The Phase 2 Valiant trial evaluated the efficacy of verekitug in adults with severe asthma, a chronic condition characterized by airway inflammation and narrowing. According to the company, the study demonstrated that doses of 100 milligrams every 12 weeks and 400 milligrams every 24 weeks successfully reduced asthma attacks and improved lung function.

Dosing Inconsistency and Investor Reaction

Performance was less stable in the lowest-frequency treatment group. Upstream Bio reported that patients receiving 100 milligrams every 24 weeks saw some positive effects, but the results lacked the consistency required to meet the trial's primary endpoints. This divergence triggered a sell-off in premarket trading, sending shares down 22% to $21.83.

Despite the setback in the low-dose group, the company remains committed to the drug's development. Upstream Bio stated that the data gathered from the Valiant trial will directly inform the design of its upcoming Phase 3 study, for which planning is already underway.