Turing Pharmaceuticals’ effort to charge $750 a pill for a 62-year-old drug is facing a new headwind: The nation’s largest prescription drug manager plans to back an alternative that costs only $1 per pill.

The prescription drug manager, Express Scripts, was expected to announce on Tuesday that it will promote use of a compounded medicine that contains the same active ingredient as the Turing drug, Daraprim.

“This could become a solution for the vast majority of patients,” Dr. Steve Miller, chief medical officer of Express Scripts, said in an interview.

The compounded medicine is already being made and sold by Imprimis Pharmaceuticals in San Diego. But the move by Express Scripts, which manages prescriptions for tens of millions of Americans, could increase sales considerably.