Tavneos Mass Tort Alert: FDA Moves to Ban Drug Linked to Fatal Liver Injuries & Manipulated Trial Data

What Is Tavneos — And Why Is It Under Fire?

Tavneos (avacopan) is a prescription drug approved by the FDA in October 2021 to treat severe active anti-neutrophil cytoplasmic autoantibody (ANCA)-associated vasculitis — specifically granulomatosis with polyangiitis (GPA) and microscopic polyangiitis (MPA) [10]. These are rare, life-threatening autoimmune conditions that cause blood vessel inflammation throughout the body. Tavneos was developed by ChemoCentryx, Inc., and was heralded as a breakthrough treatment when it was first approved [27]. Amgen acquired ChemoCentryx in October 2022 for approximately $3.7 billion [9], assuming responsibility for the drug's marketing, safety monitoring, and regulatory obligations in the United States.

Now, just a few years after its approval, Tavneos is at the center of a mounting regulatory and legal storm. The FDA has proposed withdrawing the drug's approval entirely, citing two explosive allegations: that the original clinical trial data was manipulated by unblinded study personnel, and that post-marketing surveillance has revealed serious, sometimes fatal, liver injuries in patients [5]. As of June 2026, law firms across the country are actively investigating and filing injury claims on behalf of patients who were harmed, setting the stage for what many legal observers believe could become the next significant pharmaceutical mass tort [1].

The FDA's Case Against Tavneos: Data Manipulation and Deadly Liver Injuries

The FDA's Proposed Withdrawal

In one of the most dramatic regulatory actions of 2026, the FDA's Center for Drug Evaluation and Research (CDER) officially proposed to withdraw approval of Tavneos between April 27 and 30, 2026 [5]. The agency's proposal rests on two pillars. First, the FDA asserts that "new information shows that the applicant's unblinded study personnel manipulated endpoint results for the Phase 3 study" — the pivotal ADVOCATE trial — and that the original approval application contained "untrue statements of material fact" regarding database lock, unblinding, and study analyses [11]. Second, the FDA contends that post-market safety data reveals serious liver injuries that tip the drug's benefit-risk balance unfavorably [10].

This is an extraordinary allegation. The FDA's approval of any drug is predicated on the truthfulness and integrity of submitted clinical data. When the agency finds that data may have been manipulated after unblinding — meaning study personnel knew which patients received the drug versus a placebo before finalizing endpoints — the scientific foundation of that approval crumbles. Critically, this information only came to light more than three years after Tavneos was approved, and it was derived in part from an expert report known as the "Walton Report," which was filed on May 29, 2025, in a separate shareholder securities fraud lawsuit [7].

Amgen's Response to the Information Request

The FDA sent Amgen an information request, and Amgen's response on August 22, 2025, confirmed key factual allegations from the Walton Report — though Amgen contended that the data remained accurate and that any readjudications were appropriate [7]. Despite this, the FDA moved forward with its proposed withdrawal. Amgen has refused the FDA's earlier request to voluntarily withdraw the drug from the U.S. market and has opted instead to request a formal hearing to defend the drug's approval [9]. Amgen has brought on the Duke Clinical Research Institute (DCRI) to conduct an independent review of the Phase 3 ADVOCATE study data, with Amgen's submission — including the DCRI review — due by June 29, 2026, which is also the deadline for public comments on the FDA's proposal [14].

The March 2026 FDA Drug Safety Communication

Months before the proposed withdrawal, on March 31, 2026, the FDA issued a formal Drug Safety Communication alerting patients and healthcare professionals about serious post-marketing cases of drug-induced liver injury (DILI) associated with Tavneos, including fatal cases and reports of vanishing bile duct syndrome (VBDS) [18]. This communication followed an earlier February 2026 request by the FDA that Amgen voluntarily pull the drug from market — a request Amgen declined [19].

The Science of the Harm: What Tavneos Does to the Liver

Drug-Induced Liver Injury (DILI) and Vanishing Bile Duct Syndrome (VBDS)

The primary serious conditions linked to Tavneos are drug-induced liver injury (DILI) and vanishing bile duct syndrome (VBDS) [6]. DILI is a broad term for liver damage caused directly by a drug or its metabolites. VBDS is a particularly severe and progressive form of liver injury in which the small bile ducts inside the liver are destroyed over time, impairing the liver's ability to function. VBDS can be irreversible and may progress to liver failure, requiring a liver transplant or resulting in death [15].

From Tavneos's approval in October 2021 through October 2024, the FDA Adverse Event Reporting System (FAERS) received 76 cases of drug-induced liver injury with "reasonable evidence" of a causal association to Tavneos [10]. Of these 76 cases, 74 resulted in serious outcomes — including 54 hospitalizations and eight deaths [10]. The FDA also identified seven cases of vanishing bile duct syndrome, three of which were fatal [18]. The first known case of VBDS associated with Tavneos was reported to the FDA on November 1, 2022 [12].

Symptoms of liver injury that patients and physicians should watch for include yellowing of the skin or eyes (jaundice), unusual tiredness or fatigue, severe itching (pruritus), dark or tea-colored urine, pain or swelling in the stomach or upper right abdomen, nausea and vomiting, light-colored stools, bleeding or bruising more easily, and loss of appetite [28]. Critically, symptoms of liver injury typically emerged quickly after starting the drug, with a median onset of just 46 days after treatment began [13]. Most cases of VBDS occurred within 90 days of initiating Tavneos therapy [13].

Who Is Most at Risk?

Most patients who developed vanishing bile duct syndrome were aged 65 years and older, with cases reported predominantly from Japan — though VBDS can affect patients of any age or ethnicity [6]. In Japan, Kissei Pharmaceutical (which holds rights to Tavneos there) reported 20 fatal cases of serious liver injury from over 8,500 treated patients, though a causal relationship could not always be determined in every case [4].

Amgen has pushed back on these figures. On May 15, 2026, Amgen issued a statement clarifying that the Japanese fatality figures included cases where a causal relationship was not determined, and asserting that there have been no known deaths in the U.S. linked to serious liver injury — including VBDS — among the more than 8,000 U.S. patients treated with Tavneos since its 2021 approval [17]. Amgen points to at least 23 published real-world studies globally involving more than 1,200 reported patients, and says that evidence from the ADVOCATE trial, routine post-marketing safety surveillance, and real-world evidence all demonstrate the drug's effectiveness and a favorable benefit-risk profile [22].

Serious Infections: Another Hidden Risk

In addition to liver injury, Tavneos can cause serious infections — including fatal infections — by weakening the immune system [20]. Because ANCA-associated vasculitis itself requires immunosuppressive therapy, patients on Tavneos may face a compounded infection risk. The most common serious infections reported in clinical and post-marketing settings were pneumonia and urinary tract infections (UTIs) [25]. This dual risk profile — severe liver toxicity and immune suppression — has heightened concerns among patient advocates and legal investigators alike [3].

The Legal Landscape: Lawsuits, Investigations, and the Road to Mass Tort

Active Nationwide Investigations

As of June 2026, individual lawsuits are being investigated nationwide by various law firms on behalf of patients who suffered serious liver injuries or severe infections after using Tavneos [1]. The investigations involve claims of drug-induced liver injury (DILI), vanishing bile duct syndrome (VBDS), liver failure, hospitalization, liver transplant, and wrongful death [13]. Law firms such as Levin Law, Ferrer Poirot Feller, and the Law Offices of Thomas J. Lamb are among those actively seeking clients for potential Tavneos injury claims [1][13]. Parker Waichman LLP has also reported on Tavneos liver injury lawsuits [3].

While law firms are aggressively investigating and building cases, as of June 2026 no Multi-District Litigation (MDL) or certified class action has been formally established for Tavneos patient injury claims [8]. However, the scale of the FDA's action — a full proposed withdrawal of approval based on data manipulation and fatal outcomes — dramatically increases the likelihood that litigation will consolidate and expand in the months ahead. MDL proceedings are typically initiated once a sufficient number of individual lawsuits are filed in federal courts across multiple districts, and legal experts widely view the Tavneos situation as tracking that trajectory [1].

The Shareholder Lawsuit: A Crucial Precursor

Before the patient injury lawsuits emerged, ChemoCentryx faced a shareholder securities fraud lawsuit filed in May 2021 [7]. That lawsuit alleged that ChemoCentryx knew about FDA concerns regarding Tavneos but deliberately downplayed them, misleading investors about the drug's prospects. The Walton Report — an expert report filed by plaintiffs in that securities fraud litigation on May 29, 2025 — alleged data manipulation in the ADVOCATE trial [7]. While the shareholder lawsuit was ultimately dismissed on August 15, 2025, when the court granted summary judgment in favor of ChemoCentryx [7], the Walton Report's allegations did not disappear. The FDA appears to have used that report as a springboard for its own investigation, ultimately leading to the proposed withdrawal of Tavneos [11].

This chain of events — from a shareholder lawsuit to an expert report to an FDA withdrawal proposal to patient injury investigations — is a pattern that legal scholars and mass tort practitioners recognize. It mirrors the early stages of other major pharmaceutical litigations where internal or expert-revealed misconduct served as the catalyst for sweeping regulatory and legal action.

What Injured Patients Can Claim

Patients who suffered serious harm after taking Tavneos may have viable legal claims based on several theories of liability [13]. These include:

• Failure to Warn: Plaintiffs may argue that Amgen and ChemoCentryx failed to adequately warn patients and physicians about the risk of severe liver injury and VBDS in a timely manner [12].

• Negligence: Claims that the manufacturer was negligent in its clinical trial conduct, post-market surveillance, and/or its delayed disclosure of safety risks [8].

• Fraud and Misrepresentation: Based on the FDA's allegation that the approval application contained "untrue statements of material fact" regarding the ADVOCATE study data [11].

• Products Liability — Design Defect: Arguments that the drug's molecular mechanism creates an unreasonably dangerous risk of liver toxicity [21].

• Wrongful Death: For families of patients who died from Tavneos-related liver failure or other complications [3].

No Settlements Yet — But That Can Change Quickly

As of June 2026, there are no publicly disclosed settlements or jury verdicts in patient injury cases related to Tavneos [8]. This is not surprising given the early stage of litigation. In most pharmaceutical mass torts, settlements do not emerge until after an MDL is established, bellwether trials are selected, and initial trial verdicts signal the value of cases to both sides. Given the strength of the FDA's position — including allegations of data manipulation and documented fatalities — legal analysts anticipate that settlement pressure on Amgen will grow substantially as litigation matures [1].

The Manufacturer's Defense: What Amgen Is Arguing

Amgen has mounted an aggressive defense of Tavneos. The company publicly disagrees with the FDA's assessment of both the drug's effectiveness and its safety profile [22]. Amgen maintains that evidence from the Phase 3 ADVOCATE trial, routine post-marketing safety surveillance, and real-world evidence from over 8,000 treated patients in the U.S. demonstrate the drug's effectiveness and a favorable benefit-risk profile [17]. On May 22, 2026, Amgen released a public FAQ reiterating confidence in Tavneos and noting that the FDA's proposed withdrawal does not change the drug's current approval status or availability — advising patients to continue treatment unless instructed otherwise by their physician [26].

On June 2, 2026, Amgen issued an "Important Update Regarding TAVNEOS" to healthcare professionals, emphasizing the drug's benefit-risk profile and its critical role in treating ANCA-associated vasculitis, while acknowledging the updated safety language regarding VBDS that was added to the U.S. Prescribing Information (USPI) on May 29, 2026 [29]. The company proposed additional safety language to the FDA regarding the risk of VBDS as far back as 2024, suggesting it was aware of the emerging signal [7].

Critically, Amgen has enlisted the Duke Clinical Research Institute (DCRI) to independently review the ADVOCATE study data, with its submission due June 29, 2026 [14]. This is a high-stakes gamble: if the DCRI review vindicates the original trial data, Amgen will have a powerful counter-narrative. If it corroborates the FDA's concerns, it could accelerate the regulatory and legal fallout [19].

A Timeline of Key Events

Understanding the full arc of the Tavneos controversy requires placing events in chronological order [5][10][11][18]:

• October 2021: FDA approves Tavneos for ANCA-associated vasculitis [10].

• May 2021: Shareholder securities fraud lawsuit filed against ChemoCentryx [7].

• October 2022: Amgen acquires ChemoCentryx for $3.7 billion [9].

• November 1, 2022: First known case of VBDS associated with Tavneos reported to the FDA [12].

• 2023–2025: Post-marketing surveillance identifies increasing reports of serious liver injury, including DILI and VBDS, some resulting in hospitalization and death [6].

• May 29, 2025: The Walton Report is filed in the shareholder lawsuit, alleging data manipulation in the ADVOCATE trial [7].

• August 15, 2025: Court dismisses the shareholder securities fraud lawsuit, granting summary judgment in favor of ChemoCentryx [7].

• August 22, 2025: Amgen's response to an FDA information request confirms key factual allegations from the Walton Report [7].

• February 2026: FDA requests Amgen voluntarily withdraw Tavneos; Amgen declines [19].

• March 31, 2026: FDA issues Drug Safety Communication about serious, sometimes fatal, liver injuries associated with Tavneos [18].

• April 27–30, 2026: FDA's CDER officially proposes to withdraw Tavneos approval [5].

• May 15, 2026: Amgen issues statement on Japanese fatality reports [17].

• May 22, 2026: Amgen releases FAQ reiterating confidence in Tavneos [26].

• May 29, 2026: Tavneos USPI updated with enhanced liver monitoring and VBDS warnings [29].

• June 2, 2026: Amgen issues "Important Update" to healthcare professionals [29].

• June 12, 2026: Reports confirm Amgen is preparing for FDA hearing with DCRI review [14].

• June 29, 2026: Deadline for Amgen's FDA hearing submission and public comments on proposed withdrawal [5].

The Affected Population: Who Should Be Paying Attention?

Tavneos is specifically approved for adults with severe active ANCA-associated vasculitis — a rare disease affecting a relatively small but deeply vulnerable patient population [23]. Despite the drug's narrow indication, over 8,000 patients have been treated with Tavneos in the U.S. since its approval in 2021, according to Amgen [17]. Given that 76 FAERS cases of liver injury were identified from that population through October 2024 — with 74 resulting in serious outcomes including 54 hospitalizations and 8 deaths — the proportion of patients experiencing severe harm is significant [10].

Patients who are particularly at risk include those aged 65 and older, who represented the majority of VBDS cases [6]. The drug's prescribing information has included reference to the risk of serious liver injury and specific liver monitoring guidance since 2021 [27], but legal experts argue this language may have been insufficient given the severity and rapidity of liver injury onset, with a median of just 46 days to symptom appearance [13].

If you or a loved one took Tavneos and subsequently experienced any of the following, you should contact a qualified attorney immediately: jaundice (yellowing of skin or eyes), extreme fatigue, severe itching, dark urine, abdominal pain, nausea or vomiting, liver failure, liver transplant, or death of a family member [28]. The statute of limitations for pharmaceutical injury claims varies by state, meaning delay in consulting an attorney can forfeit your legal rights [21].

Is Tavneos the Next Mass Tort? The Legal Expert Perspective

Mass torts arise when a large number of people are harmed by the same product, and the factual and legal issues are sufficiently common to justify coordinated litigation. Tavneos checks multiple boxes that have historically defined successful mass tort litigations [8]:

• FDA regulatory action: A formal proposed withdrawal of approval is among the strongest regulatory signals of a product's danger [11].

• Allegations of fraud and data manipulation: The FDA's allegation that the original approval application contained "untrue statements of material fact" creates a powerful narrative of corporate misconduct [5].

• Documented serious injuries and fatalities: With 74 serious adverse events including 8 deaths in the FAERS database through October 2024 [10], the human toll is both real and documented.

• Multiple law firms actively investigating: Levin Law, Ferrer Poirot Feller, the Law Offices of Thomas J. Lamb, and Parker Waichman LLP are among those building case inventories [1][13][3].

• A well-defined victim class: Patients with ANCA-associated vasculitis who took Tavneos and suffered liver injury constitute a clear and identifiable group [23].

The primary factor currently distinguishing Tavneos from confirmed mass torts is the absence of a formally established MDL or class action for patient injuries [8]. However, MDLs are established after lawsuits are filed, not before. The active investigation phase currently underway across multiple law firms is the necessary precursor to MDL formation [1]. Legal observers note that the FDA hearing process — with its June 29, 2026 submission deadline — will be a watershed moment: if the FDA proceeds with withdrawal despite Amgen's hearing defense, the floodgates of litigation are likely to open [14].

What Patients and Families Should Do Right Now

If you took Tavneos and experienced serious liver problems — or if a loved one died after taking the drug — here are the critical steps to take [1][13]:

1. Seek immediate medical attention if you are currently experiencing symptoms of liver injury. Do not stop taking Tavneos without consulting your physician first [26].

2. Document everything. Keep all medical records, prescriptions, pharmacy receipts, and physician notes related to your Tavneos treatment and any resulting injuries.

3. Contact a qualified mass tort attorney as soon as possible. Statutes of limitations vary by state, and waiting too long can permanently bar your ability to file a claim [21].

4. Report adverse events to the FDA through the MedWatch system at FDA.gov [18]. Your report contributes to the public health record and may help other patients.

5. Do not accept any settlements without first consulting an attorney experienced in pharmaceutical mass tort litigation [8].

Conclusion: The Storm Is Building

The Tavneos situation is, in many respects, a textbook example of how a pharmaceutical mass tort takes shape. A drug is approved based on clinical trial data later alleged to be manipulated [11]. Post-market surveillance reveals serious, sometimes fatal, injuries that were not fully apparent — or perhaps not fully disclosed — at the time of approval [10]. The FDA takes increasingly aggressive regulatory action, first with a safety communication [18], then a voluntary withdrawal request [19], and finally a formal proposed withdrawal [5]. And attorneys across the country begin mobilizing to represent the injured [1][13].

What makes Tavneos potentially unique among emerging mass torts is the explosive allegation of data manipulation at the approval stage. If proven definitively, this goes beyond a simple failure-to-warn case and enters the territory of fraud on the FDA — a claim with profound legal and financial implications for Amgen [11]. Over 8,000 patients in the U.S. have been exposed to this drug [17], 74 have already suffered serious documented harm [10], and the legal machinery is beginning to turn in earnest.

Whether Tavneos ultimately becomes the next Vioxx, Risperdal, or talc litigation remains to be seen. But the conditions are in place. The harm is documented. The regulatory action is unprecedented. And the legal community is watching closely. For patients who trusted this drug with their health, and for families who lost loved ones, the pursuit of accountability is just beginning [1][3][13].