Astellas, Taysha halt GAN gene therapy program

Sept. 20, 2023

Following feedback from regulators, Taysha Gene Therapies is discontinuing the development of its TSHA-120 program for giant axonal neuropathy (GAN) treatment, with Astellas opting not to exercise its exclusive licensing option for the program.

The two first announced their collaboration last October, when Astellas invested $50 million for a 15% stake in Taysha and gained an exclusive option for two of Taysha's clinical programs, TSHA-102 for Rett syndrome and TSHA-120 for GAN. According to a statement made this week, the decision to halt TSHA-120 development was made due to challenges in study designs for potential FDA approval.

When Taysha submitted phase 1/2 trial data for the drug to the FDA during a Type B end-of-phase 2 meeting, agency feedback emphasized their need to address disease progression variability in GAN and the limitations of the primary endpoint, MFM32 — a Motor Function Measure clinical assessment. To navigate its regulatory options for TSHA-120, Taysha submitted analyses of data from natural history and interventional trials to the FDA in June 2023, using a disease progression model in a Type C meeting request.

But the FDA maintained its recommendation for a randomized, double-blind, placebo-controlled trial as the best way to demonstrate TSHA-120's efficacy. The agency also suggested the possibility of a single-arm trial with an external control group along with longer-term follow-up.

Taysha is now looking to focus on supporting the ongoing development of TSHA-102 for Rett syndrome, a neurodevelopmental disorder with no approved treatments addressing its genetic root cause.