Upstream Bio sets Phase 3 plans for verekitug in asthma and CRSwNP

Upstream Bio, Inc. said on September 1, 2026 that it has finalized its late-stage development plans for verekitug, an antibody candidate for severe asthma and chronic rhinosinusitis with nasal polyps (CRSwNP). The Waltham, Massachusetts-based clinical-stage company announced its pivotal Phase 3 development plans for verekitug in severe asthma and CRSwNP.¹ The company describes verekitug as the only known antagonist currently in clinical development that targets and inhibits the thymic stromal lymphopoietin (TSLP) receptor.¹

The plans follow discussions with regulators. Chief Medical Officer Aaron Deykin said the End-of-Phase 2 meetings with the FDA were productive, and the company is moving to start one placebo-controlled Phase 3 trial each in severe asthma and CRSwNP.¹

Trial design specifics: the company plans a single high-dose subcutaneous regimen of 400mg administered every 12 weeks, one placebo-controlled study per indication enrolling a total of approximately 1,500 patients across both trials, and broad study populations without restriction based on baseline biomarkers.¹ Primary endpoints are annualized asthma exacerbation rates (AAER) over 48 weeks for asthma, and co-primary endpoints of change from baseline in nasal polyp score and nasal congestion score at 48 weeks for CRSwNP.¹

On timing, the company remains on schedule to begin both Phase 3 trials in the first quarter of 2027.¹ Contingent on supportive Phase 3 data, Upstream Bio expects to file a Biologics License Application with the FDA for both indications, which it said could support a launch as early as 2030.¹

The company noted its existing data base: more than 500 participants have been treated with verekitug across its clinical programs, with positive Phase 2 results reported in severe asthma and CRSwNP.¹ Verekitug is also being tested in an ongoing Phase 2 trial for chronic obstructive pulmonary disease.¹