On March 10, Acadia’s trofinetide, now marketed as Daybue, became the first treatment with an FDA approval for Rett syndrome. Anavex’s ANAVEX2-73 (blarcamesine) could be next in line, with key Phase II/III results in Rett syndrome expected in H2 2023.
In February 2022, Anavex announced ANAVEX2-73 met its primary endpoint of the Rett Syndrome Behavior Questionnaire (RSBQ) in the 33-patient Phase III AVATAR trial (NCT03941444). Anavex is also running the 92-patient Phase II/III EXCELLENCE trial (NCT04304482), which uses the same primary endpoint.
Meanwhile, Acadia’s trofinetide met its co-primary endpoints of RSBQ and Clinical Global Impression of Improvement (CGI-I) in the 187-patient Phase III LAVENDAR trial (NCT04181723). The treatment now has marketing authorization for adults and children at least two years old with Rett syndrome.
All three trials share the primary endpoint of RSBQ, a clinician-based assessment of the signs and symptoms of Rett syndrome. Though some experts have questioned the sensitivity of RSBQ, it is widely viewed as the best available outcome measure.
Rett syndrome drug development
Rett syndrome is a rare neurological disorder, occurring almost exclusively in young girls. The disease is characterized by mutations to the gene MECP2 leading to impaired movement, speech, and breathing. Rett syndrome occurs in approximately 1 out of every 10,000 female births worldwide, and symptoms usually begin within the first six to 18 months.
ANAVEX2-73, also known as blarcamesine, is a sigma-1 receptor agonist, which could restore neural cell balance in central nervous system (CNS) diseases. The small molecule is also in development for Parkinson’s disease dementia, Alzheimer’s disease, and additional CNS disorders.
Acadia’s trofinetide is a synthetic analog of peptide of IGF-1, which can reduce neuroinflammation and improve synaptic functioning. Trofinetide is also under development for Fragile X syndrome, a leading cause of intellectual disabilities. Both trofinetide and ANAVEX2-73 are oral pills.
The approval of trofinetide continues the FDA’s recent trend of approving new drugs for rare diseases. Still, clinical trials for rare diseases continue to face challenges recruiting patients, particularly for ultra-rare diseases.