Upstream Bio Inc is a clinical-stage biotechnology company developing treatments for inflammatory diseases, with an initial focus on severe respiratory disorders. It is developing verekitug, the known antagonist currently in clinical development that targets the receptor for Thymic Stromal Lymphopoietin (TSLP), a cytokine that is a clinically validated driver of inflammatory response positioned upstream of multiple signaling cascades that affect a variety of immune-mediated diseases. Verekitug has advanced into three separate world-wide, placebo-controlled, randomized Phase 2 clinical trials, two completed in chronic rhinosinusitis with nasal polyps (CRSwNP) and severe asthma, and one ongoing in chronic obstructive pulmonary disease (COPD).