Single-shot of drug cures leishmaniasis - study

* Higher dose tested when drug price came down

* Parasite infects half million worldwide

* One-day treatment makes care cost less

BOSTON, Feb 10 (Reuters) - A single large infusion of the Gilead Sciences GILD.O drug AmBisome cured nearly every case of the deadly parasitic infection visceral leishmaniasis, researchers reported on Wednesday in a study from India.

Conventional treatments for the condition, also known as kala-azar, take much longer and have a greater risk of side effects.

The researchers said using a single dose of the drug, known generically as liposomal amphotericin B, would make it possible to treat many more patients, whose initial symptoms often are fever, fatigue, and weight loss as the parasites infect cells.

The disease can be found in Europe, Asia and Africa, but it is concentrated in India.

The study found AmBisome cured all 304 patients with leishmaniasis within 30 days, compared to 98 percent of 108 volunteers in a comparison group who received 29 days of in-hospital treatment with a different form of amphotericin.

There were some relapses by the six-month mark, but the success rate of the two treatments was essentially the same -- over 95 percent.

For logistical and cost reasons, doctors have been seeking an easier treatment against the deadly parasite, which infects about a half million people worldwide and is spread by the bite of a sandfly.

Dr. Shyam Sundar of the Banaras Hindu University in Varanasi, led the new study, which was published in the New England Journal of Medicine. Sundar has been experimenting with various doses of the drug for years.

In this study, the group decided to try a high dose, which was administered over an hour, after the subsidized price of the drug dropped from $200 per vial down to $20 per vial in developing countries.

They found no evidence that the one-day treatment was less effective than the multiple treatments. In addition, AmBisome “was not associated with any safety concerns in adults or children, and compliance was guaranteed,” they reported.

With a one-dose, one-hour treatment, “you can treat 40 to 50 times more patients,” Sundar said in a telephone interview.

At $20 per vial, the drug is more expensive than the established treatment with amphotericin B deoxycholate. But the one-time infusion made overall treatment less expensive because a long hospital stay and laboratory monitoring was avoided.

Other drugs, such as oral miltefosine, are effective against the condition as well, but they must also be given over many weeks.

Editing by Maggie Fox and Paul Simao