Cardiac myosin inhibitors in hypertrophic cardiomyopathy: gaps in knowledge and future opportunities

Introduction

Hypertrophic cardiomyopathy (HCM) is the most common monogenic cardiovascular disease with an estimated prevalence of at least 1 in 500 (0.2%) (1). HCM patients have increased left ventricular (LV) wall thickness of ≥15 mm (≥13 mm in patients with a family history or pathogenic sarcomere variant), and can have small ventricular size, and normal or hyperdynamic LV ejection fraction (LVEF). Other manifestations may include systolic anterior motion (SAM) of the mitral valve resulting in mitral regurgitation and LV outflow tract (LVOT) obstruction (LVOTO). Obstructive HCM is defined by an LVOT gradient of 30 mmHg or more at rest and/or 50 mmHg or more with provocation (2,3).

LVOTO leads to reduced LV compliance and LV diastolic dysfunction (LVDD) (4). Eventually, LVDD, along with other factors such as increased pulmonary artery pressure, contributes to heart failure (HF) symptoms (5). HCM is an important cause of HF, atrial fibrillation, embolic stroke, and arrhythmic sudden death (6). Sudden cardiac death (SCD) may be the first manifestation of the disease; young patients are at the highest risk of SCD (7,8). Cardiac myosin inhibitors selectively address the pathophysiological mechanisms of HCM. The primary objective of this study was to comprehensively examine the latest research pertaining to therapeutic alternatives for HCM, with a specific focus on cardiac myosin inhibitors.

HCM phenotypes and genomics

There are four phenotypic types of HCM, each characterized by distinct patterns of hypertrophy location: (I) sigmoid type: features a prominent basal septal protuberance, a concave septum, and an ovoid LV cavity, which presents with LVOTO; (II) reverse curvature type: exhibits a convex septum, an increasing LV cavity, typically corresponds to mid-ventricular hypertrophy, and may involve mid-ventricular obstruction and/or apical aneurysm; (III) apical type: characterized by hypertrophy of the apical portion, sometimes extending to the middle segments, resulting in an “ace of spades” shaped cavity, and is more frequently observed in Asia; (IV) neutral type: involves uniform hypertrophy of the septum (9).

Importantly, these phenotypic types may coexist within the same patient or exhibit atypical or mixed localization components. While a greater extent of LV hypertrophy has been associated with younger age and a mitral valve with a higher degree of SAM and outflow obstruction, there is no clear evidence linking hypertrophy extent to symptom severity or gender (10). Thus, planning a successful treatment strategy requires precise diagnosis and phenotyping.

Approximately 60% of HCM patients exhibit a clear familial pattern, typically following an autosomal dominant inheritance with a single gene mutation responsible for the condition (11). The most prevalent causal genes, MYH7 (encodes β-Myosin heavy chain ATPase activity and forces generation) and MYBPC3 (encodes myosin binding protein-C and participates in cardiac contraction) account for around half of familial HCM cases, while TNNT2, TNNI3, and TPM1 mutations are rarer, contributing to less than 10% of cases. Additional genes like ACTC1, MYL2, MYL3, and CSRP3 are also implicated, albeit infrequently (12,13). Most prevalent genes associated with HCM’s physiopathology is demonstrated in Table 1.

Moreover, phenocopies of HCM, such as Noonan syndrome, Anderson-Fabry disease, and Danon disease, can present with various clinical manifestations, including those similar to the phenotypic types of HCM (27). The prevalence of phenocopy conditions is significant (28). These phenocopies are important to consider as they can be distinguished from HCM by their associated genetic and clinical features. For instance, mutations in lysosome-associated membrane protein 2 (LAMP-2) can cause Danon disease, a lethal disease associated with Wolff-Parkinson-White syndrome (29).

Stage-specific therapy

In 2012, Olivotto et al. classified HCM into 4 clinical stages to achieve a systematic clinical staging of the disease: non-hypertrophic HCM, classic phenotype, adverse remodeling, and overt dysfunction (30). The initial stage of addressing HCM involves the prevention of the disease in individuals who carry HCM-causing mutations but have yet to develop the hypertrophic phenotype. This can be accomplished through measures such as genetic testing, familial screening, and the use of pharmaceuticals that target pathways implicated in HCM development.

The second stage is characterized by a fully expressed hypertrophic phenotype, in which hypercontractility predominates without extensive fibrotic replacement and LV is hyperdynamic (EF >65%). The main cause of symptoms in this stage is LVOTO (31). Drugs with negative inotropic effects such as β-blockers, non-dihydropyridine calcium channel blocker (CCB), and disopyramide are commonly used to treat symptoms caused by hypercontractility. However, CCB should be avoided in patients with vasodilator effect symptoms, such as hypotension, dyspnea at rest, and very high resting gradients (e.g., >100 mmHg) (32). For refractory symptoms despite optimal medical therapy, septal reduction therapy (SRT) [surgical myectomy and alcohol septal ablation (ASA)] is considered. Allosteric cardiac myosin inhibitors such as mavacamten are considered treatment options in this stage.

In stage III (adverse remodeling), patients may develop structural abnormalities such as LV fibrosis and worsening diastolic and systolic function in a low-normal range of EF 50–65%, which can predict progression to overt LV systolic dysfunction (33). Replacement fibrosis is a therapeutic target but attempts with anti-fibrotic drugs have been elusive with spironolactone and losartan (34). Perhexiline and ranolazine, anti-anginal medications, have shown promise in reducing the 24-hour ventricular arrhythmic burden and improving angina symptoms, but their ability to mitigate the long-term effects of microvascular ischemia, including fibrosis development, is unknown (35). Mavacamten has shown some promise in reducing N-terminal pro-B-type natriuretic peptide (NT-proBNP) and troponin I in symptomatic non-obstructive HCM patients, but more definite answers are expected from the ongoing Phase 3 ODYSSEY-HCM trial (36).

Stage IV is characterized by overt LV systolic dysfunction (LVEF <50%) seen in 5–8% of HCM patients (37). Optimal guideline-directed therapy for HF should be considered, including sodium-glucose transporter 2 inhibitors, ACE inhibitors and angiotensin II receptor blockers (ARBs), HF-specific β-blockers, spironolactone, loop diuretics, cardiac resynchronization therapy (CRT) (mostly biventricular pacing), and oral anticoagulants [in case of concurrent atrial fibrillation (AF) or an apical aneurysm]. In patients with refractory HF symptoms, options are largely confined to heart transplants (38). Careful follow-up with regular cardiac function assessment and symptoms monitoring is necessary to avoid misrecognition of the disease severity.

Current management

Primary management of HCM includes symptom relief and prevention of adverse events. This may include β-blockers to control symptoms such as dyspnea and angina, as well as CCBs (verapamil or diltiazem) to slow heart rate and prolong LV filling time (Figure 1) (39). Regular monitoring of the heart function to detect any potential complications, such as the development of incident AF or HF is also needed. Up to 15% of HCM patients may develop signs and symptoms of HF despite preserved systolic function. Standard HF therapy should be introduced if LVEF is <50%, including ACE inhibitors, β-blockers, and loop diuretics. CRT and cardiac transplant may be considered in end-stage HCM patients (40,41).

Figure 1 Proposed management strategy for hypertrophic cardiomyopathy. LVOT, left ventricular outflow tract; ACC, American College of Cardiology; AHA, American Heart Association; CMI, cardiac myosin inhibitor; EF, ejection fraction; HCM, hypertrophic cardiomyopathy; NYHA, New York Heart Association; GDMT, guideline-directed medical therapy; HFrEF, heart failure with reserved ejection fraction; ICD, implantable cardioverter-defibrillator; LBBB, left bundle branch block; CRT, cardiac resynchronization therapy.

For obstructive HCM, nonvasodilating β-blockers are the most effective agents for the treatment of provokable LVOTO demonstrated in small randomized studies (42). β-blockers should be titrated to maximally tolerated dose in patients with LVOTO until resting heart rate is suppressed (43). Side effects such as fatigue should be carefully investigated to assess an optimal individual dose (39,42). Non-dihydropyridine CCBs such as verapamil and diltiazem can be used in patients who are intolerant to β-blockers (39). Disopyramide, a class IA antiarrhythmic agent, is the most effective drug for resting obstruction through its negative inotropic effect and in association with β-blockers improve symptoms and reduces intraventricular gradients (42,44). Long-term use of disopyramide has been associated with reduced subaortic gradient by 50% and reduced cardiovascular deaths, including arrhythmic sudden death, indicating an anti-arrhythmic effect (45,46).

SRT

SRT encompasses surgical septal myectomy (SM) and ASA, aimed at treating HCM with obstructive symptoms. ASA is an alternative to SM, particularly in older patients or those with significant comorbidities. ASA involves the infusion of alcohol into the septal artery to induce an iatrogenic infarction, thereby reducing septal thickness and LVOTO (47,48).

SRT, surgical SM, or ASA is indicated in patients with an LVOT gradient of more than 50 mmHg, associated with a New York Heart Association (NYHA) class ≥ III or refractory symptoms despite maximal medical therapy (Figure 1) (49). SRT is also considered for patients with less severe LVOT gradients of ≥30 to <50 mmHg who have no explanation of symptoms except HCM (50,51). Obstructive HCM with concomitant mitral valve, chordal and/or papillary muscle abnormalities may require both a myectomy and a mitral valve leaflet reduction or repair particularly if the anterior leaflet is long and causing LVOTO (Figure 1) (52). According to 2024 American Heart Association (AHA)/American College of Cardiology (ACC) guideline for the diagnosis and treatment of patients with HCM, SRT can be performed in obstructive HCM patients with persistent symptoms despite receiving β-blockers or nondihydropyridine CCBs (Class I recommendation) (43).

Apical myectomy may have a role in some patients with apical HCM with no subaortic or intraventricular gradients but develop refractory HF symptoms (53). However, apical myectomy is considered for apical variant. A trans-apical approach has been considered for mid-ventricular variant where transaortic exposure is limited, apical variants, and in patients who have limited LV cavity (54,55). SM complications include pacemaker implantation, particularly in patients with prior right bundle branch block. Low-volume centers have significantly greater odds of all-cause mortality and bleeding complications after myectomy (56).

A study of 5,679 obstructive HCM patients aged >65 years showed SM was associated with lower mortality after 2 years of follow-up and lower need for redo SRT after adjustment of confounding variables (57). Notably, patients who underwent ASA were significantly older and had a higher prevalence of comorbidities. SM was associated with higher 3-month mortality and morbidity. Additionally, both groups had reduced HF readmissions and improved quality of life in the follow-up period compared to the year before the SRT. The study also found that higher-volume centers had lower long-term mortality, but most SRT procedures (70%) were performed in low-volume centers (57). Also, it is important to note that there is reduced access to myectomy and implantable cardioverter-defibrillator (ICD) implantation in minority populations (58).

The data on long-term mortality with a follow-up of 5 years or more in seven studies exhibited higher mortality with ASA compared with myectomy (59). However, surgical myectomy can lead to complications, including atrioventricular block requiring permanent pacemaker implantation, tamponade, stroke, and death, among others, prompting a growing interest in finding an alternative therapy to reduce the need for SRT (60).

Myosin inhibitors

Myosin inhibitors are drugs that dose-dependently inhibit myosin ATPase. This class of drugs reduces the myosin duty ratio (strongly actin-bound state time to total chemo mechanical cycle time of myosin) (61). Thus, these drugs reversibly decrease the number of actin-myosin cross-bridge (Figure 2) reducing hypercontractility seen in HCM, improving myocardial energetics and ventricular compliance (62). Mavacamten, produced by Bristol Myers Squibb^TM, New York City, New York, U.S. under the tradename Camzyos, and Aficamten, produced by Cytokinetics^®, South San Francisco, California, U.S. are two drugs in this class of medication (63).

Figure 2 Mechanism of action of mavacamten. HCM, hypertrophic cardiomyopathy.

Mutations in key sarcomeric genes are responsible for causing HCM, with a notable presence in MYBP3, MYH7, TNNT2, and TNNI3 genes (26). The efficacy of mavacamten in ameliorating cellular manifestations of HCM has been demonstrated for gene variants in MYBPC3 and MYH7, achieved by enhancing the stabilization of myosin super relaxation (64,65). Mavacamten effectively counteracts both excessive contractility and compromises relaxation in the context of MYH7 (cardiac β-myosin heavy chain) mutations. By directly addressing myosin’s disorderly relaxation, it progressively diminishes the amplitude of active tension in simulated MYH7 scenarios. This leads to the deactivation of the propagated impact on thin filament activation within MYH7, thereby rectifying the decelerated relaxation. Importantly, mavacamten has exhibited the ability to reinstate contractile function, regardless of the specific mechanism driving the heightened contractility (66).

Mavacamten, with the chemical name MYK-461, was first introduced in the early 2010s. Mavacamten was granted breakthrough therapy designation by the U.S. Food and Drug Administration (FDA) in 2018 and received FDA approval for the treatment of adults with symptomatic NYHA class II–III obstructive HCM on 28 April 2022, as the first-in-class myosin inhibitor approved for this indication in the U.S. (67). It is well tolerated with minimal side effects including dizziness, syncope, fatigue, exertional dyspnea, chest pain, and flushing (68,69). Studies on cardiac myosin inhibitors are summarized in Table 2.

Aficamten has a shorter half-life (75–85 hours vs. 7–9 days in mavacamten) and, as a result, more rapid dose titrations (individualized adjustments), drug washout, and hence has a wider therapeutic window (73,74). Unlike mavacamten, it does not have significant drug-drug interactions and the β-blocker use is not associated with reduced therapeutic effect in patients receiving aficamten (68,72).

Myosin inhibitors in patients with obstructive HCM

The PIONEER-HCM phase 2 proof-of-concept trial found that mavacamten reduced post-exercise LVOT gradients and symptoms while improving exercise capacity in patients with obstructive HCM (69). Based on these promising results, the phase 3 EXPLORER-HCM trial, a multicenter, randomized, double-blind, placebo-controlled trial, was conducted. In this trial, a significantly higher proportion of patients in the mavacamten group met the primary endpoint of improved functional capacity and symptom burden after 30 weeks of treatment when compared to the placebo group. Additionally, a greater number of patients in the mavacamten group experienced symptom improvement by at least one NYHA class. Mavacamten was well-tolerated with a significant reduction in post-exercise LVOT gradient (68). Approximately 6–10% of patients in clinical trials experienced a reversible reduction in LVEF to below 50%, necessitating temporary discontinuation of the therapy (68,70).

VALOR-HCM trial phase 3 randomized trial study showed that mavacamten significantly reduced the need for SRT in the short term. After 16 weeks of treatment, 76.8% of the placebo group still met guideline criteria for SRT or elected to undergo the procedure, while 46 of 56 (82.1%) mavacamten-treated patients improved and became ineligible for SRT based on guidelines (P<0.001). Mavacamten significantly reduced both LVOT gradient at rest and after the Valsalva maneuver. The quality-of-life questionnaire [Kansas City Cardiomyopathy Questionnaire (KCCQ)] showed improvement in the mavacamten group.

The study extended the drug therapy for a maximum of 32 weeks in the mavacamten group, while the placebo group transitioned to receiving dose-blinded mavacamten from weeks 16 to 32. Eighty-eight percent of all patients (both groups) did not meet SRT criteria after week 32. The study was conducted at high-volume referral centers specializing in HCM treatment, known for achieving favorable results in SRT procedures (75). At week 56, after either 56 weeks (original mavacamten group) or 40 weeks of treatment (cross-over group), authors reported a sustained reduction in resting and Valsalva LVOT gradients. Additionally, there was an improvement in the NYHA class of 1 or higher (76). As of 2024, guidelines for management of HCM recommend myosin inhibitors for patients with obstructive HCM who have persistent symptoms due to LVOTO despite taking beta blockers or nondihydropyridine CCBs (Class I recommendation) (43).

The SEQUOIA-HCM Study on aficamten for symptomatic obstructive HCM, which was a phase III, double-blind, randomized, placebo-controlled trial, reported a significant increase in peak oxygen consumption (pVO₂) (mean change 1.8 mL/kg/min) compared to placebo (0.0 mL/kg/min) (P<0.001) in aficamten group. Additionally, there were significant improvements in Kansas City Cardiomyopathy Questionnaire Clinical Summary Score (KCCQ-CSS), of at least one NYHA functional class, a reduction in the LVOT gradient after the Valsalva maneuver, and a decrease in the total duration of eligibility for SRT at week 24 of follow-up. There were no significant difference in adverse events between two groups; 3.5% of patients in the aficamten group experienced a transient reduction in LVEF to below 50% and 4.9% of patients in the aficamten group required a per-protocol dose reduction. Of note, patients in the aficamten group with an LVEF below 50% did not experience treatment interruption or a worsening of HF symptoms (72,77). Myosin inhibitors in patients with non-obstructive HCM.

MAVERICK-HCM was a phase II multicenter, exploratory, dose-ranging, double-blind, randomized, placebo-controlled study evaluating mavacamten in non-obstructive HCM. At week 16, participants would have achieved the exploratory composite endpoint if they had an improvement of at least 1.5 mL/kg/min in pVO₂ and a reduction of ≥1 NYHA functional class or an improvement of ≥3.0 mL/kg/min in pVO₂ with no worsening in NYHA functional class compared to baseline. Mavacamten was associated with reduced NT-proBNP and cTnI levels. The mavacemten group did not show changes in the KCCQ-CSS score, NYHA functional class, pVO₂, or the composite endpoint compared with the placebo group. However, this study was likely underpowered to detect clinical benefits.

Ongoing studies

Results of treatment with mavacamten from the EXPLORER-LTE cohort of the MAVA-LTE study showed that 4.3% (10/231) patients had permanent treatment discontinuations due to treatment-emergent adverse event (TEAE). LVEF reduction, cardiac failure and arrest, acute myocardial infarction, muscular weakness, systemic lupus erythematosus, fatigue, bacterial endocarditis, and prolonged corrected QT interval (QTc) were reported TEAEs that led to permanent discontinuation (78). The EXPLORER-HCM patients who participated in the MAVA-LTE study underwent cardiac magnetic resonance imaging, which revealed mild reductions in LV mass index and LVEF between weeks 24 to 96. The myocardial contraction fraction remained unchanged, and LV end-systolic volume index increased (79).

PIONEER-OLE study reported results from 156 weeks of mavacamten treatment, indicating improvements in LVOT gradients, ratio of transmitral E velocity to the myocardial e’ velocity (E/e’), NT-proBNP, NYHA class, and Kansas City Cardiomyopathy Questionnaire Overall Summary Score (KCCQ-OSS). Reductions in left atrial volume index (LAVI) and maximum wall thickness were observed, while no notable changes occurred in posterior wall thickness. They also noted mild reductions in LVEF, which remained within the normal range, and only one patient experienced a reduction of LVEF to less than 50% (80).

REDWOOD-HCM Cohort assessed the safety and tolerability of aficamten in patients with symptomatic non-obstructive HCM (81). The LVEF reversibly dropped at an average rate of 5.5%, and no participant discontinued aficamten. The mean improvement in KCCQ-CSS was 10.6 points and 58% of the patients experienced clinical improvement. After 10 weeks of treatment, there was a significant reduction in high-sensitive cardiac Troponin and NT-proBNP levels by an average of 21% and 55%, respectively.

EXPLORER-CN, a multicenter, phase III, randomized, double-blind, placebo-controlled registration trial has been designed and implemented to evaluate the efficacy and safety of mavacamten in approximately 81 Chinese adults with symptomatic obstructive HCM during a 48-week follow-up period. This study is the first trial that is being conducted outside of Europe and the U.S. (82).

MAPLE-HCM, an ongoing trial sponsored by cytokinetics, intends to compare the efficacy and safety of aficamten with metoprolol succinate in adults with symptomatic HCM and LVOTO in a 24-week follow-up. The primary objective of this study is to assess and compare the changes in pVO₂ by cardiopulmonary exercise testing (CPET) in two groups (83).

Gaps in the knowledge

Drop in LVEF and the possibility of obstruction recurrence

As a myosin inhibitor, mavacamten disrupts the formation of myosin-actin bridges and leading to a drop in LVEF (62). However, it is unclear if this drop in EF causes patients to develop HF with reduced LVEF. As a result, the U.S. FDA issued a warning stating that the patient’s clinical status and LVEF should be assessed before and regularly during treatment, and the drug’s dosage should be adjusted accordingly (84). This program falls under the Risk Evaluation and Mitigation Strategy (REMS), which is a critical safety measure implemented by the FDA to ensure that the benefits of certain medications surpass their potential risks. Currently, mavacamten is administered only under the REMS program (85,86).

According to the 2024 guideline for the management of HCM, cardiac myosin inhibitors should be discontinued in patients who develop persistent systolic dysfunction (LVEF <50%) or interrupted and resumed at a lower dose if LVEF improves (43). Nevertheless, according to the EXPLORER-HCM and the MAVERICK-HCM trials, changes in the LVEF are temporary, and patients’ LVEF returned to baseline after mavacamten treatment was interrupted (68,70). In the VALOR-HCM trial, LVEF decreased in two patients, but returned to normal after medication discontinuation (71). In aficamten phase 2 trial, LVEF dropped in two patients, but adjustments were made to the dosage and discontinuation was not necessary (63). This indicates that LVEF drop is often asymptomatic and reversible with discontinuation or dose adjustments. Also, it is unknown whether discontinuing the drug would cause a recurrence of the obstruction, especially in patients who have undergone dose adjustment due to the LVEF drop.

Limited data in underrepresented racial and ethnic populations

Variations in disease presentation and outcomes across different racial and ethnic groups have been increasingly recognized (Figure 3). Black patients with HCM exhibit certain characteristics more frequently than White patients, such as sub-basal and diffuse hypertrophy, greater LV maximal thickness, and mid-ventricular obstruction. However, LVOTO at rest was less common in Blacks. Black patients show pathogenic and likely pathogenic HCM variants in the MYH7 and MBPC3 genes (87). Black patients with HCM are younger at the time of diagnosis and have a higher prevalence of NYHA class III or IV HF at presentation (88). Hispanic patients undergoing SRT experience higher in-hospital mortality compared with White patients receiving this treatment (89).

Figure 3 Cardiac myosin inhibitors in HCM, gaps in knowledge, and future directions. HCM, hypertrophic cardiomyopathy; SRT, septal reduction therapy.

Assessment of 2,467 patients in the U.S.-based sites of the Sarcomeric Human Cardiomyopathy Registry (SHaRe) from 1989 through 2018 showed black patients with HCM were less likely to undergo SRT compared with White patients. Black patients had lower odds of atrial fibrillation and Black race was independently associated with the development of NYHA class III or IV HF (88).

Length of stay, pacemaker and ICD implantation, acute kidney injury, blood transfusion, hospitalization costs, and discharge disposition were significantly different between different races (89). In contrast, another study assessing the trends in mortality of patients with HCM through 39,200 HCM-related deaths, reported that males, Black patients, and patients ≥75 years of age had higher mortality rates (90). Black patients with HCM have a higher rate of appropriate ICD anti-tachycardia pacing therapy or discharges, despite having similar rates of ICD insertion as White patients for primary prevention. Black patients are more likely to have massive LV hypertrophy and two or more SCD risk factors compared to White patients (87).

Although the U.S. Black population has grown to approximately 47.2 million as of 2021, racially and ethnically diverse patients are frequently underrepresented in large, multi-center studies (91,92). In the Hypertrophic Cardiomyopathy Registry (HCMR), a prospective registry across Europe and North America, only 204 (7.4%) were Black. The study population was composed of 84.4% White individuals (93). In SHaRe, of 4,591 patients with HCM studies between 1960 and December 2016, only 141 (3%) patients were Black. Hospitals from Italy, the Netherlands, the U.S., and Brazil participated in this study (94). Aside from HCMR and SHaRe, other registries on HCM patients include the European Society of Cardiology Registry of Hypertrophic Cardiomyopathy (EURObservational Research Program) and the Japanese Society of Hypertrophic Cardiomyopathy (JHCM) Registry, with the former situated in various European centers while the latter is specifically for Japan (95,96). The number of studies conducted in countries where the majority of the population is non-White (e.g., African countries) is severely limited, which could be due to a lack of financial and human resources or cultural and social constraints (97).

Only 2 (5%) patients in the MAVERIK-HCM trial, 3 (5.4%) patients in the VALOR-HCM trial, and 1 (1%) patient in the EXPLORER-HCM trial were Black patients who received mavacamten (68,71,98). In the REDWOOD-HCM trial, all patients in the aficamten-receiving group were White (63).

Better phenotyping of HCM in black patients, including echocardiography, advanced imaging data, genomics, and social determinants of health, may lead to better stratification of these patients (87,90). As mentioned earlier, machine learning (ML) can play an important role in improving the phenotyping of patients with HCM (99).

Conducting further studies on the use of mavacamten in a diverse population is needed to comprehend the interaction between biological factors (including cytochrome P450 genotypes) and behavioral, cultural, and social determinants of health. This will ensure that the administration of the drug is both safe and effective for all patients (92). Moreover, U.S. FDA will soon require researchers seeking approval for late-stage clinical trials to submit a plan that ensures diversity among trial participants (92,100).

Cost-effectiveness

As a novel and expensive drug, mavacamten’s cost may limit its use, particularly in countries with limited healthcare resources. It is worth noting that mavacamten is a relatively new and expensive drug, with a price reported to be $245.20 per capsule. For each additional quality-adjusted life year (QALY), the estimated cost would be $1.2 million (101). According to the VALOR-HCM study authors, the average cost of SRT is approximately $100,000 in the U.S. (71). For every reduction in death from HCM, mavacamten would cost $5.6 million more than myectomy and $7.0 million more than ASA (102).

While mavacamten shows clinical effectiveness, its cost is significantly higher compared to standard treatments like disopyramide (103). Based on the Institute for Clinical and Economic Review (ICER) study findings, the use of mavacamten, along with standard first-line treatment, was projected to lead to a higher number of QALYs compared to standard treatment alone. Assuming a placeholder cost of $75,000, the incremental cost-effectiveness ratio was much higher than commonly accepted thresholds ($1.2 million/QALY). When compared to disopyramide, the incremental cost per QALY was even higher ($1.5 million/QALY), and mavacamten was found to be inferior to both myectomy and ASA. The study estimated the health benefit price benchmark (HBPB) for mavacamten to be between $12,000 and $15,000 per year, and it is expected that the actual cost-effectiveness of the treatment will depend on its actual price (102). Long-term data for HF hospitalizations and mortality is needed to confidently establish the cost-effectiveness of myosin inhibitors.

Future directions

In future HCM research, prioritizing diversity, sex-specific analyses, and a global perspective is crucial for inclusivity and generalizability. HCM is a complex genetic disease with variations among different ethnic and racial groups, emphasizing the need for expanded research and understanding. Global collaboration, comprehensive registries, and data-sharing initiatives are key to advancing HCM research and improving patient outcomes. Leveraging ML and artificial intelligence (AI) can enhance HCM research by integrating various data sources and identifying biomarkers and personalized treatments. Identifying responders to myosin inhibitors therapy, analyzing real-world data, and exploring selective treatment approaches can provide valuable insights. ML tools can aid in precise phenotyping and patient selection, transforming our understanding of HCM and improving outcomes. To better understand the comparative benefits and risks of myosin inhibitors, such as mavacamten, over myectomy further investigation is warranted. It is crucial to identify patients who would benefit most from myosin inhibitors or myectomy.

Conclusions

The existing literature suggests that myosin inhibitors may provide short-term relief for HCM patients by reducing hypercontractility and improving diastolic dysfunction and myocardial energetics, thus ameliorating symptoms such as dyspnea. Additionally, myosin inhibitors may prevent the progression of HCM by slowing the rate of hypertrophy, leading to a decrease in the need for SRT. The optimal treatment modality for obstructive HCM patients, whether SRT or mavacamten, will depend on various factors, such as the functional status and co-morbidities, and concomitant mitral valve and/or papillary muscle abnormalities, which warrants further investigation.

Mavacamten might be a viable option, particularly for patients who are not eligible for SRT due to anatomical constraints or inaccessibility to specialized procedures. However, comprehensive, large-scale studies from more well-represented populations are imperative to elucidate the long-term efficacy and safety of mavacamten in managing HCM patients in diverse populations.

Acknowledgments

Figure 1, Figure 2, and Figure 3 were created with BioRender (https://www.biorender.com/).

Funding: None.

Footnote

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