The ionophore 8-hydroxyquinoline (oxine) has been used to radiolabel cells and liposomal nanomedicines with the PET radiometal manganese-52.

PET imaging with radiolabeled drugs provides information on tumor uptake and dose-dependent target interaction to support selection of an optimal dose for future efficacy testing. In this immuno-PET study of the anti–human epidermal growth factor receptor (HER3) mAb GSK2849330, we investigated the biodistribution and tumor uptake of 89 Zr-labeled GSK2849330 and evaluated target engagement as a function of antibody mass dose. Methods: 89 Zr-GSK2849330 distribution was monitored in 6 patients with HER3-positive tumors not amenable to standard treatment. Patients received 2 administrations of 89 Zr-GSK2849330. Imaging after tracer only was performed at baseline; dose-dependent inhibition of 89 Zr-GSK2849330 uptake in tumor tissues was evaluated 2 wk later using increasing doses of unlabeled GSK2849330 in combination with the tracer. Up to 3 PET scans (2 hours post infusion [p.i.] and days 2 and 5 p.i.) were performed after tracer administration. Biodistribution and tumor targeting were assessed visually and quantitatively using SUV. The 50% and 90% inhibitory mass doses (ID 50 and ID 90 ) of target-mediated antibody uptake were calculated using a Patlak transformation. Results: At baseline, imaging with tracer showed good tumor uptake in all evaluable patients. Predosing with unlabeled mAb reduced the tumor uptake rate in a dose-dependent manner. Saturation of 89 Zr-mAb uptake by tumors was seen at the highest dose (30 mg/kg). Despite the limited number of patients, an exploratory ID 50 of 2 mg/kg and ID 90 of 18 mg/kg have been determined. Conclusion: In this immuno-PET study, dose-dependent inhibition of tumor uptake of 89 Zr-GSK2849330 by unlabeled mAb confirmed target engagement of mAb to the HER3 receptor. This study further validates the use of immuno-PET to directly visualize tissue drug disposition in patients with a noninvasive approach and to measure target engagement at the site of action, offering the potential for dose selection.

The purpose of this work was to use various molecular imaging techniques to non-invasively assess GSK2849330 (anti HER3 ADCC and CDC enhanced ‘AccretaMab’ monoclonal antibody) pharmacokinetics and pharmacodynamics in human xenograft tumor-bearing mice. Immuno-PET biodistribution imaging of radiolabeled 89Zr-GSK2849330 was assessed in mice with HER3 negative (MIA-PaCa-2) and positive (CHL-1) human xenograft tumors. Dose dependency of GSK2849330 disposition was assessed using varying doses of unlabeled GSK2849330 co-injected with 89Zr-GSK2849330. In-vivo NIRF optical imaging and ex-vivo confocal microscopy were used to assess the biodistribution of GSK2849330 and the HER3 receptor occupancy in HER3 positive xenograft tumors (BxPC3, and CHL-1). Ferumoxytol (USPIO) contrast-enhanced MRI was used to investigate the effects of GSK2849330 on tumor macrophage content in CHL-1 xenograft bearing mice. Immuno-PET imaging was used to monitor the whole body drug biodistribution and CHL-1 xenograft tumor uptake up to 144 hours post injection of 89Zr-GSK2849330. Both hepatic and tumor uptake were dose dependent and saturable. The optical imaging data in the BxPC3 xenograft tumor confirmed the tumor dose response finding in the Immuno-PET study. Confocal microscopy showed a distinguished cytoplasmic punctate staining pattern within individual CHL-1 cells. GSK2849330 inhibited tumor growth and this was associated with a significant decrease in MRI signal to noise ratio after USPIO injection and with a significant increase in tumor macrophages as confirmed by a quantitative immunohistochemistry analysis. By providing both dose response and time course data from both 89Zr and fluorescently labeled GSK2849330, complementary imaging studies were used to characterize GSK2849330 biodistribution and tumor uptake in vivo. Ferumoxytol-enhanced MRI was used to monitor aspects of the immune system response to GSK2849330. Together these approaches potentially provide clinically translatable, non-invasive techniques to support dose optimization, and assess immune activation and anti-tumor responses.

Amyotrophic lateral sclerosis (ALS) is a fatal, neurodegenerative disorder in which motor neurons in the spinal cord and motor cortex degenerate. Although the majority of ALS cases are sporadic, mutations in Cu-Zn superoxide dismutase-1 (SOD1) are causative for 10-20% of familial ALS (fALS), and recent findings show that a hexanucleotide repeat expansion in the C9ORF72 gene may account for >30% of fALS cases in Europe. SOD1(G93A) transgenic mice have a phenotype and pathology similar to human ALS. In both ALS patients and SOD1(G93A) mice, the first pathological features of disease manifest at the neuromuscular junction, where significant denervation occurs prior to motor neuron degeneration. Strategies aimed at preventing or delaying denervation may therefore be of benefit in ALS. In this study, we show that Nogo-A levels increase in muscle fibres of SOD1(G93A) mice along with the elevation of markers of neuromuscular dysfunction (CHRNA1/MUSK). Symptomatic treatment of SOD1(G93A) mice from 70 days of age with an anti-Nogo-A antibody (GSK577548) significantly improves hindlimb muscle innervation at 90 days, a late symptomatic stage of disease, resulting in increased muscle force and motor unit survival and a significant increase in motor neuron survival. However, not all aspects of this improvement in anti-Nogo-A antibody-treated SOD1(G93A) mice were maintained at end-stage disease. These results show that treatment with anti-Nogo-A antibody significantly improves neuromuscular function in the SOD1(G93A) mouse model of ALS, at least during the earlier stages of disease and suggest that pharmacological inhibition of Nogo-A may be a disease-modifying approach in ALS.

Purpose: Tracking cells in vivo using imaging can provide non-invasive information to understand the pharmacology, efficacy, and safety of novel cell therapies. Zirconium-89 (t 1/2 = 78.4 h) has recently been used to synthesize [ 89 Zr]Zr(oxinate) 4 for cell tracking using positron emission tomography (PET). This work presents an in vitro approach to estimate the detection limit for in vivo PET imaging of Jurkat T cells directly labeled with [ 89 Zr]Zr(oxinate) 4 utilizing clinical PET/CT and PET/MRI. Methods: Jurkat T cells were labeled with varying concentrations of [ 89 Zr]Zr(oxinate) 4 to generate different cell-specific activities (0.43-31.91 kBq/10 6 cells). Different concentrations of labeled cell suspensions (10 4 , 10 5 , and 10 6 cells) were seeded on 6-well plates and into a 3 × 3 cubic-well plate with 1 cm 3 cubic wells as a gel matrix. Plates were imaged on clinical PET/ CT and PET/MRI scanners for 30 min. The total activity in each well was determined by drawing volumes of interest over each well on PET images. The total cell-associated activity was measured using a well counter and correlated with imaging data. Simulations for non-specific signal were performed to model the effect of non-specific radioactivity on detection. Results: Using this in vitro model, the lowest cell number that could be visualized on 6-well plate images was 6.8 × 10 4 , when the specific activity was 27.8 kBq/10 6 cells. For the 3 × 3 cubic-well, a plate of 3.3 × 10 4 cells could be detected on images with a specific activity of 15.4 kBq/10 6 cells. Conclusion: The results show the feasibility of detecting [ 89 Zr]Zr(oxinate) 4-labeled Jurkat T cells on clinical PET systems. The results provide a best-case scenario, as in vivo detection using PET/CT or PET/MRI will be affected by cell number, specific activity per cell, the density of cells within the target volume, and non-specific signal. This work has important implications for cell labeling studies in patients, particularly when using radiosensitive cells (e.g., T cells), which require detection of low cell numbers while minimizing radiation dose per cell.