Convective forces increase rostral delivery of intrathecal radiotracers and antisense oligonucleotides in the cynomolgus monkey nervous system.

BACKGROUND: The intrathecal (IT) dosing route introduces drugs directly into the CSF to bypass the blood-brain barrier and gain direct access to the CNS. We evaluated the use of convective forces acting on the cerebrospinal fluid as a means for increasing rostral delivery of IT dosed radioactive tracer molecules and antisense oligonucleotides (ASO) in the monkey CNS. We also measured the cerebral spinal fluid (CSF) volume in a group of cynomolgus monkeys. METHODS: There are three studies presented, in each of which cynomolgus monkeys were injected into the IT space with radioactive tracer molecules and/or ASO by lumbar puncture in either a low or high volume. The first study used the radioactive tracer 64Cu-DOTA and PET imaging to evaluate the effect of the convective forces. The second study combined the injection of the radioactive tracer 99mTc-DTPA and ASO, then used SPECT imaging and ex vivo tissue analysis of the effects of convective forces to bridge between the tracer and the ASO distributions. The third experiment evaluated the effects of different injection volumes on the distribution of an ASO. In the course of performing these studies we also measured the CSF volume in the subject monkeys by Magnetic Resonance Imaging. RESULTS: It was consistently found that larger bolus dose volumes produced greater rostral distribution along the neuraxis. Thoracic percussive treatment also increased rostral distribution of low volume injections. There was little added benefit on distribution by combining the thoracic percussive treatment with the high-volume injection. The CSF volume of the monkeys was found to be 11.9 ± 1.6 cm3. CONCLUSIONS: These results indicate that increasing convective forces after IT injection increases distribution of molecules up the neuraxis. In particular, the use of high IT injection volumes will be useful to increase rostral CNS distribution of therapeutic ASOs for CNS diseases in the clinic.

A phase one, single-dose, open-label, clinical safety and PET/MR imaging study of 68Ga-DOTATOC in healthy volunteers.

This prospective pilot study provides a dynamic whole body PET/MR image database, clinical safety, biodistribution profile and dosimetry of 68Ga-DOTATOC in healthy subjects, to establish a baseline and standard reference for its use in diagnosis and treatment response evaluation among patients with somatostatin receptor expressing neoplastic diseases. Dynamic whole body PET/MR imaging was performed in 12 healthy subjects (male/female: 8/4) after injection of 242.39 ± 53.38 MBq (mean ± SD) 68Ga-DOTATOC. Images were acquired 15, 60, 120, and 240 minutes post injection. Subjects were assessed at baseline and after 68Ga-DOTATOC PET/MR by monitoring vital signs, 12-lead electrocardiograms, complete blood count, comprehensive metabolic panel, and urinalysis. Adverse events were monitored for one week after injection. Organ dosimetry was estimated using OLINDA/EXM 1.1 software. Radiotracer was exclusively eliminated via urinary tract (18.8 ± 1.0% of injected dose within 4 hours) and no redistribution was observed. Bladder wall, spleen and kidneys received the highest radiation exposure (0.64 ± 0.1 mSv/MBq, 0.29 ± 0.14 mSv/MBq, and 0.1 ± 0.02 mSv/MBq, respectively). Mean effective dose yielded 0.048 ± 0.007 mSv/MBq. No adverse events were reported during the one-week follow-up period. Follow-up laboratory tests and electrocardiograms showed no changes compared to the baseline. The use of MRI provided valuable anatomical information and eliminated the risk of radiation exposure compared to CT.

High-throughput high-volume nuclear imaging for preclinical in vivo compound screening§.

BACKGROUND: Preclinical single-photon emission computed tomography (SPECT)/CT imaging studies are hampered by low throughput, hence are found typically within small volume feasibility studies. Here, imaging and image analysis procedures are presented that allow profiling of a large volume of radiolabelled compounds within a reasonably short total study time. Particular emphasis was put on quality control (QC) and on fast and unbiased image analysis. METHODS: 2-3 His-tagged proteins were simultaneously radiolabelled by 99mTc-tricarbonyl methodology and injected intravenously (20 nmol/kg; 100 MBq; n = 3) into patient-derived xenograft (PDX) mouse models. Whole-body SPECT/CT images of 3 mice simultaneously were acquired 1, 4, and 24 h post-injection, extended to 48 h and/or by 0-2 h dynamic SPECT for pre-selected compounds. Organ uptake was quantified by automated multi-atlas and manual segmentations. Data were plotted automatically, quality controlled and stored on a collaborative image management platform. Ex vivo uptake data were collected semi-automatically and analysis performed as for imaging data. RESULTS: >500 single animal SPECT images were acquired for 25 proteins over 5 weeks, eventually generating >3500 ROI and >1000 items of tissue data. SPECT/CT images clearly visualized uptake in tumour and other tissues even at 48 h post-injection. Intersubject uptake variability was typically 13% (coefficient of variation, COV). Imaging results correlated well with ex vivo data. CONCLUSIONS: The large data set of tumour, background and systemic uptake/clearance data from 75 mice for 25 compounds allows identification of compounds of interest. The number of animals required was reduced considerably by longitudinal imaging compared to dissection experiments. All experimental work and analyses were accomplished within 3 months expected to be compatible with drug development programmes. QC along all workflow steps, blinding of the imaging contract research organization to compound properties and automation provide confidence in the data set. Additional ex vivo data were useful as a control but could be omitted from future studies in the same centre. For even larger compound libraries, radiolabelling could be expedited and the number of imaging time points adapted to increase weekly throughput. Multi-atlas segmentation could be expanded via SPECT/MRI; however, this would require an MRI-compatible mouse hotel. Finally, analysis of nuclear images of radiopharmaceuticals in clinical trials may benefit from the automated analysis procedures developed.

Automated segmentation of MR imaging to determine normative central nervous system cerebrospinal fluid volumes in healthy volunteers.

An accurate non-invasive method to determine total body cerebrospinal fluid volume has a number of potential diagnostic and therapeutic applications. Herein we describe a technique for automated segmentation of total body MRI data to determine cranial and spinal CSF volume in 15 healthy adults. These in vivo estimates of CSF volume exceed the standard reported volume of 150mL in human adults and provide normative data for diagnosis of disease states such as hydrocephalus and therapy including pharmacologic dosimetry. No correlation was observed between patient height or weight and total body CSF volume.