Data from Combination Therapy with Anti-PD-1, Anti-TIM-3, and Focal Radiation Results in Regression of Murine Gliomas

Abstract

<div>Abstract<p><b>Purpose:</b> Checkpoint molecules like programmed death-1 (PD-1) and T-cell immunoglobulin mucin-3 (TIM-3) are negative immune regulators that may be upregulated in the setting of glioblastoma multiforme. Combined PD-1 blockade and stereotactic radiosurgery (SRS) have been shown to improve antitumor immunity and produce long-term survivors in a murine glioma model. However, tumor-infiltrating lymphocytes (TIL) can express multiple checkpoints, and expression of ≥2 checkpoints corresponds to a more exhausted T-cell phenotype. We investigate TIM-3 expression in a glioma model and the antitumor efficacy of TIM-3 blockade alone and in combination with anti-PD-1 and SRS.</p><p><b>Experimental Design:</b> C57BL/6 mice were implanted with murine glioma cell line GL261-luc2 and randomized into 8 treatment arms: (<a href="#bib1" target="_blank">i</a>) control, (<a href="#bib2" target="_blank">ii</a>) SRS, (<a href="#bib3" target="_blank">iii</a>) anti-PD-1 antibody, (<a href="#bib4" target="_blank">iv</a>) anti-TIM-3 antibody, (<a href="#bib5" target="_blank">v</a>) anti-PD-1 + SRS, (<a href="#bib6" target="_blank">vi</a>) anti-TIM-3 + SRS, (<a href="#bib7" target="_blank">vii</a>) anti-PD-1 + anti-TIM-3, and (<a href="#bib8" target="_blank">viii</a>) anti-PD-1 + anti-TIM-3 + SRS. Survival and immune activation were assessed.</p><p><b>Results:</b> Dual therapy with anti-TIM-3 antibody + SRS or anti-TIM-3 + anti-PD-1 improved survival compared with anti-TIM-3 antibody alone. Triple therapy resulted in 100% overall survival (<i>P</i> < 0.05), a significant improvement compared with other arms. Long-term survivors demonstrated increased immune cell infiltration and activity and immune memory. Finally, positive staining for TIM-3 was detected in 7 of 8 human GBM samples.</p><p><b>Conclusions:</b> This is the first preclinical investigation on the effects of dual PD-1 and TIM-3 blockade with radiation. We also demonstrate the presence of TIM-3 in human glioblastoma multiforme and provide preclinical evidence for a novel treatment combination that can potentially result in long-term glioma survival and constitutes a novel immunotherapeutic strategy for the treatment of glioblastoma multiforme. <i>Clin Cancer Res; 23(1); 124–36. ©2016 AACR</i>.</p></div>