Objective:To develop a novel α vβ 3-targeted theranostic agent 177Lu-Evans blue (EB)-Arg-Gly-Asp (RGD) and evaluate its value for SPECT imaging and targeted radionuclide therapy in the non-small cell lung cancer (NSCLC)-patient-derived xenografts (PDX). Methods:The α vβ 3-targeted molecule RGD was conjugated with the albumin binding moiety EB to obtain EB-RGD, and EB-RGD was further conjugated with the chelator 1, 4, 7, 10-tetraazacyclododecane-1, 4, 7, 10-tetraacetic acid (DOTA) for 177Lu radiolabeling. NSCLC-PDX mice models ( n=68) were established. 177Lu-EB-RGD SPECT imaging, biodistribution study were performed in 28 PDX mice models after being injected with 177Lu-EB-RGD or 177Lu-RGD. Targeted radionuclide therapy were subsequently performed in NSCLC-PDX mice models, saline group (group A), 18.5 MBq 177Lu-RGD group (group B), 18.5 MBq 177Lu-EB-RGD group (group C), 29.6 MBq 177Lu-EB-RGD group (group D), n=10 in each group; tumor volumes of PDX mice models in each group were observed within 50 d. Differences between 2 groups were compared using independent-sample t test. Results:177Lu-EB-RGD was radiolabeled at a specific activity of (55±14) GBq/μmol, with a radiochemical yield of more than 95% and a radiochemical purity of more than 95%. Regarding the SPECT imaging, tumors in NSCLC-PDX mice were clearly observed from 4 to 96 h post-injection and the tumor to muscle ratio (T/M) reached 7.34±0.67, 14.63±3.82, 15.69±3.58 and 15.99±5.42 at 4, 24, 72, 96 h post-injection, respectively. Biodistribution study further confirmed the findings from SPECT imaging, and the tumor uptake of 177Lu-EB-RGD were markedly increased compared to 177Lu-RGD 4 h post-injection ((10.15±1.17) vs (3.30±1.47) percent injection dose per gram (%ID/g); t=18.60, P<0.05). Regarding targeted radiotherapy, the tumor volumes were quickly increased within 50 d after treatment in group A and B, while the tumor volumes were decreased in group C and D, until the tumors in group C and D disappeared at the 28th day after initial treatment with no sign of recurrence during the observation period. Conclusions:177Lu-EB-RGD can target α vβ 3-positive NSCLC-PDX with intense tumor to background ratio and strong tumor inhibition efficacy. The preclinical data suggests that 177Lu-EB-RGD may be an effective new treatment option for advanced NSCLC patients with resistance or ineffective results for targeted therapy.

Objective:To investigate the therapeutic efficacy and potential mechanisms of integrin α vβ 3-targeted radionuclide therapy (TRT) in combination with anti-programmed cell death protein ligand 1 (PD-L1) immunotherapy. Methods:Integrin α vβ 3-targeted molecule Arg-Gly-Asp (RGD) was conjugated with Evans blue (EB) and then labeled with 177Lu to obtain 177Lu-EB-RGD. The radioactivity and radiochemical purity were determined. MicroSPECT imaging, biodistribution, and in vivo therapeutic efficacy were subsequently performed in MC38 murine colon cancer models. Volume of tumor and body mass of mice were observed to assess the therapeutic efficacy and safety ( n=9 in each group). Flow cytometry was used to evaluate therapy response of saline-treated (control, group A), 18.5 MBq 177Lu-EB-RGD-treated (group B), 10 mg/kg PD-L1 antibody-treated (group C), TRT combined with immunotherapy-treated (group D, 18.5 MBq 177Lu-EB-RGD and 10 mg/kg PD-L1 antibody) mice and alterations in tumor microenvironment (PD-L1 + immune cells, CD8 + T cells and regulatory T cells). Independent-sample t test and repeated measures analysis of variance were used for data analysis. Results:The radioactivity of 177Lu-EB-RGD was (55.85±14.00) GBq/μmol. SPECT imaging clearly visualized the MC38 tumors in mice models with high uptake and long retention time, the tumor/muscle ratio reached 14.87±0.88 at 24 h postinjection, while less uptake and retention in normal tissues. Tumor uptake of 177Lu-EB-RGD was significantly higher than that of 177Lu-RGD 4 h post-injection ((12.00±1.60) vs (3.69±0.37) %ID/g; t=8.63, P<0.01). The efficacy results between each treatment group was significantly different ( F=7.32, P=0.03) at day 6 post-treatment. The combination therapy showed the most outstanding anti-tumor efficacy with 7/9 mice showed complete response. Flow cytometry results showed that TRT up-regulated the PD-L1 expression significantly, namely, PD-L1 + immune cells in group B and group A were significantly different (CD45 + /PD-L1: 2.34% vs 0.95%, CD11b + /PD-L1: 2.41% vs 0.66%; t values: 11.17 and 8.70, both P<0.01); immunotherapy and combination therapy dramatically stimulated the infiltration of CD8 + T cells (2.07% vs 0.26%, 2.71% vs 0.26%; t values: 4.10 and 6.03, both P<0.05). Conclusion:TRT in combination with immunotherapy synergistically enhance anti-tumor efficacy, which is expected to play a role in the treatment of patients with advanced tumor where TRT can be applied.