Zenas BioPharma Stock Plunges 20.08% as Shareholder Probe and Mixed Trial Results Spur Selling

The share price fell to its lowest level so far this month, with an intraday decline of 6.22%.

Zenas BioPharma’s stock has plunged 20.08% over five consecutive trading days, driven by a shareholder investigation into director fiduciary duties and a mixed market reaction to its Phase 3 INDIGO trial results for obexelimab. The law firm Purcell & Lefkowitz LLP announced the probe, which questions whether directors breached their duties in recent corporate actions. Meanwhile, the trial for obexelimab met its primary endpoint but failed to meet Wall Street expectations, triggering concerns about its commercial potential and regulatory timelines. The company plans to submit a Biologics License Application to the FDA in Q2 2026 and a Marketing Authorization Application to the EMA in H2 2026.

Investor sentiment has been further pressured by a 12-month stock rally that may have overhyped obexelimab’s prospects. While the drug demonstrated a 56% reduction in flare risk for IgG4-RD compared to placebo, its tolerability profile and lack of significant safety advantages over existing therapies dampened enthusiasm. Zenas BioPharma’s broader pipeline, including trials for systemic lupus erythematosus and multiple sclerosis, remains a long-term catalyst. However, near-term uncertainty around the shareholder investigation and regulatory approval timelines has overshadowed these potential growth areas, leaving the stock vulnerable to continued volatility in the biotech sector.