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Ferguson B, Stern J, Oldach M, Ueda Y, Ontiveros E, Napierski N, Del Rio C, Harris S. Acute effects of a mavacamten-like myosin-inhibitor (MYK-581 in a feline model of obstructed hypertrophic cardiomyopathy: evidence of improved ventricular filling (beyond obstruction reprieve). Eur Heart J 2020. [DOI: 10.1093/ehjci/ehaa946.3713] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Abstract
Introduction
Hypertrophic cardiomyopathy (HCM) is a progressive disease characterized by cardiac remodeling, hyperdynamic contraction, and impaired ventricular filling that can lead to dynamic left-ventricular outflow-track (LVOT) obstruction and exertional intolerance. Direct myosin-inhibition with mavacamten can normalize contractility and improve exercise capacity in patients with oHCM, providing sustained symptomatic relief. However, mavacamten can also improve ventricular filling by limiting residual cross-bridges during diastole, and therefore, may offer cardiac benefits beyond obstruction reprieve. This study leveraged a feline model of oHCM, cats with the A31P MYBPC3 variant, to study the acute in vivo effects of MYK-581, a mavacamten surrogate, on cardiac hemodynamics and filling.
Methods
A31P-homozygous cats with HCM (A31P, n=10) and wild-type healthy controls (CTRL, n=9) were anesthetized and instrumented for invasive pressure-volume (PV) measurements as well as trans-thoracic echocardiographic recording. A subset of cats were assigned to receive either vehicle (VEH, n=7) or MYK-581 (MYK, n=8) with a short IV infusion. Cardiac hemodynamics, function, and geometry were assessed at steady state before and during dobutamine challenges (2.5 μg/kg/min IV).
Results
A31P cats had thicker ventricular walls (6.4±0.1 vs. 5.2±0.2 mm, P<0.05) and hyperdynamic contraction (FS: 61±4 vs. 50±3%, P<0.05) relative to controls and presented with dynamic LVOT obstruction in 54% of cases. HCM cats had elevated end-diastolic pressures (17±1.4 vs. 9±1.0 mmHg, P<0.05), with prolonged time constants of relaxation (60±4.1 vs. 36±2.4 ms, P<0.05) and elevated end-diastolic stiffness (Eed: 0.44±0.06 vs. 0.25±0.01 mmHg/mL). Acute treatment with MYK-581 alleviated LVOT obstruction (0% vs. 38%), normalized contractility (FS: −7±2%), and increased systolic/diastolic chamber dimensions (e.g., LVIDd: +13±4%) (all P<0.05), while reducing EDP (15±2 to 13±2 mmHg, P<0.05), suggesting acute improvement in ventricular distensibility. Indeed, MYK-581 treatment reduced end-diastolic stiffness (Eed: 0.48±0.11 vs. 0.36±0. 10 mmHg/mL, P<0.05) and normalized trans-mitral motion patterns during filling.
Conclusions
Bred cats, homozygous for the A31P MYBPC3 variant, presented a cardiac phenotype that models multiple characteristics of the human oHCM phenotype including dynamic LVOT obstruction. Acute treatment with the mavacamten surrogate, MYK-581, not only alleviated hypercontractility and LVOT obstruction, but improved ventricular filling and end-diastolic pressures. Taken together, these pre-clinical observations show potential salutary effects beyond obstruction relief in patients with HCM.
Funding Acknowledgement
Type of funding source: Private company. Main funding source(s): MyoKardia
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Affiliation(s)
- B.S Ferguson
- MyoKardia, South San Francisco, United States of America
| | - J.A Stern
- University of California, Department of Medicine & Epidemiology, School of Veterinary Medicine, Davis, United States of America
| | - M.S Oldach
- University of California, Department of Medicine & Epidemiology, School of Veterinary Medicine, Davis, United States of America
| | - Y Ueda
- University of California, Department of Medicine & Epidemiology, School of Veterinary Medicine, Davis, United States of America
| | - E.S Ontiveros
- University of California, Department of Medicine & Epidemiology, School of Veterinary Medicine, Davis, United States of America
| | - N.C Napierski
- University of Arizona, Department of Cellular and Molecular Medicine, Tucson, United States of America
| | - C.L Del Rio
- MyoKardia, South San Francisco, United States of America
| | - S.P Harris
- University of Arizona, Department of Cellular and Molecular Medicine, Tucson, United States of America
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Ontiveros E, Kuo L, Masters PS, Perlman S. Inactivation of expression of gene 4 of mouse hepatitis virus strain JHM does not affect virulence in the murine CNS. Virology 2001; 289:230-8. [PMID: 11689046 DOI: 10.1006/viro.2001.1167] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
The protein encoded by ORF 4 of mouse hepatitis virus (MHV) is not required for growth of some strains in tissue culture cells, but its role in pathogenesis in the murine host has not been defined previously in a controlled manner. MHV strain JHM causes acute and chronic neurological diseases in susceptible strains of rodents. To genetically manipulate the structural proteins of this and other strains of MHV, we have generalized an interspecies-targeted RNA recombination selection that was originally developed for the A59 strain of MHV. Using this approach, a recombinant MHV-JHM was constructed in which gene 4 was genetically inactivated. Virus lacking gene 4 expression replicated in tissue culture cells with similar kinetics to recombinant virus in which gene 4 expression was not disrupted. Both types of viruses exhibited similar virulence when analyzed in a murine model of encephalitis. These results establish a targeted recombination system for inserting mutations into MHV-JHM. Furthermore, the protein encoded by ORF 4 is not essential for growth in tissue culture cells or in the CNS of the infected host.
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Affiliation(s)
- E Ontiveros
- Interdisciplinary Program in Immunology, University of Iowa, Iowa City, Iowa 52242, USA
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Shor V, Santos J, Ontiveros E, Wulfovich M, Karchmer S. [Effects of weight, height, age and parity on the pregnancy, puerperium and the status of the newborn infant]. Ginecol Obstet Mex 1971; 29:463-9. [PMID: 5091931] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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Mac Gregor C, Ontiveros E, Vargas López E, Castelazo Ayala L. [Statistical analysis of molar pregnancy in the Hospital de Gineco-Obstetricia, No. 1, of the I.M.S.S]. Ginecol Obstet Mex 1966; 21:611-8. [PMID: 5994068] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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