Japan pharmaceutical firm warns against rare diseases drug after deaths

TOKYO — A Japanese pharmaceutical firm has warned doctors against prescribing a drug for rare autoimmune diseases to new patients following the deaths of 20 people who took it.

Kissei Pharmaceutical, which sells the drug Tavneos in Japan, sent a notice to healthcare professionals on Friday saying that "20 fatal cases have been reported" since the drug was launched in the country in June 2022.

The company warned doctors of "the risk of severe liver dysfunction" and asked them to stop prescribing it to new patients and assess whether current patients should continue treatment.

Both Kissei and U.S. biotech firm Amgen -- which owns the drug -- said the deaths included cases for which no causal link to the medicine could be determined.

Tavneos has been distributed to around 8,500 patients in Japan since its launch, Kissei said.

The drug is used to treat rare autoimmune diseases which cause inflammation of the blood vessels, according to the European Medicines Agency.

"There have been no known deaths in the US linked to serious liver injury... in the more than 8,000 patients in the U.S. treated with Tavneos," Amgen said in a statement on Friday.

Tavneos was approved in the United States in 2021 and European countries in 2022.

But last month, the U.S. Food and Drug Administration (FDA) proposed the withdrawal of its approval due to concerns over data tampering and other issues.

The European Medicines Agency (EMA) also said in January it had begun a review following concerns over data integrity.

© 2026 AFP