Martin Shkreli's plan to charge $750-per-pill for Daraprim just suffered a big setback

Express Scripts, one of the leading prescription-benefits managers in the US, is partnering with a compounding pharmacy to provide a $1-per-pill version of the drug that Turing Pharmaceuticals charges $750 for.

The drug, which Turing sells under the name Daraprim, is used to treat toxoplasmosis, an infection that's harmful to people with weakened immune systems.

Express Scripts announced the partnership with Imprimis Pharmaceuticals on Tuesday, and said prescriptions could be filled as soon as this week. In October, Imprimis said it would provide a customizable formulation to compete with Daraprim.

Turing, and its CEO Martin Shkreli, were thrust into the spotlight earlier this year after the company raised the price of Daraprim, a decades old treatment, from $13.50 a pill to $750 a pill at wholesale. Imprimis' compounded form of the drug will cost about $1 a pill.

In the month since that announcement, Imprimis' version of the drug has done "exceptionally well," CEO Mark Baum said in a telephone interview. The partnership with Express Scripts, which negotiates with insurance companies and drug makers to provide medicines directly to consumers at low cost, should provide a further boost, Baum said.

"What the relationships with Express Scripts and their networks do is it makes a frictionless transaction," he said.

Compounding pharmacies are different from major drug companies, which focus on developing new drugs for the US Food and Drug Administration approval. They buy FDA-approved compounds that they can then formulate into pills that can be customized to fit certain conditions.

That's what Imprimis is doing with pyrimethamine, the active part of Daraprim. Imprimis combines pyrimethamine with leucovorin, a form of B-vitamin folic acid that's recommended to treat toxoplasmosis by the US Centers for Disease Control and Prevention.

"We believe we now have an extremely cost-effective way to provide access to a Daraprim alternative," Dr. Steven Miller, the chief medical officer of Express Scripts, said in a news release.

Last week, Turing announced that it will not be lowering the wholesale price of Daraprim, but would instead provide an up to 50% price cut to hospitals administering the drug, which Turing says is about 80% of all prescriptions. The company also planned to make bottles of 30 pills, instead of 100, to make it easier for hospitals to stock the drug.

Baum said this stocking price model is very different from the way Imprimis will operate. He called Turing's hospital stocking price "a joke," comparing it to buying a gift card. Instead of a gift card that never expires, this one has a "use by" date, so if patients don't end up needing Daraprim, that cost still falls on the hospital.

"Pricing for Daraprim before he bought the drug was not complicated," he said. "It only became complicated when they bought it."