By Jonathan Gardner
Published June 26, 2026
In a high-stakes series of regulatory decisions that will reshape the European pharmaceutical landscape, the Committee for Medicinal Products for Human Use (CHMP) has delivered a landmark reversal regarding Acadia Pharmaceuticals’ Rett syndrome treatment, Daybue. The committee’s endorsement marks a significant victory for patients suffering from the rare neurodevelopmental disorder, while simultaneously signaling a harsh crackdown on other therapies deemed to pose significant safety risks.
A Turnaround for Acadia’s Daybue
The European Medicines Agency’s (EMA) scientific committee, the CHMP, has formally backed the marketing authorization for Acadia Pharmaceuticals’ Daybue (trofinetide). This decision follows a rigorous re-examination process prompted by the company after the committee initially issued a negative opinion in February 2026.
The initial rejection had cast doubt on the drug’s path to European patients. However, by leveraging additional data and engaging in a formal appeal process, Acadia successfully addressed the committee’s concerns. With this positive opinion, the recommendation now moves to the European Commission, which typically grants final authorization within 67 days.
Daybue, which was first approved by the U.S. Food and Drug Administration (FDA) in 2023, is the first and only therapy indicated for Rett syndrome—a severe, genetic condition characterized by the loss of motor skills, speech, and respiratory control.
"The CHMP’s positive opinion for Daybue is an important milestone in our mission to bring this innovative therapy to the EU, where there are no therapies specifically approved for the neurobehavioral symptoms of this devastating condition," said Acadia CEO Catherine Owen Adams in a statement following the announcement.
Chronology: The Road to European Authorization
The journey for Daybue in Europe has been marked by regulatory friction:
- 2023: The U.S. FDA grants approval for Daybue, providing a much-needed lifeline for pediatric and adult patients suffering from Rett syndrome.
- February 2026: In a major setback for Acadia, the CHMP issues a negative opinion regarding the marketing authorization of trofinetide in the European Union, citing concerns over the data package submitted by the company.
- March 2026: Acadia Pharmaceuticals formally requests a re-examination, appointing a new set of reviewers to assess the therapy’s clinical profile.
- June 2026: Following the submission of supplemental data and a comprehensive review, the CHMP reverses its stance, issuing a positive opinion that clears the path for commercialization across the 27 EU member states.
Financial Implications and Market Reaction
The market’s response to the CHMP’s shift was immediate and optimistic. Shares of Acadia Pharmaceuticals climbed as much as 12% in morning trading on June 26.
Wall Street analysts are recalibrating their models to account for the European expansion. Mizuho analyst Uy Ear noted that Acadia’s internal 2028 sales guidance of $700 million appears to incorporate only a "modest amount" of European revenue. Given the favorable regulatory outcome, Ear suggested that the existing Wall Street consensus forecast of $595 million for the company’s total sales may be significantly too conservative. The inclusion of the European market, where there is currently no competition for the symptomatic treatment of Rett syndrome, provides Acadia with a clear runway for growth.
The Downfall of Tavneos: Safety Concerns Mount
While Daybue’s prospects brightened, the CHMP dealt a devastating blow to Amgen’s Tavneos (avacopan). The committee recommended the revocation of the drug’s marketing authorization for the treatment of two rare, life-threatening inflammatory conditions that affect blood vessels.
The decision was driven by alarming safety data. Reports from Japan, shared by Amgen’s commercial partner Kissei, indicate that at least 20 patients have died after receiving the treatment. The deaths have been linked to a severe adverse event known as "vanishing bile duct syndrome," a condition that causes the progressive destruction of the bile ducts in the liver.
This development adds to an already fraught regulatory environment for Tavneos. In the United States, the FDA has previously requested that Amgen withdraw the drug from the market, alleging that ChemoCentryx—the company that originally developed the drug before its acquisition by Amgen—manipulated clinical trial data.
Amgen has remained defiant, refusing to initiate a voluntary withdrawal in the U.S. The company recently highlighted "real-world data" that it claims supports the safety and efficacy of Tavneos in patients with rare autoimmune conditions. However, the CHMP’s recommendation to pull the drug from the European market suggests that regulators are increasingly skeptical of the company’s defense.
Expansion of Oncology and Dermatology Portfolios
Beyond the high-profile drama surrounding Daybue and Tavneos, the CHMP’s June meeting resulted in a flurry of approvals aimed at expanding the therapeutic indications for several blockbuster medicines. These moves represent a significant shift toward broadening the reach of existing drugs to new patient populations.
Oncology Advancements
- Jaypirca (Eli Lilly): The committee voted to expand the use of this BTK inhibitor across all lines of therapy for chronic lymphocytic leukemia (CLL). This recommendation builds on compelling data presented at the American Society of Hematology meeting in December 2025, which demonstrated the drug’s utility in patients who have failed prior treatments.
- Datroway (AstraZeneca and Daiichi Sankyo): This antibody-drug conjugate received a recommendation for use in first-line triple-negative breast cancer (TNBC) for patients who are not eligible for immunotherapy. This is a critical development for a patient group that has historically had few effective options.
- Tecvayli (Johnson & Johnson): The bispecific antibody received a green light for expanded use in second-line multiple myeloma, marking a transition toward earlier intervention in the treatment of this blood cancer.
Dermatology and Immune-Mediated Diseases
- Opzelura (Incyte): In a major expansion, the CHMP recommended the use of Opzelura for atopic dermatitis. Previously limited to vitiligo, this approval significantly increases the addressable market for the topical treatment, positioning it as a key contender in the competitive inflammatory skin disease space.
Implications for the Pharmaceutical Industry
The CHMP’s recent session underscores a "dual-track" approach to regulation: a willingness to work with manufacturers to resolve complex clinical questions for rare disease therapies, balanced by an uncompromising stance on drug safety.
For companies like Acadia, the re-examination process serves as a vital safeguard against initial regulatory errors, provided the company can produce robust, supplemental data. Conversely, the situation with Amgen’s Tavneos serves as a stark reminder of the long-term risks associated with post-marketing safety signals. As real-world evidence becomes more integrated into the regulatory decision-making process, pharmaceutical companies must prepare for heightened scrutiny long after a drug has reached the market.
Furthermore, the broad expansion of labels for drugs like Jaypirca and Opzelura signals that the EMA is prioritizing patient access to targeted therapies. By allowing these drugs to move into earlier lines of treatment or broader therapeutic categories, regulators are essentially endorsing the shift toward precision medicine.
As the European Commission prepares to formalize these recommendations over the next two months, the industry will be watching closely to see if this trend of regulatory flexibility for rare diseases continues to define the EU’s approach to innovation in the latter half of the decade.
