- Potent anti-tumor activity following a single dose: A single dose of tetravalent anti-GITR significantly inhibited tumor growth in multiple models including CT26 and MC38. Treatment was capable of inducing complete tumor rejection, and activity was observed at doses as low as 0.08 mg/kg in both models.
- Fc-independent activity: Tetravalent anti-GITR antibody retained partial tumor growth inhibition activity even in the absence of Fc-mediated crosslinking or effector function, whereas a conventional bivalent antibody (DTA-1) required Fc function.
- Pharmacodynamic responses: Tetravalent anti-GITR antibody treatment reduced the number of T cells in the peripheral blood 3 days post-treatment. In the tumor, Treg and conventional CD4 T cells decreased, but CD8 T cell numbers were maintained. This resulted in a ratio of CD4 and CD8 effector T cells to Treg that created a favorable environment for an effective anti-tumor immune response.
- Induction of long-term immunity: Mice that eliminated CT26 tumors in response to tetravalent anti-GITR were resistant to tumor regrowth upon re-challenge with the same tumor, but not to an antigenically-unrelated tumor.
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