Zura Bio’s tibulizumab has flunked a phase 2 hidradenitis suppurativa (HS) trial, prompting the biotech to end development in the indication while continuing studies in other settings.
The failed Tibushield trial compared two doses of tibulizumab, an antibody that inhibits IL-17A and BAFF, to placebo in 247 HS patients. At Week 16, the changes from baseline in the total abscess and inflammatory nodule (AN) count were 56% and 58.1% on 300 mg and 150 mg of tibulizumab, respectively. The placebo rate was 52.5%, causing the trial to miss its primary endpoint.
Zura reported similarly slight numerical advantages over placebo on secondary endpoints. At Week 16, 48% and 52.7% of patients on 300 mg and 150 mg of tibulizumab, respectively, had the 50% or greater reduction in AN needed to meet the HiSCR50 criterion. The HiSCR50 rate on placebo was 45.5%.
HiSCR75 rates in the 300-mg, 150-mg and placebo arms were 35.3%, 34% and 28.1%, respectively.
The HiSCR50 and HiSCR75 rates on tibulizumab are in line with results for UCB’s Bimzelx, which the FDA approved in HS in 2024. Across two phase 3 trials, UCB linked (PDF) Bimzelx to Week 16 HiSCR50 rates of 48% to 52% and HiSCR75 rates of 33% to 36%.
However, while tibulizumab and Bimzelx achieved similar response rates, the placebo group performed much better in Zura’s trial. UCB reported Week 16 HiSCR50 rates of 29% to 32% and HiSCR75 rates of 16% to 18% on placebo in its phase 3 studies.
Investors sent Zura's stock down 72% to $1.12 when markets opened on Monday from a Friday closing price of $4.09.
Zura is still digging into its data, assessing pharmacokinetics and pharmacodynamics, exposure-response relationships and the impact of HS-specific factors. But the biotech has already decided to discontinue development in HS. Zura continues to study the asset in systemic sclerosis and polymyalgia rheumatica trials that are scheduled to report results in the first half of 2027 and late 2028, respectively.
The indications have “distinct and uncorrelated pathobiologies and clinical presentations from those of HS,” Zura CEO Sandeep Kulkarni, M.D., said in a statement. Given the differences, Zura is still committed to testing tibulizumab outside HS.
Safety and tolerability data from Tibushield support further development. The treatment-emergent adverse event (TEAE) rate in the study drug arms—52.4%—was only slightly higher than the 46.3% in the placebo cohort.
There was one treatment-related serious AE on tibulizumab. Up to 3.7% of patients on tibulizumab had TEAEs leading to treatment discontinuation, compared with 2.4% of people on placebo. One patient in the tibulizumab arms died of cardiac arrest, but the site investigator determined that this was unrelated to the study drug.
Zura has the funds needed to recover from the setback. Having ended September with $187.7 million in cash and equivalents, Zura forecasts having enough money to bankroll operations through at least the end of 2028. The runway extends beyond the anticipated readouts from the two remaining tibulizumab trials.