Stealth BioTherapeutics Receives Orphan Drug Designation from the European Medicines Agency for Elamipretide for the Treatment of Barth Syndrome

Stealth BioTherapeutics Corp (Nasdaq: MITO), a clinical-stage biotechnology company focused on the discovery, development, and commercialization of novel therapies for diseases involving mitochondrial dysfunction, today announced that the European Medicines Agency (EMA) has granted orphan drug designation (ODD) for elamipretide for the treatment of Barth syndrome, an ultra-rare genetic condition.

"We are pleased that EMA has recognized, by granting ODD for elamipretide for Barth syndrome, the high unmet need for innovative treatments for this ultra-rare genetic condition," said Chief Executive Officer Reenie McCarthy. "This marks an important step toward advancing our regulatory initiatives in Europe as we work towards potential ex-U.S. partnerships and approvals.  We are committed to increasing medical and regulatory awareness of this devastating condition, which is believed to contribute to often fatal, infant-onset idiopathic cardiomyopathy globally."

ODD is granted to investigational therapies intended for the safe and effective treatment of rare diseases with an unmet medical need that affect fewer than 5 in 10,000 people in the European Union. This designation provides companies with certain benefits and incentives including clinical protocol assistance, differentiated evaluation procedures for Health Technology Assessments in certain countries, access to a centralized marketing authorization procedure valid in all EU Member States, and if approved, marketing exclusivity in the EU for 10 years.

About Barth Syndrome

Barth syndrome is an ultra-rare genetic condition characterized by cardiac abnormalities often leading to heart failure and reduced life expectancy, recurrent infections, muscle weakness and delayed growth. Barth syndrome occurs almost exclusively in males and is estimated to affect one in 200,000 to 400,000 individuals worldwide. There are currently no FDA- or EMA-approved therapies for patients with Barth syndrome.

About Stealth

We are a clinical-stage biotechnology company focused on the discovery, development, and commercialization of novel therapies for diseases involving mitochondrial dysfunction. Mitochondria, found in nearly every cell in the body, are the body's main source of energy production and are critical for normal organ function. Dysfunctional mitochondria characterize a number of rare genetic diseases and are involved in many common age-related diseases, typically involving organ systems with high energy demands such as the heart, the eye, and the brain. We believe our lead product candidate, elamipretide, has the potential to treat both rare metabolic cardiomyopathies, such as Barth, Duchenne muscular dystrophy and Friedreich's ataxia, rare mitochondrial diseases entailing nuclear DNA mutations, as well as ophthalmic diseases entailing mitochondrial dysfunction, such as dry age-related macular degeneration and Leber's hereditary optic neuropathy. We are evaluating our second-generation clinical-stage candidate, SBT-272, and our new series of small molecules, SBT-550, for rare neurological disease indications following promising preclinical data. We have optimized our discovery platform to identify novel mitochondria-targeted compounds which may be nominated as therapeutic product candidates or utilized as mitochondria-targeted vectors to deliver other compounds to mitochondria.

Forward-Looking Statements

This press release contains forward-looking statements within the meaning of The Private Securities Litigation Reform Act of 1995. Such forward-looking statements include, but are not limited to, statements relating to preliminary clinical data. Statements that are not historical facts, including statements about Stealth BioTherapeutics' beliefs, plans and expectations, are forward-looking statements. The words "anticipate," "expect," "hope," "plan," "potential," "possible," "will," "believe," "estimate," "intend," "may," "predict," "project," "would" and similar expressions are intended to identify forward-looking statements, although not all forward-looking statements contain these identifying words. Stealth BioTherapeutics may not actually achieve the plans, intentions or expectations disclosed in these forward-looking statements, and you should not place undue reliance on these forward-looking statements. Actual results or events could differ materially from the plans, intentions and expectations disclosed in the forward-looking statements as a result of known and unknown risks, uncertainties and other important factors, including: those regarding Stealth BioTherapeutics' plans, strategies and expectations for its preclinical and clinical advancement of its drug development programs, including its ongoing clinical trials of elamipretide; whether results obtained in preclinical studies and clinical trials will be indicative of results that will be generated in future clinical trials; whether elamipretide will successfully advance through the clinical trial process on a timely basis, or at all; and whether the results of the company's clinical trials will warrant regulatory submissions and whether elamipretide will receive approval from the FDA or equivalent foreign regulatory agencies for GA, AMD, Barth syndrome or any other indication when expected or at all. These and other risks are described in greater detail under the caption "Risk Factors" included in the Stealth BioTherapeutics' most recent Annual Report on Form 20-F filed with the Securities and Exchange Commission ("SEC") on April 6, 2021, as well as in any future filings with the SEC.  Forward-looking statements represent management's current expectations and are inherently uncertain. Except as required by law, Stealth BioTherapeutics does not undertake any obligation to update forward-looking statements made by us to reflect subsequent events or circumstances.