For Patients & Providers

Watch the videos below to learn more about the role of mitochondria and cardiolipin in health and disease.

Mitochondria & Disease

Mitochondria, often described as the “powerhouse of the cell”, are responsible for approximately 90% of energy production in human cells.1 These “powerhouses” are found in all human cells other than mature red blood cells.2 Mitochondria produce energy through the conversion of food into adenosine triphosphate, or ATP.2 This happens through a series of reactions, controlled by the electron transport chain, within the inner folds of the mitochondria.2 In normal mitochondria, the inner mitochondrial membrane is highly folded, creating curves, called cristae.3 The cristae house the electron transport chain, which is composed of five protein complexes responsible for mitochondrial ATP production.3 Cardiolipin, a phospholipid found within the inner mitochondrial membrane, is responsible for establishing the cristae architecture and optimizing the function of ATP generating machinery, including the electron transport chain.4

Dysfunctional mitochondria can have an impaired ability to produce ATP and can generate increased levels of reactive oxygen species, or ROS, a major contributor to oxidative stress.2 Although low levels of ROS can be important signaling molecules in the cell, high levels of ROS can damage proteins and membrane lipids within the cell.  Cardiolipin in particular is highly susceptible to oxidative damage, which can result in disrupted mitochondrial structure and a cycle of increasing ROS generation that can lead to the inflammation, fibrosis, senescence and cell death implicated in many human diseases.5

Mitochondrial dysfunction is commonly observed across both common and rare diseases.  Contributors to mitochondrial dysfunction can include genetic mutations, the aging process, environmental factors, or a combination thereof.  These impairments can affect a number of different organ systems, especially those with high energetic demands such as heart, eye, brain, kidney, and skeletal muscle10-12.  Stealth is focused on mitigating mitochondrial dysfunction in rare diseases associated with cardiomyopathy, Barth syndrome, and Leber’s hereditary optic neuropathy7-8, as well as a wide range of common age-related diseases, such as dry age related macular degeneration.9-10

Mitochondrial Disease Overview

The term mitochondrial disease or disorder generally refers to a defect which exists somewhere along the energy building pathway.2,12,35 Mitochondrial diseases are typically classified and named either after the specific genetic defect (e.g. POLG mutation) or the cluster of symptoms associated with the disease (e.g. MELAS: Mitochondrial Encephalopathy, lactic acidosis, stroke, or LHON: Leber’s hereditary optic neuropathy).2,12,35 Some mitochondrial disorders are named after the clinician who first identified the disease (i.e. Leigh syndrome, Barth syndrome).36-37 Regardless of the name, the term mitochondrial disease is an umbrella term that encompasses many specific conditions caused by mitochondrial defects. 2,12,35


Barth syndrome, or Barth, is characterized by skeletal muscle weakness, delayed growth, fatigue, varying degrees of physical disability, heart muscle weakness, or cardiomyopathy, low white blood cell count, or neutropenia (which may lead to an increased risk for bacterial infections), and methylglutaconic aciduria (which is an increase in an organic acid that results in abnormal mitochondria function).22-24 We believe that the incidence of Barth to be between one in 300,000 to 400,000 births.22

Mitochondrial dysfunction has been linked with rare diseases that develop cardiomyopathy such as Duchenne muscular dystrophy (DMD), Becker muscular dystrophy (BMD) and Friedreich’s Ataxia (FA).  In these pathologies, calcium or iron overload in mitochondria leads to impaired mitochondrial function, and increased reactive oxygen species (ROS) generation.  Cardiomyopathy is a leading cause of morbidity/mortality in DMD/BMD/FA39, and in many cases the decline in mitochondrial function has been observed as a precursor to the onset of cardiac pathology.40   There are no approved therapies that specifically target the cardiac mitochondria in these inherited myopathies, highlighting an unmet need to potentially improve the lives of these patients by mitigating cardiac pathology.

Leber’s hereditary optic neuropathy, or LHON, is characterized by central vision loss.26 We estimate that approximately 10,000 individuals in the United States are diagnosed with LHON.27 There are no therapies approved by the FDA for the treatment of LHON.28

Common Diseases of Aging

Dry age-related macular degeneration, or dry AMD, the leading cause of blindness among older adults in the developed world, is characterized by symptoms such as distorted vision, reduction in low luminance visual acuity, reduced overall visual acuity and blurred vision.30-31 We estimate that dry AMD impacts more than 10 million individuals in the United States.30–33  Mitochondrial dysfunction is believed to be a significant contributor to the progression of dry AMD38, making the mitochondrial network an attractive target to improve retinal function and mitigate disease burdens in this patient population. There are no FDA or EMA approved treatments for the treatment of dry AMD.31

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Barth Syndrome Facts

Learn more about Barth Syndrome, from signs & symptoms to research & treatments.

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Mitochondria Flipbook

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Programs & Pipeline

Mitochondria, often described as the “powerhouse of the cell”, are responsible for approximately 90% of energy production in human cells.

Learn More is a database of privately and publicly funded clinical studies conducted around the world.

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We work closely with key advocacy organizations and their stakeholders to better understand the needs of people impacted by diseases involving mitochondrial dysfunction. Advocacy organizations play a vital role in helping patients, families and caregivers navigate the difficult path from diagnosis to living with diseases that are debilitating and for which there are no widely understood standards of diagnosis or care.

We collaborate with leading mitochondrial disease patient advocacy organizations to progress our closely aligned missions, by:

  • Supporting their efforts to improve patients’ lives
  • Advocating for relevant events and initiatives
  • Fostering strong relationships in the rare disease and mitochondrial disease community
  • Positively impacting the mitochondrial disease patient community

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Stealth BioTherapeutics

123 Highland Ave, Suite 201, Needham, MA 02494

(617) 600-6888

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