Cerebellar and Cerebral Amyloid Visualized by [18F]flutemetamol PET in Long-Term Hereditary V30M (p.V50M) Transthyretin Amyloidosis Survivors

Hereditary transthyretin amyloidosis in the era of RNA interference, antisense oligonucleotide, and CRISPR-Cas9 treatments

Hereditary transthyretin amyloidosis (ATTRv) is a rare autosomal dominant adult-onset disorder caused by point mutations in the transthyretin (TTR) gene encoding TTR, also known as prealbumin. ATTRv survival ranges from 3 to 10 years, and peripheral nervous system and heart are usually the 2 main tissues affected, although central nervous system and eye may also be involved. Because the liver is the main TTR protein secretor organ, it has been the main target of treatments developed these last years, including liver transplantation, which has been shown to significantly increase survival in a subset of patients carrying the so-called "early-onset Val30Met" TTR gene mutation. More recently, treatments targeting hepatic TTR RNA have been developed. Hepatic TTR RNA targeting is performed using RNA interference (RNAi) and antisense oligonucleotide (ASO) technologies involving lipid nanoparticle carriers or N-acetylgalactosamine fragments. RNAi and ASO treatments induce an 80% decrease in TTR liver production for a period of 1 to 12 weeks. ASO and RNAi phase 3 trials in patients with TTR-related polyneuropathy have shown a positive impact on neuropathy clinical scores and quality of life end points, and delayed RNAi treatment negatively affects survival. Clinical trials specifically investigating RNAi therapy in TTR cardiomyopathy are underway. Hepatic RNA targeting has revolutionized ATTRv treatment and may allow for the transforming a fatal disease into a treatable disorder. Because retina and choroid plexus secrete limited quantities of TTR protein, both tissues are now seen as the next targets for fully controlling the disease.

Molecular Design of Magnetic Resonance Imaging Agents Binding to Amyloid Deposits

The ability to detect and monitor amyloid deposition in the brain using non-invasive imaging techniques provides valuable insights into the early diagnosis and progression of Alzheimer's disease and helps to evaluate the efficacy of potential treatments. Magnetic resonance imaging (MRI) is a widely available technique offering high-spatial-resolution imaging. It can be used to visualize amyloid deposits with the help of amyloid-binding diagnostic agents injected into the body. In recent years, a number of amyloid-targeted MRI probes have been developed, but none of them has entered clinical practice. We review the advances in the field and deduce the requirements for the molecular structure and properties of a diagnostic probe candidate. These requirements make up the base for the rational design of MRI-active small molecules targeting amyloid deposits. Particular attention is paid to the novel cryo-EM structures of the fibril aggregates and their complexes, with known binders offering the possibility to use computational structure-based design methods. With continued research and development, MRI probes may revolutionize the diagnosis and treatment of neurodegenerative diseases, ultimately improving the lives of millions of people worldwide.

Distribution and progression of cerebral amyloid angiopathy in early-onset V30M (p.V50M) hereditary ATTR amyloidosis

BACKGROUND

Cerebral amyloid angiopathy (CAA) is becoming the most common and serious complications in long-lived hereditary ATTR amyloidosis patients. It is therefore imperative to elucidate the characteristics of ATTR-type CAA and develop useful biomarkers.

METHODS

We enrolled 34 ATTRv amyloidosis patients with the V30M (p.V50M) variant for analysis with three-dimensional stereotactic surface projection z score imaging of Pittsburgh compound B (PiB)-PET.

RESULTS

Eight patients exhibited central nervous system (CNS) symptoms. Seven patients suffered transient focal neurologic episodes, and 2 patients each experienced cerebellar haemorrhages or cognitive decline. The amount of ¹¹C-PiB accumulation increased as a function of disease duration. ¹¹C-PiB-PET abnormalities were seen at 8 years from onset and were associated with CNS manifestations from 12 years. The annual increase rate of the standardised uptake value ratio (SUVR) in female patients was significantly higher than in male patients. CNS amyloid deposition started in the upper middle surface of the cerebellar cortex, and then spread out over the entire surface of the cerebellum, Sylvian fissure, and anterior part of the longitudinal fissure of the cerebrum.

CONCLUSIONS

PiB-PET is a useful biomarker for the early detection and treatment evaluation of ATTR-type CAA. Female gender is associated with more rapid progression of ATTR-type CAA.