Marathon Pharmaceuticals LLC said it would delay the U.S. launch of its expensive muscular-dystrophy drug amid mounting criticism of its $89,000-a-year price, including from two members of Congress who launched an investigation Monday, and a powerful Republican member of the House of Representatives.

In a statement posted on the website of a nonprofit group involved with muscular dystrophy, Marathon CEO Jeffrey Aronin said the company was “pausing our launch,” which had been scheduled for March. The company will meet with “caregivers and explain our commercialization plans, review their concerns, discuss all options, and move forward with commercialization based on an agreed plan of action,” he said in the statement.

The delay was also announced at a Monday meeting in Washington of parents of children with Duchenne muscular dystrophy, a rare disease affecting some 12,000 boys in the U.S.

Marathon received approval last week from the U.S. Food and Drug Administration to sell the drug, deflazacort, to patients with Duchenne. The drug hadn’t been available in the U.S. previously, but many patients had been importing it from the U.K. for about $1,200 to $1,600 annually. Some families had raised objections to the new price.

Catherine Collins, who spoke at Monday’s meeting and whose son, Dylan, 11, has Duchenne, accused Marathon of “predatory pricing. Enough, gross,” she said. Ms. Collins, of New York, says she pays between $800 and $1,000 a year now for deflazacort that she imports from overseas.