Japanese pharmaceutical company Kissei Pharmaceutical has warned doctors not to prescribe the drug Tavneos to new patients after reports of 20 deaths among people taking the medication, according to Medical Xpress.

On Friday, the company, which markets Tavneos in Japan, sent a notice to healthcare professionals stating that “20 fatal cases” had been reported since the drug entered the Japanese market in June 2022.

At the same time, doctors were warned about the “risk of severe liver dysfunction” and advised not to prescribe the medication to new patients, while also reconsidering continued treatment for those already receiving the therapy.

Both Amgen, which owns the rights to the drug, and Kissei Pharmaceutical emphasized that in some of the reported cases, a causal relationship between the patients’ deaths and the medication had not been established.

According to Kissei Pharmaceutical, Tavneos has been prescribed to approximately 8,500 patients in Japan since its launch.

Tavneos (international nonproprietary name: avacopan) is used to treat rare autoimmune diseases that cause inflammation of blood vessels, particularly ANCA-associated vasculitis.

According to the European Medicines Agency, the drug helps reduce inflammation and lowers the need for long-term use of high doses of corticosteroids.

It is noted that in the United States, no confirmed deaths related to severe liver damage have been reported among more than 8,000 patients treated with Tavneos.

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

However, in April, U.S. health authorities proposed withdrawing the drug’s approval due to concerns about possible data falsification and other irregularities during clinical trials.

In January, the European Medicines Agency also launched its own review after questions emerged regarding the reliability of the submitted data.