Zenas BioPharma reported top-line data from its registrational Phase III INDIGO trial evaluating obexelimab in patients with immunoglobulin G4-related disease (IgG4-RD). The randomized, double-blind study demonstrated a 56% reduction in flare risk compared to placebo over a 52-week treatment period, meeting all primary and key secondary endpoints. Obexelimab-treated patients showed sustained improvements in disease activity scores, with 68% achieving complete remission at week 24 versus 30% in the control arm. Safety findings were consistent with prior studies, with no new serious adverse events attributed to obexelimab and a discontinuation rate of 8%, comparable to placebo.

Despite the positive efficacy and safety data, Zenas BioPharma’s shares plunged nearly 52% following the announcement. Trading volume surged to 14.3 million shares, roughly four times the three-month daily average, as investors expressed concerns over anticipated pricing and reimbursement challenges in a rare-disease market. Analysts from three major brokerage firms revised 12-month price targets downward by an average of 35%, citing potential delays in regulatory approval timelines and the need for additional health-economic analyses before launch.