Towards personalized treatment of prostate cancer: PSMA I&T, a promising prostate-specific membrane antigen-targeted theranostic agent

Prostate-specific membrane antigen (PSMA) is a well-established target for nuclear imaging and therapy of prostate cancer (PCa). Radiolabeled small-molecule PSMA inhibitors are excellent candidates for PCa theranostics-they rapidly and efficiently localize in tumor lesions. However, high tracer uptake in kidneys and salivary glands are major concerns for therapeutic applications. Here, we present the preclinical application of PSMA I&T, a DOTAGA-chelated urea-based PSMA inhibitor, for SPECT/CT imaging and radionuclide therapy of PCa. 111In-PSMA I&T showed dose-dependent uptake in PSMA-expressing tumors, kidneys, spleen, adrenals, lungs and salivary glands. Coadministration of 2-(phosphonomethyl)pentane-1,5-dioic acid (2-PMPA) efficiently reduced PSMA-mediated renal uptake of 111In-PSMA I&T, with the highest tumor/kidney radioactivity ratios being obtained using a dose of 50 nmol 2-PMPA. SPECT/CT clearly visualized subcutaneous tumors and sub-millimeter intraperitoneal metastases; however, high renal and spleen uptake in control mice (no 2-PMPA) interfered with visualization of metastases in the vicinity of those organs. Coadministration of 2-PMPA increased the tumor-to-kidney absorbed dose ratio during 177Lu-PSMA I&T radionuclide therapy. Hence, at equivalent absorbed dose to the tumor (36 Gy), coinjection of 2-PMPA decreased absorbed dose to the kidneys from 30 Gy to 12 Gy. Mice injected with 177Lu-PSMA I&T only, showed signs of nephrotoxicity at 3 months after therapy, whereas mice injected with 177Lu-PSMA I&T + 2-PMPA did not. These data indicate that PSMA I&T is a promising theranostic tool for PCa. PSMA-specific uptake in kidneys can be successfully tackled using blocking agents such as 2-PMPA

Elucidating the Influence of Tumor Presence on the Polymersome Circulation Time in Mice

The use of nanoparticles as tumor-targeting agents is steadily increasing, and the influence of nanoparticle characteristics such as size and stealthiness have been established for a large number of nanocarrier systems. However, not much is known about the impact of tumor presence on nanocarrier circulation times. This paper reports on the influence of tumor presence on the in vivo circulation time and biodistribution of polybutadiene-polyethylene oxide (PBd-PEO) polymersomes. For thi

Radioimmunotherapy Improves Survival of Rats with Microscopic Liver Metastases of Colorectal Origin

BACKGROUND: Half of the patients with colorectal cancer develop liver metastases during the course of their disease. The aim of the present study was to assess the efficacy of radioimmunotherapy (RIT) with a radiolabeled monoclonal antibody (mAb) to treat experimental colorectal liver metastases. METHODS: Male Wag/Rij rats underwent a minilaparotomy with intraportal injection of 1 x 10(6) CC531 tumor cells. The biodistribution of (111)In-labeled MG1, 1 day after intravenous administration, was determined in vivo and compared with that of an isotype-matched control antibody (UPC-10). The maximal tolerated dose (MTD) of (177)Lu-labeled MG1 was determined and the therapeutic efficacy of (177)Lu-MG1 at MTD was compared with that of (177)Lu-UPC-10 and saline only. RIT was administered either at the day of tumor inoculation or 14 days after tumor inoculation. Primary endpoint was survival. RESULTS: (111)In-MG1 preferentially accumulated in CC531 liver tumors (9.2 +/- 3.7%ID/g), whereas (111)In-UPC-10 did not (0.8 +/- 0.1%ID/g). The MTD of (177)Lu-MG1 was 400 MBq/kg body weight. Both the administration of (177)Lu-MG1 and (177)Lu-UPC-10 had no side-effects except a transient decrease in body weight. The survival curves of the group that received (177)Lu-UPC-10 and the group that received saline only did not differ (P = 0.407). Administration of (177)Lu-MG1 RIT immediately after surgery improved survival significantly compared with administration of (177)Lu-UPC-10 (P = 0.009) whereas delayed treatment did not (P = 0.940). CONCLUSION: This study provides proof of principle that RIT can be an effective treatment modality for microscopic liver metastases, whereas RIT is not effective in larger tumors

Lesion detection by [89Zr]Zr-DFO-girentuximab and [18F]FDG-PET/CT in patients with newly diagnosed metastatic renal cell carcinoma

Purpose: The main objective of this preliminary analysis of the IMaging PAtients for Cancer drug selecTion (IMPACT)-renal cell cancer (RCC) study is to evaluate the lesion detection of baseline contrast-enhanced CT, [89Zr]Zr-DFO-girentuximab-PET/CT and [18F]FDG-PET/CT in detecting ccRCC lesions in patients with a good or intermediate prognosis metastatic clear cell renal cell carcinoma (mccRCC) according to the International Metastatic Database Consortium (IMDC) risk model. Methods: Between February 2015 and March 2018, 42 newly diagnosed mccRCC patients with good or intermediate prognosis, eligible for watchful waiting, were included. Patients underwent CT, [89Zr]Zr-DFO-girentuximab-PET/CT and [18F]FDG-PET/CT at baseline. Scans were independently reviewed and lesions of ≥10 mm and lymph nodes of ≥15 mm at CT were analyzed. For lesions with [89Zr]Zr-DFO-girentuximab or [18F]FDG-uptake visually exceeding background uptake, maximum standardized uptake values (SUVmax) were measured. Results: A total of 449 lesions were detected by ≥1 modality (median per patient: 7; ICR 4.25–12.75) of which 42% were in lung, 22% in lymph nodes and 10% in bone. Combined [89Zr]Zr-DFO-girentuximab-PET/CT and CT detected more lesions than CT alone: 91% (95%CI: 87–94) versus 56% (95%CI: 50–62, p = 0.001), respectively, and more than CT and [18F]FDG-PET/CT combined (84% (95%CI:79–88, p < 0.005). Both PET/CTs detected more bone and soft tissue lesions compared to CT alone. Conclusions: The addition of [89Zr]Zr-DFO-girentuximab-PET/CT and [18F]FDG-PET/CT to CT increases lesion detection compared to CT alone in newly diagnosed good and intermediate prognosis mccRCC patients eligible for watchful waiting

Multiscale imaging of therapeutic anti-PD-L1 antibody localization using molecularly defined imaging agents

BACKGROUND: While immune checkpoint inhibitors such as anti-PD-L1 antibodies have revolutionized cancer treatment, only subgroups of patients show durable responses. Insight in the relation between clinical response, PD-L1 expression and intratumoral localization of PD-L1 therapeutics could improve patient stratification. Therefore, we present the modular synthesis of multimodal antibody-based imaging tools for multiscale imaging of PD-L1 to study intratumoral distribution of PD-L1 therapeutics. RESULTS: To introduce imaging modalities, a peptide containing a near-infrared dye (sulfo-Cy5), a chelator (DTPA), an azide, and a sortase-recognition motif was synthesized. This peptide and a non-fluorescent intermediate were used for site-specific functionalization of c-terminally sortaggable mouse IgG1 (mIgG1) and Fab anti-PD-L1. To increase the half-life of the Fab fragment, a 20 kDa PEG chain was attached via strain-promoted azide-alkyne cycloaddition (SPAAC). Biodistribution and imaging studies were performed with (111)In-labeled constructs in 4T1 tumor-bearing mice. Comparing our site-specific antibody-conjugates with randomly conjugated antibodies, we found that antibody clone, isotype and method of DTPA conjugation did not change tumor uptake. Furthermore, addition of sulfo-Cy5 did not affect the biodistribution. PEGylated Fab fragment displayed a significantly longer half-life compared to unPEGylated Fab and demonstrated the highest overall tumor uptake of all constructs. PD-L1 in tumors was clearly visualized by SPECT/CT, as well as whole body fluorescence imaging. Immunohistochemistry staining of tumor sections demonstrated that PD-L1 co-localized with the fluorescent and autoradiographic signal. Intratumoral localization of the imaging agent could be determined with cellular resolution using fluorescent microscopy. CONCLUSIONS: A set of molecularly defined multimodal antibody-based PD-L1 imaging agents were synthesized and validated for multiscale monitoring of PD-L1 expression and localization. Our modular approach for site-specific functionalization could easily be adapted to other targets. GRAPHICAL ABSTRACT: [Image: see text] SUPPLEMENTARY INFORMATION: The online version contains supplementary material available at 10.1186/s12951-022-01272-5

Cetuximab Reduces the Accumulation of Radiolabeled Bevacizumab in Cancer Xenografts without Decreasing VEGF Expression

Bevacizumab and cetuximab are approved for the treatment of cancer. However, in advanced colorectal cancer, addition of cetuximab to chemotherapy with bevacizumab did not improve survival. The reason for the lack of activity remains unclear. The aim of this study was to determine the effect of cetuximab on VEGF expression and targeting of bevacizumab to the tumor. Mice with subcutaneous SUM149 or WiDr xenografts were treated with cetuximab, bevacizumab, or a combination of the two. Before the start of cetuximab treatment and after 7 and 21 days of treatment, the uptake of radiolabeled bevacizumab in the tumor was measured by immunoSPECT/CT. Tumor growth of SUM149 xenografts was significantly inhibited by cetuximab, bevacizumab, or their combination, whereas growth of WiDr xenografts was not affected. Cetuximab caused a significant reduction of bevacizumab uptake in SUM149 xenografts, whereas tumor-to-blood ratios in mice with WiDr xenografts did not change. Biodistribution studies with an irrelevant antibody in the SUM149 model also showed significantly reduced tumor-to-blood ratios. Cetuximab treatment did not decrease VEGF expression. Without decreasing VEGF levels, cetuximab reduces tumor targeting of bevacizumab. This could, at least partly, explain why the combination of bevacizumab and cetuximab does not result in improved therapeutic efficacy