Using heart imaging to study Lewy body disease

This is a Phase 2 study evaluating the positron-emitting radiopharmaceutical 18F-mFBG as an imaging agent for quantification of the effect of neurodegenerative diseases on myocardial sympathetic innervation. Effectiveness of 18F-mFBG imaging of the heart will be judged in terms of the quantitative difference between results for subjects with Lewy body and non-Lewy body neurologic disease as compared to historical data for healthy control subjects.

Over the past 40 years, significant efforts have been made to develop imaging techniques to monitor the heart's autonomic nervous system, particularly the sympathetic system and its key neurohormone, norepinephrine (NE). In heart disease, NE function is often disrupted, leading to reduced NE uptake and transporter expression, which can contribute to heart failure, arrhythmias, and sudden cardiac death. Similar NE system dysfunction is also seen in neurological conditions like pure autonomic failure (PAF), Parkinson's disease (PD), and Dementia with Lewy Bodies (DLB), which are associated with Lewy body deposits in the nervous system. Most research on myocardial sympathetic neuronal imaging has focused on NE-analogues labeled with gamma- or positron-emitting radioisotopes. The most commonly studied agent is 123I-mIBG, which provides semi-quantitative data. However, its results depend heavily on imaging equipment and techniques, making global standardization difficult. Additionally, accurately measuring myocardial uptake and clearance is challenging with SPECT, even when using correction methods. While most cardiac mIBG research has focused on patients with heart disease, a significant number of studies have examined the effect of Lewy body disease on myocardial sympathetic innervation. These studies have consistently demonstrated a significant reduction in myocardial mIBG uptake. mIBG scintigraphy has high sensitivity (88%) and specificity (85%) for distinguishing Parkinson's disease (PD) from other Parkinsonism disorders. In a study of 123I-mIBG scans, the heart/mediastinum ratio (HMR) showed 68.9% sensitivity and 89.1% specificity for differentiating dementia with Lewy bodies (DLB) from Alzheimer's disease (AD). Neurologists and movement disorder specialists find mIBG imaging helpful for assessing suspected Lewy body disease. Positron-emission tomography (PET) is the preferred method for high-resolution imaging of cellular functions. This study uses 18F-meta-fluorobenzylguanidine (18F-mFBG), a new radiopharmaceutical similar in structure to 123I-mIBG but with faster pharmacokinetics and elimination. Compared to 123I-mIBG, 18F-mFBG clears more quickly from the blood and target organs, resulting in better heart imaging quality and reliability. While most research on 18F-mFBG has focused on imaging neural crest tumors like neuroblastoma and pheochromocytoma, its performance is expected to be strong based on prior experience with 123I-mIBG. With the greater sensitivity and resolution of PET imaging compared to planar and SPECT techniques, it is expected that 18F-mFBG imaging will be less procedure-dependent than 123I-mIBG and provide the reliable and reproducible quantitative accuracy necessary to support use of this agent for clinical patient studies.