PUBLISHED FEBRUARY 18, 2015
`Cardiac Fibrosis: New Treatments in Cardiovascular
`Medicine
`
`Kristin Reilly, PharmD
`Freelance Medical Writer
`East Windsor, New Jersey
`
`US Pharm. 2015;40(2):32-35.
`
`ABSTRACT: Almost 6 million people in the United States have heart
`failure. When heart failure develops, cardiac output decreases and
`compensatory mechanisms activate. One of these mechanisms is
`cardiac fibrosis, a scarring process that over time impacts cardiac
`structure and function. Historically, cardiac fibrosis has not been a focus
`for treatment; however, it is now believed that therapy directed at cardiac
`fibrosis could reduce the progression of heart failure and other
`cardiovascular diseases. Medications that target the renin-angiotensin
`system, transforming growth factor-beta, and endothelin are in various
`stages of development.
`
`Heart failure is a complex clinical syndrome in which structural or
`functional abnormalities impair the heart’s ability to fill with or pump
`blood. Affecting nearly 6 million people in the United States, heart
`1,2
`
`Lassen - Exhibit 1054, p. 1
`
`

`

`failure is the leading reason for hospitalization in patients aged 65 years
`and older, as well as a major cause of impaired quality of life and
`chronic disability.
`1-3
`
`Heart failure can result from systolic dysfunction, diastolic dysfunction,
`or both. The most common risk factors for developing heart failure
`1
`include coronary heart disease (often with myocardial infarction [MI]),
`hypertension, diabetes, and cardiomyopathy.
`3,4
`
`Heart failure is initiated by any event that impairs the heart’s ability to
`contract and/or relax, resulting in reduced cardiac output. As cardiac
`1
`output decreases, compensatory mechanisms activate to restore
`cardiac output through increased preload, tachycardia,
`vasoconstriction, ventricular hypertrophy, and remodeling. At the
`1,4
`cellular level, ventricular hypertrophy and remodeling are accompanied
`by cardiomyocyte hypertrophy, necrosis, apoptosis, fibroblast
`proliferation, and increased deposition of fibrous collagen, the last two
`of which are collectively termed cardiac fibrosis. This article will focus
`4
`on cardiac fibrosis, including its mediators, assessment, and potential
`treatments.
`
`Structure of the Heart Wall
`The heart wall is composed of three layers: the epicardium (outer layer),
`the myocardium (middle layer), and the endocardium (interior layer).
`5
`Fibrosis can occur in any layer and in various locations of the heart (i.e.,
`the four heart chambers and valves). The discussion in this article will
`3
`be limited to myocardial fibrosis.
`
`The myocardium contains a variety of cell types, including
`cardiomyocytes and fibroblasts. Fibroblasts are found within the
`6
`heart’s connective tissue and account for approximately two-thirds of
`cardiac cells.
`Fibroblasts are involved in many aspects of cardiac
`6-8
`function, including regulating the balance of the extracellular matrix
`(ECM), ECM remodeling, electrical activity, production of growth factors
`and cytokines, and intercellular signaling.
`6
`
`Lassen - Exhibit 1054, p. 2
`
`

`

`The structural component of the myocardium is the ECM. Collagen, a
`1
`fibrous protein found in ECM and connective tissue, is composed of
`amino acids.
`1
`
`Pathogenesis of Cardiac Fibrosis
`Ventricular remodeling, a natural compensatory process that precedes
`the development of heart failure symptoms, results in progressive
`changes in the structure and function of the heart, including cardiac
`hypertrophy, loss of cardiac muscle cells, and ECM alterations. Some
`1
`types of hypertrophy are accompanied by fibrosis.
`1
`
`Cardiac fibrosis occurs when fibroblasts are activated to
`myofibroblasts and produce elevated amounts of ECM proteins that
`form scar tissue and alter normal degradation of ECM (FIGURE 1).
`4,7,8
`Both processes lead to a buildup of collagen, which impacts both
`systolic and diastolic function.
`7,9
`
`Lassen - Exhibit 1054, p. 3
`
`

`

`Cardiac fibrosis, which is part of the normal aging process, is
`associated with many cardiovascular diseases, including heart failure,
`hypertension, and cardiomyopathies; it also is found in hearts that have
`been damaged by MI or radiation.
`Fibrosis progresses over time
`3,10-12
`and is accompanied by ongoing deterioration of heart function.
`13
`
`Types of Fibrosis
`Two forms of fibrosis—replacement fibrosis and reactive interstitial, or
`perivascular, fibrosis—have been identified. Replacement fibrosis
`10
`occurs in response to an injury causing cardiomyocyte death, as in the
`case of MI; a reparative response is activated in the heart, causing
`replacement of dead cells and formation of a collagen-based scar.
`10,14
`In reactive interstitial fibrosis, the cardiac interstitial space expands
`without significant cardiomyocyte loss.
`Reactive fibrosis allows the
`3,14
`heart to adapt to injury and retain its pressure-generating ability.
`14
`Pressure or volume overload, ischemia, and cardiomyopathies are
`examples of reactive fibrosis.
`14
`
`Mediators of Fibrosis
`Increases in various circulating hormones, cytokines, and proteins
`triggered by stress or injury contribute to fibroblast activation and
`differentiation and, ultimately, to cardiac fibrosis. Although many
`7,8
`substances have been identified as playing a part in this process,
`several studies suggest that the renin-angiotensin system (RAS),
`transforming growth factor (TGF)-beta, and endothelin (ET) are key
`elements in the cascade. These elements will be the focus of this
`discussion.
`8
`
`The RAS regulates the production and activity of fibroblasts. When the
`11
`heart is injured, macrophages and fibroblasts produce renin and ACE,
`which in turn generate angiotensin II (Ang II). Ang II interacts with Ang
`9
`II receptor type 1 (AT ) receptors, which promote hypertrophy, stimulate
`1
`
`Lassen - Exhibit 1054, p. 4
`
`

`

`In addition,
`fibroblast proliferation, and increase collagen synthesis.
`9,15
`Ang II suppresses collagenase (an enzyme that breaks down collagen),
`which may lead to increased collagen accumulation and fibrosis.
`13
`
`Aldosterone has also been identified as a mediator of fibrosis. It affects
`fibroblast proliferation and collagen deposition in the ECM, heightening
`expression of cytokines and chemokines, signaling macrophages, and
`activating cardiomyocyte fibrogenic signals.
`1,9,12,13
`
`TGF-beta is a cytokine in the heart that is activated by cardiac injury,
`generation of reactive oxygen species, Ang II, high glucose, altered pH,
`and certain proteases. Once activated, TGF-beta increases ECM
`4,9
`production and decreases ECM breakdown.
`4,9
`
`It has
`ET is a protein that is released by endothelial cells in the heart.
`8
`been found to increase fibroblast differentiation into myofibroblasts
`and the production of ECM.
`8
`
`Assessment of Fibrosis
`Historically, the only measures of cardiac fibrosis have been
`echocardiograms that indirectly measure left ventricle mass and
`endomyocardial biopsies that measure collagen volume fraction
`(CVF). Newer techniques involve laboratory assessment of
`11
`biomarkers and cardiac imaging.
`11
`
`Several biomarkers for fibrosis have been identified, most of which are
`focused on ECM structure. Researchers can measure biomarkers of
`11
`the synthesis and degradation of collagen types I and III, the main
`components of ECM. Collagen types I and III are synthesized as
`11
`procollagens, which are then processed into mature collagen molecules
`by a peptidase cleaving their propeptide domain.
`During collagen
`6,11
`synthesis, propeptides from the amino-terminals (PINP and PIIINP) or
`carboxy-terminals (PICP and PIIICP) of collagen types I and III are
`released and measured as biomarkers. During collagen degradation,
`6
`
`Lassen - Exhibit 1054, p. 5
`
`

`

`telopeptides in the amino-terminals (NITP, NIIITP) or carboxy-terminals
`(CITP, CIIITP) of collagen types I and III are cleaved and act as
`biomarkers.
`6
`
`Biomarkers may be used to identify fibrosis before symptoms of
`disease are present, as well as to assess the efficacy of medications.
`Biomarkers are commonly used as endpoints in clinical trials.
`11
`
`MRI is useful for visualizing certain types of fibrosis. Contrast-
`11
`enhanced cardiac MRI can readily visualize “patchy,” or regional,
`myocardial fibrosis from MI or infiltration.
`Diffuse fibrosis is much
`11,12
`more difficult to visualize, and research into enhanced MRI techniques
`may prove beneficial in identifying this and other forms of fibrosis.
`11
`Other imaging techniques that have shown promise in identifying
`cardiac fibrosis include single photon emission CT and positron
`emission tomography scanning; more studies are required, however.
`11
`
`Potential Treatments
`For certain conditions that cause fibrosis, such as volume or pressure
`overload, the best treatment is to prevent fibrosis by controlling risk
`factors.
`For patients in whom prevention is not possible or has failed,
`9,14
`existing drugs and new chemical entities are in various stages of
`development; these products may have a significant effect on the
`management of many cardiovascular diseases.
`8,11
`
`Agents That Impact the RAS: As stated previously, the RAS plays a
`central role in fibroblast activation; as such, it is an important target for
`drug therapy. A significant amount of research has been conducted
`11
`on how drugs that modify this system affect cardiac fibrosis; specific
`information is provided in TABLE 1.
`
`Lassen - Exhibit 1054, p. 6
`
`

`

`Several antihypertensive classes, including beta-blockers and calcium
`channel blockers, have shown efficacy in reducing fibrosis in animals;
`however, results in humans have been inconsistent.
`RAS inhibitors,
`8,11
`such as ACE inhibitors, Ang II receptor blockers (ARBs), and
`aldosterone antagonists, have demonstrated positive results in animals
`and humans. One study of lisinopril versus hydrochlorothiazide
`11
`(HCTZ) in patients with hypertension, left ventricular hypertrophy, and
`left ventricular diastolic dysfunction found that lisinopril decreased CVF
`significantly compared with HCTZ. Blood pressure (BP) was
`13
`controlled in both treatment groups, but the effect on fibrosis differed.
`13
`
`ARBs also are effective for reducing fibrosis. Losartan and olmesartan
`11
`have favorable animal data, and candesartan and losartan have reduced
`fibrosis biomarkers in humans.
`In a 1-year study of losartan versus
`8,11
`amlodipine, losartan significantly decreased fibrosis, whereas
`amlodipine did not; both drugs affected BP similarly, however. These
`11
`studies of lisinopril and losartan show that treatments can impact
`fibrosis and hypertension independently of each other.
`11
`
`Lassen - Exhibit 1054, p. 7
`
`

`

`Unlike ACE inhibitors and ARBs, aldosterone antagonists directly block
`aldosterone, which may be a more effective way of reducing its
`profibrotic effects. Spironolactone and eplerenone have been shown
`11
`to reduce myocardial fibrosis in animals and humans, though results in
`humans are mixed.
`2,11
`
`Vaccines with anti–Ang II effects are being researched in animals and
`humans, mostly for hypertension.
`One vaccine effectively decreased
`11,16
`cardiac fibrosis in immunized mice; Ang II signaling was inhibited, and
`anti–Ang II antibodies increased.
`11
`
`In
`The RAS is a complex system with two counterbalancing axes.
`11,15
`addition to the familiar ACE/Ang II/AT axis, an ACE2/Ang-(1-7)/Mas
`1
`receptor axis has been identified.
`ACE2 hydrolyzes Ang II into
`11,15
`Ang-(1-7), and Mas is a protein receptor for Ang-(1-7).
`The
`11,15
`ACE2/Ang-(1-7)/Mas receptor axis has shown antifibrogenic and
`antiproliferative effects in various organs, including the heart. Several
`15
`animal studies have provided strong evidence that administration of
`Ang-(1-7) and overexpression of ACE2 can reduce cardiac fibrosis.
`15
`While therapeutic agents for these areas have not yet been developed,
`the foundation for future research has been built.
`15
`
`TGF-beta Inhibitors: As previously discussed, TGF-beta plays a central
`role in activating cardiac fibrosis, and inhibiting its actions could have
`profound effects on reducing fibrosis. Several approaches to inhibiting
`4
`TGF-beta are being researched; two agents, pirfenidone and tranilast,
`are the furthest developed. Although the exact mechanisms of action
`are not completely understood, these drugs appear to inhibit TGF-beta
`and other growth factors.
`4
`
`Pirfenidone, an oral medication, was approved in October 2014 for the
`treatment of idiopathic pulmonary fibrosis.
`In animal studies,
`17
`pirfenidone has shown efficacy in reducing cardiac fibrosis, decreasing
`left atrial remodeling, and reducing diastolic stiffness, but not restoring
`cardiac contractility.
`4
`
`Lassen - Exhibit 1054, p. 8
`
`

`

`Tranilast has been used in Japan for more than 20 years to treat
`asthma, allergic rhinitis, and atopic dermatitis.
`In animal studies,
`4,18
`tranilast reduced cardiac fibrosis without affecting BP, suggesting a
`direct effect on fibrosis.
`In a human study examining prevention of
`4
`restenosis after percutaneous coronary intervention, however,
`quantitative measures of efficacy were not found; moreover, several
`laboratory abnormalities were detected that could impact the use of
`tranilast, including increased bilirubin, liver enzymes exceeding three
`times the upper limit of normal, and serum creatinine increases of 50%.
`Research is being conducted on new compounds that could overcome
`some of these potential safety concerns.
`4
`
`ET Inhibitors: Currently, several ET receptor inhibitors are approved in
`the U.S. for the treatment of pulmonary hypertension, including the dual
`ET subtype A/ET subtype B (ETA/ETB) inhibitors bosentan and
`macitentan and the ETA inhibitor ambrisentan.
`It is postulated that
`8,19-21
`it may be necessary to target dual ETA/ETB inhibition, since both
`receptors impact fibrosis.
`In animal studies, bosentan has been
`22
`demonstrated to inhibit ECM formation, decrease collagen synthesis,
`and increase collagenase suppression. Studies examining its use in
`22
`fibrosis are ongoing.
`8
`
`Drugs Impacting Other Mediators of Fibrosis: Histone deacetylases
`(HDACs) are enzymes that play a key role in regulating gene
`transcription throughout the body. HDACs may be linked to the
`7
`signaling of some cellular molecules that have an effect on cardiac
`fibrosis, as well as inflammation. Animal studies have revealed that
`7
`HDAC inhibitors can stop, or even reverse, cardiac fibrosis. One
`7
`inhibitor has positive results in reducing cardiac fibrosis, as well as
`levels of Ang II receptors and TGF-beta. Although a great deal of
`7
`research is needed, HDAC inhibitors hold promise as future treatment.
`
`7
`
`Ivabradine is an oral medication currently available outside the U.S. that
`provides selective heart rate reduction by inhibiting the f-channel of the
`sinoatrial node.
`In August 2014, the FDA granted fast-track
`23
`
`Lassen - Exhibit 1054, p. 9
`
`

`

`designation for this compound in the treatment of chronic heart
`failure.
`In animal models, ivabradine effectively reduced fibrosis and
`23
`circulating Ang II and aldosterone levels.
`11
`
`Additional agents, including diltiazem, tadalafil, isosorbide dinitrate and
`hydralazine, erythropoietin, cyclosporine, thalidomide, and anti-
`inflammatory drugs impacting cytokines (e.g., tumor necrosis factor-
`alpha, interleukin [IL]-1, and IL-6), are being evaluated for fibrosis.
`11
`Transplantation of a variety of stem cells following MI has been
`demonstrated to decrease cardiac fibrosis and cardiac muscle
`apoptosis.
`11,14
`
`Conclusion
`Cardiac fibrosis is believed to be the final pathway leading to heart
`failure, which is an extremely common syndrome in the U.S. Much of
`the pathophysiology of cardiac fibrosis is known. Many drug treatments
`have been studied and seem promising, but data in humans are both
`limited and mixed. Although more studies must be conducted to
`evaluate the safety and efficacy of possible treatments for cardiac
`fibrosis, there is great hope for the future.
`
`REFERENCES
`1. Parker RB, Nappi JM, Cavallari LH. Chronic heart failure. In: DiPiro JT, Talbert RL, Yee GC, et
`al, eds. Pharmacotherapy: A Pathophysiologic Approach. 9th ed. New York, NY: McGraw-Hill
`Education; 2014.
`2. Rich MW. Heart failure. In: Halter JB, Ouslander JG, Tinetti ME, et al, eds. Hazzard’s Geriatric
`Medicine and Gerontology. 6th ed. McGraw-Hill; 2009.
`3. Biernacka A, Frangogiannis NG. Aging and cardiac fibrosis. Aging Dis. 2011;2:158-173.
`4. Edgley AJ, Krum H, Kelly DJ. Targeting fibrosis for the treatment of heart failure: a role for
`transforming growth factor-beta. Cardiovasc Ther. 2012;30:e30-e40.
`5. Mescher AL. Junqueira’s Basic Histology: Text and Atlas. 13th ed. New York, NY: McGraw-Hill;
`2013:212-233.
`6. Fan D, Takawale A, Lee J, Kassiri Z. Cardiac fibroblasts, fibrosis and extracellular matrix
`remodeling in heart disease. Fibrogenesis Tissue Repair. 2012;5:15.
`7. Tao H, Shi KH, Yang JJ, et al. Histone deacetylases in cardiac fibrosis: current perspectives
`for therapy. Cell Signal. 2014;26:521-527.
`8. Leask A. Potential therapeutic targets for cardiac fibrosis: TGFbeta, angiotensin, endothelin,
`CCN2, and PDGF, partners in fibroblast activation. Circ Res. 2010;106:1675-1680.
`
`Lassen - Exhibit 1054, p. 10
`
`

`

`9. Kong P, Christia P, Frangogiannis NG. The pathogenesis of cardiac fibrosis. Cell Mol Life Sci.
`2014;71:549-574.
`10. Krenning G, Zeisberg EM, Kalluri R. The origin of fibroblasts and mechanism of cardiac
`fibrosis. J Cell Physiol. 2010;225:631-637.
`11. Roubille F, Busseuil D, Merlet N, et al. Investigational drugs targeting cardiac fibrosis. Expert
`Rev Cardiovasc Ther. 2014;12:111-125.
`12. Bashore TM, Granger CB, Jackson K, Patel MR. Heart disease. In: Papadakis MA, McPhee
`SJ, eds. Current Medical Diagnosis & Treatment 2015. New York, NY: McGraw-Hill Education;
`2015.
`13. Brilla CG, Funck RC, Rupp H. Lisinopril-mediated regression of myocardial fibrosis in
`patients with hypertensive heart disease. Circulation. 2000;102:1388-1393.
`14. Elnakish MT, Kuppusamy P, Khan M. Stem cell transplantation as a therapy for cardiac
`fibrosis. J Pathol. 2013;229:347-354.
`15. Simões e Silva AC, Silveira KD, Ferreira AJ, Teixeira MM. ACE2, angiotensin-(1-7) and Mas
`receptor axis in inflammation and fibrosis. Br J Pharmacol. 2013;169:477-492.
`16. Bairwa M, Pilania M, Gupta V, Yadav K. Hypertension vaccine may be a boon to millions in
`developing world. Hum Vaccin Immunother. 2014;30:708-713.
`17. FDA. FDA approves Esbriet to treat idiopathic pulmonary fibrosis.
`www.fda.gov/NewsEvents/Newsroom/PressAnnouncements/ucm418991.htm. Accessed
`October 27, 2014.
`18. Kissei Pharmaceutical Co. Kissei entered into an agreement with Nuon Therapeutics, Inc on
`Tranilast. www.kissei.co.jp/e_contents/relation/2007/20070723.html. Accessed October 22,
`2014.
`19. Tracleer (bosentan) product information. South San Francisco, CA: Actelion
`Pharmaceuticals US, Inc; October 2012.
`20. Letairis (ambrisentan) product information. Foster City, CA: Gilead Sciences, Inc; May 2014.
`21. Opsumit (macitentan) product information. South San Francisco, CA: Actelion
`Pharmaceuticals US, Inc; October 2013.
`22. Clozel M, Salloukh H. Role of endothelin in fibrosis and anti-fibrotic potential of bosentan.
`Ann Med. 2005;37:2-12.
`23. Amgen. FDA grants Amgen priority review designation for ivabradine for the treatment of
`chronic heart failure. www.amgen.com/media/media_pr_detail.jsp?releaseID=1961392.
`Accessed October 22, 2014.
`
`To comment on this article, contact rdavidson@uspharmacist.com.
`
`We recommend
`
`A Pharmacist’s Guide for Systolic Heart Failure
`Angela R. Thomason et al., US Pharmacist,
`2006
`
`Managing Hypertrophic Cardiomyopathy
`
`Protein Kinase Cε-Calcineurin Cosignaling
`Downstream of Toll-Like Receptor 4
`Downregulates Fibrosis and Induces Wound
`Healing Gene Expression in Cardiac
`Myofibroblasts
`Mol Cell Biol, 2014
`
`Lassen - Exhibit 1054, p. 11
`
`

`

`Manouchkathe Cassagnol et al., US
`Pharmacist, 2016
`
`Aortic Stenosis: Evidence Supports Surgery
`Mary Ann E. Zagaria et al., US Pharmacist,
`2011
`
`Management of Arrhythmias, Part II:
`Ventricular Arrhythmias
`Mindi S. Miller et. al., US Pharmacist, 2006
`
`Rate Control in Atrial Fibrillation
`Mary Ann E. Zagaria et al., US Pharmacist,
`2007
`
`Powered by
`
`Deficiency of Cardiomyocyte-specific
`MicroRNA-378 Contributes to the
`Development of Cardiac Fibrosis Involving a
`Transforming Growth Factor β (TGFβ1)
`-dependent Paracrine Mechanism
`Raghu S. Nagalingam et al., Journal of
`Biological Chemistry, 2014
`
`Cell-specific ablation of Hsp47 defines the
`collagen producing cells in the injured heart
`
`Hadi Khalil et al., JCI Insight, 2019
`
`191 Role of mir-214 in angiotensin ii induced
`hypertensive heart disease
`Eilidh McGinnigle et al., Heart, 2017
`
`Myocyte-Derived Hsp90 Modulates Collagen
`Upregulation via Biphasic Activation of
`STAT-3 in Fibroblasts during Cardiac
`Hypertrophy
`Mol Cell Biol, 2017
`
`Copyright © 2000 - 2019 Jobson Medical Information LLC unless otherwise noted. All
`rights reserved. Reproduction in whole or in part without permission is prohibited.
`
`Lassen - Exhibit 1054, p. 12
`
`