NEW YORK, December 30, 2025, 02:05 PM ET — Regular session
Zenas BioPharma Inc shares fell $2.02, or 5.2%, to $37.03 in afternoon trading on Tuesday, after ending the prior session at $39.05. The stock ranged from $36.94 to $40.50, with about 123,000 shares traded.
The drop came as biotech stocks eased in thin year-end trading, with the Nasdaq Biotechnology Index down about 1%. That matters now because smaller, cash-burning drug developers often move with risk appetite as much as on headlines.
Wall Street’s main indexes were largely muted as investors waited for minutes from the Federal Reserve’s December meeting later Tuesday for clues on the path of interest rates. “It’s just a healthy rebalancing of allocations more so than an emotionally driven sell-off,” said Mark Hackett, chief market strategist at Nationwide. Reuters
Zenas, which trades on Nasdaq under the symbol ZBIO, is a clinical-stage biotech focused on autoimmune diseases. Its lead candidate, obexelimab, is a monoclonal antibody designed to bind CD19 and FcγRIIb to rein in B-cell activity, and the company is studying it in IgG4-related disease, relapsing multiple sclerosis and systemic lupus erythematosus, a Reuters company profile shows.
In November, the company said it expects topline results from the Phase 3 INDIGO trial of obexelimab in IgG4-related disease around year-end 2025, and additional 24-week data from its Phase 2 MoonStone study in relapsing multiple sclerosis in the first quarter of 2026. Zenas also said it has a funding agreement with Royalty Pharma that could provide up to $300 million tied to development and regulatory milestones.
Phase 3 trials are late-stage studies designed to confirm a drug’s benefit and safety in larger groups of patients, often a key step toward regulatory approval. Topline results are the first summary readout on whether a study met its main endpoint.
IgG4-related disease is a rare immune disorder that can damage organs through inflammation and scarring. Investors typically focus on the strength and durability of symptom control, as well as safety signals that can emerge as more patients are treated.
The stock’s intraday swing underscored the volatility common in smaller biotech names, especially in late December when trading volumes can be light. Moves can become exaggerated when fewer investors are active.
Technically, the $36.94 low marked the near-term support area, while the $40.50 high set the first resistance level. A sustained break in either direction can draw momentum-focused trading.
Absent fresh company-specific news, investors are likely to keep one eye on the macro backdrop and another on any update to the INDIGO timetable. Fed minutes and year-end positioning could shape risk appetite into the final sessions of 2025.
