A small-scale study from Viking Therapeutics shows its weight loss injectable helped patients lose weight and maintain results, sending the company’s stock price soaring.

Viking Therapeutics Inc. shares rose sharply after the company announced positive results from a small exploratory study of its dual-target injectable obesity drug, which helped patients achieve weight loss and maintain the effect even when dosing frequency was reduced. The company drew conclusions based on data from the study’s extended patient cohort. The research was originally designed to determine the optimal dose of the drug, which regulates weight through two distinct pathways. The results are a major boost for Viking, which had faced setbacks in prior trials. The company said patients on a moderate weekly dose in the main trial phase saw the best outcomes, shedding up to 19% of their body weight over roughly five months. A 13-patient "exploratory" group continued on a slightly lower dose for an additional three months, achieving 22% weight loss with no plateau observed. Viking noted that when patients switched to a less frequent dosing regimen (once or twice monthly), some were able to maintain 90% to 97% of their weight loss. Side effects were mostly mild and eased over time, with only one patient discontinuing treatment due to adverse events. During low-frequency maintenance dosing, gastrointestinal side effects were comparable to those in the placebo group. Viking’s stock jumped as much as 36.6% during New York trading, marking its largest intraday gain since July 2024, before paring some of those gains.