CytRx Corp. said Monday that the Food and Drug Administration wants more data from an early animal toxicology study before the company’s human clinical trial of a drug for Lou Gehrig’s disease can resume.

The Food and Drug Administration told the Los Angeles drug developer to halt its study of arimoclomol last month. Lou Gehrig’s disease, also known as amyotrophic lateral sclerosis or ALS, has no cure or treatment.

The FDA’s decision pertained to concerns from a study in rats and wasn’t related to data generated from any human trials, the Los Angeles-based biotech company said in a statement, citing a letter from the agency that clarified its concerns.

CytRx said it is analyzing the data to prepare a response to the FDA’s concerns. It may also conduct toxicology studies before, or at the same time as, resumption of the Phase IIb trial.

Shares in CytRx lost 6.2 percent to $2.12 in early trading Monday on the Nasdaq.