Stealth BioTherapeutics Granted Pre-NDA Meeting For Elamipretide As A Treatment For Cardiomyopathy In Barth Syndrome

Date : January 6, 2021

BOSTON, Jan. 5, 2021 /PRNewswire/ -- 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 its plan to meet with the FDA's Division of Cardiology and Nephrology (DCN) regarding its upcoming NDA submission for elamipretide for the treatment of cardiomyopathy in Barth syndrome.

This Type B Pre-NDA meeting follows prior interactions in 2019 with the Division of Neurology Products (DNP) and in 2019 and 2020 with the Division of Rare Disease and Medical Genetics (DRDMG) during which the Agency encouraged the Company to generate additional clinical data to support its Barth NDA submission, including by implementing a withdrawal protocol for the patients remaining on open-label extension. More recently, the Company met with DCN to discuss an NDA submission for the treatment of cardiomyopathy in Barth syndrome, which included a discussion of cardiac-focused protocol designs.  During this meeting, DCN suggested that, based on the short half-life of elamipretide, a short-term withdrawal period could be sufficient to measure durable effect on functional or structural cardiac endpoints by demonstrating that improvement is not dependent on continuous exposure to the drug.  Although DCN reiterated the prior feedback from DRDMG regarding the insufficiency of the current data package for NDA submission, the Company believes that the existing data with additional analyses could meet the requirements for an NDA.  The Company is proposing that a short-term withdrawal protocol for open-label extension participants be conducted in parallel with NDA review and that a larger Phase 3b/4 withdrawal study in treatment-naïve patients be completed as a post-marketing confirmatory study.  The Company plans to discuss this and other aspects of the anticipated NDA submission during the Pre-NDA meeting next month.

"We are encouraged by the agency's acceptance of our Pre-NDA meeting request," said Reenie McCarthy, chief executive officer of Stealth. "We are keenly aware of the urgent unmet need facing the Barth syndrome community as described in the recent petition signed by over 4,000 members of the Barth community and addressed to the FDA and us.  We view this upcoming meeting as an important next step toward our goal of bringing elamipretide to patients suffering from this ultra-rare disease and hope that it may also inform our future development efforts in other rare cardiomyopathies." 

About the Company's Barth Development Program

SPIBA-201 was a Phase 2/3 double-blind, placebo-controlled crossover trial in which 12 subjects with Barth syndrome received elamipretide or placebo during one of two 3-month treatment periods (Part 1) followed by an open-label extension to evaluate long-term trends in efficacy (Part 2).  Although statistically significant improvements in distance walked on the six-minute walk test (6MWT) and fatigue were not observed after 3-months of therapy, improvements were observed in biomarkers of cardiac function, including medium-chain acylcarnitines which are known to be elevated in Barth syndrome and in other forms of heart failure, and, for 10 of the 12 subjects, in echocardiographic parameters following elamipretide therapy.  Notably, in the context of the proposed withdrawal protocols discussed with DCN, the improvements in cardiac function appeared to persist and, in some cases, increase following discontinuation of elamipretide therapy in the subset of participants that were crossed over to placebo during Part 1, consistent with what has been previously observed in several preclinical models.  During Part 2, improvements were observed in all primary and secondary endpoints including a >100-meter increase in 6MWT distance, an increase in left ventricular volumes, which were severely reduced at baseline, and a reduction for all subjects in the ratio of abnormal to normal cardiolipin (MLCL:CL ratio), which is diagnostic for the disease.

SPIBA-001 was a pivotal Phase 3 non-interventional trial which compared long-term interventional data from SPIBA-201 Part 2 with prognostically matched natural history controls.  The data demonstrated that the elamipretide-mediated improvements in 6MWT and certain secondary endpoints including left ventricular stroke volume would not be expected in the natural course of the disease. 

Conference Call

Management will host a conference call tomorrow at 8:30 am ET to provide additional detail regarding its preliminary interactions with DCN and anticipated NDA submission timelines. The call can be accessed by dialing (877) 407-0989 or (201) 389-0921 (international) and referencing conference ID 13714601. A live audio webcast of the event can be accessed by visiting the Investors & News section of Stealth's Investor website, A replay of the webcast will be archived on Stealth's website for 30 days following the event.

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, such as POLG-related disorders, 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 scaffolds 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' plans, strategies and expectations for its clinical advancement of its drug development programs, including its plans for the potential submission of an NDA and the potential benefits of Stealth BioTherapeutics' product candidates.  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 U.S. 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.

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