Kezar Life Sciences, Inc. announced that it has received clearance of its Investigational New Drug application from the U.S. Food and Drug Administration for zetomipzomib, its first-in-class, selective immunoproteasome inhibitor, for the treatment of autoimmune hepatitis. AIH is a rare, chronic disease in which the immune system attacks the liver and causes inflammation and tissue damage, severely impacting patients' physical health and quality of life. Lifelong maintenance therapy is required to avoid relapse and burdensome adverse effects.

If left untreated, AIH can lead to cirrhosis, liver failure and hepatocellular carcinoma. In the United States, AIH affects approximately 140,000 individuals, with incidence rates increasing. The cause of this condition remains unclear.

Females are affected four times as often as males. Standard of care treatment for AIH is immunosuppressive treatment with chronic corticosteroids that can lead to additional morbidity and mortality. There is a significant need for treatment regimens that reduce or remove the need for chronic immunosuppression using corticosteroids.

The PORTOLA trial (KZR-616-208) is a randomized, double-blind, placebo-controlled Phase 2a clinical trial evaluating the safety and efficacy of zetomipzomib in patients with AIH that are insufficiently responding to standard of care or have relapsed. The target enrollment will be 24 patients, who will be randomly assigned (2:1) to receive either zetomipzomib with prednisone or placebo with prednisone for 24 weeks, with a protocol-directed steroid taper by Week 14. The primary efficacy endpoint will measure the proportion of patients who achieve a complete response measured as normalization of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) levels with a successful corticosteroid taper by Week 24.