Design of the SILICOFCM study: Effect of sacubitril/valsartan vs lifestyle intervention on functional capacity in patients with hypertrophic cardiomyopathy.

BACKGROUND
Hypertrophic cardiomyopathy (HCM) is the most common genetic cardiovascular disease with a broad spectrum of disease severity. HCM ranges from a benign course to a progressive disorder characterized by angina, heart failure, malignant arrhythmia, syncope, or sudden cardiac death. So far, no medical treatment has reliably shown to halt or reverse progression of HCM or to alleviate its symptoms. While the angiotensin receptor neprilysin inhibitor sacubitril/valsartan has shown to reduce mortality and hospitalization in heart failure with reduced ejection fraction, data on its effect on HCM are sparse.


HYPOTHESIS
A 4-month pharmacological (sacubitril/valsartan) or lifestyle intervention will significantly improve exercise tolerance (ie, peak oxygen consumption) in patients with nonobstructive HCM compared to the optimal standard therapy (control group).


METHODS
SILICOFCM is a prospective, multicenter, open-label, randomized, controlled, three-arm clinical trial (NCT03832660) that will recruit 240 adult patients with a confirmed diagnosis of nonobstructive HCM. Eligible patients are randomized to sacubitril/valsartan, lifestyle intervention (physical activity and dietary supplementation with inorganic nitrate), or optimal standard therapy alone (control group). The primary endpoint is the change in functional capacity (ie, peak oxygen consumption). Secondary endpoints include: (a) Change in cardiac structure and function as assessed by transthoracic echocardiography and cardiac magnetic resonance (MRI imaging), (b) change in biomarkers (ie, CK, CKMB, and NT-proBNP), (c) physical activity, and (d) quality of life.


RESULTS
Until December 2019, a total of 41 patients were recruited into the ongoing SILICOFCM study and were allocated to the study groups and the control group. There was no significant difference in key baseline characteristics between the three groups.


CONCLUSION
The SILICOFCM study will provide novel evidence about the effect of sacubitril/valsartan or lifestyle intervention on functional capacity, clinical phenotype, injury and stretch activation markers, physical activity, and quality of life in patients with nonobstructive HCM.

There was no significant difference in key baseline characteristics between the three groups.

Conclusion:
The SILICOFCM study will provide novel evidence about the effect of sacubitril/valsartan or lifestyle intervention on functional capacity, clinical phenotype, injury and stretch activation markers, physical activity, and quality of life in patients with nonobstructive HCM. still under-recognized in clinical practice and its initial diagnosis is often delayed. 2 Approximately one third of patients with HCM have the nonobstructive form of the disease that was shown to be associated with a frequently underestimated adverse outcome. 1,3 The clinical diagnosis of HCM is based on left-ventricular hypertrophy without cavity dilatation that cannot be explained by another cardiac, systemic, metabolic, or syndromic disease. 2,[4][5][6] The course of HCM is highly variable, ranging from an asymptomatic, benign condition with a normal life expectancy to an advanced disease characterized by angina, dyspnea, heart failure, atrial fibrillation, malignant arrhythmia, syncope, or sudden cardiac death. 2 Disease progression in nonobstructive HCM is associated with increasing myocardial fibrosis, microvascular ischemia, and abnormal cardiac function. 3 The predominant cause are mutations of genes that encode protein components of the cardiac sarcomere and are transmitted in an autosomal-dominant pattern. 1 The mechanisms that lead from a sarcomere gene mutation to the phenotypic expression of HCM are poorly understood, which impedes the search for a treatment that can disrupt this pathophysiological process. 7 So far, no medical treatment has reliably shown to prevent, halt, or reverse disease progression and targeted pharmacologic options are scarce. 8 Clinical trials demonstrated limited or no effect of angiotensin receptor blockers or late sodium current inhibitor on disease progression, cardiac structure and function, exercise tolerance, and quality of life in patients with HCM. 9 Accordingly, treatment recommendations are focused on the alleviation of symptoms, prevention of thromboembolic events, and the prophylactic implantation of cardioverterdefibrillators in patients at high-risk of sudden cardiac death. 4,6 The angiotensin receptor neprilysin inhibitor (ARNI) sacubitril/ valsartan is a novel treatment shown to reduce hospitalizations and mortality in heart failure with reduced ejection fraction, 10 while there was no significant benefit of sacubitril/valsartan on the rate of total hospitalizations for heart failure and cardiovascular death among patients with heart failure with preserved ejection fraction in the recently published PARAGON-HF trial. 11 However, sacubitril/valsartan was shown to be more effective for the management of hypertensive patients, compared with an angiotensin receptor blocker. 12 Moreover, new preliminary data suggest that sacubitril/valsartan improves exercise tolerance and left ventricular wall motion, while reducing markers of left ventricular wall stress. 13 As sacubitril/valsartan has not yet been evaluated in HCM, this is the first clinical trial to investigate its effects on cardiovascular performance in patients with HCM.
Lifestyle intervention is safe and can improve symptoms and signs in patients with heart failure. Physical activity intervention is associated with a significant increase in exercise tolerance, but appears to have limited effect on measures of cardiac morphology or function in patients with HCM. 14 Table S3). The Steering Committee is responsible for protocol development, protocol and regulatory compliance, safety of participants at each site, analysis and review of the data, and preparation of written reports for publication. Special emphasis is put on close a collaboration between the five participating institutions, which is ensured by monthly teleconferences and biannual personal meetings.
The study is approved by each participating institution Research Ethics Committee / Institutional Review Board and will be conducted within the principles of Good Clinical Practice and in accordance with the Declaration of Helsinki. The study is registered with ClinicalTrials. gov (ClinicalTrials.gov-identifier: NCT03832660) and received funding from the European Union's Horizon 2020 Research and Innovation Programme. Obtained data will be shared with the project partners for joint analysis.
Recruitment was started in May 2019 and enrolment is expected to be completed in May 2021. As duration of follow-up for each patient will be 7 months, data analysis will be finished by November 2021 and a final report will be available at the beginning of 2022.

| Subjects
Stable outpatients with a history of nonobstructive HCM or borderline left ventricular hypertrophy are eligible if they have a left ventricular wall thickness of ≥15 mm or ≥13 mm in a first degree relative of someone with HCM and meet the inclusion and exclusion criteria listed in Table 2. Patients are screened for eligibility and informed consent is obtained from all eligible patients who are willing to participate in the study.

| Screening
After providing signed informed consent, participants undergo a screening visit to document age, weight/height, vital parameters, current symptoms, medical and family history, as well as prior, and concomitant medication. A physical examination, a 12-lead-electrocardiogram and a transthoracic echocardiography are performed. All participants undergo progressive cardiopulmonary exercise testing (CPET) using a cycle ergometer to evaluate their exercise tolerance, that is, peak oxygen consumption, at baseline. A venous blood sample is drawn to examine a comprehensive panel of serum and whole blood markers (eg, electrolytes, blood count, markers of renal function, muscle and liver enzymes, NT-proBNP, lipid profile, HbA1c, TSH, and markers of inflammation).
Habitual physical activity (daily number of steps) is evaluated using pedometers. Quality of life is assessed by the Minnesota Living with Heart Failure Questionnaire, the Hospital Anxiety and Depression Scale as well as the SF12-v2. At the time of enrolment, all participants must be on optimal standard therapy for HCM, conforming to contemporary guidelines such as the European Society of Cardiology guidelines. All cardiac medications must remain unchanged for at least 2 weeks before screening and randomization.

| Randomization
Eligible participants with signed informed consent are randomly allocated to the study groups-receiving either treatment with sacubitril/ valsartan or lifestyle intervention-or the control group (optimal standard therapy) using consecutively numbered sealed envelopes. Randomization will be stratified by patients giving or declining informed consent for the optional cardiac MRI-imaging. If 10 patients are randomized within the cardiac MRI-stratum, no further patients will be added to this stratum.

| Pharmacological intervention
Participants who are allocated to the pharmacological study group and have previously received an angiotensin-converting enzyme inhibitor-or angiotensin receptor blocker-therapy will require a 36-hour washout period before initiation of sacubitril/valsartan to reduce the risk of angioedema. 18 The treatment period begins with the initial dosing of sacubitril/valsartan, followed by up-titration every 14  2. Clinical cardiac decompensation in the previous 3 months, defined as New York Heart Association class IV congestive heart failure symptoms 3. Resting blood pressure >180/100 mmHg or systolic blood pressure <100 mmHg 4. Hypotensive response to exercise testing (≥20 mmHg decrease of systolic blood pressure from baseline blood pressure or an initial increase in systolic blood pressure followed by a decrease of systolic blood pressure ≥20 mmHg) 5. Concomitant use of angiotensin converting inhibitors or angiotensin receptor blockers; patients previously receiving angiotensin-converting enzyme inhibitor or angiotensin receptor blocker therapy will require a 36-hour washout period before initiation of Sacubitril/Valsartan  20 Adherence to the lifestyle intervention will be tracked by completion of activity logs and self-reported diaries, weekly telephone follow-ups, as well as pedometers.

| Optimal standard therapy (control group)
Participants in the control group receive optimal standard therapy for HCM as advocated in the current guideline of the European Society of Cardiology. 6 Optimal standard therapy may include an appropriate lifestyle, adequate management of heart failure symptoms and atrial fibrillation as well as risk stratification and preventive measures against sudden cardiac death.

| Electrocardiogram and ECG holter monitoring
The ECG will be performed using a standard 12-leadelectrocardiogram in supine position. To identify sporadic arrhythmia, all participants are asked to wear an ECG-holter-monitor for 24 hours and to keep a diary of activities and symptoms. The ECG-holterrecording is then correlated with the participants' activities and symptoms.

| Assessment of quality of life and habitual physical activity
Participants are asked to complete the validated and self-administered

| Optional genetic testing
Participants who have given written informed consent are offered an optional genetic testing for mutations in genes associated with HCM. An investigator, who is well-qualified in cardiac genetic counseling, clarifies what genetic testing might reveal and how family members might benefit from that knowledge. If participants choose to be genetically tested, they will be asked to provide written informed consent.
The genetic testing requires a blood sample and is performed at

| Optional cardiac MRI-imaging
Participants who have given written informed consent are offered an optional cardiac MRI-examination. If patients choose to participate in the cardiac MRI-examination, they will be asked to provide written informed consent. The cardiac MRI-examination is implemented to evaluate cardiac morphology as well as systolic and diastolic function.
Perfusion imaging is performed to assess first-pass perfusion during bolus injection of 0.1 mmol/kg of gadolinium contrast agent. Phase sensitive 2D inversion-recovery prepared gradient Echo imaging will be done 15-20 minutes post injection to evaluate for delayed enhancement of the myocardium. Please refer to the online supplement for details on cardiac MRI imaging.

| Follow-up
The study schedule for participants is illustrated in Figure 1. Following screening and randomization, all participants attend clinic visits after 4 and 7 months, during which the assessments performed at baseline are replicated (Table 3). Moreover, participants in the study group are  3 | STATISTICAL ANALYSIS

| Sample size and power calculation
The aim of the present study is to provide novel evidence about the efficacy and safety of sacubitril/valsartan vs lifestyle intervention in patients with nonobstructive HCM. In the absence of preliminary data regarding expectable treatment effects, we aim to enroll a total of 240 participants randomized into one of the three study arms. The average peak oxygen consumption in patient with HCM is suggested to be approximately 22 mL/kg/min. 14 The same study in patients with HCM has demonstrated a 10% increase in peak oxygen consumption with 8-12 weeks of lifestyle/exercise intervention. 14 Assuming a similar effect, the present study plans to enroll 80 patients per intervention to have 90% power to detect a significant difference in peak oxygen consumption between the groups, at a two-tailed significance level of 0.05 or less.

| Analysis population
The primary analyses will be based on the intention-to-treat (ITT) analysis set, consisting of all patients who entered the study (ie, all patients who received a patient identification number). However, sensitivity analyses will be done on a per-protocol (PP) analysis set that is composed of the ITT analysis set without major protocol violations.
The latter serves to assess the robustness of the results. All safety data will be analyzed by means of the safety population of all study patients who had at least one post-baseline safety assessment. The statement that a patient had no adverse events also constitutes a safety assessment.

| Data analysis
Statistical analyses will be performed using SPSS software version 24.0 or higher (IBM SPSS Statistics, Armonk, New York). Data will be described as mean and SD for normally distributed data, as median (25.;75. percentile) for non-normally distributed data and as numbers and percentages of participants for categorical variables. Differences in baseline characteristics, and outcome variables between the treatment-and control-group will be compared using the analysis of variance (ANOVA) for normally distributed continuous variables, the Kruskal-Wallis test for non-normally distributed continuous variables and the Persons chi-square test for categorical variables. A two-sided P-value of ≤.05 will be considered statistically significant for all analyses. As all secondary endpoints are of exploratory character, no adjustment for multiple testing will be performed.

| RESULTS
Until December 2019, a total of 41 patients were recruited into the ongoing SILICOFCM study and were allocated to the study groupsreceiving either treatment with sacubitril/valsartan (n = 14) or lifestyle intervention (n = 7)-and the control group (optimal standard therapy; n = 20). The mean age of the study population was 59.7 ± 13.4 years and 62% were male. Patients were diagnosed with hypertrophic nonobstructive cardiomyopathy with a mean maximum wall thickness of 19 ± 4 mm. There was no significant difference in key baseline characteristics between the three groups. Please refer to Table 4 for more details on key baseline characteristics.

| DISCUSSION
Until recently, nonobstructive HCM was predominantly regarded as a pathophysiologically benign disorder without significant symptoms, high-risk characteristics or the necessity for major treatment options. 5 However, nonobstructive HCM has been linked to increased morbidity due to a high risk for malignant ventricular arrhythmia 3 that may be caused by myocardial fibrosis and microvascular ischemia. 24

| Assessment of sacubitril/valsartan in patients with nonobstructive HCM
Having once been considered as contraindicated due to concerns for potential hemodynamic complications, CPET is nowadays a wellestablished clinical tool in the comprehensive evaluation of HCM patients. 25,26 The medical benefits of CPET in HCM comprise the differentiation of mild left ventricular hypertrophy from physiological hypertrophy, 27 a better prediction of disease progression as well as the objective evaluation of therapeutic strategies and treatment effects. 25,26 The change in peak VO 2 in CPET was chosen as primary endpoint of this study, because peak VO 2 is considered a factual parameter for assessing exercise capacity in patients with HCM. 28 Moreover, low peak VO 2 is generally acknowledged as an independent predictor for major adverse events in HCM, while normal peak VO 2 is associated with a favorable clinical outcome. 25 Besides, the SILICOFCM trial covers a wide range of secondary outcome parameters, for example, clinical phenotypic characteristics, injury and stretch activation markers, quality of life, and physical activity, that will be assessed in an exploratory manner.
Accordingly, the SILICOFCM aims to evaluate the effect of sacubitril/valsartan vs lifestyle intervention on nonobstructive HCM in a comprehensive way.

| Potential mechanisms of action of sacubitril/ valsartan intervention in nonobstructive HCM
The underlying pathophysiology and mechanisms of HCM lead to increased myocardial fibrosis and hypertrophy. This may be mediated by microvascular ischemia and an up-regulated feedback loop of the renin-angiotensin-aldosterone system. 8 By simultaneously blocking the renin-angiotensin-aldosterone system and augmenting natriuretic peptides through neprilysin inhibition, 29 the ARNI sacubitril/valsartan promotes vasodilatation, natriuresis and inhibition of fibrosis and hypertrophy. 30,31 Thus, sacubitril/valsartan has already emerges as an innovative and promising therapeutic approach in heart failure with reduced ejection fraction. 10 So far, the potentially beneficial effects of sacubitril/valsartan in HCM has not been evaluated in clinical trials. Therefore, first mechanistic insight must be derived from experimental data and a single case report: Sacubitril/valsartan was shown to attenuate left ventricular remodeling and dysfunction by inhibiting cardiac fibrosis and hypertrophy in both in vivo-and in vitro-analyses. 29 The first positive response to treatment with sacubitril/valsartan in HCM has been described in a case report by Rubis et al. 32

| Genetic testing
As a particular feature of the present study, all participants are offered comprehensive genetic testing for mutations in genes associated with HCM. Due to variable penetrance and expression, 39 the phenotypic characteristics of HCM are multifaceted and may be influenced by other factors beyond single pathogenic mutations. 40 The complex genotype-phenotype characteristics of HCM were potentially underrecognized in the past, which may have resulted in an unsatisfactory efficacy of drug management. 40 Therefore, our clinical trial may contribute to a better understanding of the association between sarcomere mutations and phenotype characteristics and disease severity as well as its impact on treatment response.

| LIMITATIONS
The design of the SILICOFCM has a few limitations to be considered, in particular the short treatment period. Preliminary data about expectable treatment effects of sacubitril/valsartan in patients with nonobstructive HCM is missing to date. The sample size of this trial was considered sufficient to get robust effect estimates in regard to the efficacy and safety of the study treatments.
Participants undergo study treatment for 4 months, which was deemed sufficient to observe potentially beneficial effects of the complementary addition of sacubitril/valsartan to the optimal standard therapy of HCM. Comparable treatment durations with sacubitril/valsartan were previously shown to significantly reduce NT-proBNP in patients with heart failure with preserved ejection fraction 41 and to improve cardiac function in the above mentioned case report of a patient with HCM. 32 Due to the above-mentioned limitations, the results of our trial may have to be interpreted with caution. However, they may pave the way for future clinical trials on patients with nonobstructive HCM.

| CONCLUSION
Over the past decade, we have gained a better understanding of the clinical management of patients with HCM. There have been considerable advances in treatment strategies directed at symptomatic relief and the prevention of sudden cardiac death. Henceforth, new approaches need to be evaluated regarding their potential to halt the phenotypic expression and progression of HCM.
In this aspect, SILICOFCM will provide novel data on whether the complementary addition of sacubitril/valsartan or lifestyle intervention to the optimal standard therapy improves cardiovascular performance in patients with nonobstructive HCM as well as their clinical phenotypic characteristics, injury and stretch activation markers, habitual physical activity, and quality of life. The SILICOFCM study has the potential to generate rational hypotheses regarding the effect of sacubitril/valsartan or lifestyle intervention on functional capacity in patients with nonobstructive HCM that then need to be confirmed in larger randomized clinical trials.
Thus, SILICOFCM will clearly contribute to optimizing the management of patients with nonobstructive HCM and to improving their clinical outcome.