Larimar Stock Plummets 28% on Allergic Reactions in Ataxia Drug Trial

Shares of Larimar Therapeutics (NASDAQ: LRMR) plunged nearly 28% in heavy trading after the company revealed that patients in a pivotal study for its Friedreich's ataxia drug candidate, nomlabofusp, experienced severe allergic reactions.

The sharp sell-off was triggered by an update on the company's ongoing long-term, open-label study, where , a serious and potentially life-threatening allergic reaction. All seven patients were subsequently withdrawn from the trial. According to the company, the events were resolved with standard treatment and all participants returned to their usual state of health.

This development casts a significant shadow over the safety profile of nomlabofusp, Larimar's lead asset. The company is developing the therapy to treat Friedreich's ataxia, a rare, inherited disease that causes progressive nervous system damage and movement problems. The news was first highlighted in a report noting .

In response to the safety events, Larimar announced it has amended the study's protocol after consulting with the U.S. Food and Drug Administration (FDA). The new regimen includes administering premedication for the first month of dosing and using a lower initial test dose to . While the company stated that such reactions are a known risk for protein-based therapies, the frequency in the study alarmed investors, driving trading volume to over four times the daily average.

This is not the first time safety concerns have emerged for nomlabofusp. A patient in a previous also experienced a severe allergic reaction and was withdrawn from that trial. While Larimar noted that daily administration of the drug has been generally well-tolerated by other long-term participants, the repeated instances of anaphylaxis create a significant hurdle for the drug's path to potential regulatory approval and commercial viability.