Low Prevalence of Clinically Apparent Cardiac Amyloidosis Among Carriers of Transthyretin V122I Variant in a Large Electronic Medical Record

Navigating the penetrance and phenotypic spectrum of inherited cardiomyopathies

Inherited cardiomyopathies are genetic diseases that can lead to heart failure and sudden cardiac death. These conditions tend to run in families, following an autosomal dominant pattern where first-degree relatives have a 50% chance of carrying the pathogenic variant. Despite significant advancements and increased accessibility of genetic testing, accurately predicting the phenotypic expression of these conditions remains challenging due to the inherent variability in their clinical manifestations and the incomplete penetrance observed. This poses challenges in providing patient care and effectively communicating the potential risk of future disease to patients and their families. To address these challenges, this review aims to synthesize the available evidence on penetrance, expressivity, and factors influencing disease expression to improve communication and risk assessment for patients with inherited cardiomyopathies and their family members.

Practical Guidance for the Use of Patisiran in the Management of Polyneuropathy in Hereditary Transthyretin-Mediated Amyloidosis

Variant transthyretin amyloidosis (ATTRv) is an autosomal dominant inherited genetic disorder that affects 5000-10,000 people worldwide. It is caused by mutations in the transthyretin (TTR) gene and results in amyloid deposition in a variety of organs due to abnormal accumulation of TTR protein fibrils. Although this is a multisystem disorder, the heart and peripheral nerves are the preferentially affected organs. Over 150 TTR gene mutations have been associated with this disease and the clinical phenotype can vary significantly. Severe forms of the disorder can be fatal. Fortunately, the oligonucleotide-based therapy era has resulted in the development of several novel treatment options. Patisiran is a small interfering RNA (siRNA) encapsulated in a lipid nanoparticle that targets both mutant and wild-type TTR and results in significant reductions of the TTR protein in the serum and in tissue deposits. Patisiran has been approved for treatment of adults with polyneuropathy due to hereditary TTR-mediated amyloidosis in both the United States (US) and European Union (EU). In this review, we will discuss the development of patisiran, the clinical trials that lead to treatment approval, and provide guideline parameters for use in clinical practice.  .

Gene Editing as the Future of Cardiac Amyloidosis Therapeutics

BACKGROUND AND SIGNIFICANCE

Cardiac Amyloidosis (CA) is a manifestation of a systemic disorder resulting from the deposition of the transthyretin (TTR) in the myocardium, resulting in a myriad manifestations ranging from conduction defects to heart failure. Several proteins, many of which have a genetic predisposition, are responsible for its presentation. Clustered Regularly Interspaced Short Palindromic Repeats of genetic information-Cas9 endonuclease (CRISPR-Cas9) is a RNA-guided endonuclease, which can be targeted using an RNA guide to specific locations in the genome. Until recently, CRISPR-Cas9 was studied in small animal models for its ability to decrease extracellular deposition and accumulation of amyloid in tissues.

OBSERVATIONS

Previously considered a rare disease, but recent advances in diagnostics and therapeutics have revealed the prevalence to be higher than estimated. There are two major classes of treatments for transthyretin cardiac amyloidosis (ATTR-CA): TTR stabilizers, such as tafamidis and AG10, and RNA interference (siRNA), such as patisiran and vutrisiran. Recently, gene editing has demonstrated some early clinical promise as an emerging therapeutic modality in the treatment of CA.

CONCLUSIONS AND RELEVANCE

In an introductory gene editing human trial involving 12 subjects with TTR amyloidosis and amyloid cardiomyopathy (ATTR-CM), CRISPR-Cas9 therapy has demonstrated a reduction of approximately 90% of serum TTR proteins after 28 days. In this article, the authors review the current literature on therapeutic gene editing as a prospective curative treatment modality for cardiac amyloidosis.