Viking Therapeutics shares slumped as much as 41% on Tuesday after mid-stage data from its oral obesity pill VK2735 failed to meet the market’s loftier expectations. The decline, the steepest since the company went public in 2015, erased roughly $1.8 billion in market value and delivered an estimated $514 million one-day windfall to short sellers, according to S3 Partners. The 280-patient Phase 2 VENTURE-Oral study showed that once-daily VK2735 cut body weight by up to 12.2%—equivalent to 26.6 pounds—after 13 weeks. All doses above 15 mg achieved statistically significant reductions versus the 1.3% loss seen with placebo and met key secondary endpoints, including the share of patients achieving at least 10% weight loss. Tolerability, however, proved a concern. Gastrointestinal side effects such as nausea and vomiting led 28% of VK2735 recipients to stop treatment, compared with 18% in the placebo arm. At the highest 120-mg dose, discontinuations rose to 38%. Viking said slower dose escalation and lower maintenance doses may improve adherence in future trials. The result puts VK2735 in the range of other oral contenders but below the 15% reduction some investors had hoped for and behind injectable leaders such as Novo Nordisk’s Wegovy. Eli Lilly’s oral orforglipron produced 12.4% loss over 72 weeks, while Novo’s oral semaglutide cut weight by 15% over 68 weeks. Several banks, including JPMorgan and Jefferies, called Tuesday’s share rout an overreaction, arguing the drug’s efficacy remains competitive if safety can be managed.