Stealth Bio's FORZINITY Launch Marks New Era for Mitochondrial Medicine

NEEDHAM, Mass. – January 06, 2026 – Stealth BioTherapeutics has officially entered the commercial arena, announcing that its landmark drug, FORZINITY™ (elamipretide), is now available for U.S. patients battling the rare and devastating genetic disorder, Barth syndrome (BTHS). The move follows the U.S. Food and Drug Administration's (FDA) accelerated approval of the drug in September 2025, marking a pivotal moment for the company and a long-awaited breakthrough for a patient community that has never had an approved therapy.

This commercial launch represents a critical transition for the biotechnology firm, which is now balancing the complex logistics of bringing its first product to market with an ambitious research and development agenda. The company's strategy hinges on leveraging its lead compound, elamipretide, to tackle a spectrum of diseases rooted in mitochondrial dysfunction, from ultra-rare conditions like Barth syndrome to widespread age-related ailments like dry age-related macular degeneration (AMD).

"Since receiving accelerated approval for FORZINITY in September, we've built a robust commercial foundation and are working closely with prescribers and payers to ensure access for eligible patients with Barth syndrome," said Reenie McCarthy, Chief Executive Officer of Stealth BioTherapeutics, in a statement. "We remain committed to accelerating innovation across our pipeline to address urgent unmet needs in rare and age-related diseases of mitochondrial dysfunction."

A Watershed Moment for a Rare Disease

For the small community of individuals affected by Barth syndrome, the availability of FORZINITY is nothing short of historic. BTHS is an ultra-rare genetic condition that primarily affects males and is characterized by mitochondrial abnormalities leading to severe muscle weakness, debilitating fatigue, heart failure, and a significantly reduced life expectancy. With no previously approved treatments, management has been purely supportive.

FORZINITY, a mitochondrial cardiolipin binder designed to improve the function of cellular powerhouses, was approved to improve muscle strength in BTHS patients weighing at least 30 kg (approximately 66 pounds). The approval provides a tangible therapeutic option that targets the underlying cellular dysfunction of the disease. The news has been described by clinicians involved in the field as an emotional and pivotal victory for families who have navigated the disease's challenges for decades without a targeted therapy.

However, the celebration is tempered by a remaining unmet need. The current approval's weight threshold excludes many younger and smaller children who are often severely affected by the disease. Stealth has acknowledged this gap and confirmed it will meet with the FDA in early 2026 to discuss a regulatory path forward for this younger population. In the interim, the company has committed to providing uninterrupted access to elamipretide for these children through its expanded access program (EAP).

Navigating the Commercial Landscape

Bringing a first-in-class drug for an ultra-rare disease to market is a formidable challenge. Stealth has established a specialized infrastructure to manage this process, partnering with AnovoRx Specialty Pharmacy as the exclusive U.S. distributor. Prescriptions began being filled in December 2025, and the company reports that early demand from physicians has already exceeded its internal expectations.

In a potentially significant finding, the company noted that preliminary data suggests the use of diagnostic codes for BTHS may meaningfully exceed prior U.S. patient prevalence estimates, which stood at approximately 150 individuals. This could indicate a larger-than-anticipated addressable market, though further data will be needed to confirm this trend.

To facilitate patient access, Stealth has launched Mito Assist™, a comprehensive support program designed to help patients and providers navigate the complexities of insurance coverage and reimbursement. Such programs are critical for rare disease therapies, which often carry high price tags and require extensive documentation for payer approval. The company has already engaged with pharmacy benefit providers covering over 40% of U.S. lives to educate them on the therapy's value proposition.

A Pipeline with Broader Ambitions

While the FORZINITY launch is the immediate focus, Stealth's long-term strategy is anchored in its broader R&D pipeline. The company is positioning itself as a leader in the burgeoning field of mitochondrial medicine, exploring the potential of its compounds across multiple indications.

Elamipretide itself is being evaluated for other conditions. The company plans to meet with the FDA in early 2026 to discuss a development path for primary mitochondrial disease (PMD) due to nDNA mutations, which could become the drug's next rare disease indication. Farther afield, a fully enrolled Phase 3 trial is testing elamipretide in patients with dry AMD, a leading cause of vision loss in older adults. The results from this trial, expected in late 2027, represent a major potential catalyst for the company, promising a gateway into a vastly larger market.

Beyond elamipretide, Stealth is advancing a next-in-class compound, bevemipretide. An eye drop formulation is in development for dry AMD, with plans to initiate a Phase 2 trial by the end of 2026. Simultaneously, a systemic formulation of bevemipretide has shown promise in preclinical studies for Parkinson's disease, demonstrating neuroprotective effects in research supported by the Michael J. Fox Foundation. This dual-pronged approach highlights the platform's versatility in targeting mitochondrial dysfunction whether it manifests in the eye or the brain.

The Promise and Perils of Accelerated Approval

FORZINITY's journey to market utilized the FDA's accelerated approval pathway, a program designed to speed the availability of drugs for serious conditions with unmet needs. This pathway allows for approval based on a surrogate endpoint—in this case, an improvement in knee extensor muscle strength—that is considered reasonably likely to predict a real clinical benefit to patients.

While this mechanism provides earlier patient access, it comes with a significant string attached: the company must conduct post-marketing confirmatory trials to verify that the improvement in muscle strength translates into a tangible clinical benefit, such as improved mobility or quality of life. Continued FDA approval is contingent on the success of this trial.

Stealth is on track to initiate this FDA-required confirmatory study in the first half of 2026. Successfully completing such trials can be challenging, as patient recruitment can be difficult once a drug is commercially available. However, demonstrating definitive clinical benefit is crucial for securing long-term reimbursement and solidifying the drug's place in the standard of care. The increased regulatory scrutiny on the timely completion of these studies adds pressure on companies like Stealth to execute flawlessly.

The coming year will be a critical test of the company's dual strategy. Its ability to successfully scale the commercial launch of FORZINITY while simultaneously advancing its diverse and ambitious pipeline will determine its trajectory in the competitive biotech landscape and its ultimate impact on the burgeoning field of mitochondrial medicine.