Shares of Larimar Therapeutics Inc (NASDAQ:LRMR) jumped 32% in premarket trading on Tuesday following an FDA decision to grant Breakthrough Therapy Designation to nomlabofusp for the treatment of Friedreich's ataxia. The designation is intended to accelerate development and regulatory review for therapies addressing serious conditions.
The FDA's decision was based on preliminary data from Larimar's ongoing open-label study. According to the company, the study showed increases in skin frataxin to levels expected in asymptomatic carriers. In addition, Larimar reported consistent directional improvement across four clinical outcome measures after one year of treatment: the modified Friedreich Ataxia Rating Scale score, FARS-Activities of Daily Living, the 9 Hole Peg Test, and the Modified Fatigue Impact Scale.
Larimar said it has continued alignment with the FDA following a recent START pilot program meeting. Regulators indicated willingness to consider skin frataxin as a novel surrogate endpoint that could support a Biologics License Application submission seeking accelerated approval. The agency also agreed on the relevant clinical outcomes and the analyses needed to characterize exposure-response relationships.
Under the current timetable provided by the company, Larimar is targeting submission of a BLA in June 2026. Topline results from the open-label study are expected in the second quarter of 2026. If the pathway succeeds to approval, the company aims to launch nomlabofusp in the United States in the first half of 2027.
The FDA noted that the adequacy of the safety database will be evaluated at the time of BLA submission. Regulators also confirmed that the Upright Stability Score is a reasonable choice for the primary endpoint in the planned Phase 3 confirmatory study.
Nomlabofusp is a frataxin protein replacement therapy developed for adults and children with Friedreich's ataxia. The condition is a rare disease estimated to affect approximately 5,000 people in the United States. Larimar plans to begin screening for its global Phase 3 study in the second quarter of 2026, with first patient dosing expected in mid-2026.
Context and next steps
The Breakthrough Therapy Designation reflects preliminary clinical findings that the FDA judged sufficient to warrant an expedited development path. Larimar's near-term milestones include reporting topline open-label data in Q2 2026, initiating Phase 3 screening in Q2 2026, dosing the first Phase 3 patient by mid-2026, and preparing a BLA submission targeted for June 2026. The company and the agency will review safety data as part of the BLA assessment, and the Upright Stability Score will serve as the Phase 3 primary endpoint.
These regulatory interactions and planned timelines set a sequence of milestones investors and stakeholders will monitor closely over the next year.