– Data from Phase 1 dose escalation trial will inform planned Phase 2 trial for dry AMD –

NEEDHAM, Mass., April 27, 2026 /PRNewswire/ — Stealth BioTherapeutics (the “Company” or “Stealth”), a commercial-stage biotechnology company focused on the discovery, development, and commercialization of novel therapies for diseases involving mitochondrial dysfunction, today announced that it has completed enrollment in its Phase 1 dose escalation trial evaluating the safety, tolerability, and pharmacokinetics of bevemipretide eye drops. These data are intended to inform further development of bevemipretide, the Company’s second-generation investigational mitochondrial-targeted therapeutic candidate, for the noninvasive treatment of dry age-related macular degeneration (AMD). Preliminary results from both the single ascending dose (SAD) and multiple ascending dose (MAD) parts of the trial will be presented at the 2026 Association for Research in Vision and Ophthalmology (ARVO) Annual Meeting, to be held on May 3-7 in Denver, Colo.

“Vision loss in dry AMD is caused by progressive and irreparable photoreceptor loss, making early intervention critical for protecting vision,” said David R. Lally, MD, FASRS, Director of the Retina Research Institute at New England Retina Consultants and Clinical Assistant Professor at the UMass Chan Medical School-Baystate. “A noninvasive eye-drop therapy has the potential to improve patient adoption and adherence earlier in trajectory of this progressive disease. I look forward to the potential that this much-needed investigational treatment option brings to patients with dry AMD.”

“Completion of our bevemipretide Phase 1 dose escalation trial is a significant milestone as we work toward initiating development of bevemipretide eye drops for devastating ophthalmic conditions including dry AMD,” said Reenie McCarthy. “We are committed to advancing innovative mitochondrial-targeted treatments that have the potential to improve outcomes and quality of life for patients.”

Stealth’s ARVO presentation is as follows:
Poster: “Bevemipretide Eye Drops for Dry AMD: A Phase 1 Dose Escalation Trial to Evaluate Safety, Tolerability, and Pharmacokinetics”

• Posterboard Number: 145 – 0175
• Presenter: Anthony Abbruscato, Pharm.D., Senior Vice President of Clinical Development, Stealth BioTherapeutics
• Presentation Time: May 3, 2026 from 8:00 AM to 9:45 AM
• Location: Poster Hall
• Session 106: “AMD: New drugs, delivery systems, and mechanisms of action I”

The Company expects that the final results from the Phase 1 trial will be presented by Dr. Lally at 2026 ASRS. The Company is actively working to initiate a Phase 2 trial of bevemipretide eye-drops for dry AMD in late 2026.

About the Bevemipretide Phase 1 Dose Escalation Trial
Bevemipretide, a mitochondrial cardiolipin binder, is an investigational drug being developed as an eye drop that reaches key retinal cells including the retinal pigment epithelium and photoreceptors to offer a noninvasive treatment option for dry AMD. The Phase 1 trial of bevemipretide in healthy volunteers is designed to determine an appropriate safe and tolerable concentration range of bevemipretide to be used in subsequent clinical studies in patients with dry AMD and other ophthalmic conditions.

In this Phase 1 single ascending dose (SAD) and 28-day multiple ascending dose (MAD) escalation trial, Part A consists of three SAD cohorts of six healthy volunteers each, receiving one drop of topical bevemipretide (1%, 2%, or 3%) or vehicle, randomized by participant to their trial eye or fellow eye. After each cohort, safety assessments and PK samples will be analyzed to determine the dosing regimen for Part B, which consists of three MAD cohorts of eight participants each, randomized in a 3:1 ratio to receive one drop of topical bevemipretide (1%, 2%, or 3%) or vehicle into both eyes, once or twice daily.

About Dry AMD
Dry AMD is the leading cause of blindness among older adults in the developed world. Common symptoms such as distorted vision, reduction in low luminance visual acuity, reduced overall visual acuity, and blurred vision. Dry AMD is estimated to affect more than 10 million individuals in the United States. Mitochondrial dysfunction is believed to be a significant contributor to the progression of dry AMD, making the mitochondrial network an attractive target to improve retinal function and mitigate disease burden in this patient population. There are no FDA or EMA approved treatments for the treatment of dry AMD.

About Stealth BioTherapeutics
The Company’s mission is to develop novel therapies to improve the lives of patients living with diseases of mitochondrial dysfunction. The Company’s first commercial product was granted accelerated approval by the U.S. Food & Drug Administration (FDA) in September 2025. The Company is studying elamipretide in additional indications, including dry age-related macular degeneration and primary mitochondrial disease due to nuclear DNA mutations, including in polymerase gamma, and is developing its next-in-class clinical-stage candidate, bevemipretide, for ophthalmic and neurological disease indications. The Company’s preclinical pipeline candidates include SBT-589 and SBT-255, which are both progressing through developmental milestones.

Stealth Media Contact
Ascent Strategic Communications
Anna Stallmann
anna@ascentcomms.com

Stealth Investor Contact
Precision AQ
Austin Murtagh
Austin.Murtagh@precisionaq.com

Stealth Patient Advocacy
Patient.Advocacy@stealthbt.com

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SOURCE Stealth BioTherapeutics Inc.