Copper-64-Labeled 1C1m-Fc, a New Tool for TEM-1 PET Imaging and Prediction of Lutetium-177-Labeled 1C1m-Fc Therapy Efficacy and Safety

Simple Summary

The prevalence of TEM-1 in the vasculature and the stroma of solid tumors and in malignant cells of sarcomas suggests that targeting TEM-1 could have therapeutic benefit. In this context, an anti-TEM-1 companion diagnostic may assist in the personalized medicine approach, whereby TEM-1 expression is exploited as a biomarker to select patients that would most benefit from a treatment directed toward the TEM-1 antigen. In our previous works, we have selected 1C1m-Fc, a fusion protein antibody, radiolabeled it with ¹⁷⁷Lu and demonstrated that [¹⁷⁷Lu]Lu-1C1m-Fc has interesting therapeutic performance. To define a suitable radiopharmaceutical companion for theranostic applications, ⁶⁴Cu was chosen to radiolabel the fusion protein antibody. The aim of this work was thus to determine if [⁶⁴Cu]Cu-1C1m-Fc can be considered for TEM-1 PET imaging and to predict the dosimetry of the [¹⁷⁷Lu]Lu-1C1m-Fc companion therapy.

Abstract

1C1m-Fc, a promising anti-TEM-1 DOTA conjugate, was labeled with ⁶⁴Cu to target cancer cells for PET imaging and predicting the efficacy and safety of a previously studied [¹⁷⁷Lu]Lu-1C1m-Fc companion therapy. DOTA-conjugated 1C1m-Fc was characterized by mass spectrometry, thin layer chromatography and immunoreactivity assessment. PET/CT and biodistribution studies were performed in human neuroblastoma xenografted mice. Absorbed doses were assessed from biodistribution results and extrapolated to ¹⁷⁷Lu based on the [⁶⁴Cu]Cu-1C1m-Fc data. The immunoreactivity was ≥ 70% after 48 h of incubation in serum, and the specificity of [⁶⁴Cu]Cu-1C1m-Fc for the target was validated. High-resolution PET/CT images were obtained, with the best tumor-to-organ ratios reached at 24 or 48 h and correlated with results of the biodistribution study. Healthy organs receiving the highest doses were the liver, the kidneys and the uterus. [⁶⁴Cu]Cu-1C1m-Fc could be of interest to give an indication of ¹⁷⁷Lu dosimetry for parenchymal organs. In the uterus and the tumor, characterized by specific TEM-1 expression, the ¹⁷⁷Lu-extrapolated absorbed doses are overestimated because of the lack of later measurement time points. Nevertheless, 1C1m-Fc radiolabeled with ⁶⁴Cu for imaging would appear as an interesting radionuclide companion for therapeutic application with [¹⁷⁷Lu]Lu-1C1m-Fc.

Endosialin (TEM1) as a Diagnostic, Progression, and Prognostic Serum Marker for Patients With Colorectal Cancer-A Preliminary Study

Colorectal cancer (CRC) is one of the most common cancers worldwide usually diagnosed in the advanced stage. In this study, the serum concentration of tumor endothelial marker 1 (TEM1) was measured and correlated with clinicopathological features to evaluate whether TEM1 might serve as a biomarker for early CRC diagnosis, progression, and prognosis. The concentration of TEM1 was measured in the serum samples of 45 patients with CRC and 35 healthy individuals using enzyme-linked immunosorbent assay test. The mean serum concentration of TEM1 was significantly higher in the patients with CRC compared to the healthy individuals (1.31 ± 0.16 vs 0.92 ± 0.90 ng/mL; P < .001). The mean concentration of TEM1 significantly increased in the patients having CRC with early stage (stage I + II) compared to noncancer control individuals (stage I + II vs control 1.21 ± 0.13 ng/mL: 0.92 ± 0.90 ng/mL; P < .001). The TEM1 concentration in blood serum also showed a significant association with the development of T stages (P < .001), N stages (P < .001), and M stages (P = .006). The TEM1 sensitivity and specificity in CRC detection are higher than routinely used blood markers (carcinoembryonic antigen [CEA] and carbohydrate antigen [Ca 19-9]). Patients with high TEM1 concentration (≥1.055 ng/mL) had a worse overall survival rate compared to the patients having CRC with low TEM1 concentration (<1.055 ng/mL). In conclusion, TEM1 can act as a potential diagnostic, progression, and prognostic serum biomarker for patients with CRC; TEM1 might be a good supplement for commonly used markers CEA and Ca 19-9.