Stealth BioTherapeutics

What Stealth BioTherapeutics does

Stealth BioTherapeutics, which rebranded to Mighty Therapeutics in 2025-2026, is a clinical-stage and now early-commercial biopharmaceutical company developing mitochondria-targeted therapeutics for rare genetic and age-related diseases of mitochondrial dysfunction. The company's core technology is a proprietary platform of small molecules designed to localize to mitochondria and improve mitochondrial function, with elamipretide (branded FORZINITY) as the lead asset. FORZINITY received FDA accelerated approval on September 19, 2025, as the first-ever approved treatment for Barth syndrome, an ultra-rare genetic condition affecting approximately 150 individuals in the United States. The clinical pipeline includes bevemipretide eye drops for dry age-related macular degeneration (Phase 1 enrollment complete, Phase 2 planned for late 2026), SBT-255 for cardiac conditions, SBT-272 for dry AMD (Phase 1 results shared at ARVO 2025), and SBT-589 for neurological disorders including Leigh syndrome (preclinical, supported by an MRC Business Engagement Fund grant awarded in 2026).

The company monetizes its lead product through a specialty pharmaceutical distribution model. FORZINITY is priced at up to approximately $800,000 annually per patient, reflecting the ultra-rare disease pricing paradigm. Exclusive US distribution is handled through AnovoRx Specialty Pharmacy (commercial availability from December 2025), supported by the Mito Assist patient financial assistance program. Revenue streams are therefore concentrated in pharmaceutical product sales for an ultra-rare indication, with the broader pipeline representing optionality on future indications. The customer base is composed entirely of patients with ultra-rare mitochondrial diseases — initially Barth syndrome, with potential expansion into POLG1-related disease, Leigh syndrome, dry AMD, and cardiac conditions of mitochondrial dysfunction. The company is headquartered in Newton, Massachusetts, employs 51-100 people, and has raised approximately $171M+ in disclosed funding rounds led by Morningside Ventures and Pivotal bioVenture Partners.

Name

Stealth BioTherapeutics

Legal name

Stealth BioTherapeutics Inc.

Website

https://mightytx.com/

Company type

Private

Founded year

2007

Operating status

Operating

Headcount range

51–100 employees

Short description

Stealth BioTherapeutics (now Mighty Therapeutics) is a clinical-stage biopharmaceutical company developing mitochondria-targeted therapeutics for ultra-rare genetic and age-related diseases, with FDA-approved FORZINITY (elamipretide) for Barth syndrome and a pipeline spanning dry AMD, cardiac, and neurological indications.

Ownership category

akta.pro rank

Product category

Mitochondrial Therapeutics

NAICS

Biological Product (except Diagnostic) Manufacturing (325414), Research and Development in Biotechnology (except Nanobiotechnology) (541714)

SIC

Pharmaceutical Preparations (2834)

akta.pro primary industry

Genetic & Genomic Rare Disease Therapeutics (HLAIAIAA)

akta.pro secondary industries

Rare Ophthalmology Disorder Therapies (HLAIAIAK), Enzyme Replacement & Metabolic Disorder Therapies (HLAIAIAB)

Keywords

• Mitochondrial therapeutics
• Rare disease drugs
• Mitochondria-targeted medicine
• Ultra-rare disease treatment
• Ophthalmic drug development

Headquarters

HQ city

Newton

HQ country

United States

HQ region

North America

Markets served

GTM type

B2B

Offering type

Hardware or Manufacturing

Cost components

Technology or R&D, Personnel, Operations, Marketing or Sales, Supply Chain

Revenue model

1. Pharmaceutical Product Sales: Revenue from commercial sale of FDA-approved drug Forzinity (elamipretide) for Barth syndrome, distributed through specialty pharmacy partners.

Pricing tiers

Go-to-market motion1 record

Distribution channels1 record

Marketing channels3 records

Core offering

Stealth BioTherapeutics (now Mighty Therapeutics) is a clinical-stage biopharmaceutical company developing mitochondria-targeted therapeutics for ultra-rare genetic mitochondrial diseases and age-related conditions. Its lead approved product is FORZINITY (elamipretide), the first FDA-accelerated approved treatment for Barth syndrome, with a clinical pipeline including bevemipretide eye drops for dry AMD and earlier-stage candidates (SBT-255, SBT-589, SBT-272) targeting cardiac, neurological, and ophthalmic conditions associated with mitochondrial dysfunction.

Product overview

Stealth BioTherapeutics (now Mighty Therapeutics) is a mitochondrial medicine company with a focused pipeline targeting mitochondrial dysfunction across rare and age-related diseases. The company's approved product is FORZINITY (elamipretide), which received FDA accelerated approval in September 2025 as the first treatment for Barth syndrome. The clinical pipeline includes bevemipretide eye drops for dry age-related macular degeneration (Phase 1 completed enrollment, Phase 2 planned for late 2026), SBT-255 for cardiac conditions, SBT-589 for neurological disorders including Leigh syndrome (with MRC grant support), and SBT-272 for dry AMD. The company supports patients through its Mito Assist patient assistance program.

Differentiator

Problem solved

Functional benefit

Brands

• Mito Assist™: Patient support program providing support and financial assistance to patients with Barth syndrome receiving FORZINITY treatment.
• FORZINITY™

Products and services

• FORZINITY (elamipretide) FDA-accelerated approved injectable therapy indicated for Barth syndrome. It is the first-ever approved mitochondria-targeted therapeutic, addressing an ultra-rare genetic condition with no prior disease-modifying treatment options. Distributed via specialty pharmacy to prescribing physicians for affected patients.
• Bevemipretide Eye Drops Clinical-stage non-invasive ophthalmic formulation for dry age-related macular degeneration (dry AMD), a condition affecting approximately 10 million individuals in the United States with no FDA- or EMA-approved treatments currently available.
• SBT-255 Pipeline compound in development for cardiac conditions associated with mitochondrial dysfunction.
• SBT-589 Pipeline candidate being evaluated in preclinical studies for neurological disorders, including Leigh syndrome, under an MRC-funded research collaboration.
• SBT-272 Clinical candidate for dry age-related macular degeneration with Phase I results shared at ARVO 2025.
• Mito Assist Patient support program offering financial assistance and support services to patients with Barth syndrome prescribed FORZINITY.

Quantifiable outcome

• Phase 3 NuPOWER results supporting elamipretide in POLG1-related mitochondrial disease
• +1 more outcomes

Named customers1 record

Segments2 records

Ideal customer profiles3 records

Technology focussed Yes

API detail

Has API

No

API docs

API detail

Core technology

AI maturity

App detail

Feature5 records

Partnerships

Four partnerships are on record, tiered core and major.

• UK Medical Research Council (MRC)coreStrategic or Co-development Partner · 23 March 2026Awarded MRC Business Engagement Fund grant to support preclinical evaluation of SBT-589 in mouse models of Leigh syndrome. Part of broader efforts to accelerate clinical translation of mitochondrial therapies.
• Mary Lyon Centre at MRC HarwellmajorStrategic or Co-development Partner · 23 March 2026Research collaboration partner for preclinical evaluation of SBT-589 in mouse models of Leigh syndrome, part of MRC National Mouse Genetics Network.
• University College LondonmajorStrategic or Co-development Partner · 23 March 2026Academic research partner collaborating on mitochondrial disease research including preclinical evaluation of SBT-589 and prior clinical research in primary mitochondrial myopathy.
• AnovoRx Specialty PharmacycoreChannel Partner/ Reseller/ Distributor · 9 October 2025Exclusive commercial distribution partner for FORZINITY (elamipretide) injection in the United States. Commercial product availability expected from December 2025 through this specialty pharmacy channel.

Scale indicators5 records

Recent moves7 records

Expansion highlights6 records

Emerging players

• Iveric Bio (Astellas): Developed an FDA-approved complement inhibitor for geographic atrophy in dry AMD, now part of Astellas. Direct competitive overlap with Stealth BioTherapeutics' bevemipretide dry AMD program.
• Homology Medicines: Clinical-stage genetic medicines company developing treatments for rare genetic diseases using proprietary platform technology. Comparable in platform-based approach to addressing rare genetic conditions with limited treatment options.
• Mereo BioPharma: Clinical-stage biopharmaceutical company focused on rare diseases with a pipeline of specialty therapeutics. Comparable ultra-rare disease focus and small-cap clinical development approach.
• Apellis Pharmaceuticals: Focused on complement inhibition therapies with an approved treatment for geographic atrophy secondary to dry AMD. Direct competitor in the dry AMD space where Stealth BioTherapeutics' bevemipretide is being developed.

Direct peers

• BioMarin Pharmaceutical: Specialized rare disease biopharmaceutical company with multiple approved enzyme replacement and gene therapy products. Comparable in business model of developing and commercializing ultra-rare disease therapeutics at premium prices through specialty distribution.
• Ultragenyx Pharmaceutical: Focused exclusively on rare and ultra-rare genetic diseases with multiple approved products and a deep clinical pipeline. Highly comparable target patient populations and ultra-rare disease commercialization approach to Stealth BioTherapeutics.
• Amicus Therapeutics: Develops therapies for rare metabolic diseases including Pompe and Fabry disease using proprietary biologics and small molecules. Comparable in targeting rare genetic metabolic disorders with disease-modifying mechanisms.
• PTC Therapeutics: Rare disease biopharmaceutical company with approved products for Duchenne muscular dystrophy and other genetic disorders. Comparable rare disease pipeline strategy and use of accelerated regulatory pathways.
• Sarepta Therapeutics: Specializes in genetic medicines for rare neuromuscular diseases with premium-priced approved products. Comparable business model of developing first-in-class therapies for small rare disease populations under accelerated regulatory pathways.

Broad incumbents

• Reata Pharmaceuticals: Developed novel mitochondria-targeted therapies (bardoxolone) for rare diseases including Alport syndrome, now part of Biogen. Closest historical peer in the mitochondrial-targeted therapeutics category, validating the commercial viability of this mechanism.

Market position

Strengths5 records

Weaknesses5 records

Competitive moat4 records

Key risks7 records

Key highlights7 records

Customer concentration

• Xx.com/StealthBT

Revenue estimate

Valuation estimate

Number of profiles

Profiles5 records

Funding overview

Funding rounds9 records

Investors10 records

Funding detail is available on the Subscription and Enterprise plan.Contact sales →

M&A

Investments

M&A and investment is available on the Subscription and Enterprise plan.Contact sales →

Frequently asked questions about Stealth BioTherapeutics