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Radioimmunotherapy with an ²¹¹ At-labeled anti-tissue factor antibody protected by sodium ascorbate.

ABSTRACT: Tissue factor (TF), the trigger protein of the extrinsic blood coagulation cascade, is abundantly expressed in various cancers including gastric cancer. Anti-TF monoclonal antibodies (mAbs) capable of targeting cancers have been successfully applied to armed antibodies such as antibody-drug conjugates (ADCs) and molecular imaging probes. We prepared an anti-TF mAb, clone 1084, labeled with astatine-211 (²¹¹ At), as a promising alpha emitter for cancer treatment. Alpha particles are characterized by high linear energy transfer and a range of 50-100 µm in tissue. Therefore, selective and efficient tumor accumulation of alpha emitters results in potent antitumor activities against cancer cells with minor effects on normal cells adjacent to the tumor. Although the ²¹¹ At-conjugated clone 1084 (²¹¹ At-anti-TF mAb) was disrupted by an ²¹¹ At-induced radiochemical reaction, we demonstrated that astatinated anti-TF mAbs eluted in 0.6% or 1.2% sodium ascorbate (SA) solution were protected from antibody denaturation, which contributed to the maintenance of cellular binding activities and cytocidal effects of this immunoconjugate. Although body weight loss was observed in mice administered a 1.2% SA solution, the loss was transient and the radioprotectant seemed to be tolerable in vivo. In a high TF-expressing gastric cancer xenograft model, ²¹¹ At-anti-TF mAb in 1.2% SA exerted a significantly greater antitumor effect than nonprotected ²¹¹ At-anti-TF mAb. Moreover, the antitumor activities of the protected immunoconjugate in gastric cancer xenograft models were dependent on the level of TF in cancer cells. These findings suggest the clinical availability of the radioprotectant and applicability of clone 1084 to ²¹¹ At-radioimmunotherapy.

SUBMITTER: Takashima H

PROVIDER: S-EPMC8088967 | biostudies-literature |

REPOSITORIES: biostudies-literature

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Project description:PurposeIncreased angiogenesis is a marker of aggressiveness in many cancers. Targeted radionuclide therapy of these cancers with angiogenesis-targeting agents may curtail this increased blood vessel formation and slow the growth of tumors, both primary and metastatic. CD105, or endoglin, has a primary role in angiogenesis in a number of cancers, making this a widely applicable target for targeted radioimmunotherapy.MethodsThe anti-CD105 antibody, TRC105 (TRACON Pharmaceuticals), was conjugated with DTPA for radiolabeling with 177Lu (t 1/2 6.65 days). Balb/c mice were implanted with 4T1 mammary carcinoma cells, and five study groups were used: 177Lu only, TRC105 only, 177Lu-DTPA-IgG (a nonspecific antibody), 177Lu-DTPA-TRC105 low-dose, and 177Lu-DTPA-TRC105 high-dose. Toxicity of the agent was monitored by body weight measurements and analysis of blood markers. Biodistribution studies of 177Lu-DTPA-TRC105 were also performed at 1 and 7 days after injection. Ex vivo histology studies of various tissues were conducted at 1, 7, and 30 days after injection of high-dose 177Lu-DTPA-TRC105.ResultsBiodistribution studies indicated steady uptake of 177Lu-DTPA-TRC105 in 4T1 tumors between 1 and 7 days after injection (14.3 ± 2.3%ID/g and 11.6 ± 6.1%ID/g, respectively; n = 3) and gradual clearance from other organs. Significant inhibition of tumor growth was observed in the high-dose group, with a corresponding significant increase in survival (p < 0.001, all groups). In most study groups (all except the nonspecific IgG group), the body weights of the mice did not decrease by more than 10%, indicating the safety of the injected agents. Serum alanine transaminase levels remained nearly constant indicating no damage to the liver (a primary clearance organ of the agent), and this was confirmed by ex vivo histological analyses.Conclusion177Lu-DTPA-TRC105, when administered at a sufficient dose, is able to curtail tumor growth and provide a significant survival benefit without off-target toxicity. Thus, this targeted agent could be used in combination with other treatment options to slow tumor growth allowing the other agents to be more effective.

Project description:BackgroundProgrammed cell death 1 ligand 1(PD-L1) is overexpressed in many tumors. The radionuclide-labeled anti-PD-L1 monoclonal antibody can be used for imaging and therapy of PD-L1 overexpressing cancer. Here, we described 131I-labeled Atezolizumab (131I-Atezolizumab, targeting PD-L1) as a therapeutic agent for colorectal cancer with PD-L1 overexpression.Methods131I-Atezolizumab was prepared by the Iodogen method. The expression levels of PD-L1 in different human colorectal cells were determined by flow cytometry, western blot and cell binding assay. The immunoreactivity of 131I-Atezolizumab to PD-L1 high-expressing cells was determined by immunoreactive fraction. The killing abilities of different concentrations of 131I-Atezolizumab on cells with high and low expression of PD-L1 were detected by the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) method. Cerenkov luminescence imaging (CLI) and radioimmunotherapy (RIT) of 131I-Atezolizumab were performed on two human colorectal cancer models. The distribution and tumor targeting of 131I-Atezolizumab were evaluated by imaging. Tumor volume and survival time were used as indicators to evaluate the anti-tumor effect of 131I-Atezolizumab.ResultsThe expression level of PD-L1 in vitro determined by the cell binding assay was related to the data of flow cytometry and western blot. 131I-Atezolizumab can specifically bind to PD-L1 high-expressing cells in vitro to reflect the expression level of PD-L1. Immunoreactive fraction of PD-L1 high-expressing RKO cells with 131I-Atezolizumab was 52.2%. The killing ability of 131I-Atezolizumab on PD-L1 high-expressing cells was higher than that of low-expressing cells. CLI proved that the specific uptake level of tumors depends on the expression level of PD-L1. Effect of 131I-Atezolizumab RIT showed an activity-dependent tumor suppressor effect on RKO tumor-bearing mice with high PD-L1 expression. 131I-Atezolizumab (37 MBq) can improve the median survival time of mice (34 days), compared to untreated mice (27 days) (P = 0.027). Although a single activity(37 MBq) of 131I-Atezolizumab also inhibited the tumors of HCT8 tumor-bearing mice with low PD-L1 expression (P < 0.05), it could not prolong the survival of mice(P = 0.29).Conclusion131I-Atezolizumab can be used as a CLI agent for screening PD-L1 expression levels. It may be used as a radioimmunotherapy drug target for PD- L1 overexpressing tumors.

Project description:ObjectivePancreatic cancer is an aggressive tumor and the prognosis remains poor. Therefore, development of more effective therapy is needed. We previously reported that 89Zr-labeled TSP-A01, an antibody against transferrin receptor (TfR), is highly accumulated in a pancreatic cancer xenograft, but not in major normal organs. In the present study, we evaluated the efficacy of radioimmunotherapy (RIT) with 90Y-TSP-A01 in pancreatic cancer mouse models.MethodsTfR expression in pancreatic cancer cell lines (AsPC-1, BxPC-3, MIAPaCa-2) was evaluated by immunofluorescence staining. 111In-labeled anti-TfR antibodies (TSP-A01, TSP-A02) were evaluated in vitro by cell binding assay with the three cell lines and by competitive inhibition assay with MIAPaCa-2. In vivo biodistribution was evaluated in mice bearing BxPC-3 and MIAPaCa-2 xenografts. Tumor volumes of BxPC-3 and MIAPaCa-2 were sequentially measured after 90Y-TSP-A01 injection and histological analysis of tumors was conducted.ResultsMIAPaCa-2 cells showed the highest TfR expression, followed by AsPC-1 and BxPC-3 cells. 111In-TSP-A01 and 111In-TSP-A02 bound specifically to the three cell lines according to TfR expression. The dissociation constants for TSP-A01, DOTA-TSP-A01, TSP-A02, and DOTA-TSP-A02 were 0.22, 0.28, 0.17, and 0.22 nM, respectively. 111In-TSP-A01 was highly accumulated in tumors, especially in MIAPaCa-2, but this was not true of 111In-TSP-A02. The absorbed dose for 90Y-TSP-A01 was estimated to be 8.3 Gy/MBq to BxPC-3 and 12.4 Gy/MBq to MIAPaCa-2. MIAPaCa-2 tumors treated with 3.7 MBq of 90Y-TSP-A01 had almost completely disappeared around 3 weeks after injection and regrowth was not observed. Growth of BxPC-3 tumors was inhibited by 3.7 MBq of 90Y-TSP-A01, but the tumor size was not reduced.Conclusion90Y-TSP-A01 treatment achieved an almost complete response in MIAPaCa-2 tumors, whereas it merely inhibited the growth of BxPC-3 tumors. 90Y-TSP-A01 is a promising RIT agent for pancreatic cancer, although further investigation is necessary to improve the efficacy for the radioresistant types like BxPC-3.

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Radioimmunotherapy with an ²¹¹ At-labeled anti-tissue factor antibody protected by sodium ascorbate.

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