A medication against hereditary degeneration of the retina that can lead to total blindness, will be sold for $850,000 (Rs 5,39,79,250) in the United States, making it one of the world's most expensive medical treatments.

According to the manufacturer, Philadelphia-based Spark Therapeutics, the drug Luxturna is administered in a single dose. It is considered the first American medication to emerge from gene therapy, which consists of repairing a defective gene.

The announcement comes amid a growing debate in the United States over the high cost of medicine, particularly for supposedly innovative treatments. Anticipating criticism, Spark promised to reimburse patients if the treatment proves to be ineffective.

The company is following the lead of Novartis, which sells Kymriah, a treatment for a very aggressive form of leukemia in children and young adults. The Swiss drug maker has pledged to reimburse insurers and patients if the $475,000 drug doesn't work.