD. Agonist anti-GITR monoclonal antibody induces melanoma tumor immunity in mice by altering regulatory T cell stability and intra-tumor accumulation. PLoS One. 2010; 5:e10436. https://doi.org/10.1371/journal.pone.0010436. [PubMed].

41. Loddenkemper C, Hoffmann C, Stanke J, Nagorsen D, Baron U, Olek S, Huehn J, Ritz JP, Stein H, Kaufmann AM, Schneider A, Cichon G. Regulatory (FOXP3+) T cells as target for immune therapy of cervical intraepithelial neoplasia and cervical cancer. Cancer Sci. 2009; 100:1112–17. https://doi.org/10.1111/j.1349-7006.2009.01153.x. [PubMed].

42. Lu L, Xu X, Zhang B, Zhang R, Ji H, Wang X. Combined PD-1 blockade and GITR triggering induce a potent antitumor immunity in murine cancer models and synergizes with chemotherapeutic drugs. J Transl Med. 2014; 12:36. https://doi.org/10.1186/1479-5876-12-36. [PubMed].

43. Villarreal DO, Chin D, Smith MA, Luistro LL, Snyder LA. Combination GITR targeting/PD-1 blockade with vaccination drives robust antigen-specific antitumor immunity. Oncotarget. 2017; 8:39117–30. https://doi.org/10.18632/oncotarget.16605. [PubMed].

44. Wang B, Zhang W, Jankovic V, Golubov J, Poon P, Oswald EM, Gurer C, Wei J, Ramos I, Wu Q, Waite J, Ni M, Adler C, et al. Combination cancer immunotherapy targeting PD-1 and GITR can rescue CD8(+) T cell dysfunction and maintain memory phenotype. Sci Immunol. 2018; 3:eaat7061. https://doi.org/10.1126/sciimmunol.aat7061. [PubMed].

45. Balmanoukian AS, Infante JR, Aljumaily R, Naing A, Chintakuntlawar AV, Rizvi NA, Ross HJ, Gordon M, Mallinder PR, Elgeioushi N, González-García I, Standifer N, Cann J, et al. Safety and Clinical Activity of MEDI1873, a Novel GITR Agonist, in Advanced Solid Tumors. Clin Cancer Res. 2020; 26:6196–203. https://doi.org/10.1158/1078-0432.CCR-20-0452. [PubMed].

46. Davar D, Zappasodi R, Wang H, Naik GS, Sato T, Bauer T, Bajor D, Rixe O, Newman W, Qi J, Holland A, Wong P, Sifferlen L, et al. Phase IB Study of GITR Agonist Antibody TRX518 Singly and in Combination with Gemcitabine, Pembrolizumab, or Nivolumab in Patients with Advanced Solid Tumors. Clin Cancer Res. 2022; 28:3990–4002. https://doi.org/10.1158/1078-0432.CCR-22-0339. [PubMed].

47. Geva R, Voskoboynik M, Dobrenkov K, Mayawala K, Gwo J, Wnek R, Chartash E, Long GV. First-in-human phase 1 study of MK-1248, an anti-glucocorticoid-induced tumor necrosis factor receptor agonist monoclonal antibody, as monotherapy or with pembrolizumab in patients with advanced solid tumors. Cancer. 2020; 126:4926–35. https://doi.org/10.1002/cncr.33133. [PubMed].

48. Heinhuis KM, Carlino M, Joerger M, Di Nicola M, Meniawy T, Rottey S, Moreno V, Gazzah A, Delord JP, Paz-Ares L, Britschgi C, Schilder RJ, O’Byrne K, et al. Safety, Tolerability, and Potential Clinical Activity of a Glucocorticoid-Induced TNF Receptor-Related Protein Agonist Alone or in Combination With Nivolumab for Patients With Advanced Solid Tumors: A Phase 1/2a Dose-Escalation and Cohort-Expansion Clinical Trial. JAMA Oncol. 2020; 6:100–7. https://doi.org/10.1001/jamaoncol.2019.3848. [PubMed].

49. Papadopoulos KP, Autio K, Golan T, Dobrenkov K, Chartash E, Chen Q, Wnek R, Long GV. Phase I Study of MK-4166, an Anti-human Glucocorticoid-Induced TNF Receptor Antibody, Alone or with Pembrolizumab in Advanced Solid Tumors. Clin Cancer Res. 2021; 27:1904–11. https://doi.org/10.1158/1078-0432.CCR-20-2886. [PubMed].

50. Piha-Paul SA, Geva R, Tan TJ, Lim DW, Hierro C, Doi T, Rahma O, Lesokhin A, Luke JJ, Otero J, Nardi L, Singh A, Xyrafas A, et al. First-in-human phase I/Ib open-label dose-escalation study of GWN323 (anti-GITR) as a single agent and in combination with spartalizumab (anti-PD-1) in patients with advanced solid tumors and lymphomas. J Immunother Cancer. 2021; 9:e002863. https://doi.org/10.1136/jitc-2021-002863. [PubMed].

51. Tran B, Carvajal RD, Marabelle A, Patel SP, LoRusso PM, Rasmussen E, Juan G, Upreti VV, Beers C, Ngarmchamnanrith G, Schöffski P. Dose escalation results from a first-in-human, phase 1 study of glucocorticoid-induced TNF receptor-related protein agonist AMG 228 in patients with advanced solid tumors. J Immunother Cancer. 2018; 6:93. https://doi.org/10.1186/s40425-018-0407-x. [PubMed].

52. Wang R, Baxi V, Li Z, Locke D, Hedvat C, Sun Y, Walsh AM, Shao X, Basavanhally T, Greenawalt DM, Patah P, Novosiadly R. Pharmacodynamic activity of BMS-986156, a glucocorticoid-induced TNF receptor-related protein agonist, alone or in combination with nivolumab in patients with advanced solid tumors. ESMO Open. 2023; 8:100784. https://doi.org/10.1016/j.esmoop.2023.100784. [PubMed].

53. Lakhani N, Hamid O, Braña I, Reguera Puertas P, Lopez Criado MP, Swiecicki PL, De Miguel Luken MJ, Gil Martín M, Khong H, Moreno Garcia V, Lostes Bardaji MJ, Sun F, Sandigursky S, et al. 196TiP A phase I study of REGN6569, a GITR monoclonal antibody (mAb), in combination with cemiplimab in patients with advanced solid tumour malignancies. Immuno-Oncology and Technology. 2022; 16:100308. https://doi.org:https://doi.org/10.1016/j.iotech.2022.100308.

54. Tigue NJ, Bamber L, Andrews J, Ireland S, Hair J, Carter E, Sridharan S, Jovanović J, Rees DG, Springall JS, Solier E, Li YM, Chodorge M, et al. MEDI1873, a potent, stabilized hexameric agonist of human GITR with regulatory T-cell targeting potential. Oncoimmunology. 2017; 6:e1280645. https://doi.org/10.1080/2162402X.2017.1280645. [PubMed].

55. Richards DM, Marschall V, Billian-Frey K, Heinonen K, Merz C, Redondo Müller M, Sefrin JP, Schröder M, Sykora J, Fricke H, Hill O, Gieffers C, Thiemann M. HERA-GITRL activates T cells and promotes anti-tumor efficacy independent of FcγR-binding functionality. J Immunother Cancer. 2019; 7:191. https://doi.org/10.1186/s40425-019-0671-4. [PubMed].

56. Chan S, Belmar N, Ho S, Rogers B, Stickler M, Graham M, Lee E, Tran N, Zhang D, Gupta P, Sho M, MacDonough T, Woolley A, et al. An anti-PD-1-GITR-L bispecific agonist induces GITR clustering-mediated T cell activation for cancer immunotherapy. Nat Cancer. 2022; 3:337–54. https://doi.org/10.1038/s43018-022-00334-9. [PubMed].

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