European Commission Approves DAYBU® (trofinetide) as the First and Only Treatment for Neurobehavioral Symptoms of Rett Syndrome in the European Union

Acadia Pharmaceuticals Inc. (Nasdaq: ACAD) today announced that the European Commission (EC) has granted marketing authorization for DAYBU (trofinetide) for the treatment of neurobehavioral symptoms of Rett syndrome in adults and pediatric patients aged five years and older, making it the first and only treatment approved for Rett syndrome in the European Union (EU).

“The approval of DAYBU marks a significant milestone for the Rett syndrome community in the EU and advances our mission to bring this innovative treatment to patients and families who have long faced a profound unmet medical need,” said Catherine Owen Adams, Acadia’s Chief Executive Officer. “For people living with Rett syndrome, a devastating rare neurodevelopmental disorder, there have been no approved treatment options in the EU. We are proud to make DAYBU available and look forward to supporting patients, caregivers, and healthcare providers gain access to treatment."

The DAYBU marketing authorization in the EU is primarily based on results from the Phase 3 LAVENDER™ study, which demonstrated statistically significant and clinically meaningful improvements in core features of Rett syndrome, as measured by the Rett Syndrome Behaviour Questionnaire (RSBQ) and Clinical Global Impression-Improvement (CGI-I) scale co-primary endpoints.

“Rett syndrome places a profound burden on individuals, families, and caregivers, yet treatment options have remained extremely limited,” said Prof. Nadia Bahi, MD, PhD, Pediatric Neurology at Necker-Enfants Malades University Hospital, Paris Cité University, Paris, France. “Today's approval in the European Union is an important milestone that recognizes the significant unmet medical need in this rare disease. It provides clinicians with a new treatment option to help address the neurobehavioral symptoms of Rett syndrome and represents progress for the Rett community.”

With this approval, DAYBU is authorized to be marketed in all 27 EU member states, as well as Iceland, Liechtenstein, and Norway. As a next step, Acadia will now begin pricing and reimbursement negotiations with relevant national authorities to potentially bring DAYBU to patients across the EU.

About Rett Syndrome

Rett syndrome is a rare, complex, neurodevelopmental disorder and occurs in approximately one of every 10,000 to 15,000 female births worldwide.^1-3 A child with Rett syndrome generally exhibits an early period of apparently normal development until six to 18 months, when many of their skills seem to slow down or stagnate. This is typically followed by a regression phase when the child loses acquired communication skills and purposeful hand use. The child may then experience a plateau period in which they could show mild recovery in cognitive interests, but body movements remain severely diminished. As they age, those individuals living with Rett may continue to experience a stage of motor deterioration, which can last the rest of the patient’s life.² Rett syndrome is typically caused by a genetic mutation on the MECP2 gene.⁴ In preclinical studies, deficiency in MeCP2 function is thought to lead to impairment in synaptic communication and brain plasticity, and the deficits in synaptic function may be associated with Rett manifestations.^4-6

Symptoms of Rett syndrome may also include development of hand stereotypies, such as hand wringing and clapping, and gait abnormalities.⁷ Most individuals living with Rett syndrome typically live into adulthood and require intense round-the-clock care.^1,8 Rett syndrome is associated with a substantial physical, psychological, social, and economic burden, significantly affecting the quality of life of both patients and their caregivers.^9-11

About DAYBU^® (trofinetide)

In Rett syndrome, levels of insulin-like growth factor 1 (IGF-1) in the brain are lower than normal, which is thought to affect nerve function. IGF-1 is a hormone that is important for the normal development and functioning of the nervous system. The active substance in DAYBU (trofinetide), is made up of a molecule derived from IGF-1.

Trofinetide is approved for use under the name DAYBUE^® and DAYBUE^®STIX in the United States and under the name DAYBUE^® in Canada and DAYBU^® in the European Union.

About Acadia Pharmaceuticals

Acadia is committed to turning scientific promise into meaningful innovation that makes the difference for underserved neurological and rare disease communities around the world. Our commercial portfolio includes the first and only FDA-approved treatments for Parkinson’s disease psychosis and Rett syndrome. We are developing the next wave of therapeutic advancements with a robust and diverse pipeline that includes mid- to late-stage programs in Alzheimer’s disease psychosis and Lewy body dementia psychosis, along with earlier-stage programs that address other underserved patient needs. At Acadia, we’re here to be their difference. For more information, visit us at acadia.com and follow us on LinkedIn and X.

Forward-Looking Statements

This press release contains forward-looking statements within the meaning of the Private Securities Litigation Reform Act of 1995. Forward-looking statements include all statements other than statements of historical fact and can be identified by terms such as “may,” “will,” “should,” “could,” “would,” “expects,” “plans,” “anticipates,” “believes,” “potential,” and similar expressions (including the negative thereof) intended to identify forward-looking statements. Forward-looking statements contained in this press release include, but are not limited to, statements about the importance of DAYBU as a treatment for neurobehavioral symptoms of Rett syndrome in adults and pediatric patients aged five years and older, the anticipated benefits of DAYBU to patients, caregivers, healthcare providers, and the Rett community, the clinical benefit of DAYBU, the ability of patients to gain access to DAYBU, and our expectations regarding the future occurrence of pricing and reimbursement negotiations, including our ability to timely gain pricing and reimbursement of DAYBU^® in EU member states, Iceland, Liechtenstein, and Norway. Forward-looking statements are subject to known and unknown risks, uncertainties, assumptions and other factors that may cause our actual results, performance or achievements to differ materially and adversely from those anticipated or implied by our forward-looking statements. Such risks, uncertainties and other factors include, but are not limited to, the inherent uncertainty regarding the pricing and reimbursement negotiations; our dependency on the continued successful commercialization of our products and our ability to maintain or increase sales of our products; our ability to obtain necessary regulatory approvals to commercialize our products and product candidates; if and when approved, market acceptance of our products and our ability to continue to stay in compliance with applicable laws and regulations. Given the risks and uncertainties, you should not place undue reliance on these forward-looking statements. For a discussion of these and other risks, uncertainties and other factors that may cause our actual results, performance or achievements to differ, please refer to our quarterly report on Form 10-Q for the period ended June 30, 2026, filed on August 5, 2026, as well as our subsequent filings with the Securities and Exchange Commission from time to time. The forward-looking statements contained herein are made as of the date hereof, and we undertake no obligation to update them after this date, except as required by law.

References

¹ Fu C, Armstrong D, Marsh E, et al. Consensus guidelines on managing Rett syndrome across the lifespan. BMJ Paediatrics Open. 2020;4:e000717.
² Kyle SM, Vashi N, Justice MJ. Rett syndrome: a neurological disorder with metabolic components. Open Biol. 2018; 8:170216.
³ May DM, Neul JL, Satija A, et al. Real-world clinical management of individuals with Rett syndrome: a physician survey. J Med Econ. 2023;26(1):1570-1580.
⁴ Amir RE, Van den Veyver IB, Wan M, et al. Rett syndrome is caused by mutations in X-linked MECP2, encoding methyl-CpG-binding protein 2. Nat Genet. 1999; 23(2):185-188.
⁵ Fukuda T, Itoh M, Ichikawa T, et al. Delayed maturation of neuronal architecture and synaptogenesis in cerebral cortex of Mecp2-deficient mice. J Neuropathol Exp Neurol. 2005; 64(6):537-544.
⁶ Asaka Y, Jugloff DG, Zhang L, et al. Hippocampal synaptic plasticity is impaired in the Mecp2-null mouse model of Rett syndrome. Neurobiol Dis. 2006; 21(1):217-227.
⁷ Neul JL, Kaufmann WE, Glaze DG, et al. Rett syndrome: revised diagnostic criteria and nomenclature. Ann Neurol. 2010; 68(6):944-950.
⁸ Tarquinio DO, Hou W, Neul JL, et al. The changing face of survival in Rett syndrome and MECP2-related disorders. Pediatr Neurol. 2015; 53(5):402-411.
⁹ Prange EO, Beisang A, Pehlivan D, et al. Expert Consensus on Real-World Use of Trofinetide for Rett Syndrome Using a Modified Delphi Method. Annals of the Child Neurology Society. 2026; 38–51.
¹⁰ Kaufmann WE, Percy AK, Neul JL, et al. Burden of illness in Rett syndrome: initial evaluation of a disorder-specific caregiver survey. Orphanet J Rare Dis. 2024;19(1):296.
¹¹ Gold WA, Percy AK, Neul JL, et al. Rett syndrome. Nat Rev Dis Primers. 2024;10(1):84.

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