 Shares of Forte Biosciences Inc. FBRX, -4.45 plummeted 81.2 on heavy volume toward a record low in premarket trading Friday, after the biopharmaceutical company said it will no longer advance its lead product candidate FB-401, a treatment for atopic dermatitis. Trading volume spiked to 2.8 million shares ahead of the open, compared with the full-day average of about 754,000 shares. 