Mr. Shkreli said on a conference call with KaloBios investors last week that if the company won F.D.A. approval for benznidazole, it would have exclusive rights to sell it in the United States for at least five years. He said the price would be similar to that of hepatitis C drugs, which cost $60,000 to nearly $100,000 for a course of treatment.

In Latin America, benznidazole costs $50 to $100 for the typical two-month course of treatment.

KaloBios’s price would be “pretty devastating,” said Dr. Meymandi of U.C.L.A. “The people with Chagas for the most part are poor” and many lack insurance, she said.

It is estimated that 300,000 people in the United States have Chagas disease, virtually all of them immigrants from Latin America who were infected before they came.

Chagas is caused by a parasite, Trypanosoma cruzi, that is in the feces of an insect called the kissing bug, because it often bites people on the face. The first phase of the infection, the acute phase, can last a few weeks or as long as three months. In most cases, people have no symptoms, though some have fever or swelling at the bite site and in rare cases more severe complications. The parasite persists in the body, and roughly 30 percent of people will develop serious heart problems many years later. The disease can also cause difficulty in swallowing and defecating.

Benznidazole, first used in the 1970s, was developed by Roche. But in 2003, with sales slow, Roche donated its remaining supply and the rights to Lafepe, a company owned by a state government in Brazil. A severe shortage occurred a few years ago. A company in Argentina, Elea Laboratories, then became a supplier.

While the disease control centers provide the drug free, many doctors are deterred by the paperwork involved in applying for each patient. So specialists say that having a commercial supplier with an approved drug, which would allow doctors to simply write a prescription, would be better, if the price was reasonable.

Image A kissing bug, the insect that spreads the parasite that causes Chagas disease, which can lead to fatal heart problems. Credit... David Scharf/Corbis

KaloBios paid only $2 million initially for worldwide rights to a version of benznidazole developed by Savant Neglected Diseases, a tiny company in California. It might have to pay an additional $20 million over time plus royalties on sales.