Rett Syndrome Awareness Month: Acadia Extends Drug Protection as Taysha Gene Therapy Nears Pivotal Data
Acadia has the first approved Rett syndrome treatment and a path to five more years of U.S. exclusivity. Taysha has finished dosing a pivotal trial of a one-time gene therapy aimed at the disease’s genetic cause.
The two public companies most active in Rett syndrome each have news this October, which the International Rett Syndrome Foundation recognizes as Rett Syndrome Awareness Month. On September 28, Acadia Pharmaceuticals (NASDAQ: ACAD) received a Notice of Allowance for a patent covering DAYBUE (trofinetide). Taysha Gene Therapies (NASDAQ: TSHA) heads to the Child Neurology Society Annual Meeting with dosing complete in the pivotal REVEAL trial of TSHA-102.
Rett syndrome is a rare neurodevelopmental disorder, typically caused by mutations in the MECP2 gene. Acadia estimates it occurs in roughly one in every 10,000 to 15,000 female births. Children usually develop normally until six to 18 months of age, then lose communication skills and purposeful hand use. Most live into adulthood and require round-the-clock care.
New Acadia Patent Would Protect Its Rett Syndrome Drug Through 2041
The allowed application covers the weight-banded dosing regimen for trofinetide, which Acadia sells as DAYBUE and DAYBUE STIX. Once issued, and including six months of pediatric exclusivity, the patent is expected to protect trofinetide in the U.S. through March 28, 2041. The existing method-of-use patent expires in July 2036.
“We are pleased that this patent is expected to extend protections for trofinetide in the United States from 2036 into 2041,” said Catherine Owen Adams, Chief Executive Officer of Acadia.
The franchise is still growing. DAYBUE net sales reached $124.8 million in the second quarter, up 30% year over year, with Acadia attributing the growth almost entirely to volume. Acadia raised its 2026 DAYBUE guidance to $480 million to $510 million. It reported diluted EPS of $0.18 for the quarter and $956.5 million in cash and investments.
Since its second-quarter report, Acadia has also received European Commission approval for trofinetide, marketed as DAYBU, to treat neurobehavioral symptoms of Rett syndrome in patients aged five and older. It is the first Rett treatment approved in the EU, and Acadia is now beginning pricing and reimbursement negotiations country by country.
Taysha’s Rett Syndrome Gene Therapy Heads Toward Pivotal Data in 2027
TSHA-102 takes a different approach to the disease. It is a one-time AAV9 gene therapy, delivered intrathecally, that carries a functional form of MECP2 into the central nervous system. Too little MECP2 causes Rett syndrome, and too much causes a separate duplication disorder. Taysha’s miRARE technology is designed to regulate expression cell by cell to avoid both outcomes.
REVEAL Part A gave Taysha the basis for its pivotal design. All 12 patients with at least 12 months of follow-up gained or regained at least one developmental milestone, against an FDA-aligned success threshold of 33% for the pivotal trial. Patients recorded 310 functional gains in total. Across 33 patients dosed in REVEAL and ASPIRE, Taysha has reported no severe treatment-related serious adverse events or dose-limiting toxicities.
The pivotal trial dosed 17 females aged 6 to 21. Taysha expects topline data from a six-month interim analysis, along with FDA feedback on the submission pathway, in the first half of 2027. It expects to complete its BLA-enabling manufacturing campaign this quarter. Taysha reported $455.4 million in cash at June 30 and expects runway into the second half of 2028.
At the Child Neurology Society meeting in Montréal, which runs October 14 through 17, principal investigator Elsa Rossignol, M.D., will give an oral presentation of the Part A data on October 15.
The 2027 readout will show whether Taysha’s Part A results hold in a larger group. The company has set the bar at a 33% response rate. Part A cleared it at 100%.
