Retrophin Inc said its drug to treat a rare kidney disorder was found effective in a mid-stage study, sending the company’s shares up 25 percent in premarket trading on Wednesday.

The drug, sparsentan, was tested on 109 patients with focal segmental glomerulosclerosis (FSGS), which is characterized by a progressive kidney scarring and often leads to kidney failure.

While there is no specific treatment for FSGS, Retrophin’s sparsentan aims to treat a key symptom, proteinuria, or excess serum protein in the urine.

The drug is designed to lowering proteinuria levels, thereby reducing the risk of patients progressing to kidney failure.

Patients given sparsentan experienced a 44.8 percent mean reduction in proteinuria after eight weeks, compared with an 18.5 percent reduction in patients given irbesartan, a generic drug used in lieu of an approved FSGS therapy, Retrophin said.

Sparsentan’s efficacy was better than expected and at the high end of what other drugs in its class have shown in similar kidney-related syndromes, Leerink Partners analysts said in a note.

FSGS affects up to 40,000 people in the United States and Leerink estimated sparsentan would be used in about 30 percent of the cases.

Leerink forecast about $600 million in probability-weighted sales for sparsentan, based on a 65 percent probability of success and a $950 million peak gross revenue opportunity.

Retrophin licensed the rights to sparsentan from Ligand Pharmaceuticals Inc in 2012. Ligand is eligible to receive a 9 percent royalty on sales of the drug, which was originally developed by Bristol-Myers Squibb Co.

Retrophin shares were up 25 percent at $20.40 in premarket trading. Ligand shares edged up about 2 percent in low volumes.

Retrophin was founded by Martin Shkreli, a former pharmaceutical executive who last year became a lightning rod for criticism of soaring prescription drug prices. Shkreli led Retrophin till 2014.


(Reporting by Natalie Grover in Bengaluru; Editing by Savio D’Souza)

Source: Reuters Health