By Jonathan Gardner | June 26, 2026
In a landmark decision that promises to reshape the treatment landscape for rare genetic disorders in Europe, the European Medicines Agency’s (EMA) Committee for Medicinal Products for Human Use (CHMP) has issued a positive opinion recommending the marketing authorization of Acadia Pharmaceuticals’ Daybue (trofinetide). The move marks a dramatic reversal of the committee’s earlier stance and comes as part of a sweeping series of regulatory updates that also saw the recommendation to revoke the authorization of Amgen’s inflammatory drug, Tavneos.
For Acadia, the recommendation is a significant victory following a grueling period of clinical review and administrative appeals. For the broader pharmaceutical market, the day’s events underscore the rigorous, often volatile nature of EU drug oversight, where safety signals can swiftly dismantle commercial portfolios even as new therapies for unmet needs gain hard-won access to the market.
The Path to Approval: A Chronology of Daybue’s Journey
The journey of Daybue (trofinetide) in Europe has been anything but straightforward. The therapy, which is the first of its kind to target the neurobehavioral symptoms of Rett syndrome—a severe, rare genetic brain disorder—was initially met with skepticism by European regulators.
- February 2026: In a major setback for Acadia, the CHMP issued a negative opinion regarding the marketing authorization for Daybue. The committee expressed concerns over the robustness of the clinical data provided, stalling the drug’s expansion into the 27-nation European Union.
- March 2026: Undeterred, Acadia Pharmaceuticals filed a formal request for a re-examination of the CHMP’s decision. This process allowed the company to present additional analyses and address the specific concerns raised by the scientific committee.
- June 2026: Following a comprehensive review of the supplemental data, the CHMP reversed its previous position, issuing a positive opinion that clears the way for a final decision by the European Commission.
The European Commission typically follows the CHMP’s lead, and a final, binding approval is expected within the next 67 days. This timeline brings hope to families across Europe, where there currently exists a void in approved therapies for the specific neurobehavioral manifestations of Rett syndrome.
Understanding the Clinical Impact
Rett syndrome is a devastating condition that primarily affects females, often manifesting in early childhood. It leads to a loss of communication skills, impaired motor coordination, and significant cognitive challenges. Until now, European patients have largely relied on palliative care and symptom management rather than targeted therapies.
"The CHMP’s positive opinion for Daybue is an important milestone in our mission to bring this innovative therapy to the EU," said Acadia CEO Catherine Owen Adams in a statement following the announcement. "We are moving closer to addressing the urgent needs of a patient population that has lived for too long without a specifically approved treatment for this devastating condition."
The drug’s mechanism, known as trofinetide, works by reducing neuroinflammation and supporting synaptic function. Having already secured U.S. Food and Drug Administration (FDA) approval in 2023, the drug has established a clinical footprint that Acadia now hopes to mirror across the Atlantic.
Market Implications and Financial Forecasts
The news of the CHMP’s positive opinion sent ripples through the financial markets, with Acadia’s shares surging as much as 12% in morning trading on June 26. Investors have been closely monitoring the European expansion, viewing it as a critical pillar for the company’s long-term growth.
Mizuho analyst Uy Ear, in a recent client note, suggested that the market may be underestimating the potential of the European market for Daybue. Acadia has previously issued 2028 sales guidance of $700 million, a figure that includes what the company describes as a "modest amount" of European revenue. However, with the regulatory hurdle cleared, analysts like Ear argue that the Wall Street consensus forecast of $595 million may be overly conservative.
The Downward Spiral of Tavneos
While Acadia celebrated, Amgen faced a significant regulatory blow as the CHMP recommended the revocation of marketing authorization for Tavneos (avacopan). Used for the treatment of two rare, severe forms of vasculitis—a group of conditions characterized by blood vessel inflammation—Tavneos has been under intense scrutiny due to its safety profile.
The Safety Crisis
The primary driver for the recommendation to pull the drug is the emergence of serious side effects, specifically "vanishing bile duct syndrome." Reports from Japan, facilitated by Amgen’s commercial partner Kissei, indicate that 20 patients treated with the medication have died. This safety signal has triggered a global re-evaluation of the drug’s benefit-risk profile.
The U.S. vs. EU Conflict
The situation is further complicated by the divergent paths taken by regulatory bodies in the United States and Europe. In the U.S., the FDA has explicitly requested that Amgen withdraw Tavneos from the market. The FDA’s request is rooted not only in safety concerns but also in allegations that the drug’s developer, ChemoCentryx (which Amgen acquired), manipulated clinical trial data to present a more favorable safety and efficacy profile.
Amgen has staunchly defended the drug, declining the FDA’s withdrawal request. In a bid to maintain market presence, the company recently presented "real-world data" at the European Alliance of Associations for Rheumatology (EULAR) 2026 conference, arguing that the evidence supports the drug’s continued use in specific patient populations. The CHMP’s recommendation to revoke approval suggests that European regulators remain unconvinced by these arguments, prioritizing the safety risks over the presented real-world evidence.
A Broader Expansion of the Therapeutic Pipeline
The CHMP’s meeting this week was not limited to these two high-profile cases. In a move reflecting the rapid evolution of oncology and immunology, the committee recommended the expansion of several key therapies:
- Jaypirca (Eli Lilly): The BTK inhibitor is now poised for a broader application across all lines of chronic lymphocytic leukemia. The decision follows compelling data presented by Lilly at the American Society of Hematology (ASH) meeting last December, where the drug demonstrated superior efficacy in patients who had failed earlier lines of treatment.
- Datroway (AstraZeneca/Daiichi Sankyo): This antibody-drug conjugate has received support for use in first-line triple-negative breast cancer. Specifically, it is aimed at patients who do not qualify for traditional immunotherapy, potentially opening a new standard of care for a notoriously difficult-to-treat cancer.
- Tecvayli (Johnson & Johnson): The committee recommended expanding the use of this bispecific antibody for second-line multiple myeloma treatment, a significant step forward in the sequencing of care for blood cancer patients.
- Opzelura (Incyte): Already a known treatment for vitiligo, the committee’s backing for its use in atopic dermatitis marks a major expansion, positioning it as a significant competitor in the dermatology space.
Conclusion: Balancing Innovation and Safety
The June 2026 CHMP session serves as a microcosm of the modern pharmaceutical landscape. On one hand, the green-lighting of Daybue highlights the industry’s success in identifying and developing treatments for rare, underserved conditions. It is a testament to the power of re-examination and the persistence of developers in the face of initial regulatory rejection.
On the other hand, the move to revoke Tavneos serves as a sobering reminder of the "post-approval" reality. Regulatory vigilance does not end with the first authorization; it is a continuous process that demands transparency and long-term safety monitoring. As Amgen and the European Commission enter the final stages of the revocation process, the industry will be watching closely to see how the company navigates the legal and reputational fallout.
As these medicines move toward the next phase of their lifecycle—whether toward launch or withdrawal—the primary focus remains on the patient. For those with Rett syndrome, the path ahead looks brighter, while for those affected by vasculitis, the regulatory debate underscores the ongoing challenge of ensuring that life-saving innovations do not come at an unacceptable cost to patient health.
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