Shares of CymaBay Therapeutics Inc. /zigman2/quotes/201917619/composite CBAY +3.89% are down 77% in premarket trading after the biopharmaceutical company ended two studies and halted a third for its experimental drug seladelpar. CymaBay had been testing the therapy as a treatment for non-alcoholic steatohepatitis (NASH) and in patients with primary sclerosing cholangitis and primary biliary cholangitis, both liver diseases. "We are very disappointed in having to halt the development of seladelpar at this time but patient safety and care is paramount," CEO Sujal Shah said in a news release. CymaBay stock has fallen 29% year-to-date. The S&P 500 /zigman2/quotes/210599714/realtime SPX +1.05% is up 24%.