Immune checkpoint blockers (ICBs) targeting programmed death receptor 1 (PD-1) ligand 1 (PD-L1) for immunotherapy have radically reformed oncology. It is of great significance to enhance the response rate of ICB in cancer patients. Here, a radioiodinated anti-PD-L1 antibody ( 131 I-αPD-L1) was developed for PD-L1-targeted single-photon emission computed tomography (SPECT) imaging and αPD-L1 immunotherapy. Flow cytometry and immunofluorescence staining were performed to identify PD-L1 upregulation in a time-and dose-dependent manner after being induced by 131 I-αPD-L1. ImmunoSPECT imaging and biodistributions of 131 I-αPD-L1 in CT26, MC38, 4T1, and B16F10 tumor models were conducted to visualize the high tumor uptake and low background signal. Compared to monotherapy alone, concurrent administration of αPD-L1 mAb and 131 I-αPD-L1 revealed improved tumor control in murine tumor models. The combination of 11.1 MBq of 131 I-αPD-L1 and 200 μg of αPD-L1 mAb resulted in significant tumor growth delay and prolonged survival. This radioligand synergized immunotherapy strategy holds great potential for cancer management.

We put forward a novel targeting-triggering-therapy (TTT) scheme that combines 64Cu-based targeted radionuclide therapy (TRT) with programmed death-ligand 1 (PD-L1)-based immunotherapy for enhancing therapeutic efficacy. The αvβ3 integrin-targeted 64Cu-DOTA-EB-cRGDfK (64Cu-DER) was synthesized. Flow cytometry, immunofluorescence staining, and RT-qPCR were performed to verify PD-L1 upregulation after irradiation with 64Cu-DER. Positron emission tomography imaging was performed to investigate the prominent tumor retention property of 64Cu-DER. In the MC38 tumor model, anti-PD-L1 antibody (αPD-L1 mAb) was delivered in a concurrent or sequential manner after 64Cu-DER was injected, followed by the testing of changes in tumor microenvironment (TME). PD-L1 was upregulated in a time- and dose-dependent manner after being induced by 64Cu-DER. The combination of 64Cu-DER TRT (925 MBq/kg) and αPD-L1 mAb (10 mg/kg) resulted in significant delay in tumor growth and protected against tumor rechallenge. Blockade of PD-L1 at 4 h after 64Cu-DER TRT (64Cu-DER + αPD-L1 mAb @ 4 h combination group) was able to achieve 100% survival rate, prevent tumor relapse, and evidently prolong the survival of mice. In summary, the combination of 64Cu-DER and αPD-L1 mAb in a time-dependent manner could be a promising approach to improve therapeutic efficacy. Understandably, this strategy has the potential to extend the scope of 64Cu-based TTT and merits translation into clinical practice for the better management of immune checkpoint blockade immunotherapy.

The therapeutic alliance of 177 Lu radioligand therapy and immune checkpoint blockade (ICB) has gained increasing attention. This study aims to investigate the immunomodulatory effect (targeting-triggering-therapy) of 177 Lu-DOTA-EB-cRGDfK ( 177 Lu-DER) and to optimize the therapeutic efficacy by combining targeted radionuclide therapy (TRT) and ICB. Flow cytometry, immunofluorescence analysis, and RT-qPCR are conducted to confirm the change of PD-L1 expression. Tumor uptakes of 177 Lu-DER in CT26 and MC38 colorectal tumor models are verified through single photon emission computed tomography imaging. Further, the radionuclide dose and the treatment schedule to optimize the therapeutic scheme are carefully titrated and the mechanism of the synergy between TRT and ICB is explored. The results demonstrate that PD-L1 expression is upregulated after irradiation of 177 Lu. The combination of 9.25 MBq 177 Lu-DER TRT with 200 µg 𝜶PD-L1 immunotherapy significantly inhibits tumor growth and protects against tumor recurrence. It is also found that 4-h interval is an effective time window between radioligand administration and ICB therapy. In conclusion, a promising scheme for tumor immunotherapy is realized based on the sequential administration of integrin 𝜶 v 𝜷 3 -targeted radioligand and PD-L1 immune checkpoint blocker, emphasizing the potential of combining radiotheranostics with ICB for precision cancer therapy.

Noninvasive single-photon emission computed tomography (SPECT) imaging with [ 99m Tc]Tc-HYNFA via folate receptor (FR) targeting was proposed to assess the inflammation and therapeutic effect of systemic sclerosis (SSc) in model mice. The radiochemical yield and purity of [ 99m Tc]Tc-HYNFA were over 95%, with a specific activity of about 9.36 ± 0.17 MBq/nmol. At the end of induction, the uptake ratios of bleomycin-injected regions on the back-to-muscle (R/M) and lung-to-muscle (L/M) derived from SPECT images were 7.27 ± 0.50 and 4.25 ± 0.15, respectively. The radioactivity uptakes could be blocked by excessive folic acid (FA), and R/M and L/M obviously decreased to 2.78 ± 0.57 and 2.51 ± 0.79, respectively. R/M (2.22 ± 0.71) and L/M (1.62 ± 0.28) decreased very close to those of the control mice group (R/M = 1.99 ± 0.36, L/M = 1.50 ± 0.14) when macrophages had been depleted in advance. After being treated with cyclophosphamide (CTX) or methotrexate (MTX), R/M and L/M decreased to 3.58 ± 0.52 and 2.03 ± 0.32 (CTX treatment) or 2.48 ± 0.64 and 1.83 ± 0.06 (MTX treatment). R/M and L/M were highly correlated with pathological changes. The trend of hydroxyproline content in lungs at the later non-inflammatory phase of each group was similar to the uptake values of the lung in the 4th week from the beginning of induction. [ 99m Tc]Tc-HYNFA had an ideal uptake in SSc lesions. R/M and L/M had a high consistency with pathological changes. SPECT imaging-targeted FR could monitor the therapeutic effect of CTX and MTX. It is expected to be an effective means to evaluate SSc.