Kezar slumps as top-line results from zetomipzomib trial disappoint

Shares of clinical-stage drug developer Kezar Life Sciences (Nasdaq: KZR) plunged more than 24% to $9.35 in after-hours trading on Tuesday as the company announced mixed top-line results from the PRESIDIO Phase II clinical trial of zetomipzomib (formerly KZR-616) in patients with dermatomyositis (DM) and polymyositis (PM).

In PRESIDIO, 25 patients enrolled with either DM (n=13) or PM (n=12) with active disease despite best available treatments, and 20 patients completed through end-of-treatment. During the 32-week study period, all patients received 16 weeks of zetomipzomib treatment: patients received either 45mg of zetomipzomib or placebo subcutaneously (SC) once weekly for 16 weeks on top of standard of care, followed by a crossover to the other arm of placebo or zetomipzomib, respectively, for an additional 16 weeks. Patients continued their background therapy but could taper medications as clinically indicated. The primary endpoint of PRESIDIO was the mean change in the Total Improvement Score (TIS).

Little differentiation to placebo