Shares of Rafael Holdings Inc. /zigman2/quotes/206275218/composite RFL -0.54% plummeted 78% in active premarket trading Thursday, to pace all premarket decliners, after the developer of cancer treatments said a Phase 3 trial of CPI-613 (devimistat) in patients with relapsed or refractory acute myeloid leukemia failed to meet its primary endpoint. Trading volume swelled to 1.5 million shares ahead of the open, compared with the full-day average of about 173,400 shares. The company said devimistat, given with Folfirinox (mFFX), a current standard of care chemotherapy regimen, did not significantly improve overall survival. "While we are disappointed by the outcomes of these well-designed and well-executed studies, we remain committed to furthering our research and development in cancer metabolism for the treatment of hard-to-treat cancers, as our other studies continue," said Rafael Chief Executive Sanjeev Luther. The stock had rallied 29.4% year to date through Wednesday, while the iShares Biotechnology ETF /zigman2/quotes/206189322/composite IBB -2.54% had gained 4.0% and the S&P 500 /zigman2/quotes/210599714/realtime SPX -4.04% had climbed 21.2%.