title: Agonist anti-GITR monoclonal antibody and stereotactic radiation induce immune-mediated survival advantage in murine intracranial glioma.
abstract: BACKGROUND
  Glioblastoma (GBM) is a poorly immunogenic neoplasm treated with focused radiation. Immunotherapy has demonstrated synergistic survival effects with stereotactic radiosurgery (SRS) in murine GBM. GITR is a co-stimulatory molecule expressed constitutively on regulatory T-cells and by effector T-cells upon activation. We tested the hypothesis that anti-GITR monoclonal antibody (mAb) and SRS together would confer an immune-mediated survival benefit in glioma using the orthotopic GL261 glioma model.
  
  
  METHODS
  Mice received SRS and anti-GITR 10 days after implantation. The anti-GITR mAbs tested were formatted as mouse IgG1 D265A (anti-GITR (1)) and IgG2a (anti-GITR (2a)) isotypes. Mice were randomized to four treatment groups: (1) control; (2) SRS; (3) anti-GITR; (4) anti-GITR/SRS. SRS was delivered to the tumor in one fraction, and mice were treated with mAb thrice. Mice were euthanized on day 21 to analyze the immunologic profile of tumor, spleen, and tumor draining lymph nodes.
  
  
  RESULTS
  Anti-GITR (1)/SRS significantly improved survival over either treatment alone (p < .0001) with a cure rate of 24 % versus 0 % in a T-lymphocyte-dependent manner. There was elevated intratumoral CD4+ effector cell infiltration relative to Treg infiltration in mice treated with anti-GITR (1)/SRS, as well as significantly elevated IFNγ and IL-2 production by CD4+ T-cells and elevated IFNγ and TNFα production by CD8+ T-cells. There was increased mRNA expression of M1 markers and decreased expression of M2 markers in tumor infiltrating mononuclear cells. The anti-GITR (2a)/SRS combination did not improve survival, induce tumor regression, or result in Treg depletion.
  
  
  CONCLUSIONS
  These findings provide preclinical evidence for the use of anti-GITR (1) non-depleting antibodies in combination with SRS in GBM.
authors.affiliation: The Johns Hopkins University School of Medicine, Baltimore, USA.
authors.forename: Mira A
authors.initials: MA
authors.lastname: Patel
authors.affiliation: The Johns Hopkins University School of Medicine, Baltimore, USA.
authors.forename: Jennifer E
authors.initials: JE
authors.lastname: Kim
authors.affiliation: The Johns Hopkins University School of Medicine, Baltimore, USA.
authors.forename: Debebe
authors.initials: D
authors.lastname: Theodros
authors.affiliation: Department of Oncology, Baltimore, USA.
authors.forename: Ada
authors.initials: A
authors.lastname: Tam
authors.affiliation: Department Radiation Oncology, Baltimore, USA.
authors.forename: Esteban
authors.initials: E
authors.lastname: Velarde
authors.affiliation: Department of Oncology, Baltimore, USA.
authors.forename: Christina M
authors.initials: CM
authors.lastname: Kochel
authors.affiliation: Department of Oncology, Baltimore, USA.
authors.forename: Brian
authors.initials: B
authors.lastname: Francica
authors.affiliation: Department of Oncology, Baltimore, USA.
authors.forename: Thomas R
authors.initials: TR
authors.lastname: Nirschl
authors.affiliation: Department of Oncology, Baltimore, USA.
authors.forename: Ali
authors.initials: A
authors.lastname: Ghasemzadeh
authors.affiliation: Department of Neurosurgery, The Johns Hopkins University School of Medicine, 600 N. Wolfe St. Phipps Building Rm 123, Baltimore, 21287 MD USA.
authors.forename: Dimitrios
authors.initials: D
authors.lastname: Mathios
authors.affiliation: Department of Neurosurgery, The Johns Hopkins University School of Medicine, 600 N. Wolfe St. Phipps Building Rm 123, Baltimore, 21287 MD USA.
authors.forename: Sarah
authors.initials: S
authors.lastname: Harris-Bookman
authors.affiliation: Department of Neurosurgery, The Johns Hopkins University School of Medicine, 600 N. Wolfe St. Phipps Building Rm 123, Baltimore, 21287 MD USA.
authors.forename: Christopher C
authors.initials: CC
authors.lastname: Jackson
authors.affiliation: Department of Neurosurgery, The Johns Hopkins University School of Medicine, 600 N. Wolfe St. Phipps Building Rm 123, Baltimore, 21287 MD USA.
authors.forename: Christina
authors.initials: C
authors.lastname: Jackson
authors.affiliation: Department of Neurosurgery, The Johns Hopkins University School of Medicine, 600 N. Wolfe St. Phipps Building Rm 123, Baltimore, 21287 MD USA.
authors.forename: Xiaobu
authors.initials: X
authors.lastname: Ye
authors.affiliation: Department of Oncology, Baltimore, USA.|Department Radiation Oncology, Baltimore, USA.|and the Brady Urological Institute, Baltimore, USA.
authors.forename: Phuoc T
authors.initials: PT
authors.lastname: Tran
authors.affiliation: Department of Neurosurgery, The Johns Hopkins University School of Medicine, 600 N. Wolfe St. Phipps Building Rm 123, Baltimore, 21287 MD USA.
authors.forename: Betty
authors.initials: B
authors.lastname: Tyler
authors.affiliation: Bristol-Myers Squibb Company, San Francisco, CA USA.
authors.forename: Vladimir
authors.initials: V
authors.lastname: Coric
authors.affiliation: Bristol-Myers Squibb Company, San Francisco, CA USA.
authors.forename: Mark
authors.initials: M
authors.lastname: Selby
authors.affiliation: The Johns Hopkins University School of Medicine, Baltimore, USA.|Department of Neurosurgery, The Johns Hopkins University School of Medicine, 600 N. Wolfe St. Phipps Building Rm 123, Baltimore, 21287 MD USA.
authors.forename: Henry
authors.initials: H
authors.lastname: Brem
authors.affiliation: and the Brady Urological Institute, Baltimore, USA.
authors.forename: Charles G
authors.initials: CG
authors.lastname: Drake
authors.affiliation: Department of Oncology, Baltimore, USA.
authors.forename: Drew M
authors.initials: DM
authors.lastname: Pardoll
authors.affiliation: The Johns Hopkins University School of Medicine, Baltimore, USA.|Department of Neurosurgery, The Johns Hopkins University School of Medicine, 600 N. Wolfe St. Phipps Building Rm 123, Baltimore, 21287 MD USA.
authors.forename: Michael
authors.initials: M
authors.lastname: Lim
keywords: Antibody; GITR; Gioblastoma; Immune checkpoint; Immunotherapy; Radiation