For the second time, Astellas is walking away from Taysha Gene Therapies, this time choosing not to license the biotech’s adeno-associated-virus-based therapy designed to treat a rare neurodevelopmental condition.
The Big Pharma’s window to take up exclusive rights to Taysha’s lead asset, dubbed TSHA-102, has officially closed, according to an Oct. 16 release shared after market close. The one-time gene therapy is designed to help patients with Rett syndrome, a condition that causes severe intellectual disability and mainly occurs in females.
Back in 2022, Astellas put down $50 million in exchange for a 15% stake in Taysha and the option to license clinical-stage candidates for two rare neurological disorders.
A year later, the pharma turned down its option to license TSHA-120 in a neurodegenerative disorder called giant axonal neuropathy (GAN).
Astellas’ decision followed an end-of-phase 2 meeting with the FDA in which the agency emphasized the need to address the heterogeneity of disease progression in GAN and expressed concern about the primary endpoint at the meeting. The program has since been removed from Taysha’s pipeline.
Now, the 2022 deal has expired, and Astellas is once again walking away empty-handed.
This rejection comes after Taysha turned over a TSHA-102 data package to Astellas in mid-2025. The clinical data drop, which included findings from adult and pediatric phase 1/2 studies, triggered a 90-day review for Astellas to decide whether it would exercise its option for the therapy.
The data showed a “generally well-tolerated safety profile” and a 100% response rate of the gain or regain of a defined developmental milestone, according to the biotech. The data shared with Astellas underpinned the FDA’s breakthrough therapy designation for TSHA-102.
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The Texas biotech now holds full rights to TSHA-102, which CEO Sean Nolan is “thrilled” about, because it “enables full strategic flexibility and optionality as we continue to advance the program and focus on driving long-term value,” according to the release.
The biotech plans to advance the asset into late-stage development with the dosing of a first patient in a pivotal trial slated for this quarter.
The FDA has signed off on the trial’s protocol and statistical analysis plan, including a six-month interim analysis that could possibly serve as the basis for a biologics license application, according to Taysha.
The single-arm, open-label trial is set to enroll 15 females with Rett syndrome who are between the ages of 6 and 21 years. The primary endpoint will assess the percentage of patients who gain or regain one or more developmental milestones from a list of 28 measures across communication, fine motor and gross motor skills.
“With an estimated 15,000 to 20,000 patients across the U.S., EU and U.K. suffering from Rett syndrome, we believe the profound unmet medical need paired with the robust clinical data observed in part A of our REVEAL trials highlight the significant market opportunity for TSHA-102,” Nolan said.
Currently, there aren’t any disease-modifying therapies that treat the genetic root cause of Rett disease on the market.
Taysha’s gene therapy is designed to mediate levels of MECP2—a gene that codes for the MeCP2 protein, which is believed to be essential in neurodevelopment. The program also holds regenerative medicine advanced therapy, fast track and orphan drug and rare pediatric disease tags from the FDA.
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For Astellas, the move comes amid an organizationwide reprioritization zeroing in on later-stage opportunities.
Over the last few years, Astellas invested heavily in novel technologies that are risky and are not necessarily the most successful or popular in the industry, including cell and gene therapies.
But, after a few setbacks and an industrywide pullback among large pharmas, Astellas’ cell and gene assets remained in the early stages, prompting the new focus on more advanced programs.
