Zealand Pharma fell as much as 25% on Monday after full late-stage survodutide data showed 19% of patients quit treatment over gastrointestinal side effects, versus 2.9% on placebo.
More than 40% of patients reported vomiting, and analysts at Barclays and Citi said the tolerability profile could undermine the drug's commercial viability against Lilly's tirzepatide and Novo Nordisk's semaglutide.
The 76-week study still met key goals: topline data released in April showed average weight loss of up to 16.6%, compared with 3.2% for placebo, in adults with obesity or overweight without type 2 diabetes.
The selloff deepens Zealand's nearly 50% year-to-date decline and follows March disappointment over petrelintide, another obesity candidate whose newer data did little to improve analysts' view.
The setback lands as obesity-drug competition intensifies, with developers under pressure to differentiate on tolerability, muscle preservation, oral delivery and related-disease benefits rather than weight loss alone.