Predictive imaging of the immunotherapy and radioimmunotherapy response by immunoPET via a new target (CD103) and innovative protein formats in preclinical NSCLC.

Abstract

2559 Background: Immune checkpoint immunotherapies (ICI) have transformed cancer treatment, but patients have varied responses and potential risks of autoimmune disease. To improve ICI, we need to identify biomarkers to select responding patients and research new approaches. To this, resident memory T cells (TRM) LT CD8 + CD103 + , have been identified as a promising tumor-specific biomarker for studying therapeutic efficacy involving ICI. Internal radiotherapy appears to be a promising approach. Our objective is to develop new therapeutic approaches combining radiotherapy and ICI (radioimmunotherapy) using CD8 + CD103 + immunoPET imaging as a predictive biomarker of efficacy. Methods: After developing and characterizing a new CD103 radiotracer and validating the dual 18 F PET-Scan imaging for CD8 + and CD103 + in C57BL/6 mouse models, we implanted mice subcutaneously with MC38 and othotopically syngenetically with LLC. We evaluated the efficacy of radioimmunotherapy vs ICI and the predictive effect of TRM in this syngeneic orthotopic model. To this, we implanted two syngeneic NSCLC cell lines, either LLC for a cold tumor or CMT167 for a warmer tumor. We performed double imaging prior to treatment with [ 18 F]-CD8 mutated FcRn and [ 18 F]-CD103 minibody on 2 consecutive days. We treated our mice 3 times, 3 days apart, with the first dose of either cold Avelumab or [ 177 Lu]-Avelumab (8MBq). The second and third doses were cold Avelumab. We performed double post-treatment imaging with [ 18 F]-CD8 mutated FcRn and [ 18 F]-CD103 minibody on 2 consecutive days, as well as ex vivo analyses and a survival study. Results: There was a trend towards improved survival in [ 177 Lu]-Avelumab treated mice vs Avelumab treated mice but more markedly in the immunogenic model (30d vs 21d). The impact on tumor growth was assessed by comparing the two treatment groups with untreated mice. Radioimmunotherapy induced a significant decrease in overall tumor growth compared with mice treated with ICI (0.45 ccm vs 0.68 ccm, *p < 0.05 turkey's multiple comparison test) in the immunogenic model. In the cold tumor model, there was a significant difference in the tumor size ratio before and after treatment, for mice treated with radioimmunotherapy vs ICI (12.96 vs 26.08, ***p < 0.001 Uncorrected Fisher's LSD). An increase in immune infiltration was validated by PET and flow cytometry for the immunogenic model (pre-treatment: 5.00%ID/cc max, versus post-treatment 8.23%ID/cc max for CD8, *p < 0.05 two way-Anova). More heterogeneous results were observed in the cold tumor model. Conclusions: Radio-immunotherapy reduces tumour growth and stimulates the immune system by circulating LT CD8 . The dual 18 F PET-Scan imaging for CD8 + and CD103 + offer a promising non-invasive visualization of tumor-infiltrating CD103 + TRMs. We need to correlate LT CD8+ /CD103+ infiltration with therapeutic response.