What happened

Shares of Travere Therapeutics (TVTX -9.42%) are regaining some of the heavy losses its shareholders suffered in May. Enthusiasm for the biotech following another interim readout for sparsentan has driven the stock 15.5% higher as of 12:14 p.m. EDT on Monday.

So what 

Shares of Travere Therapeutics tanked in May after the FDA said it wouldn't accept the interim data the pivotal Duplex study with focal segmental glomerulosclerosis (FSGS) patients produced in February. The company and its investors had hoped proteinuria data at 36 weeks from the Duplex trial would be sufficient evidence of efficacy to support an application for accelerated approval.

Smiling scientist with a microscope.

Image source: Getty Images.

The stock is climbing now in response to positive proteinuria results the company read out today for immunoglobulin A nephropathy (IgAN) patients treated with sparsentan in the pivotal Protect study. After 36 weeks, patients receiving sparsentan achieved an average reduction of protein leaking through their kidneys and into their urine of 49.8% after 36 weeks of treatment. Patients randomized to receive standard treatment achieved an average reduction of just 15.1% compared to baseline.

Now what

The proteinuria improvements Travere Therapeutics has posted so far are a great sign for sparsentan's future as a treatment for two rare kidney disorders in need of better treatment options. Unfortunately for Travere, the FDA appears more interested in estimated glomerular filtration rate, or eGFR improvements, than simple proteinuria. In fact, eGFR improvement after 108 weeks of treatment is the Duplex trial's confirmatory endpoint.

Travere Therapeutics stock would have shot up a lot higher today, but the company still hasn't shared 36-week eGFR data from Duplex or Protect. It's probably best to tread carefully around this risky biotech stock until the company can share some positive eGFR data.