Vasculitis Treatment Drug: Protect Patients from Serious Adverse Effects

Editorial

16:07 JST, May 31, 2026

There has been a spate of cases in which patients died after developing liver dysfunction, believed to be a side effect, after taking medication for vasculitis, a condition in which the inflammation of blood vessels causes various symptoms.

Twenty deaths have been reported since the drug went on sale in 2022.

This drug, called Tavneos, is taken orally and manufactured in the United States. In Western countries, questions have been raised not only regarding its safety but also its efficacy, sparking calls for the withdrawal of its approval.

Meanwhile, Kissei Pharmaceutical Co., which handles sales in Japan, has urged doctors to take precautions when administering the drug to patients. However, is this truly a sufficient response? The Health, Labor and Welfare Ministry, which approved the drug, also needs to urgently take measures.

Many of the patients who died developed severe liver dysfunction within three months after starting the medication. Among them, 13 patients died due to vanishing bile duct syndrome, in which the bile ducts in the liver disappear.

The drug was developed by a subsidiary of the major U.S. pharmaceutical company Amgen Inc. In Japan, an estimated 8,500 people have taken it. While a causal relationship between the deaths and the drug is unclear, the situation is serious.

Tavneos is administered to patients with severe forms of vasculitis, which the government has designated as an intractable disease.

Previously, these patients were often treated with high doses of steroids, but this places a heavy burden on their body. Tavneos was expected to alleviate this strain. The patients likely took the drug with desperate hope.

Following the spate of fatal cases, at the instruction of the government, Kissei Pharmaceutical has issued to health care professionals a rapid safety communication, which is put out when serious side effects occur. The company has also asked for patients currently taking the drug to take steps such as undergoing liver function tests.

It is important to ensure that people are fully informed, to prevent harm caused by the drug from spreading. Medical institutions should also carefully explain the risks of the drug to patients currently taking it and discuss future treatment plans with them.

Questions have also emerged in the United States and European countries over the efficacy of Tavneos.

Last month, the U.S. Food and Drug Administration proposed withdrawing approval of the drug in the United States, citing suspicions that data regarding the drug’s efficacy was manipulated and concealed during the preapproval clinical trial phase. The European Medicines Agency is also conducting a review of the drug, citing questions over the integrity of the data.

If the data cited as evidence of efficacy is found to be false, this would constitute a serious problem.

Kissei Pharmaceutical must take responsibility for verifying the facts with the drug’s developer. The Japanese government should also gather information from regulatory authorities in Western countries and conduct its own investigation. It is unacceptable that patients in Japan could suffer further harm due to delays in tackling this issue.

(From The Yomiuri Shimbun, May 31, 2026)