The FDA has placed Larimar Therapeutics’ phase 1 trial of its experimental Friedrich’s ataxia drug, CTI-1601, on clinical hold, a significant setback for the company as the recombinant fusion protein is the only drug candidate in its pipeline.

The clinical hold on the single-dose human trial came about following Laramar’s alert to the FDA that primates had died in an ongoing 180-day nonhuman primate (NHP) toxicology study designed to support the extended dosing of patients with its drug candidate.

The FDA’s clinical hold letter stated that the agency requires a full study report from that ongoing toxicology study and until the agency reviews the report and gives the OK, Larimar may not move forward with any additional clinical trials, according to the company.