Why AnaptysBio Stock Plummeted, Reversing A 70% Monthlong Run

Core Insights - AnaptysBio's stock experienced a significant decline of over 15% following the failure of its experimental ulcerative colitis drug, rosnilimab, in midstage testing, reversing a previous 70% increase since late September [1][4]. Company Performance - The drug was found to be safe and tolerable, but it did not meet the primary and secondary goals of the study, leading AnaptysBio to discontinue the study [2]. - The stock price fell to 33.33, down from a breakout point of 28.50 established on September 30, when the company announced plans to separate its biopharma business from its royalty assets by the end of 2026 [4][5]. - Following the disappointing results, Leerink Partners analyst David Risinger reduced the price target for AnaptysBio stock from 62 to 58, reflecting a low probability of success for the drug [3]. Market Reaction - The stock's decline sent it back below a profit-taking zone, which is typically a signal for investors to take profits after a significant rise [5]. - AnaptysBio had previously shown improving price performance, earning an upgrade to its IBD Relative Strength Rating, but the recent developments have negatively impacted investor sentiment [6][7].