In vitro and in vivo pharmacokinetic characterization of mavacamten, a first-in-class small molecule allosteric modulator of beta cardiac myosin

Advances in Cardiovascular Pharmacotherapy. I. Cardiac Myosin Inhibitors

Hypertrophic cardiomyopathy (HCM) is the most common inherited cardiomyopathy. The disease is characterized by asymmetric left ventricular (LV) remodeling with myocyte disarray and interstitial fibrosis, a hypercontractile state, dynamic subaortic obstruction of the LV outflow tract, impaired LV diastolic function, atrial and ventricular arrhythmias, and sudden cardiac death. HCM occurs as a result of pathological alterations in the cardiac myocyte's chemomechanical cycle, in which an enhanced rate of myosin-actin crossbridge formation and destabilization of the energy-conserving "super-relaxed off-actin state" of myosin play essential roles. For decades, management of HCM has been limited almost exclusively to medications (eg, beta-blockers, calcium channel blockers, disopyramide) and interventions (eg, septal reduction therapy, implanted cardioverter-defibrillator devices) that palliate symptoms, but do not address the disease's underlying causative mechanisms. A new class of cardiovascular medications, cardiac myosin inhibitors, has surged to the forefront of HCM treatment in recent years. These drugs, including mavacamten and aficamten, show great promise to profoundly affect the disease's clinical course. In this article, the authors review the molecular mechanisms of action of cardiac myosin inhibitors, discuss in detail the most recent data from mavacamten and aficamten clinical trials, describe future planned studies designed to address unanswered questions about their clinical utility in HCM phenotypes, and comment on their potential application to patients with other forms of heart failure with preserved ejection fraction. The possible anesthetic implications of mavacamten and aficamten are also discussed because it is highly likely that patients who are treated with these medications will begin to present for perioperative care with increasing regularity.

French-Speaking Network of Pharmacogenetics (RNPGx) Recommendations for Clinical Use of Mavacamten

Mavacamten, the first drug in the class of β-cardiac myosin modulator, is used for the treatment of patients with hypertrophic cardiomyopathy. This orally administered drug demonstrates wide interpatient variability in pharmacokinetics parameters, due in part to variant CYP2C19 alleles. Individuals who are CYP2C19 poor metabolizers have increased exposure and are at increased risk of reduced cardiac hypercontractility. To ensure the safety of all patients, European Medicines Agency recommends CYP2C19 preemptive genotyping, and consecutively, to adapt maintenance and initial mavacamten doses, and to manage drug-drug interactions, according to CYP2C19 phenotype. In this article, we summarize evidence from the literature supporting the association between CYP2C19 phenotype and pharmacological features of mavacamten and provide, beyond biologic guidelines, therapeutic recommendations for the use of mavacamten based on CYP2C19 and CYP3A4/CYP3A5 genotype.

Novel Selective Cardiac Myosin-Targeted Inhibitors Alleviate Myocardial Ischaemia-Reperfusion Injury

PURPOSE

Reperfusion of the ischaemic heart is essential to limit myocardial infarction. However, reperfusion can cause cardiomyocyte hypercontracture. Recently, cardiac myosin-targeted inhibitors (CMIs), such as Mavacamten (MYK-461) and Aficamten (CK-274), have been developed to treat patients with cardiac hypercontractility. These CMIs are well tolerated and safe in clinical trials. We hypothesised that, by limiting hypercontraction, CMIs may reduce hypercontracture and protect hearts in the setting of ischaemia and reperfusion (IR).

METHODS

We investigated the ability of MYK-461 and CK-274 to inhibit hypercontracture of adult rat cardiomyocytes (ARVC) in vitro following ATP depletion. A suitable dose of CMIs for subsequent in vivo IR studies was identified using cardiac echocardiography of healthy male Sprague Dawley rats. Rats were anaesthetized and subject to coronary artery ligation for 30 min followed by 2 h of reperfusion. Prior to reperfusion, CMI or vehicle was administered intraperitoneally. Ischaemic preconditioning (IPC) was used as a positive control group. Infarct size was assessed by tetrazolium chloride staining and extent of hypercontracture was assessed by histological staining.

RESULTS

Treatment with CMIs inhibited ARVC hypercontracture in vitro. MYK-461 (2 mg/kg) and CK-274 (0.5 mg/kg to 2 mg/kg) significantly reduced infarct size vs. vehicle. IR caused extensive contraction band necrosis, which was reduced significantly by IPC but not by CMIs, likely due to assay limitations. GDC-0326, an inhibitor of PI3Kα, abrogated CK-274-mediated protection following IR injury. GDC-0326 reduced phosphorylation of AKT when administered together with CK-274.

CONCLUSION

This study identifies CMIs as novel cardioprotective agents in the setting of IR injury.

Drug-Drug Interaction Potential of Mavacamten with Midazolam: Combined Results from Clinical and Model-Based Studies

Mavacamten is a potential inducer of cytochrome P450 (CYP) 3A4 and could reduce the effectiveness of concomitant drugs that are metabolized by CYP3A4, such as midazolam. This study aimed to determine if repeat doses of mavacamten achieving clinically relevant exposures affected midazolam exposure. This was a single-center, open-label study in healthy participants. Participants received: on day 1, midazolam 5 mg; on days 2-3, mavacamten 25 mg; on days 4-16, mavacamten 15 mg; and on day 17, mavacamten 15 mg and midazolam 5 mg. Plasma concentrations of mavacamten, midazolam, and the midazolam metabolite 1'-hydroxymidazolam were measured. A physiologically based pharmacokinetic (PBPK) model was used to simulate the effect of mavacamten-mediated CYP3A4 induction on midazolam exposure by CYP2C19 phenotype. Thirteen adult participants were enrolled (46.2% were female; mean [SD] age: 34.0 [9.0] years). Compared with midazolam alone, midazolam coadministered with mavacamten decreased the maximum observed plasma concentration (Cmax), area under the drug concentration-time curve (AUC) from time zero to infinity (AUC0-inf), and AUC from time zero to last measurable concentration (AUC0-last) for midazolam by 7%, 13%, and 24%, respectively; for 1'-hydroxymidazolam, AUC0-inf and AUC0-last increased by 20% and 11%, respectively. Ten participants experienced adverse events and the majority were mild in severity. The PBPK model predicted the clinical trial data well. The PBPK simulation assessed that the overall impact of mavacamten on midazolam Cmax and AUC was predicted to be weak regardless of CYP2C19 phenotype. At clinically relevant exposures, mavacamten had a negligible effect on midazolam exposure.

Long-term effect of mavacamten in obstructive hypertrophic cardiomyopathy

BACKGROUND AND AIMS

Long-term safety and efficacy of mavacamten in patients with obstructive hypertrophic cardiomyopathy (HCM) are unknown. MAVA-LTE (NCT03723655) is an ongoing, 5-year, open-label extension study designed to evaluate the long-term effects of mavacamten.

METHODS

Participants from EXPLORER-HCM (NCT03470545) could enrol in MAVA-LTE upon study completion.

RESULTS

At the latest data cut-off, 211 (91.3%) of the 231 patients originally enrolled in MAVA-LTE still received mavacamten. Median (range) time on study was 166.1 (6.0-228.1) weeks; 185 (80.1%) and 99 (42.9%) patients had completed the Week 156 and 180 visits, respectively. Sustained reductions from baseline to Week 180 occurred in left ventricular outflow tract gradients [mean (standard deviation): resting, -40.3 (32.7) mmHg; Valsalva, -55.3 (33.7) mmHg], N-terminal pro B-type natriuretic peptide [median (interquartile range): -562 (-1162.5, -209) ng/L], and EQ-5D-5L score [mean (standard deviation): 0.09 (0.17)]. Mean left ventricular ejection fraction (LVEF) decreased from 73.9% (baseline) to 66.6% (Week 24) and 63.9% (Week 180). At Week 180, 74 (77.9%) of the 95 patients improved by at least one New York Heart Association class from baseline. Over 739 patient-years exposure, 20 patients (8.7%; exposure-adjusted incidence: 2.77/100 patient-years) experienced 22 transient reductions in LVEF to <50% resulting in temporary treatment interruption (all recovered LVEF of ≥50%). Five (2.2%) patients died (all considered unrelated to mavacamten).

CONCLUSIONS

Long-term mavacamten treatment resulted in sustained improvements in cardiac function and symptoms in patients with obstructive HCM, with no new safety concerns identified. Transient, reversible reductions in LVEF were observed in a small proportion of patients during long-term follow-up.

Cardiac Myosin Inhibitors for Obstructive Hypertrophic Cardiomyopathy: A Meta-analysis of Randomized Placebo-Controlled Trials

BACKGROUND

Cardiac myosin inhibitors (CMI) have emerged as the first disease-specific, noninvasive therapy with promising results in patients with hypertrophic cardiomyopathy. However, its role in obstructive hypertrophic cardiomyopathy (oHCM) remains uncertain, especially in secondary endpoints of randomized controlled trials (RCTs).

METHODS

We systematically searched PubMed, Embase, Web of Science, and Clinicaltrials.gov from inception to June 2024 for RCTs comparing CMI versus placebo in patients with oHCM. We applied a random-effects model to evaluate efficacy and safety outcomes and primary or secondary outcomes of RCTs.

RESULTS

We included five RCTs comprising 767 patients, of whom 402 (52.5%) were randomized to CMI. Relative to placebo, CMI were associated with a higher rate of improvement of at least one New York Heart Association (NYHA) functional class [risk ratio (RR) 2.33; 95% confidence interval (CI) 1.92-2.82]. In addition, CMI reduced resting left ventricular outflow tract (LVOT) [mean difference (MD) - 42.51 mmHg; 95% CI - 59.27 to - 25.75] and the provoked LVOT gradients (MD - 46.12 mmHg; 95% CI - 55.70 to - 36.54). However, CMI significantly increased the risk of reaching a left ventricular ejection fraction below 50% (RR 4.80; 95% CI 1.42-16.20), affecting 8% of patients during long-term follow-up of up to 120 weeks. There was no significant interaction across subgroups of class representatives, pointing to a class effect. The benefit-risk analysis indicated a larger benefit for NYHA class improvement than risk for systolic dysfunction.

CONCLUSION

In patients with oHCM, mavacamten and aficamten as a class improve clinical and hemodynamic endpoints compared with placebo, albeit with a higher incidence of a reduction in left ventricular ejection fraction.

REGISTRATION

PROSPERO CRD42023468079.

Obstructive hypertrophic cardiomyopathy: from genetic insights to a multimodal therapeutic approach with mavacamten, aficamten, and beyond

BACKGROUND

A cardiac condition marked by excessive growth of heart muscle cells, hypertrophic cardiomyopathy (HCM) is a complex genetic disorder characterized by left ventricular hypertrophy, microvascular ischemia, myocardial fibrosis, and diastolic dysfunction. Obstructive hypertrophic cardiomyopathy (oHCM), a subset of HCM, involves significant obstruction in the left ventricular outflow tract (LVOT), leading to symptoms like dyspnea, fatigue, and potentially life-threatening cardiac events. With advancements in genetic understanding and the introduction of novel pharmacologic agents, including cardiac myosin inhibitors like mavacamten and aficamten, there is a paradigm shift in the therapeutic approach to oHCM.

MAIN BODY

The underlying mechanisms of HCM are closely tied to genetic mutations affecting sarcomere proteins, particularly those encoded by the MYH7 and MYBPC3 genes. These mutations lead to disrupted sarcomere function, resulting in hypertrophic changes and LVOT obstruction. While genetic heterogeneity is a hallmark of HCM, clinical diagnosis relies heavily on imaging techniques such as Echocardiography and cardiac magnetic resonance imaging to assess the extent of hypertrophy and obstruction. Current pharmacological management of obstructive HCM (oHCM) focuses on alleviating symptoms rather than modifying disease progression. Beta-blockers and calcium channel blockers are primary treatment options, although their effectiveness varies among patients. Recent clinical trials have highlighted the potential of novel cardiac myosin inhibitors, including mavacamten and aficamten, in enhancing exercise capacity, reducing LVOT obstruction, and improving overall cardiac function. These innovative agents represent a significant breakthrough in targeting the fundamental pathophysiological mechanisms driving oHCM. A comprehensive literature review was conducted, utilizing top-tier databases such as PubMed, Scopus, and Google Scholar, to compile an authoritative and up-to-date overview of the current advancements in the field. This review sheds light on the updated 2024 American Heart Association (AHA) guidelines for HCM management, emphasizing the treatment cascade and tailored management for each stage of oHCM. By introducing a new paradigm for personalized medicine in oHCM, this research leverages advanced genomics, biomarkers, and imaging techniques to optimize treatment strategies.

CONCLUSIONS

The introduction of cardiac myosin inhibitors heralds a new era in the management of oHCM. By directly targeting the molecular mechanisms underpinning the disease, these novel therapies offer improved symptom relief and functional outcomes. Ongoing research into the genetic basis of HCM and the development of targeted treatments holds promise for further enhancing patient care. Future studies should continue to refine these therapeutic strategies and explore their long-term benefits and potential in diverse patient populations. This review makes a significant contribution to the field by synthesizing the most recent AHA guidelines, emphasizing the crucial role of tailored management strategies in optimizing outcomes for patients with oHCM, and promoting the incorporation of cutting-edge genomics and imaging modalities to enhance personalized care.

A comprehensive review of new small molecule drugs approved by the FDA in 2022: Advance and prospect

In 2022, the U.S. Food and Drug Administration approved a total of 16 marketing applications for small molecule drugs, which not only provided dominant scaffolds but also introduced novel mechanisms of action and clinical indications. The successful cases provide valuable information for optimizing efficacy and enhancing pharmacokinetic properties through strategies like macrocyclization, bioequivalent group utilization, prodrug synthesis, and conformation restriction. Therefore, gaining an in-depth understanding of the design principles and strategies underlying these drugs will greatly facilitate the development of new therapeutic agents. This review focuses on the research and development process of these newly approved small molecule drugs including drug design, structural modification, and improvement of pharmacokinetic properties to inspire future research in this field.

Mavacamten in hypertrophic obstructive cardiomyopathy: Prospects for AI integration and mitigating healthcare disparities

Hypertrophic obstructive cardiomyopathy (HOCM) is an autosomal dominant condition that still remains significantly under-diagnosed worldwide. Early detection through clinical evaluation, imaging, and familial history is crucial to prevent severe complications such as heart failure and sudden cardiac death. While cuddsnt management strategies primarily offer symptomatic relief through pharmacotherapy or invasive procedures, their effectiveness and accessibility are limited, revealing substantial gaps in care. The emergence of Mavacamten, a recently FDA-approved drug, could potentially revolutionize HOCM management as it addresses the underlying pathophysiology by inhibiting cardiac myosin ATPase, showing promise in reducing obstruction and improving cardiac function. Our review aims to assess mavacamten's efficacy, emphasizing the pivotal role of genetic testing in identifying at-risk individuals and guiding precise diagnoses for personalized treatments. Additionally, we aim to highlight disparities in access to advanced diagnostics and therapies, particularly affecting underserved populations globally and within communities, as well as explore the potential of artificial intelligence (AI) in enhancing early detection and monitoring treatment responses in HOCM. This review thus offers valuable insights to inform future research directions and clinical practices aimed at optimizing outcomes for individuals with HOCM.

Mavacamten for Obstructive Hypertrophic Cardiomyopathy: Rationale for Clinically Guided Dose Titration to Optimize Individual Response

Mavacamten is the first and only cardiac myosin inhibitor approved in 5 continents for the treatment of adults with symptomatic New York Heart Association class II and III obstructive hypertrophic cardiomyopathy. An evidence-based rationale was used to develop individualized mavacamten dosing, guided by commonly used clinical parameters. Echocardiography is recommended as part of routine clinical assessment of patients with hypertrophic cardiomyopathy, and left ventricular (LV) outflow tract gradient and LV ejection fraction are parameters that can be readily assessed and monitored by echocardiography. Therefore, an echocardiography-based, clinically guided dose-titration strategy was developed to optimize patient benefit from mavacamten for the treatment of symptomatic obstructive hypertrophic cardiomyopathy while minimizing the risk of LV ejection fraction reduction. Results from clinical trials paired with extensive modeling and simulation analyses support a dose-titration and monitoring strategy based on serial echocardiographic measures of Valsalva LV outflow tract gradient and LV ejection fraction. This dosing approach allows for the identification of the lowest individualized mavacamten dose and exposure required to provide improvements in LV outflow tract obstruction, functional capacity, and symptoms. Mavacamten is primarily metabolized by CYP2C19 (cytochrome P450 2C19), and CYP2C19 metabolizer phenotype has an effect on mavacamten exposure. Therefore, this approach has also been demonstrated to provide a favorable safety profile irrespective of patients' CYP2C19 metabolizer status. The dose-titration strategy includes additional considerations for the potential onset of systolic dysfunction in the context of intercurrent illness, and for the potential of drug-drug interactions with inhibitors and substrates of cytochrome P450 enzymes. This posology is reflected in the mavacamten US prescribing information.

Characterization of mavacamten pharmacokinetics in patients with hypertrophic cardiomyopathy to inform dose titration

Mavacamten is a selective, allosteric, reversible cardiac myosin inhibitor that has been developed for the treatment of adults with symptomatic obstructive hypertrophic cardiomyopathy (HCM). A population pharmacokinetic (PopPK) model was developed to characterize mavacamten pharmacokinetics (PK) and the variation in mavacamten exposure associated with intrinsic and extrinsic factors. Data from 12 clinical studies (phases 1, 2, and 3) were used. Evaluable participants were those who had at least one mavacamten concentration measurement with associated sampling time and dosing information. The base model included key covariates: body weight, cytochrome P450 isozyme 2C19 (CYP2C19) phenotype with respect to PK, and formulation. The final model was generated using stepwise covariate testing and refinement processes. Simulations were performed to evaluate PK: apparent clearance (CL/F); apparent central and peripheral volumes of distribution; and steady-state average, trough, and maximum concentrations. Overall, 9244 measurable PK observations from 497 participants were included. A two-compartment model structure was selected. After stepwise covariate model building and refinement, additional covariates included were: specified mavacamten dose, omeprazole or esomeprazole administration, health/disease status, estimated glomerular filtration rate, fed status, and sex. The final PopPK model accurately characterized mavacamten concentrations. At any given dose, CYP2C19 phenotype was the most influential covariate on exposure parameters (e.g., median CL/F was reduced by 72% in CYP2C19:poor metabolizers compared with the reference participant [CYP2C19:normal metabolizer]). CL/F was also approximately 16% higher in women than in men but lower in participants receiving concomitant omeprazole or esomeprazole (by 33% and 42%, respectively) than in participants not receiving such concomitant therapy.

Recommendation of mavacamten posology by model-based analyses in adults with obstructive hypertrophic cardiomyopathy

Mavacamten is the first cardiac myosin inhibitor approved by the US Food and Drug Administration for the treatment of adults with symptomatic obstructive hypertrophic cardiomyopathy (HCM). The phase III EXPLORER-HCM (NCT03470545) study used a dose-titration scheme based on mavacamten exposure and echocardiographic assessment of Valsalva left ventricular outflow tract gradient (VLVOTg) and left ventricular ejection fraction (LVEF). Using population pharmacokinetic/exposure-response modeling and simulations of virtual patients, this in silico study evaluated alternative dose-titration regimens for mavacamten, including regimens that were guided by echocardiographic measures only. Mavacamten exposure-response models for VLVOTg (efficacy) and LVEF (safety) were developed using patient data from five clinical studies and characterized using nonlinear mixed-effects models. Simulations of five echocardiography-guided regimens were performed in virtual cohorts constructed based on either expected or equal population distributions of cytochrome P450 2C19 (CYP2C19) metabolizer phenotypes. Each regimen aimed to maximize the proportions of patients who achieved a VLVOTg below 30 mm Hg while maintaining LVEF above 50% over 40 weeks and 104 weeks, respectively. The exposure-response models successfully characterized mavacamten efficacy and safety parameters. Overall, the simulated regimen with the optimal benefit-risk profile across CYP2C19 phenotypes had steps for down-titration at weeks 4 and 8 (for VLVOTg <20 mm Hg), and up-titration at week 12 (for VLVOTg ≥30 mm Hg and LVEF ≥55%), and every 12 weeks thereafter. This simulation-optimized regimen is recommended in the mavacamten US prescribing information.

Evolving Strategies for the Management of Obstructive Hypertrophic Cardiomyopathy

For many years, treatment of hypertrophic cardiomyopathy (HCM) has focused on non-disease-specific therapies. Cardiac myosin modulators (ie, mavacamten and aficamten) reduce the pathologic actin-myosin interactions that are characteristic of HCM, leading to improved cardiac energetics and reduction in hypercontractility. Several recently published randomized clinical trials have demonstrated that mavacamten improves exercise capacity, left ventricular outflow tract obstruction and symptoms in patients with obstructive HCM and may delay the need for septal-reduction therapy. Long-term data in real-world populations will be needed to fully assess the safety and efficacy of mavacamten. Importantly, HCM is a complex and heterogeneous disease, and not all patients will respond to mavacamten; therefore, careful patient selection and shared decision making will be necessary in guiding the use of mavacamten in obstructive HCM.

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

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.

Evaluation of mavacamten in patients with hypertrophic cardiomyopathy

AIMS

We aimed to comprehensively assess the safety and efficacy of mavacamten in hypertrophic cardiomyopathy (HCM) patients.

METHODS

A systematic review and meta-analysis was conducted, and efficacy [changes in postexercise left ventricular outflow tract (LVOT) gradient, left ventricular ejection fraction (LVEF), peak oxygen consumption (pVO 2 ), Kansas City Cardiomyopathy Questionnaire Clinical Summary Score (KCCQ CSS), and the proportion of patients exhibiting an improvement of at least one New York Heart Association (NYHA) functional class from baseline)], safety (total count of treatment-emergent adverse events and SAEs, as well as the proportion of patients experiencing at least one adverse event or SAE), and cardiac biomarkers (NT-proBNP and cTnI) outcomes were evaluated.

RESULTS

We incorporated data from four randomized controlled trials, namely EXPLORER-HCM, VALOR-HCM, MAVERICK-HCM, and EXPLORER-CN. Mavacamten demonstrated significant efficacy in reducing the postexercise LVOT gradient by 49.44 mmHg ( P  = 0.0001) and LVEF by 3.84 ( P  < 0.0001) and improving pVO 2 by 0.69 ml/kg/min ( P  = 0.4547), KCCQ CSS by 8.11 points ( P  < 0.0001), and patients with at least one NYHA functional class improvement from baseline by 2.20 times ( P  < 0.0001). Importantly, mavacamten increased 1.11-fold adverse events ( P  = 0.0184) 4.24-fold reduced LVEF to less than 50% ( P  = 0.0233) and 1.06-fold SAEs ( P  = 0.8631). Additionally, mavacamten decreased NT-proBNP by 528.62 ng/l ( P  < 0.0001) and cTnI by 8.28 ng/l ( P  < 0.0001).

CONCLUSION

Mavacamten demonstrates both safety and efficacy in patients with HCM, suggesting its potential as a promising therapeutic strategy for this condition. Further research is warranted to confirm these results and explore its long-term effects.

Promising therapies for adults with symptomatic obstructive hypertrophic cardiomyopathy: 2023 and beyond

INTRODUCTION

Hypertrophic cardiomyopathy (HCM) is a heterogeneous genetic heart disease with an estimated prevalence in the general population of 0.2% to 0.6%. Clinically, HCM can range from no symptoms to severe symptoms such as heart failure or sudden cardiac death. Currently, the management of HCM involves lifestyle modifications, familial screening, genetic counseling, pharmacotherapy to manage symptoms, sudden cardiac death risk assessment, septal reduction therapy, and heart transplantation for specific patients. Multicenter randomized controlled trials have only recently explored the potential of cardiac myosin inhibitors (CMIs) such as mavacamten as a directed pharmacological approach for managing HCM.

AREAS COVERED

We will assess the existing medical treatments for HCM: beta-blockers, calcium channel blockers, disopyramide, and different CMIs. We will also discuss future HCM pharmacotherapy guidelines and underline this patient population's unfulfilled needs.

EXPERT OPINION

Mavacamten is the first-in-class CMI approved by the FDA to target HCM pathophysiology specifically. Mavacamten should be incorporated into the standard therapy for oHCM in case of symptom persistence despite using maximally tolerated beta blockers and/or calcium channel blockers. Potential drug-drug interactions should be assessed before initiating this drug. More studies are needed on the use of CMIs in patients with kidney and/or liver failure and pregnant/breastfeeding patients.

Apical hypertrophic cardiomyopathy: pathophysiology, diagnosis and management

Since the first description of apical hypertrophic cardiomyopathy (ApHCM) in 1976, contrasting information from all over the world has emerged regarding the natural history of the disease. However, the recommended guidelines on hypertrophic cardiomyopathy (HCM) pay a cursory reference to ApHCM, without ApHCM-specific recommendations to guide the diagnosis and management. In addition, cardiologists may not be aware of certain aspects that are specific to this disease subtype, and a robust understanding of specific disease features can facilitate recognition and timely diagnosis. Therefore, the review covers the incidence, pathogenesis, and characteristics of ApHCM and imaging methods. Echocardiography and cardiovascular magnetic resonance imaging (CMR) are the most commonly used imaging methods. Moreover, this review presents the management strategies of this heterogeneous clinical entity. In this review, we introduce a novel transapical beating-heart septal myectomy procedure for ApHCM patients with a promising short-time result.

Myosin folding boosts solubility in cardiac muscle sarcomeres

The polymerization of myosin molecules into thick filaments in muscle sarcomeres is essential for cardiac contractility, with the attenuation of interactions between the heads of myosin molecules within the filaments being proposed to result in hypercontractility, as observed in hypertrophic cardiomyopathy (HCM). However, experimental evidence demonstrates that the structure of these giant macromolecular complexes is highly dynamic, with molecules exchanging between the filaments and a pool of soluble molecules on the minute timescale. Therefore, we sought to test the hypothesis that the enhancement of interactions between the heads of myosin molecules within thick filaments limits the mobility of myosin by taking advantage of mavacamten, a small molecule approved for the treatment of HCM. Myosin molecules were labeled in vivo with a green fluorescent protein (GFP) and imaged in intact hearts using multiphoton microscopy. Treatment of the intact hearts with mavacamten resulted in an unexpected > 5-fold enhancement in GFP-myosin mobility within the sarcomere. In vitro biochemical assays suggested that mavacamten enhanced the mobility of GFP-myosin by increasing the solubility of myosin molecules, through the stabilization of a compact/folded conformation of the molecules, once disassociated from the thick filaments. These findings provide alternative insight into the mechanisms by which molecules exchange into and out of thick filaments and have implications for how mavacamten may affect cardiac contractility.

Mavacamten for Obstructive Hypertrophic Cardiomyopathy With or Without Hypertension: Post-Hoc Analysis of the EXPLORER-HCM Trial

BACKGROUND

Hypertension (HTN) is common in patients with hypertrophic cardiomyopathy (HCM), but its effect on the treatment of left ventricular outflow tract (LVOT) obstruction is undefined. Although elevated systolic blood pressure (SBP) may impact dynamic LVOT gradients, its response to cardiac myosin inhibition is unknown.

OBJECTIVES

In a post hoc exploratory analysis of the EXPLORER-HCM trial (Clinical Study to Evaluate Mavacamten [MYK-461] in Adults With Symptomatic Obstructive Hypertrophic Cardiomyopathy), the authors examined the characteristics of patients with obstructive HCM and HTN and the associations between HTN, SBP, and the response to mavacamten treatment of LVOT obstruction.

METHODS

Patients were stratified by baseline history of HTN and mean SBP during 30-week treatment with mavacamten or placebo. The study estimated treatment differences and evaluated HTN and SBP groups by treatment interaction. Analysis of covariance was used to model changes in continuous endpoints, and a generalized linear model was used for binary endpoints.

RESULTS

HTN was present in 119 of 251 patients (47.4%), including 60 receiving mavacamten and 59 receiving placebo. Patients with HTN vs no HTN were older (63.4 vs 54.0 years; P < 0.001), had higher SBP (134 ± 15.1 mm Hg vs 123 ± 13.8 mm Hg; P < 0.001), more comorbidities, and lower peak oxygen consumption (19 ± 3 vs 20 ± 4 mL/kg/min; P = 0.021). Patients with HTN had similar NYHA functional class (NYHA functional class II, 72% vs 73%), Valsalva LVOT gradients (72 ± 34 mm Hg vs 74 ± 30 mm Hg), Kansas City Cardiomyopathy Questionnaire-Clinical Summary Scores (70.6 ± 18.8 vs 68.9 ± 23.1), and NT pro-B-type natriuretic peptide levels (geometric mean 632 ± 129 pg/mL vs 745 ± 130 pg/mL). Mavacamten-treated patients had improvement in all primary, secondary, and exploratory endpoints regardless of HTN status or mean SBP.

CONCLUSIONS

The clinical benefits of mavacamten in symptomatic, obstructive HCM were similar in patients with and without HTN, despite differences in baseline characteristics. (Clinical Study to Evaluate Mavacamten [MYK-461] in Adults With Symptomatic Obstructive Hypertrophic Cardiomyopathy [EXPLORER-HCM]; NCT03470545).

Discerning the stability behaviour of mavacamten availing liquid chromatography-mass spectrometry and nuclear magnetic resonance spectroscopy: In silico toxicity and mutagenicity prediction of degradation products

The present study aimed to separate, identify, and characterise the degradation products formed when mavacamten is exposed to stress degradation as well as the stability of the drug in various environments and also to understand its degradation chemistry. Prediction of in silico toxicity and mutagenicity was aimed at the observed degradation products. Stress degradation along with stability studies and degradation kinetics were performed on mavacamten, and separation of degradation products was carried out by high-performance liquid chromatography. Tandem mass spectrometry studies were executed to characterise the structures of degradation products using product ion fragments. Orthogonally, nuclear magnetic resonance experiments were conducted to elucidate the structures having ambiguity in characterising them. Deductive Estimation of Risk from Existing Knowledge and Structure Activity Relationship Analysis using Hypotheses software were used to establish in silico toxicity and mutagenic profiles of mavacamten and its degradation products. Two degradation products of mavacamten found in acidic hydrolytic stress conditions were separated, identified, characterised, and proposed as 1-isopropylpyrimidine-2,4,6(1H,3H,5H)-trione and 1-phenylethanamine. Mavacamten was found to be stable under different pH and gastrointestinal conditions. The degradation kinetics of mavacamten under 1 N acidic condition followed zero-order kinetics, and it was degraded completely within 6 h. In silico toxicity and mutagenicity studies revealed that 1-phenylethanamine can be a skin sensitiser. A high-performance liquid chromatography method was developed for the separation of degradation products of mavacamten and characterised by liquid chromatography-tandem mass spectrometry and nuclear magnetic resonance. During the manufacturing and storage of drug product, precautions need to be taken when dealing with acidic solutions as the drug is prone to hydrolysis in acidic conditions. The formation of 1-phenylethanamine under these conditions is to be monitored as it is a skin sensitiser.

Cardiac Myosin Inhibitors: Expanding the Horizon for Hypertrophic Cardiomyopathy Management

OBJECTIVE

To review the current literature on the efficacy and safety of cardiac myosin inhibitors (CMIs) for the treatment of hypertrophic cardiomyopathy (HCM).

DATA SOURCES

A literature search was conducted on PubMed from origin to April 2023, using the search terms "MYK-461," "mavacamten," "CK-3773274," and "aficamten." Studies were limited to English-based literature, human subjects, and clinical trials resulting in the inclusion of 13 articles. ClinicalTrials.gov was also used with the same search terms for ongoing and completed trials.

STUDY SELECTION AND DATA EXTRACTION

Only phase II and III studies were included in this review except for pharmacokinetic studies that were used to describe drug properties.

DATA SYNTHESIS

CMIs enable cardiac muscle relaxation by decreasing the number of myosin heads that can bind to actin and form cross-bridges. Mavacamten, the first Food and Drug Administration (FDA)-approved drug in this class, has been shown to improve hemodynamic, functional, and quality of life measures in HCM with obstruction. In addition, aficamten is likely to become the next FDA-approved CMI with promising phase II data and an ongoing phase III trial expected to release results in the next year.

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE IN COMPARISON WITH EXISTING DRUGS

CMIs provide a novel option for obstructive hypertrophic cardiomyopathy, particularly in those not suitable for septal reduction therapy. Utilization of these agents requires knowledge of drug interactions, dose titration schemes, and monitoring parameters for safety and efficacy.

CONCLUSIONS

CMIs represent a new class of disease-specific drugs for treatment of HCM. Cost-effectiveness studies are needed to delineate the role of these agents in patient therapy.

A systematic review of present and future pharmaco-structural therapies for hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a common contemporary, treatable, genetic disorder that can be compatible with normal longevity. While current medical therapies are ubiquitous, they are limited by a lack of solid evidence, are often inadequate, poorly tolerated, and do not alter the natural disease course. As such, there has long been a need for effective, evidence-based, and targeted disease-modifying therapies for HCM. In this review, we redefine HCM as a treatable condition, evaluate current strategies for therapeutic intervention, and discuss novel myosin inhibitors. The majority of patients with HCM have elevated left ventricular outflow tract gradients, which predicts worse symptoms and adverse outcomes. Conventional pharmacological therapies for symptomatic HCM can help improve symptoms but are often inadequate and poorly tolerated. Septal reduction therapies (surgical myectomy and alcohol septal ablation) can safely and effectively reduce refractory symptoms and improve outcomes in patients with obstructive HCM. However, they require expertise that is not universally available and are not without risks. Currently, available therapies do not alter the disease course or the progressive cardiac remodeling that ensues, nor subsequent heart failure and arrhythmias. This has been regarded as an unmet need in the care of HCM patients. Novel targeted pharmacotherapies, namely cardiac myosin inhibitors, have emerged to reverse key pathophysiological changes and alter disease course. Their favorable outcomes led to the early Food and Drug Administration approval of mavacamten, a first-in-class myosin modulator, changing the paradigm for the pharmacological treatment of HCM.

Mavacamten Treatment for Symptomatic Obstructive Hypertrophic Cardiomyopathy: Interim Results From the MAVA-LTE Study, EXPLORER-LTE Cohort

BACKGROUND

Data assessing the long-term safety and efficacy of mavacamten treatment for symptomatic obstructive hypertrophic cardiomyopathy are needed.

OBJECTIVES

The authors sought to evaluate interim results from the EXPLORER-Long Term Extension (LTE) cohort of MAVA-LTE (A Long-Term Safety Extension Study of Mavacamten in Adults Who Have Completed EXPLORER-HCM; NCT03723655).

METHODS

After mavacamten or placebo withdrawal at the end of the parent EXPLORER-HCM (Clinical Study to Evaluate Mavacamten [MYK-461] in Adults With Symptomatic Obstructive Hypertrophic Cardiomyopathy; NCT03470545), patients could enroll in MAVA-LTE. Patients received mavacamten 5 mg once daily; adjustments were made based on site-read echocardiograms.

RESULTS

Between April 9, 2019, and March 5, 2021, 231 of 244 eligible patients (94.7%) enrolled in MAVA-LTE (mean age: 60 years; 39% female). At data cutoff (August 31, 2021) 217 (93.9%) remained on treatment (median time in study: 62.3 weeks; range: 0.3-123.9 weeks). At 48 weeks, patients showed improvements in left ventricular outflow tract (LVOT) gradients (mean change ± SD from baseline: resting: -35.6 ± 32.6 mm Hg; Valsalva: -45.3 ± 35.9 mm Hg), N-terminal pro-B-type natriuretic peptide (NT-proBNP) levels (median: -480 ng/L; Q1-Q3: -1,104 to -179 ng/L), and NYHA functional class (67.5% improved by ≥1 class). LVOT gradients and NT-proBNP reductions were sustained through 84 weeks in patients who reached this timepoint. Over 315 patient-years of exposure, 8 patients experienced an adverse event of cardiac failure, and 21 patients had an adverse event of atrial fibrillation, including 11 with no prior history of atrial fibrillation. Twelve patients (5.2%) developed transient reductions in site-read echocardiogram left ventricular ejection fraction of <50%, resulting in temporary treatment interruption; all recovered. Ten patients discontinued treatment due to treatment-emergent adverse events.

CONCLUSIONS

Mavacamten treatment showed clinically important and durable improvements in LVOT gradients, NT-proBNP levels, and NYHA functional class, consistent with EXPLORER-HCM. Mavacamten treatment was well tolerated over a median 62-week follow-up.

Biomechanical response of ultrathin slices of hypertrophic cardiomyopathy tissue to myosin modulator mavacamten

Hypertrophic cardiomyopathy (HCM) is the most common inherited myocardial disorder of the heart, but effective treatment options remain limited. Mavacamten, a direct myosin modulator, has been presented as novel pharmacological therapy for HCM. The aim of this study was to analyze the biomechanical response of HCM tissue to Mavacamten using living myocardial slices (LMS). LMS (n = 58) from patients with HCM (n = 10) were cultured under electromechanical stimulation, and Verapamil and Mavacamten were administered on consecutive days to evaluate their effects on cardiac biomechanics. Mavacamten and Verapamil reduced contractile force and dF/dt and increased time-to-relaxation in a similar manner. Yet, the time-to-peak of the cardiac contraction was prolonged after administration of Mavacamten (221.0 ms (208.8 - 236.3) vs. 237.7 (221.0 - 254.7), p = 0.004). In addition, Mavacamten prolonged the functional refractory period (FRP) (330 ms (304 - 351) vs. 355 ms (313 - 370), p = 0.023) and better preserved twitch force with increasing stimulation frequencies, compared to Verapamil. As such, Mavacamten reduced (hyper-)contractility and prolonged contraction duration of HCM LMS, suggesting a reduction in cardiac wall stress. Also, Mavacamten might protect against the development of ventricular tachyarrhythmias due to prolongation of the FRP, and improve toleration of tachycardia due to better preservation of twitch force at tachycardiac stimulation frequencies.

Analyzing safety and effectiveness of Mavacamten in comparison with placebo for managing hypertrophic cardiomyopathy: a systemic review and meta-analysis

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is a hereditary myocardial disorder, often due to sarcomere gene mutations, characterized by the left ventricular hypertrophy. Current treatments offer symptomatic relief but lack specificity. Mavacamten, an allosteric inhibitor, has shown significant improvements in HCM patients in trials, reducing the requirement for invasive treatments. This meta-analysis assesses Mavacamten's efficacy and safety as a targeted HCM intervention.

METHODS

This study examined four randomized controlled trials comparing Mavacamten to placebo in HCM patients. Each trial had a unique primary endpoint, and secondary outcomes included improvements in NYHA-FC, eligibility for septal reduction therapy (SRT) or undergoing it, adverse events (serious and treatment-related), atrial fibrillation, and non-sustained ventricular tachycardia. Statistical analysis involved calculating risk ratios (RRs) and assessing heterogeneity.

RESULTS

The four included studies showed minimal risk of bias and involved 503 patients with HCM (273 Mavacamten and 230 placebo). Mavacamten significantly increased the primary endpoint (RR 2.15, 95% CI 1.20-3.86, P = 0.01) and ≥ 1 NYHA-FC class (RR 2.21, 95% CI 1.48-3.3, P = 0.0001). Mavacamten group had lower rates of SRT compared to those receiving placebo (RR, 0.30, 95% CI 0.22-0.40; P < 0.00001). No significant differences existed in rates adverse events between the Mavacamten and placebo groups.

CONCLUSIONS

Our study suggests that Mavacamten may have therapeutic benefits for HCM patients, as indicated by its positive impact on certain endpoints. Further research with larger samples, longer follow-up, and comprehensive analysis is needed to understand Mavacamten's safety and efficacy in HCM patients.

Effects of Omeprazole and Verapamil on the Pharmacokinetics, Safety, and Tolerability of Mavacamten: Two Drug-Drug Interaction Studies in Healthy Participants

Two open-label, Phase 1 studies assessed the effects of omeprazole (a weak to moderate cytochrome P450 [CYP] 2C19 inhibitor) and verapamil (a moderate CYP3A4 inhibitor) on the pharmacokinetics, safety, and tolerability of mavacamten. In the omeprazole study, healthy participants received mavacamten 15 mg alone or with a 31-day course of omeprazole 20 mg once daily. In the verapamil study, healthy participants received mavacamten 25 mg alone or with a 28-day course of verapamil 240 mg once daily. In the omeprazole study, 27 of 29 randomized participants completed the study. Nine participants receiving mavacamten alone were normal metabolizers (NMs) of CYP2C19 substrates, and 6 were rapid metabolizers; 8 NMs and 6 rapid metabolizers received mavacamten + omeprazole. In both studies, mavacamten showed no safety signals and was generally well tolerated. Overall mavacamten exposure (area under the plasma concentration-time curve) increased by approximately 50% with omeprazole coadministration; maximum observed concentration (Cmax ), time to Cmax , and elimination half-life were not affected appreciably. In the verapamil study, 25 of 26 randomized participants received the study drug(s) and were included in the pharmacokinetic analyses; 24 completed the study. In the pharmacokinetic population, 12 participants received mavacamten alone (11 NMs, 1 poor metabolizer) and 13 received mavacamten + verapamil (7 NMs, 4 intermediate metabolizers, 2 poor metabolizers). Following verapamil coadministration in NMs and intermediate metabolizers, mavacamten area under the plasma concentration-time curve was minimally increased (by less than 20%), and Cmax was modestly increased (by 52%). These results suggest that mavacamten can be coadministered with weak CYP2C19 and moderate CYP3A4 inhibitors.

Differentiating Cardiac Troponin Levels During Cardiac Myosin Inhibition or Cardiac Myosin Activation Treatments: Drug Effect or the Canary in the Coal Mine?

PURPOSE OF REVIEW

Cardiac myosin inhibitors (CMIs) and activators are emerging therapies for hypertrophic cardiomyopathy (HCM) and heart failure with reduced ejection fraction (HFrEF), respectively. However, their effects on cardiac troponin levels, a biomarker of myocardial injury, are incompletely understood.

RECENT FINDINGS

In patients with HCM, CMIs cause substantial reductions in cardiac troponin levels which are reversible after stopping treatment. In patients with HFrEF, cardiac myosin activator (omecamtiv mecarbil) therapy cause modest increases in cardiac troponin levels which are reversible following treatment cessation and not associated with myocardial ischaemia or infarction. Transient changes in cardiac troponin levels might reflect alterations in cardiac contractility and mechanical stress. Such transient changes might not indicate cardiac injury and do not appear to be associated with adverse outcomes in the short to intermediate term. Longitudinal changes in troponin levels vary depending on the population and treatment. Further research is needed to elucidate mechanisms underlying changes in troponin levels.

Mavacamten: a first-in-class myosin inhibitor for obstructive hypertrophic cardiomyopathy

Mavacamten is a first-in-class, targeted, cardiac-specific myosin inhibitor approved by the US Food and Drug Administration for the treatment of adults with symptomatic New York Heart Association Classes II and III obstructive hypertrophic cardiomyopathy (oHCM). Mavacamten was developed to target the hyper-contractile phenotype, which plays a critical role in the pathophysiology of the disease. In Phase 2 and 3 clinical trials, mavacamten was well tolerated, reduced left ventricular outflow tract gradients, improved exercise capacity and symptoms, and was associated with improvements in other clinically relevant parameters, such as patient-reported outcomes and circulating biomarkers. In addition, treatment with mavacamten was associated with evidence of favourable cardiac remodelling in multi-modality imaging studies. Mavacamten substantially reduced guideline eligibility for septal reduction therapy candidates with oHCM and drug-refractory symptoms. In this article, the available efficacy and safety data from completed and ongoing clinical studies of mavacamten in patients with symptomatic oHCM are reviewed. Longer term extension studies may help address questions related to the positioning of mavacamten in current oHCM management algorithms, interactions with background therapy, as well as the potential for disease modification beyond symptomatic relief of left ventricular outflow tract obstruction.

Drug-Drug Interaction Potential of Mavacamten with Oral Contraceptives: Results from a Clinical Pharmacokinetic Study and a Physiologically Based Pharmacokinetic Model

Mavacamten is a potential inducer of cytochrome P450 (CYP) 3A4 and, as such, could reduce the exposure of the active components of oral contraceptives, ethinyl estradiol (EE) and norethindrone (NOR), where CYP3A4 is involved in metabolism. This study assessed if repeat doses of mavacamten led to a drug-drug interaction with EE and/or NOR. This was an open-label study in healthy women. In Period 1, participants received 35 mcg of EE and 1 mg of NOR. In Period 2, participants received oral loading doses of mavacamten 25 mg on Days 1-2, 15 mg/day on Days 3-17, and 35 mcg of EE and 1 mg of NOR on Day 15. Plasma concentrations of mavacamten, EE, and NOR were obtained before dosing and up to 72 hours after dosing. For EE only, a physiologically based pharmacokinetic model was used to simulate mavacamten-mediated CYP3A4 induction with EE for various CYP2C19 phenotypes. In total, 13 women were enrolled (mean age, 38.9 [standard deviation, 9.65] years). After mavacamten administration, modest increases in area under the concentration-time curves were observed for both EE and NOR. The maximum concentrations and half-lives for EE and NOR were not affected by coadministration with mavacamten. Criteria for bioequivalence were met or nearly met for EE and NOR exposure with geometric mean ratios between 0.8 and 1.25. All adverse events were mild. The physiologically based pharmacokinetic model predicted a less than 15% decrease in EE exposure across CYP2C19 phenotypes. Coadministration of mavacamten at a therapeutically relevant dose with EE and NOR did not decrease the exposure to either EE or NOR to a level that may lead to reduced effectiveness.

Alcohol Septal Ablation or Mavacamten for Obstructive Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a genetic disease characterized by an increased left ventricular wall thickness in the absence of increased afterload conditions. In addition to diastolic dysfunction, obstruction of the left ventricular outflow tract is common in HCM and has an important influence on symptoms and outcome. Over the last five decades or two decades, respectively, surgical myectomy and alcohol septal ablation were the only therapeutic options if standard medical care was not sufficient. Recently, a new option has become available that has the potential to revolutionize the therapeutic strategies for patients with HCM. Mavacamten is a myosin inhibitor that belongs to a completely new drug class and targets the excessive actin-myosin cross-bridging that is the underlying pathology of HCM. By reducing the actin-myosin interactions, mavacamten not only reduces the left ventricular outflow tract (LVOT) obstruction but also seems to have positive effects on the diastolic function, microcirculation, and cardiac structure. This article summarizes the current evidence on alcohol septal ablation and reviews the preclinical and clinical data on mavacamten for the treatment of patients with obstructive HCM.

Physiologically Based Pharmacokinetic Modeling and Simulation of Mavacamten Exposure with Drug-Drug Interactions from CYP Inducers and Inhibitors by CYP2C19 Phenotype

Mavacamten is a first-in-class, oral, selective, allosteric, reversible cardiac myosin inhibitor approved by the US Food and Drug Administration for the treatment of adults with symptomatic New York Heart Association functional class II-III obstructive hypertrophic cardiomyopathy. Mavacamten is metabolized in the liver, predominantly via cytochrome P450 (CYP) enzymes CYP2C19 (74%), CYP3A4 (18%), and CYP2C9 (8%). A physiologically-based pharmacokinetic (PBPK) model was developed using Simcyp version 19 (Certara, Princeton, NJ). Following model verification, the PBPK model was used to explore the effects of strong CYP3A4 and CYP2C19 inducers, and strong, moderate, and weak CYP2C19 and CYP3A4 inhibitors on mavacamten pharmacokinetics (PK) in a healthy population, with the effect of CYP2C19 phenotype predicted for poor, intermediate, normal, and ultrarapid metabolizers. The PBPK model met the acceptance criteria for all verification simulations (> 80% of model-predicted PK parameters within 2-fold of those observed clinically). A weak induction effect was predicted when mavacamten was administered with a strong CYP3A4 inducer in poor metabolizers. Moderate reductions in mavacamten exposure were predicted with a strong CYP2C19/CYP3A4 inducer in all CYP2C19 phenotypes. Except for the effect of strong CYP2C19 inhibitors on ultrarapid metabolizers, steady-state area under plasma concentration-time curve and maximum plasma concentration values were weakly affected (< 2-fold) or not affected (< 1.25-fold), regardless of CYP2C19 phenotype. In conclusion, a fit-for-purpose PBPK model was developed and verified, which accurately predicted the available clinical data and was used to simulate the potential impact of CYP induction and inhibition on mavacamten PKs, stratified by CYP2C19 phenotype.

Unmet needs and future directions in hypertrophic cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is a highly treatable monogenetic disorder affecting nearly 0.2% of the population. The high burden of this disease demands suitable measures for early diagnosis and preventing as well as tackling misdiagnosis. While conventionally available therapies have been efficacious in reducing symptoms, they have not been able to change the natural history of the disease. The landscape of medical treatment is rapidly changing with advent of novel pharmacotherapies such as cardiac myosin inhibitors. Ongoing investigations in gene editing have demonstrated benefits in correcting underlying genetic mutations and this is where the future of treatment lies. Contemporary procedural techniques as alternatives to available septal reduction therapies independent of coronary vascular anatomy are also emerging. This review details the recent developments, unmet needs and future directions in diagnosis, medical and invasive treatment of HCM.

Aficamten: A Breakthrough Therapy for Symptomatic Obstructive Hypertrophic Cardiomyopathy

Aficamten is a novel cardiac myosin inhibitor that has demonstrated its ability to safely lower left ventricular outflow tract (LVOT) gradients and improve heart failure symptoms in patients with obstructive hypertrophic cardiomyopathy (HCM). Based on the REDWOOD-HCM open label extension (OLE) study, participants receiving aficamten had significantly reduced resting and Valsalva LVOT gradient within 2 weeks after initiating treatment, with ongoing improvements over 24 weeks, and recent evidence suggests effects can sustain up to 48 weeks. While beta-blockers, calcium channel blockers, and disopyramide have shown some benefits in managing HCM, they have limited direct impact on the underlying disease process in patients with obstructive HCM. Aficamten achieves its therapeutic effect by reducing hypercontractility and improving diastolic function in obstructive HCM. Mavacamten was the first cardiac myosin inhibitor approved for symptomatic obstructive HCM. However, aficamten has a shorter human half-life (t1/2) and fewer drug-drug interactions, making it a preferable treatment option. This review evaluates the long-term clinical value and safety of aficamten in patients with obstructive HCM based on available data from completed and ongoing clinical trials. Additionally, the molecular basis of sarcomere-targeted therapy in reducing LVOT gradients is explored, and its potential in managing obstructive HCM is discussed.

Hypertrophic Cardiomyopathy versus Storage Diseases with Myocardial Involvement

One of the main causes of heart failure is cardiomyopathies. Among them, the most common is hypertrophic cardiomyopathy (HCM), characterized by thickening of the left ventricular muscle. This article focuses on HCM and other cardiomyopathies with myocardial hypertrophy, including Fabry disease, Pompe disease, and Danon disease. The genetics and pathogenesis of these diseases are described, as well as current and experimental treatment options, such as pharmacological intervention and the potential of gene therapies. Although genetic approaches are promising and have the potential to become the best treatments for these diseases, further research is needed to evaluate their efficacy and safety. This article describes current knowledge and advances in the treatment of the aforementioned cardiomyopathies.

Cardiac Myosin Inhibitors for Managing Obstructive Hypertrophic Cardiomyopathy: JACC: Heart Failure State-of-the-Art Review

Hypertrophic cardiomyopathy (HCM) is frequently caused by pathogenic variants in genes encoding sarcomere proteins and is characterized by left ventricular (LV) hypertrophy, hypercontractility, and-in many cases-left ventricular outflow tract (LVOT) obstruction. Despite standard management, obstructive HCM (oHCM) can still cause substantial morbidity, highlighting the critical need for more effective disease-specific therapeutic approaches. Over the past decade, improved understanding of the molecular pathobiology of HCM has culminated in development of cardiac myosin inhibitors (CMIs), a novel drug class that in recent randomized clinical trials has been shown to decrease LVOT obstruction, improve exercise capacity, and ameliorate symptom burden in patients with oHCM. Although promising, areas of uncertainty remain, including the long-term safety and efficacy of CMIs and whether they have the potential to modify progression of disease. Herein, we review key milestones in the clinical development of CMIs, contextualize CMIs with established oHCM therapies, and discuss future challenges and opportunities for the use of CMIs across the HCM spectrum.

Clinical Trials in Hypertrophic Cardiomyopathy Therapy: A Comprehensive Analysis of Trials Registered in Global Clinical Databases

Background

With the disappointing results associated with the use of cardiac myosin inhibitors in the treatment of hypertrophic cardiomyopathy (HCM), the development of new therapies in clinical trials for HCM has rapidly increased. We assessed the characteristics of therapeutic intervention in HCM registered on ClinicalTrials.gov and the International Clinical Trials Registry Platform (ICTRP).

Methods

We conducted a cross-sectional, descriptive study of clinical trials for therapeutic intervention in HCM registered on ClinicalTrials.gov and ICTRP.

Results

This study analyzed 137 registered trials. Regarding study designs of these trials, 77.37% were purpose of treatment, 59.12% were randomized, 50.36% were parallel assignment, 45.26% were performed with masking, 48.18% recruited less than 50 participants, and 27.74% were Phase 2 trials. In total, 67 trials were new drug trials, of which 35 drugs were tested in these trials, and 13 trials involved treatment with mavacamten. Of these 67 clinical drug trials, 44.78% of trials involved the study of amines, and 16.42% involved 1-ring heterocyclic compounds. Regarding the NCI Thesaurus Tree, 23.81% of trials involved myosin inhibitors, 23.81% of trials involved drugs belonging to agents affecting the cardiovascular system, and 20.63% were involved in testing cation channel blockers. The drug-target network showed that myosin-7, potassium voltage-gated channel subfamily h member 2, beta-1 adrenergic receptor, carnitine o-palmitoyltransferase 1, and liver isoform were the most targeted pathways of the clinical trials analyzed in the drug-target network.

Conclusion

The number of clinical trials investigating therapeutic interventions for HCM has increased in recent years. Ultimately, recent HCM therapeutic clinical trials generally did not incorporate either randomized controlled trials or masking and were small studies recruiting fewer than 50 participants. Although recent research has focused on targeting myosin-7, the molecular signaling mechanisms involved in the pathogenesis of HCM have the potential to elucidate novel target pathways.

Effects of CYP2C19 inhibitors on mavacamten pharmacokinetics in rats based on UPLC-MS/MS

CONTEXT

CYP2C19 is an important member of the human cytochrome P450 2C (CYP2C) family. Mavacamten is a novel treatment of patients with symptomatic obstructive hypertrophic cardiomyopathy (HCM) which was metabolized mainly by CYP2C19.

OBJECTIVE

In this study, we firstly reported and validated a quantitative analysis method of mavacamten in rat plasma based on ultra-performance liquid chromatography tandem mass spectrometry (UPLC-MS/MS), which was applied to the drug-drug interaction (DDI) study between mavacamten and CYP2C19 inhibitors (fluvoxamine, fluoxetine and fluconazole) in rats.

MATERIALS AND METHODS

Vericiguat was used as the internal standard (IS), and the analyte and IS were measured with electrospray ion (ESI) source in positive ion mode on a XEVO TQ-S triple quadrupole tandem mass spectrometer in multiple reaction monitoring (MRM) mode.

RESULTS

In the scope of 1.0-100 ng/mL, this assay had excellent linearity. Both intra-day and inter-day accuracy of the analyte ranged from -2.4% to 9.1%, while the precision was ≤4.2%. Matrix effect, recovery, and stability were evaluated and validated to meet the requirements for the guidelines of bioanalytical assay. When compared with the control group, AUC_0→∞ of mavacamten in fluconazole, fluoxetine and fluvoxamine were increased by 125.5%, 110.7% and 43.6%, respectively, which demonstrated that CYP2C19 inhibitors could inhibit mavacamten metabolism.

CONCLUSIONS

The results showed that CYP2C19 inhibitors could significantly improve the bioavailability of mavacamten in rats, which indicated that we should pay more attention to the patient's condition to prevent the occurrence of side effects when used mavacamten in combination with CYP2C19 inhibitors.

Mavacamten-A Targeted Therapy for Hypertrophic Cardiomyopathy

ABSTRACT

The pathophysiology of hypertrophic cardiomyopathy is primarily comprised of dynamic left ventricular outflow tract obstruction, mitral regurgitation, and diastolic dysfunction. Symptoms such as dyspnea, angina, or syncope can occur because of left ventricular (LV) hypertrophy and reduced LV cavity size. Currently, focus on symptom relief through optimizing LV preload and reducing inotropy is the mainstay of therapy through the use of β-blockers, nondihydropyridine calcium channel blockers, and disopyramide. Mavacamten is a novel cardiac myosin inhibitor recently approved by the Food and Drug Administration for the treatment of obstructive hypertrophic cardiomyopathy. Mavacamten normalizes myosin and actin cross-bridging to decrease contractility and ultimately reduce LV outflow tract gradients to maximize cardiac output. In this review, we report on the mechanism of action of mavacamten, safety profile, and phase 2 and 3 clinical trial data. Because of the risk of heart failure resulting from systolic dysfunction, careful patient selection and close monitoring are key for implementing this therapy into cardiovascular practice.

Current and emerging pharmacotherapy for the management of hypertrophic cardiomyopathy

INTRODUCTION

Hypertrophic cardiomyopathy (HCM) is one of the most common genetic causes of heart disease. Since the initial description of HCM, there have been minimal strides in management options. Obstructive HCM constitutes a larger subset of patients with increased left ventricular outflow tract gradients causing symptoms. Septal reduction therapy (SRT) has been successful, but it is not the answer for all patients and is not disease modifying.

AREAS COVERED

Current guideline recommendations include beta-blockers, calcium channel blockers, or disopyramides for medical management, but there lacks evidence of much benefit with these drugs. In recent years, there has been the emergence of cardiac myosin inhibitors (CMI) which have demonstrated positive results in patients with both obstructive and non-obstructive HCM. In addition to CMIs, other drugs have been investigated as we have learned more about HCM's pathological mechanisms. Drugs targeting sodium channels and myocardial energetics, as well as repurposed drugs that have demonstrated positive remodeling are being investigated as potential therapeutic targets. Gene therapy is being explored with vast potential for the treatment of HCM.

EXPERT OPINION

The armamentarium of therapeutic options for HCM is continuously increasing with the emergence of CMIs as mainstays of treatment. The future of HCM treatment is promising.

Mavacamten, a First-in-Class Cardiac Myosin Inhibitor for Obstructive Hypertrophic Cardiomyopathy

OBJECTIVE

To assess mavacamten's role in hypertrophic cardiomyopathy treatment.

DATA SOURCES

In addition to clinical guidelines, package inserts, and general reviews, we searched PubMed using the term mavacamten from inception to June 11, 2022.

STUDY SELECTION AND DATA EXTRACTION

English language studies describing mavacamten's mechanism of action, pharmacokinetics, drug interactions, clinical and economic outcomes, and adverse events.

DATA SYNTHESIS

Mavacamten reduces left ventricular outflow obstruction and New York Heart Association functional class while improving Kansas City Cardiomyopathy Questionnaire-Clinical Summary Scores in patients with obstructive hypertrophic cardiomyopathy. With an acquisition cost of $245.20 per capsule, it would cost $1.2 million for every additional quality-adjusted life year. In those with unobstructive hypertrophic cardiomyopathy, there were improvements in N-terminal probrain natriuretic peptide and high-sensitivity cardiac troponin biochemical markers. Mavacamten is a substrate for CYP2C19 and CYP3A4, and a CYP enzyme inducer.

RELEVANCE TO PATIENT CARE AND CLINICAL PRACTICE

Patients with obstructive hypertrophic cardiomyopathy and an ejection fraction ≥55% have a new option if they remain symptomatic despite maximally tolerated β-blocker or non-dihydropyridine calcium channel blocker therapy. It is an alternative to disopyramide therapy, which has poor patient tolerance, or septal reduction therapies, which are invasive. However, mavacamten is not cost-effective and its role in nonobstructive hypertrophic cardiomyopathy is not well established.

CONCLUSIONS

Mavacamten is a new option for patients with refractory obstructive hypertrophic cardiomyopathy and an ejection fraction ≥55% but its pricing makes therapy not cost-effective. Final health outcomes are not fully elucidated and additional studies are needed to determine long-term effects.

Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is the most common genetic cardiomyopathy resulting from a mutation in one of several cardiac sarcomeric proteins [...]

An evaluation of mavacamten for the treatment of symptomatic obstructive hypertrophic cardiomyopathy in adults

INTRODUCTION

Hypertrophic cardiomyopathy (HCM) is a genetic cardiac disorder leading to hypertrophy of the left ventricle excluding other etiologies. Patients can experience exertional chest pain, dyspnea, syncope or even sudden cardiac death (SCD). Traditional medical management consists of beta blockers (BB), nondihydropyridine calcium channel blockers and disopyramide. Mavacamten, a novel cardiac myosin inhibitor, has recently been shown to improve both quantitative and qualitative measures of obstructive HCM allowing some patients to defer septal reduction therapy.

AREAS COVERED

This review delves into the pharmacotherapy of mavacamten, the evidence behind this first-in-class drug for HCM, guidance for clinical usage, and possible future uses for cardiac myosin inhibitors.

EXPERT OPINION

Mavacamten should be incorporated into the standard armamentarium of medications used to treat obstructive HCM. PIONEER-HCM, EXPLORER-HCM and VALOR-HCM demonstrated improvements in peak LVOT gradient both at rest and post-exercise, cardiac biomarkers, New York Heart Association (NYHA) functional class and Kansas City Cardiomyopathy Questionnaire (KCCQ) scores. Unlike other medications utilized for treatment, mavacamten can delay or even obviate the need for septal reduction therapy.

Review of Mavacamten for Obstructive Hypertrophic Cardiomyopathy and Future Directions

Hypertrophic cardiomyopathy (HCM) is a condition with abnormal hypertrophy of the left ventricle in the absence of common causes. The most common form involves the basal septum and can lead to obstruction of the left ventricular outflow tract. Patients can experience exertional symptoms such as chest pain, dyspnea and syncope. Traditional treatment has included beta blockers and nondihydropyridine calcium channel blockers with second-line therapy being disopyramide. Recently, mavacamten, a cardiac myosin inhibitor, has demonstrated improvement in quantitative measures of obstruction and symptom relief to such a degree that patients were able to defer invasive management of the disease. This review focuses on the pharmacology of mavacamten, its clinical trial data and guidance on how to incorporate this drug into clinical practice. Furthermore, it discusses emerging therapies currently being investigated for HCM.

Mavacamten: A Novel Disease-Specific Treatment for Hypertrophic Cardiomyopathy

Hypertrophic cardiomyopathy (HCM) is characterized by an abnormal thickening of the myocardium, leading to left ventricular outflow tract obstruction. Current treatments for HCM include non-disease-specific medications such as beta blockers or invasive interventions. Mavacamten has been studied for its effects on adenosine triphosphatase, myocardial-specific sarcomeric proteins, and myocardial tissue calcium sensitivity. Given these properties, mavacamten could be used as a disease-specific treatment for HCM. Clinical trials of mavacamten have shown improvements in left ventricular outflow tract obstruction among other favorable improvements in biochemical markers and the clinical symptoms of the disease. While trials to date have been relatively small, mavacamten shows promise as a future disease-specific treatment for HCM.

New Era: Mavacamten for Obstructive Hypertrophic Cardiomyopathy

Obstructive hypertrophic cardiomyopathy results from asymmetric septal hypertrophy, which eventually obstructs the outflow of the left ventricle. Obstructive hypertrophic cardiomyopathy is linked to mutations in genes that encode for sarcomere proteins, including actin, β-myosin heavy chain, titin, and troponin. The mutations lead to structural abnormalities in myocytes and myofibrils, causing conduction irregularities and abnormal force generation. Obstructive hypertrophic cardiomyopathy is a chronic disease that worsens over time, and patients become at higher risk of developing atrial fibrillation, heart failure, and stroke. Up until recently, there were no disease- specific medications for obstructive hypertrophic cardiomyopathy. Nevertheless, the US Food and Drug Administration approved mavacamten on April 28, 2022, for the treatment of symptomatic obstructive hypertrophic cardiomyopathy (New York Heart Association class II to III) in adults to improve functional capacity and symptoms. Its approval was based on data from EXPLORER- HCM and EXPLORER-LTE (NCT03723655). Mavacamten is a novel, first-in-class, orally active, allosteric inhibitor of cardiac myosin ATPase, which decreases the formation of actin- myosin cross-bridges, and thus, it reduces myocardial contractility, and it improves myocardial energetics. It represents a paradigm-shifting pharmacological treatment of obstructive hypertrophic cardiomyopathy. In this review, we describe its chemical and mechanistic aspects as well as its pharmacokinetics, adverse effects and warnings, potential drug-drug interactions, and contraindications.

Mavacamten Treatment for Hypertrophic Cardiomyopathy: A Systematic Review and Meta-Analysis of Randomized Controlled Trials

BACKGROUND

Hypertrophic cardiomyopathy (HCM) is the most common heritable cardiomyopathy, yet pharmacological therapy has been unchanged for decades until the recent introduction of mavacamten, a first-in-class cardiac myosin inhibitor. We assessed the efficacy and safety of mavacamten in HCM.

METHODS

To date, only 3 randomized controlled trials (RCTs) compared the outcomes of mavacamten versus placebo for HCM. We used a fixed effects model to calculate risk ratios (RRs) with 95% confidence intervals (CIs). The primary composite endpoint (PCE) was defined as either ≥1.5 mL/kg/min increase in peak oxygen consumption (pVO2) with ≥1 New York Heart Association functional class (NYHA-FC) improvement or ≥3.0 mL/kg/min increase in pVO2 without worsening of NYHA-FC. Secondary outcomes included ≥1 NYHA-FC improvement, septal reduction therapy (SRT) or guideline eligible for SRT, ≥1 serious adverse event (SAE), ≥1 treatment emergency adverse event (TEAE), atrial fibrillation (AF), and nonsustained ventricular tachycardia (NSVT).

RESULTS

Three RCTs (n=422, mean follow-up 24 weeks) were included. Compared to placebo, mavacamten achieved higher rates of PCE (RR 1.92; 95% CI 1.28-2.88; p=0.002) and ≥1 NYHA-FC improvement (RR 2.10; 95% CI 1.66-2.67; p<0.00001) and lower rates of SRT or guideline eligible for SRT (RR 0.29; 95% CI 0.22-0.39; p<0.00001). There were no differences between both groups in ≥1 SAE, AF, and NSVT, however mavacamten had higher rates of ≥1 TEAE.

CONCLUSIONS

In patients with HCM, mavacamten helps improve pVO2 and NYHA-FC and reduces SRT but may be associated with TEAE. Further research is warranted to evaluate the efficacy, safety, and long-term outcomes of mavacamten.

Hypertrophic cardiomyopathy: an up-to-date snapshot of the clinical drug development pipeline

INTRODUCTION

Hypertrophic cardiomyopathy (HCM) is a complex cardiac disease with highly variable phenotypic expression and clinical course most often caused by sarcomeric gene mutations resulting in left ventricular hypertrophy, fibrosis, hypercontractility, and diastolic dysfunction. For almost 60 years, HCM has remained an orphan disease and still lacks a disease-specific treatment.

AREAS COVERED

This review summarizes recent preclinical and clinical trials with repurposed drugs and new emerging pharmacological and gene-based therapies for the treatment of HCM.

EXPERT OPINION

The off-label drugs routinely used alleviate symptoms but do not target the core pathophysiology of HCM or prevent or revert the phenotype. Recent advances in the genetics and pathophysiology of HCM led to the development of cardiac myosin adenosine triphosphatase inhibitors specifically directed to counteract the hypercontractility associated with HCM-causing mutations. Mavacamten, the first drug specifically developed for HCM successfully tested in a phase 3 trial, represents the major advance for the treatment of HCM. This opens new horizons for the development of novel drugs targeting HCM molecular substrates which hopefully modify the natural history of the disease. The role of current drugs in development and genetic-based approaches for the treatment of HCM are also discussed.

A Phase 1 Dose-Escalation Study of the Cardiac Myosin Inhibitor Aficamten in Healthy Participants

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Certain genetic hypertrophic cardiomyopathies may result from hypercontractility of cardiac muscle, caused by pathogenic variants in genes encoding proteins of the cardiac sarcomere.

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Aficamten (formerly CK-3773274) is a small-molecule selective inhibitor of the cardiac myosin ATPase, which reduces the contractility of cardiomyocytes in vitro and decreases measures of ventricular contractility in animal studies.

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In this first-in-human, phase 1 study in healthy adults, aficamten was well tolerated; adverse events were generally mild and comparable in frequency to those seen with placebo.

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Aficamten demonstrated dose-proportional pharmacokinetics with a half-life of 75 to 85 hours.

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Pharmacodynamically active doses of aficamten decreased left ventricular ejection fraction from baseline in a concentration-dependent manner, informing the design of a phase 2 trial in patients with hypertrophic cardiomyopathy.

This phase 1, randomized, double-blind, placebo-controlled study of aficamten (formerly CK-3773274) in healthy adults identified a pharmacologically active range of doses and exposures. At doses that were pharmacologically active (single doses of ≤50 mg or daily dosing of ≤10 mg for 14 or 17 days), aficamten appeared to be safe and well tolerated. Adverse events were generally mild and no more frequent than with placebo. Pharmacokinetic assessments showed dose proportionality over the range of single doses administered, and pharmacokinetics were not affected by administration with food or in otherwise healthy individuals with a cytochrome P450 2D6 poor metabolizer phenotype. (A Single and Multiple Ascending Dose Study of CK-3773274 in Health Adult Subjects; NCT03767855)