Amgen's rare disease drug linked to deaths, liver injuries in Japan

About 20 deaths linked to serious liver dysfunction have been reported in Japan in patients treated with Amgen's rare disease drug Tavneos, according to a safety notice issued by partner Kissei Pharmaceutical on Friday (May 15).

Kissei has asked doctors to stop prescribing Tavneos to new patients and to review ongoing treatment due to the risk of liver damage.

The company also said some of the deaths as of April 27 were tied to a severe liver condition that destroys bile ducts, though a direct link to the drug had not been confirmed in all cases.

The drug, which is approved to ​treat anti-neutrophil cytoplasmic autoantibody (ANCA)-associated vasculitis, a group of rare autoimmune diseases that cause inflammation in small- to medium-sized blood vessels, is under growing regulatory scrutiny.

Kissei said most severe liver injury cases occurred within three months of starting treatment.

It added that about 8,503 patients in Japan have been treated with Tavneos since its launch in 2022 and urged regular liver function monitoring and prompt discontinuation if abnormalities are detected.

The Wall Street Journal first reported the development earlier on Friday.

US regulators have already flagged serious liver injury cases and begun steps to withdraw the treatment, though Amgen has maintained the drug has a favourable risk profile.

Tavneos was approved in the United States in 2021 and launched in Japan a year later. Amgen acquired the drug through its US$3.7 billion (S$30 million) purchase of developer ChemoCentryx in 2022.

The FDA earlier this year asked Amgen to voluntarily pull the drug from the US market, but the company declined.

The regulator has since moved to formally begin withdrawal proceedings after identifying dozens of liver injury cases globally, many of them in Japan.

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