In-vivo CRISPR editing for ATTR-CM: therapeutic transthyretin silencing through hepatic genome correction

Dear Editor, Transthyretin Cardiac Amyloidosis (ATTR-CM) is an infiltrative, fatal, and progressive cardiomyopathy resulting from systemic misfolding of the transthyretin (TTR) protein because of genetic mutation (hATTR) or aging (wtATTR). Its pathogenesis begins with hepatic production of unstable TTR tetramers that break apart and aggregate to form toxic amyloid fibrils, resulting in myocardial rigidity and restrictive cardiac failure. ATTR-CM prevalence is rising, with an estimated 200 000 to 300 000 individuals affected globally, with significant mortality if left untreated. Clinical manifestations of the disease are diastolic dysfunction, arrhythmias, progressive dyspnea, and reduced exercise tolerance, leading to substantial morbidity. Diagnostic approaches incorporate echocardiography and non-invasive technetium-pyrophosphate scintigraphy, followed by genetic testing for variant identification in hATTR. Current pharmacological treatments, such as TTR stabilizers including tafamidis, aim to slow down disease progression but do not stop or cure the existing amyloid burden[1,2]. CRISPR-Cas9-mediated TTR silencing is a revolutionary therapeutic approach that targets the hepatic genomic source of pathogenic protein synthesis by delivering a gene-editing complex into hepatocytes via lipid nanoparticles (LNPs). When the Cas9 ribonucleoprotein complex is internalized by hepatocytes, the TTR gene breaks in a double-strand DNA form, causing irreversible interference with the expression of TTR and profound, long-lasting TTR knockdown. The mechanism of this technique consists of the induction of double-strand DNA breaks followed by error-prone repair to provide a long-term decrease in the synthesis of amyloidogenic proteins. Preliminary clinical results are promising, and the majority of patients report an effective and sustainable decline in protein levels. This significantly reduces fibril deposition and decreases the rate of cardiomyopathic progression. The therapy is highly potent and is also being investigated for other genetic diseases that need hepatic protein knockdown, including acute hepatic porphyria, familial hypercholesterolemia polyneuropathy and mixed phenotype ATTR and its primary application in ATTR-CM[3]. Early-phase combined literature from clinical trials supports the unparalleled effectiveness and favorable safety profile of in vivo TTR gene editing. The pivotal Phase 1 study of the investigational CRISPR therapeutic NTLA-2001 in ATTR amyloidosis showed rapid, deep, and durable serum TTR declines exceeding 85–90% by day 28, with symptomatic alleviation and encouraging cardiological results in majority of treated patients[3]. Comparative evidence positions CRISPR-mediated TTR editing as a potent modality with an expanding safety profile, with most adverse effects being mild transient infusion-related reactions and no significant off-target editing events reported across initial patient cohorts. The high rate of TTR knockdown confirms the platform’s potential, essential for amyloid regression and cardiac remodeling[4,5]. Regardless of promising clinical validation, translating genome editing into routine ATTR-CM care presents significant logistical and scientific challenges. A major limitation is the inherent risk of unintended, low-frequency off-target genomic edits, whose long-term biological consequences remain difficult to fully predict across decades. Furthermore, the high initial cost of developing and deploying a single-administration, curative LNP-based therapeutic makes the treatment inaccessible to a large group of patients worldwide, an inherent obstacle to all gene therapies. A third significant gap is the limited clinician familiarity with managing genome editing products, which requires extensive, specialized training on safe and standard administration. These factors highlight the importance of rigorous, long-term safety data collection and infrastructure development before widespread adoption[6,7]. In summary, in vivo CRISPR editing for ATTR-CM represents a novel paradigm having the potential to change the disease course considerably. Future initiatives should aim at subsidized access, increased awareness globally, and increasing outreach to patients on a broader basis to ensure equitable uptake. Further clinical studies are needed to prove that TTR inhibition can be translated into better hard cardiac outcomes, leading to global regulatory approval and universal awareness among clinicians. This letter to the editor adheres to the Transparency in the Reporting of Artificial Intelligence in Research (TITAN) guideline[8].