Evidence-Based Severity Assessment of Animal Models for Pancreatic Cancer.

Animal models are crucial to preclinical oncological research and drug development. Animal experiments must be performed in accordance with the 3R principles of replacement and reduction, if possible, and refinement where these procedures remain crucial. In addition, European Union legislations demand a continuous refinement approach, as well as pro- and retrospective severity assessment. In this study, an objective databased severity assessment was performed in murine models for pancreatic cancer induced by orthotopic, subcutaneous, or intravenous injection of Panc02 cells. Parameters such as body weight change, distress score, perianal temperature, mouse grimace scale, burrowing, nesting behavior, and the concentration of corticosterone in plasma and its metabolites in feces were monitored during tumor progression. The most important parameters were combined into a score and mapped against a reference data set by the Relative Severity Assessment procedure (RELSA) to obtain the maximum achieved severity for each animal (RELSAmax). This scoring revealed a significantly higher RELSAmax for the orthotopic model than for the subcutaneous and intravenous models. However, compared to animal models such as pancreatitis and bile duct ligation, the pancreatic cancer models are shown to be less severe. Data-based animal welfare assessment proved to be a valuable tool for comparing the severity of differently induced cancer models.

Preclinical Comparison of the 64Cu- and 68Ga-Labeled GRPR-Targeted Compounds RM2 and AMTG, as Well as First-in-Humans [68Ga]Ga-AMTG PET/CT.

Despite the recent success of prostate-specific membrane antigen (PSMA)-targeted compounds for theranostic use in prostate cancer (PCa), alternative options for the detection and treatment of PSMA-negative lesions are needed. We have recently developed a novel gastrin-releasing peptide receptor (GRPR) ligand with improved metabolic stability, which might improve diagnostic and therapeutic efficacy and could be valuable for PSMA-negative PCa patients. Our aim was to examine its suitability for theranostic use. We performed a comparative preclinical study on [64Cu]Cu-/[68Ga]Ga-AMTG ([64Cu]Cu-/[68Ga]Ga-α-Me-l-Trp8-RM2) using [64Cu]Cu-/[68Ga]Ga-RM2 ([64Cu]Cu-/[68Ga]Ga-DOTA-Pip5-Phe6-Gln7-Trp8-Ala9-Val10-Gly11-His12-Sta13-Leu14-NH2) as a reference compound and investigated [68Ga]Ga-AMTG in a proof-of-concept study in a PCa patient. Methods: Peptides were labeled with 64Cu (80 °C, 1.0 M NaOAc, pH 5.50) and 68Ga (90 °C, 0.25 M NaOAc, pH 4.50). GRPR affinity (half-maximal inhibitory concentration, room temperature, 2 h) and GRPR-mediated internalization (37 °C, 60 min) were examined on PC-3 cells. Biodistribution studies were performed at 1 h after injection in PC-3 tumor-bearing mice. For a first-in-humans application, 173 MBq of [68Ga]Ga-AMTG were administered intravenously and whole-body PET/CT scans were acquired at 75 min after injection. Results: 64Cu- and 68Ga-labeling proceeded almost quantitatively (>98%). All compounds revealed similarly high GRPR affinity (half-maximal inhibitory concentration, 1.5-4.0 nM) and high receptor-bound fractions (79%-84% of cell-associated activity). In vivo, high activity levels (percentage injected dose per gram) were found in the PC-3 tumor (14.1-15.1 %ID/g) and the pancreas (12.6-30.7 %ID/g), whereas further off-target accumulation was low at 1 h after injection, except for elevated liver uptake observed for both 64Cu-labeled compounds. Overall biodistribution profiles and tumor-to-background ratios were comparable but slightly enhanced for the 68Ga-labeled analogs in most organs. [68Ga]Ga-AMTG confirmed the favorable pharmacokinetics-as evident from preclinical studies-in a patient with metastasized castration-resistant PCa showing intense uptake in several lesions. Conclusion: AMTG is eligible for theranostic use, as labeling with 64Cu and 68Ga, as well as 177Lu (known from previous study), does not have a negative influence on its favorable biodistribution pattern. For this reason, further clinical evaluation is warranted.

Targeting pancreatic cancer with combinatorial treatment of CPI-613 and inhibitors of lactate metabolism.

Pancreatic cancer is the fourth leading cause of cancer death, with a 5-year survival rate of 10%. A stagnant high mortality rate over the last decades highlights the need for innovative therapeutic approaches. Pancreatic tumors pursue an altered metabolism in order to maintain energy generation under low nutrient influx and hypoxic conditions. Targeting these metabolic strategies might therefore be a reasonable therapeutic approach for pancreatic cancer. One promising agent is CPI- 613, a potent inhibitor of two enzymes of the tricarboxylic acid cycle. The present study evaluated the anti-cancerous efficacy of CPI-613 in combination with galloflavin, a lactate dehydrogenase inhibitor or with alpha-cyano-4-hydroxycinnamic acid, an inhibitor of monocarboxylate transporters. The efficacy of both combination therapies was tested in vitro on one human and two murine pancreatic cancer cell lines and in vivo in an orthotopic pancreatic cancer model. Tumor progression was evaluated by MRI and 18F-FDG PET-CT. Both combinatorial treatments demonstrated in vitro a significant inhibition of pancreatic cancer cell proliferation and induction of cell death. In contrast to the in vitro results, both combination therapies did not significantly reduce tumor growth in vivo. The in vitro results suggest that a combined inhibition of different metabolic pathways might be a promising approach for cancer therapy. However, the in vivo experiments indicate that applying a higher dosage or using other drugs targeting these metabolic pathways might be more promising.

[68Ga]-NODAGA-RGD Positron Emission Tomography (PET) for Assessment of Post Myocardial Infarction Angiogenesis as a Predictor for Left Ventricular Remodeling in Mice after Cardiac Stem Cell Therapy.

Angiogenesis plays a central role in the healing process following acute myocardial infarction. The PET tracer [68Ga]-NODAGA-RGD, which is a ligand for the αvß3 integrin, has been investigated for imaging angiogenesis in the process of healing myocardium in both animal and clinical studies. It´s value as a prognostic marker of functional outcome remains unclear. Therefore, the aim of this work was to establish [68Ga]-NODAGA-RGD for imaging angiogenesis in the murine infarct model and evaluate the tracer as a predictor for cardiac remodeling in the context of cardiac stem cell therapy. [68Ga]-NODAGA-RGD PET performed seven days after left anterior descending coronary artery (LAD) occlusion in 129S6 mice showed intense tracer accumulation within the infarct region. The specificity was shown in a sub-group of animals by application of the competitive inhibitor cilengitide prior to tracer injection in a subgroup of animals. Myocardial infarction (MI) significantly reduced cardiac function and resulted in pronounced left ventricular remodeling after three weeks, as measured by cardiac MRI in a separate group. Cardiac induced cells (CiC) that were derived from mESC injected intramyocardially in the therapy group significantly improved left ventricular ejection fraction (LVEF). Surprisingly, CiC transplantation resulted in significantly lower tracer accumulation seven days after MI induction. Accordingly, we successfully established the PET tracer [68Ga]-NODAGA-RGD for the assessment of αvß3 integrin expression in the healing process after MI in the mouse model. Yet, our results indicate that the mere extent of angiogenesis following MI does not serve as a sufficient prognostic marker for functional outcome.

A Comparative Study on the Thermodynamics of Halogen Bonding of Group†10 Pincer Fluoride Complexes.

The thermodynamics of halogen bonding of a series of isostructural Group 10 metal pincer fluoride complexes of the type [(3,5-R2 -tBu POCOPtBu )MF] (3,5-R2 -tBu POCOPtBu =κ3 -C6 HR2 -2,6-(OPtBu2 )2 with R=H, tBu, COOMe; M=Ni, Pd, Pt) and iodopentafluorobenzene was investigated. Based on NMR experiments at different temperatures, all complexes 1-tBu (R=tBu, M=Ni), 2-H (R=H, M=Pd), 2-tBu (R=tBu, M=Pd), 2-COOMe (R=COOMe, M=Pd) and 3-tBu (R=tBu, M=Pt) form strong halogen bonds with Pd complexes showing significantly stronger binding to iodopentafluorobenzene. Structural and computational analysis of a model adduct of complex 2-tBu with 1,4-diiodotetrafluorobenzene as well as of structures of iodopentafluorobenzene in toluene solution shows that formation of a type I contact occurs.