Doctors in Japan can again prescribe Amgen’s rare autoimmune disease drug Tabneos (abacopan) after the drug’s local license holder last week asked the company to pause the start of new patient admissions, albeit with revised safety warnings on the product packaging.
The temporary disruption for Tabneos, overseen in Japan by Matsumoto-based Kissei Pharmaceutical Co., Ltd., comes as the ANCA-associated vasculitis (AAV) drug faces increased scrutiny over trial data and safety in other major markets, including Europe and the United States.
Despite recent setbacks, Amgen remains supportive of Tabneos, which it acquired in 2022 in the $3.37 billion Chemocentrics acquisition. Earlier this year, the company resisted FDA pressure to withdraw the complement 5α receptor (C5aR) antagonist from the U.S., where Amgen holds the rights to sell Tavneos.
Kissei on Thursday revealed new precautions for Tabneos’ Japanese package insert in a filing with the Tokyo Stock Exchange (PDF), and an Amgen spokesperson also confirmed the development to Fierce. The company said the change in guidance was based on discussions between Kissei and Japan’s Ministry of Health, Labor and Welfare.
“We understand that Japanese regulatory authorities are working with Kissei to update TABNEOS prescribing information in Japan, including warnings for serious liver damage, specific liver monitoring recommendations, and criteria for treatment discontinuation,” an Amgen spokesperson said in an emailed statement.
“Importantly, the Ministry of Health, Labor and Welfare (MHLW) has updated its recommendation to say that healthcare providers can prescribe Tabneos to new patients, starting May 15, 2026,” the spokesperson added.
Last Friday, Kissei called on Japanese healthcare professionals to refrain from using Tabneos in new patients “for the time being” and to “carefully assess the need to continue administering it to patients currently receiving treatment,” after 20 deaths from severe liver damage among Tabneos patients were reported in the country, according to a filing by the Japanese company.
Amgen said in a company release at the time that these deaths occurred in more than 8,500 patients treated with Tabneos in Japan, and included “cases in which a causal relationship to the product could not be determined.”
“Based on all available data, Amgen continues to believe that Tabneos has demonstrated efficacy and a favorable benefit-risk profile for patients with AAV,” the company said last week.
Kissei acquired the Japanese rights to Tabneos in 2017 through an agreement with Vifor Fresenius Medical Care Renal Pharma and secured domestic approval in September 2021 for the treatment of granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA), two major types of anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis.
AAV is a rare and severe autoimmune disease that causes damage to various organs, including the kidneys, lungs, and nervous system. At the time of approval, Kissei estimated that there were more than 10,000 people living with this condition in Japan.
The revised package insert for Tabneos in Japan falls under the Precautions section and includes a warning that serious liver dysfunction, including bile duct vanishing syndrome, may occur, and cases of death have been reported. Kissei’s filing recommends that physicians perform liver function tests on patients before and periodically during treatment, and monitor patients closely thereafter.
The package insert also states that if liver dysfunction occurs, it often occurs within the first 3 months after administering the drug. The document also provides information about the timing of liver function tests and the types of observations that may require intervention by a health care professional.
Kissei added that it has set up a “drug consultation center” for healthcare workers and patients, where they can also respond to questions about the situation.
“Since FDA approval in 2021, the U.S. prescribing information includes information about the risk of serious liver damage (hepatotoxicity), liver monitoring and treatment discontinuation guidance for physicians and patients,” an Amgen spokesperson told Fierce of Tabneos’ U.S. label on Thursday.
The spokesperson added: “These updates from the Ministry of Health, Labor and Welfare will help ensure that healthcare providers and patients in Japan have the most up-to-date information to support treatment decisions for ANCA-associated vasculitis, a rare and potentially life-threatening disease.”
Concerns about liver damage have also put Tabneos under intense scrutiny in the U.S., where the FDA asked Amgen to withdraw the drug in mid-January amid a review of the drug’s risk-benefit profile over questions about the integrity of the data behind the drug’s pivotal clinical trial conducted by Chemocentrics.
However, Amgen pushed back, writing in its fourth-quarter earnings release that it was “not aware of any problems with the patient data underlying the Chemocentrics clinical trial.” The company said it supports Tabneos and will discuss next steps with the FDA to “determine a path forward.”
Days before Amgen announced its U.S. status, European Union regulators also announced they would be reviewing Tabneos, citing Phase 3 data concerns.
Then, in late March, the FDA issued a safety notice warning of 76 cases of drug-induced liver injury for which “reasonable evidence” of a causal relationship to Tabneos was reported to the agency’s Adverse Event Reporting System (FAERS) between the drug’s approval in 2021 and October 2024. The cases recorded in the database led to 54 hospitalizations and eight deaths, although that alone does not establish a causal relationship, the FDA said. time.
At the time, an Amgen representative told Fierce that “patient safety is always our top priority and we are in regular communication with the FDA regarding the safety of our medicines,” adding that the company remains confident in the drug’s risk-benefit profile.
A company spokesperson stressed on Thursday that “out of the more than 8,000 patients in the U.S. treated with Tabneos, there have been no confirmed deaths in the U.S. related to severe liver damage, including vanishing bile duct syndrome (VBDS).”
Meanwhile, late last month, the FDA stepped up its oversight of the drug and proposed withdrawing Tabneos’ U.S. approval, citing new information suggesting that vital data was “manipulated” to give the green light. In addition to questioning the drug’s effectiveness, the FDA’s Center for Drug Evaluation and Research also noted that there are “increasing concerns about the safety of Tabneos” related to cases of severe drug-induced liver injury.
The FDA gave Amgen the option of removing Tabneos from the market or requesting a hearing. In a statement to Mr. Fiers in late April, Amgen said it disagreed with the FDA’s position and was considering its next options.
