STEALTH BIOTHERAPEUTICS ANNOUNCES DATA FROM RECLAIM-2 PHASE 2 TRIAL OF ELAMIPRETIDE IN GEOGRAPHIC ATROPHY

Study did not meet primary endpoints of mean change in low luminance visual acuity (LLVA) and geographic atrophy (GA) progression

Categorical improvement in LLVA, with >15% of elamipretide-treated patients gaining 2+ lines of vision at Week 48

Elamipretide demonstrated enhanced ellipsoid zone preservation through reduction of progressive attenuation, an important indicator of photoreceptor loss.

Company to host conference call and webcast today at 8:30 a.m. ET

BOSTON, May 2, 2022 /PRNewswire/ -- Stealth Biotherapeutics (Nasdaq: MITO), a clinical-stage biotechnology company focused on the discovery, development and commercialization of novel therapies for diseases involving mitochondrial dysfunction, today announced top-line data from its Phase 2 ReCLAIM-2 trial evaluating elamipretide in patients with geographic atrophy (GA) secondary to dry age-related macular degeneration. Although the trial did not meet its primary endpoints assessing mean changes in LLVA and GA, a key secondary endpoint showed however that elamipretide categorically improved visual function for patients with GA. Additionally, elamipretide demonstrated proof of mechanism by reducing progressive ellipsoid zone loss, a key biomarker of retinal mitochondrial health which has been shown to be predictive of long-term GA growth and development. Based on these data, the Company currently plans to progress development initiatives intended to better position this indication for potential partnering consistent with previous guidance.

“The categorical improvement in LLVA is a potentially important finding for patients with GA, who experience increasing impairment in their daily functioning due to the otherwise progressive and irreversible vision loss that characterizes this disease,” said Jeffrey Heier, M.D., principal investigator of the ReCLAIM-2 study and director, retina service and director, retinal research, Ophthalmic Consultants of Boston. “This approach shows the possibility to improve visual function for patients with this devastating disease, and we look forward to the Company’s continued development efforts.”

ReCLAIM-2 was a randomized, double-masked, parallel-group, placebo-controlled trial to evaluate the efficacy and safety of elamipretide over 48 weeks in 176 patients with GA. Elamipretide improved LLVA relative to placebo, although the mean change (primary endpoint) was not statistically significant. Administration of elamipretide resulted in a 2 or more line gain in LLVA for greater than 15% of patients completing the 48-week trial (p=0.04). Although this improvement in visual function was not associated with reduced GA progression (primary endpoint), a significant reduction in ellipsoid zone loss (p=0.0034) was observed.

“We are excited by this finding that elamipretide resulted in reduction of progressive ellipsoid zone attenuation and may be a leading indicator for progression to more advanced disease,” said Justis P. Ehlers, M.D., Advanced OCT Analysis Director for ReCLAIM-2. “We believe that mitochondrial dysfunction plays an important role in AMD progression and ellipsoid zone loss on OCT is a potential important biomarker and endpoint for both intermediate AMD and evaluating long-term GA progression risk. Advanced technologies for enabling the quantification of these ellipsoid zone alterations provide new avenues for better evaluating treatment response and disease features.”

Elamipretide was generally well tolerated in ReCLAIM-2. Injection site reactions were the most commonly observed adverse events and in some cases led to early termination. The rate of new-onset exudations was 5% for patients treated with elamipretide versus 7% for patients treated with placebo.

“Although we are disappointed that the trial did not meet its primary endpoints, we are pleased to observe that elamipretide improved visual function for patients with GA, a finding we also saw in our Phase 1 ReCLAIM trial,” said Reenie McCarthy, CEO of Stealth BioTherapeutics. “We are also encouraged by this evidence that elamipretide is improving mitochondrial function in the retina, which may offer us important enrichment strategies as we consider pivotal trial design and, importantly, demonstrates in vivo proof of mechanism. We are committed to making a meaningful difference for patients living with dry AMD and other diseases of mitochondrial dysfunction, and we believe that this demonstration of elamipretide’s potential to improve mitochondrial health in older adults underscores the potential of our platform.”

Conference Call Information

Stealth will host a conference call and webcast today at 8:30 am ET to discuss the ReCLAIM-2 trial. The call can be accessed by dialing 1-877-407-0989 (toll free) or 1-201-389-0921 (international) and referencing conference ID 13729736. A live audio webcast of the event can be accessed by visiting the Investors & News section of Stealth’s Investor website, https://investor.stealthbt.com/. A replay of the webcast will be archived on Stealth’s website for 30 days following the event.

About Geographic Atrophy

Geographic atrophy (GA) is an advanced form of dry age-related macular degeneration (AMD), a leading cause of blindness. GA lesions affect the central portion of the retina, known as the macula, which is responsible for central vision. GA is progressive and irreversible, leading to central visual impairment and permanent loss of vision. Based on published studies, more than five million people have GA globally including an estimated two million people in the United States. There are currently no approved treatments for GA.

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 eye, the neuromuscular system, the heart and the brain. We believe our lead product candidate, elamipretide, has the potential to treat ophthalmic diseases entailing mitochondrial dysfunction, such as dry AMD, rare neuromuscular disorders, such as primary mitochondrial myopathy and Duchenne muscular dystrophy, and rare cardiomyopathies, such as Barth syndrome. We are evaluating our second-generation clinical-stage candidate, SBT-272, for rare neurological disease indications, such as amyotrophic lateral sclerosis and frontotemporal lobar dementia, 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 those regarding Stealth BioTherapeutics’ expectations for its clinical development of elamipretide for GA associated with dry AMD and other indications, the potential benefits of elamipretide and potential regulatory interactions. 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: Stealth BioTherapeutics’ ability to obtain additional funding and to continue as a going concern; the impact of the COVID-19 pandemic; the ability to successfully demonstrate the efficacy and safety of Stealth BioTherapeutics’ product candidates and future product candidates; the preclinical and clinical results for Stealth BioTherapeutics’ product candidates, which may not support further development and marketing approval; the potential advantages of Stealth BioTherapeutics’ product candidates; the content and timing of decisions made by the FDA, the EMA or other regulatory authorities, investigational review boards at clinical trial sites and publication review bodies, which may affect the initiation, timing and progress of preclinical studies and clinical trials of Stealth BioTherapeutics product candidates; Stealth BioTherapeutics’ ability to obtain and maintain requisite regulatory approvals and to enroll patients in its planned clinical trials; unplanned cash requirements and expenditures; competitive factors; Stealth BioTherapeutics’ ability to obtain, maintain and enforce patent and other intellectual property protection for any product candidates it is developing; and general economic and market conditions. 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”), 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.

Investor Relations
Kendall Investor Relations
Adam Bero, 617-914-0008
IR@StealthBT.com

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