Sarepta’s early-stage clinical trial for a gene therapy for Duchenne muscular dystrophy is back on schedule, the Cambridge biotech said Monday. The Food and Drug Administration had put the trial on hold in July.

The FDA ordered the hold after small fragments of DNA turned up in the treatment, which is being used at Nationwide Children’s Hospital in Columbus, Ohio. The contaminated lot was never used in patients, but the company said it would switch to a clinical-grade supplier for plasmids.

The treatment is meant to increase the amount of a protein called microdystrophin — a smaller version of the dystrophin gene that people with Duchenne lack — throughout the body.

“We have been able to address the clinical hold in record time and without delay to this profoundly important clinical program,” Doug Ingram, Sarepta’s president and chief executive officer, said in a statement.

The company expects to start a registered clinical trial with the therapy — an important step toward an FDA decision — by the end of the year.

Before the hold, Sarepta’s trial had been using research-grade plasmids. The lot with these particular plasmids hadn’t been used in any patients, but four people had received a dose made using a different lot from the same supplier. No issues linked with those treatments had been reported in July.

The FDA, Sarepta, and Nationwide Children’s Hospital did not immediately reply to a request for comment.