An Improved Synthesis of N-(4-[18F]Fluorobenzoyl)-Interleukin-2 for the Preclinical PET Imaging of Tumour-Infiltrating T-cells in CT26 and MC38 Colon Cancer Models.

Positron emission tomography (PET) imaging of activated T-cells with N-(4-[18F]fluorobenzoyl)-interleukin-2 ([18F]FB-IL-2) may be a promising tool for patient management to aid in the assessment of clinical responses to immune therapeutics. Unfortunately, existing radiosynthetic methods are very low yielding due to complex and time-consuming chemical processes. Herein, we report an improved method for the synthesis of [18F]FB-IL-2, which reduces synthesis time and improves radiochemical yield. With this optimized approach, [18F]FB-IL-2 was prepared with a non-decay-corrected radiochemical yield of 3.8 ± 0.7% from [18F]fluoride, 3.8 times higher than previously reported methods. In vitro experiments showed that the radiotracer was stable with good radiochemical purity (>95%), confirmed its identity and showed preferential binding to activated mouse peripheral blood mononuclear cells. Dynamic PET imaging and ex vivo biodistribution studies in naïve Balb/c mice showed organ distribution and kinetics comparable to earlier published data on [18F]FB-IL-2. Significant improvements in the radiochemical manufacture of [18F]FB-IL-2 facilitates access to this promising PET imaging radiopharmaceutical, which may, in turn, provide useful insights into different tumour phenotypes and a greater understanding of the cellular nature and differential immune microenvironments that are critical to understand and develop new treatments for cancers.

Dopamine transporter neuroimaging accurately assesses the maturation of dopamine neurons in a preclinical model of Parkinson's disease.

BACKGROUND: Significant developments in stem cell therapy for Parkinson's disease (PD) have already been achieved; however, methods for reliable assessment of dopamine neuron maturation in vivo are lacking. Establishing the efficacy of new cellular therapies using non-invasive methodologies will be critical for future regulatory approval and application. The current study examines the utility of neuroimaging to characterise the in vivo maturation, innervation and functional dopamine release of transplanted human embryonic stem cell-derived midbrain dopaminergic neurons (hESC-mDAs) in a preclinical model of PD. METHODS: Female NIH RNu rats received a unilateral stereotaxic injection of 6-OHDA into the left medial forebrain bundle to create the PD lesion. hESC-mDA cell and sham transplantations were carried out 1 month post-lesion, with treated animals receiving approximately 4 × 105 cells per transplantation. Behavioural analysis, [18F]FBCTT and [18F]fallypride microPET/CT, was conducted at 1, 3 and 6 months post-transplantation and compared with histological characterisation at 6 months. RESULTS: PET imaging revealed transplant survival and maturation into functional dopaminergic neurons. [18F]FBCTT-PET/CT dopamine transporter (DAT) imaging demonstrated pre-synaptic restoration and [18F]fallypride-PET/CT indicated functional dopamine release, whilst amphetamine-induced rotation showed significant behavioural recovery. Moreover, histology revealed that the grafted cells matured differently in vivo producing high- and low-tyrosine hydroxylase (TH) expressing cohorts, and only [18F]FBCTT uptake was well correlated with differentiation. CONCLUSIONS: This study provides further evidence for the value of in vivo functional imaging for the assessment of cell therapies and highlights the utility of DAT imaging for the determination of early post-transplant cell maturation and differentiation of hESC-mDAs.

Longitudinal [18F]FB-IL-2 PET Imaging to Assess the Immunopathogenicity of O'nyong-nyong Virus Infection.

O'nyong-nyong virus (ONNV) is an arthritogenic alphavirus that caused two large epidemics in 1959 and 1996, affecting millions of people in Africa. More recently, sero-surveillance of healthy blood donors conducted in 2019 revealed high rates of unreported ONNV infection in Uganda. Due to similar clinical symptoms with other endemic mosquito-borne pathogens in the region, including chikungunya virus, dengue virus and malaria, ONNV infections are often un- or misdiagnosed. Elucidating the immunopathogenic factors of this re-emerging arbovirus is critical with the expanding geographic distribution of competent vectors. This study reports the establishment of an immune competent C57BL6/J mouse model to mechanistically characterize ONNV infection and assess potential treatment efficacy. This mouse model successfully recapitulated arthralgia and viremia profiles seen in ONNV patients. Furthermore, longitudinal in-vivo PET imaging with [18F]FB-IL-2 (CD25+CD4+ binding probe) and histopathological assessment in this model demonstrated the pathogenic role of CD4+ T cells in driving joint pathology. Concordantly, in vivo CD4+ T cell depletion, or suppression with fingolimod, an FDA-approved immunomodulating drug, abrogated CD4+ T cell-mediated disease. This study demonstrates the importance of this immune competent ONNV model for future studies on factors influencing disease pathogenesis, which could shape the discovery of novel therapeutic strategies for arthritogenic alphaviruses.

Examining Immunotherapy Response Using Multiple Radiotracers.

PURPOSE: Cancer immunotherapy has shown huge potential in the fight against cancer, but only a small proportion of patients respond successfully to treatment. Non-invasive methods to stratify responders from non-responders are critically important as immune therapies are often associated with immune-related side effects. Currently, conventional clinical imaging modalities do not provide a useful measure of immune therapy efficacy. Sensitive imaging biomarkers that provide information about the tumoural microenvironment may provide useful insights allowing for improved patient management. PROCEDURES: We have assessed the ability of a number of radiopharmaceuticals to non-invasively measure different aspects of the tumour microenvironment and correlated tumour uptake to immune therapy response in a syngeneic model of colon cancer, CT26-WT. Four radiopharmaceuticals, [18F]FDG (a glucose analogue), [18F]FEPPA (a marker for macrophage activation), [18F]FB-IL2 (a marker for CD25+ cells) and [68Ga] Ga-mNOTA-GZP (a marker for granzyme B, the serine protease downstream effector of cytotoxic T cells), were assessed as potential biomarkers to help stratify response to PD-1 monotherapy or combined anti-PD1 and CLTA4 therapy in vivo correlating tumour uptake with changes in tumour-associated immune cell populations. RESULTS: [18F]FDG, [18F]FEPPA and [18F]FB-IL2 (a marker for CD25+ cells) showed limited ability to determine therapy response and showed little correlation to tumour-associated immune cell changes. However, [68Ga] Ga-mNOTA-GZP showed good predictive ability and correlated well with changes in tumour-associated T cells, especially CD8+ T cells. CONCLUSIONS: [68Ga]Ga-mNOTA-GZP uptake correlates well with changes in CD8+ T cell populations supporting continued development of granzyme B-based imaging agents for stratification of response to immunotherapy. Early assessment of immunotherapy efficacy with [68Ga]Ga-mNOTA-GZP may allow for the reduction of unnecessary side effects while significantly improving patient management.

Empirical and Computational Insights into N-Arylation Reactions Catalyzed by Palladium meta-Terarylphosphine Catalyst.

An in situ generated Pd-Cy*Phine catalyst has been successfully applied to the N-arylation of primary and secondary amines, and it exhibited high performance across multiple substrate classes. The performance induced by the meta-terarylphosphine motif of the Cy*Phine ligand for C-N cross-coupling displayed only subtle differences to that of its biarylphosphine congener XPhos. DFT studies demonstrated comparable reaction energetics in the catalytic cycle steps for both Pd-Cy*Phine and Pd-XPhos, which was consistent with previous findings. The computational investigation also indicated that a putative rate-determining step occurred after amine binding, which was likely to have annulled the expected benefits of having a meta-terarylphosphine ligand architecture.

Manganese-catalyzed cross-coupling reactions of nitrogen nucleophiles with aryl halides in water.

A facile and convenient strategy for the assembly of N-arylated heterocycles has been demonstrated using a MnCl2.4H2O/trans-1,2-diaminocyclohexane catalyst and K3PO4 as the base in water.