Stealth BioTherapeutics Expands Pipeline, Advances New Compound

Stealth BioTherapeutics accelerates the development of a new pipeline candidate into Investigational New Drug enabling studies by leveraging Evotec's INDiGO platform

BOSTON,Aug. 15,2018 --Stealth BioTherapeutics (Stealth),a clinical-stage biopharmaceutical company developing a first-in-class platform of novel therapeutic compounds for the treatment of diseases associated with mitochondrial dysfunction,announced today that it is advancing a new pipeline candidate into investigational new drug (IND) enabling studies in collaboration with long-term partner Evotec AG.

Stealth's nomination of this novel pipeline candidate marks the culmination of a development initiative resulting in a diverse proprietary pipeline of compounds for the treatment of mitochondrial dysfunction arising in the context of both genetic mitochondrial diseases as well as age-related diseases. Stealth's lead candidate,elamipretide,has received Orphan Drug and Fast Track designation with respect to late stage clinical development efforts in primary mitochondrial myopathy (PMM),Barth syndrome and Leber's hereditary optic neuropathy (LHON).Stealth is also developing elamipretide for dry age-related macular degeneration,the leading cause of blindness in the elderly.With this new pipeline candidate progressing toward IND,Stealth hopes to broaden its therapeutic horizons to address other areas of unmet medical need.

"We believe that our first-in-class mitochondrial medicines offer a novel approach to the treatment of human disease," said Reenie McCarthy,chief executive officer of Stealth. "We hope to utilize our deep knowledge of mitochondrial therapeutics to improve the treatment paradigm for patients suffering from genetic diseases involving mitochondrial dysfunction,as well as to potentially extend health span in the context of age-related diseases to which mitochondrial dysfunction is a known contributor."

Stealth expects to advance its new pipeline candidate to clinical-stage studies by the end of 2019 utilizing Evotec's INDiGO platform. INDiGO is a market-leading integrated drug development solution that accelerates early drug candidates into the clinic by reducing time from nomination to IND submission,typically in less than 52 weeks. Under the terms of the collaboration,Evotec will be responsible for all preclinical and toxicology/safety studies ahead of clinical trials in 2019.

"Our team at Stealth evaluated all options to help support the progression of our newest pipeline candidate through IND filing,and we are confident that Evotec,with its INDiGO platform and the team of experts they have assembled,is the best option to ensure the rapid and high-quality advancement of the compound," said Mark Bamberger,chief scientific officer of Stealth.

"Our INDiGO platform reduces time and cost while consistently producing a quality data package for clinical trial agreements and investigational new drug filings," said Dr. Mario Polywka,chief operating officer of Evotec. "We have a great scientific and personal relationship with Stealth and are excited for the opportunity to continue to help advance their programs."

About Stealth

We are a privately held clinical-stage biotechnology company focused on the development of therapeutics for diseases involving mitochondrial dysfunction. We believe there is a strong rationale for our lead product candidate,in indications in these diseases based on encouraging preclinical and early clinical data. We are investigating elamipretide in three primary mitochondrial diseases – primary mitochondrial myopathy (PMM),Barth syndrome and Leber's hereditary optic neuropathy (LHON) – for which we have both Fast Track and Orphan Drug designation. We are also investigating elamipretide in dry age-related macular degeneration,the leading cause of blindness in the elderly.We have a broad pipeline of novel mitochondria-targeting compounds we are evaluating for new indications,including neurodegenerative diseases.To learn more information about us and our pipeline,visitwww.stealthbt.com.

About Evotec AG

Evotec is a drug discovery alliance and development partnership company focused on rapidly progressing innovative product approaches with leading pharmaceutical and biotechnology companies,academics,patient advocacy groups and venture capitalists. We operate worldwide providing the highest quality stand-alone and integrated drug discovery solutions,covering all activities from target-to-clinic to meet the industry's need for innovation and efficiency in drug discovery. The INDiGO platform is a key value-generating component of Evotec's broad EVT Execute business and represents a logical extension of its broad discovery platform. INDiGO accelerates early drug candidates into the clinic by reducing time from nomination to regulatory submission in 52 weeks,and under certain circumstances,even less. Accelerated development is achieved by tightly integrating traditional drug development activities into a single project managed under one roof. The program has been proven to reduce time and cost while achieving a quality data package for CTA/IND level regulatory filings. The scale of this capability means that Evotec works on 10-15 INDiGO's at any one time. For additional information please go to www.evotec.com and follow us on Twitter @EvotecAG.

Forward Looking Statements

Information set forth in this press release contains forward-looking statements,which involve a number of risks and uncertainties. The forward-looking statements contained herein represent the judgement of Evotec as of the date of this press release. Such forward-looking statements are neither promises nor guarantees,but are subject to a variety of risks and uncertainties,many of which are beyond our control,and which could cause actual results to differ materially from those contemplated in these forward-looking statements. We expressly disclaim any obligation or undertaking to release publicly any updates or revisions to any such statements to reflect any change in our expectations or any change in events,conditions or circumstances on which any such statement is based.

Media Relations

dna Communications

Kate Contreras,617-520-7088

Media@StealthBT.com

Investor Relations

Stern IR

Rachel Frank,212-362-1200

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