Kissei Pharmaceutical advises “refrain from use” after 20 deaths after using vasculitis drug

From The Asahi Shimbun

May 16 2026

Matsumoto, Nagano Pref – Kissei Pharmaceutical Co., Ltd. announced that for its vasculitis treatment drug “Tavneos” (generic name: avacopan), 20 deaths have been reported in Japan among patients who took the medication. This figure includes cases where a causal relationship is unclear. On the 15th, the company called on healthcare professionals to refrain from administering the drug to new patients.

Tavneos was developed by a company under the U.S. pharmaceutical firm Amgen. Kissei acquired the rights and has been selling it in Japan since June 2022; it is estimated that 8,503 patients had used it by April 27, 2026.

Among patients who took the drug, 22 cases of a liver condition known as “vanishing bile duct syndrome” were reported; this accounted for 13 of the 20 deaths. Twenty cases developed within three months of starting the medication.

As of May 1, Kissei added “vanishing bile duct syndrome” to the list of serious side effects under liver function disorders. Although the drug remains approved in Japan, healthcare providers are being asked to explain risks such as liver dysfunction to patients currently taking it and to decide whether to continue treatment.

Kissei stated that it has “been providing information on side effects as needed.”

Regarding Tavneos, the U.S. Food and Drug Administration issued a notice on March 31, 2026, warning patients and healthcare professionals after identifying severe drug-induced liver injury in users. Furthermore, on April 27, the FDA’s Center for Drug Evaluation and Research (CDER) proposed withdrawing approval in the United States, citing newly obtained information showing a lack of demonstrated efficacy and the inclusion of materially inaccurate statements in the approval application documents.