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Aficamten is a small-molecule cardiac myosin inhibitor designed to treat hypertrophic cardiomyopathy.

ABSTRACT: Hypertrophic cardiomyopathy (HCM) is an inherited disease of the sarcomere resulting in excessive cardiac contractility. The first-in-class cardiac myosin inhibitor, mavacamten, improves symptoms in obstructive HCM. Here we present aficamten, a selective small-molecule inhibitor of cardiac myosin that diminishes ATPase activity by strongly slowing phosphate release, stabilizing a weak actin-binding state. Binding to an allosteric site on the myosin catalytic domain distinct from mavacamten, aficamten prevents the conformational changes necessary to enter the strongly actin-bound force-generating state. In doing so, aficamten reduces the number of functional myosin heads driving sarcomere shortening. The crystal structure of aficamten bound to cardiac myosin in the pre-powerstroke state provides a basis for understanding its selectivity over smooth and fast skeletal muscle. Furthermore, in cardiac myocytes and in mice bearing the hypertrophic R403Q cardiac myosin mutation, aficamten reduces cardiac contractility. Our findings suggest aficamten holds promise as a therapy for HCM.

SUBMITTER: Hartman JJ

PROVIDER: S-EPMC11358156 | biostudies-literature | 2024 Aug

REPOSITORIES: biostudies-literature

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Aficamten is a small-molecule cardiac myosin inhibitor designed to treat hypertrophic cardiomyopathy.

Hartman James J JJ Hwee Darren T DT Robert-Paganin Julien J Chuang Chihyuan C Chin Eva R ER Edell Samantha S Lee Ken H KH Madhvani Roshni R Paliwal Preeti P Pernier Julien J Sarkar Saswata Sankar SS Schaletzky Julia J Schauer Kristine K Taheri Khanha D KD Wang Jingying J Wehri Eddie E Wu Yangsong Y Houdusse Anne A Morgan Bradley P BP Malik Fady I FI

Nature cardiovascular research 20240723 8

Hypertrophic cardiomyopathy (HCM) is an inherited disease of the sarcomere resulting in excessive cardiac contractility. The first-in-class cardiac myosin inhibitor, mavacamten, improves symptoms in obstructive HCM. Here we present aficamten, a selective small-molecule inhibitor of cardiac myosin that diminishes ATPase activity by strongly slowing phosphate release, stabilizing a weak actin-binding state. Binding to an allosteric site on the myosin catalytic domain distinct from mavacamten, afic ...[more]

PMID: 39196032

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Project description:BackgroundUnlike other suggested therapies, myosin inhibitors have been shown to change the course of hypertrophic cardiomyopathy by altering the contractile mechanics of cardiomyocytes. This meta-analysis sought to determine the efficacy of mavacamten and aficamten in hypertrophic cardiomyopathy.MethodsThe online databases were searched from inception to July 2024, including the Cochrane Central Register of Controlled Trials (CENTRAL), PubMed, ClinicalTrials.gov. The meta-analytical data were pooled using risk ratios (RRs) with 95% CI, standard mean difference (SMD) and SE.ResultsA total of 6 randomised controlled trials with 826 hypertrophic cardiomyopathy patients (mean age±SD up to 59.8±14.2 years in intervention vs 60.9±10.5 years in placebo) were included in our study. Of these, 443 received a cardiac myosin inhibitor and 383 received a placebo. The resting left ventricular outflow tract (LVOT) gradient between the two groups was considerably improved by cardiac myosin inhibitors (MD -57.27; 95% CI -63.05 to -51.49). Significant differences were also observed in the post-Valsalva LVOT gradient between the two groups (MD -55.86; 95% CI -65.55 to -46.18). Significantly decreased left ventricle ejection fraction (LVEF) was also seen (MD -4.74; 95% CI -7.22 to -2.26). The New York Health Association (NYHA) class improvement between the two groups also changed significantly (RR 2.21; 95% CI 1.75 to 2.80). Cardiac myosin inhibitors also caused significant improvement in the Kansas City Cardiomyopathy Questionnaire in a Clinical Summary Score between the two groups (MD 7.71; 95% CI 5.37 to 10.05) and significant reduction in the N-terminal pro-B-type natriuretic peptide (SMD -13.27; 95% CI -17.51 to -9.03) and the cardiac troponin I (SMD -11.90; 95% CI -15.07 to -8.72).ConclusionAccording to our meta-analysis, cardiac myosin inhibitors significantly improve the resting and post-Valsalva LVOT gradient, reduce the LVEF and improve the NYHA class and cardiac biomarkers when compared with the placebo.Prospero registration numberCRD52024586161.

Project description:AimsA 25-base pair deletion in the cardiac myosin binding protein-C (cMyBP-C) gene (MYBPC3), proposed to skip exon 33, modifies the C10 domain (cMyBP-CΔC10mut) and is associated with hypertrophic cardiomyopathy (HCM) and heart failure, affecting approximately 100 million South Asians. However, the molecular mechanisms underlying the pathogenicity of cMyBP-CΔC10mutin vivo are unknown. We hypothesized that expression of cMyBP-CΔC10mut exerts a poison polypeptide effect leading to improper assembly of cardiac sarcomeres and the development of HCM.Methods and resultsTo determine whether expression of cMyBP-CΔC10mut is sufficient to cause HCM and contractile dysfunction in vivo, we generated transgenic (TG) mice having cardiac-specific protein expression of cMyBP-CΔC10mut at approximately half the level of endogenous cMyBP-C. At 12 weeks of age, significant hypertrophy was observed in TG mice expressing cMyBP-CΔC10mut (heart weight/body weight ratio: 4.43 ± 0.11 mg/g non-transgenic (NTG) vs. 5.34 ± 0.25 mg/g cMyBP-CΔC10mut, P < 0.05). Furthermore, haematoxylin and eosin, Masson's trichrome staining, as well as second-harmonic generation imaging revealed the presence of significant fibrosis and a greater relative nuclear area in cMyBP-CΔC10mut hearts compared with NTG controls. M-mode echocardiography analysis revealed hypercontractile hearts (EF: 53.4%±2.9% NTG vs. 66.4% ± 4.7% cMyBP-CΔC10mut; P < 0.05) and early diastolic dysfunction (E/E': 28.7 ± 3.7 NTG vs. 46.3 ± 8.4 cMyBP-CΔC10mut; P < 0.05), indicating the presence of an HCM phenotype. To assess whether these changes manifested at the myofilament level, contractile function of single skinned cardiomyocytes was measured. Preserved maximum force generation and increased Ca2+-sensitivity of force generation were observed in cardiomyocytes from cMyBP-CΔC10mut mice compared with NTG controls (EC50: 3.6 ± 0.02 µM NTG vs. 2.90 ± 0.01 µM cMyBP-CΔC10mut; P < 0.0001).ConclusionExpression of cMyBP-C protein with a modified C10 domain is sufficient to cause contractile dysfunction and HCM in vivo.

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Aficamten is a small-molecule cardiac myosin inhibitor designed to treat hypertrophic cardiomyopathy.

Publications

Aficamten is a small-molecule cardiac myosin inhibitor designed to treat hypertrophic cardiomyopathy.

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