Zenas plummets 50% after weak data for immune disorder drug

Zenas BioPharma

05/01/2026 18:40

** Zenas BioPharma ZBIO.O shares plunging on Mon after its experimental drug for a rare autoimmune disease, obexelimabin, showed weaker-than-expected efficacy in a late-stage study

** ZBIO shares last down 56% to $15.18, lowest since mid-Aug, and on course for biggest daily pct drop on record

** The drug showed a 56% reduction in risk of flare-ups for immunoglobulin G4-related disease, falling short of analyst expectations and lagging the 87% risk reduction shown by rival Amgen's AMGN.O approved drug Uplizna

** Despite the data, co plans to seek U.S. and European regulatory approval this year, noting the therapy was well tolerated with no new safety concerns reported in the trial

** In addition, ZBIO said in a filing it's currently not eligible for milestone payments with Royalty Pharma Investments (RPI) under prior agreements tied to its INDIGO trial for obexelimabin

** ZBIO said it's in active discussions with RPI, adding "There is no assurance the Company will receive any future milestones payments under the Royalty Purchase Agreement," per the filing

** ZBIO shares, which more than quadrupled in 2025, are now trading about 66% below their all-time intraday peak of $44.60 hit in Dec

** All 8 analysts are bullish on the stock, including 5 "strong buy" ratings; median PT is $45.50, per LSEG data

(Lance Tupper is a Reuters market analyst. The views expressed are his own)

((lance.tupper@tr.com 1-646-279-6380))