IRSF 2026: TSHA-102 Maintains the Crown in Rett Syndrome

Research evidence excerpt

IRSF 2026: TSHA-102 Maintains the Crown in Rett Syndrome

June 30, 2026

says patients are still able to spontaneously gain certain milestones.

●NGNE had just two patients over the age of 14, one of whom didn't

meet the response criteria until Month 15. TSHA had six patients over

the age of 14 and the company tells us they are not seeing differences

in the time to onset based on age.

●We emphasize this point because we think TSHA's population is more

in-line with what will be observed commercially (~over 85% of the

prevalent pool is ten years or older) and a more diverse patient pool.

●While numerically NGNE showed more developmental milestones vs.

TSHA, we believe the above factors are important considerations, in

addition to differences in how milestones are captured, etc.

●TSHA reported that 83% and 100% of patients achieved at least one

developmental milestone by six and 12 months, respectively. This

compares to NGNE who showed 70% and 80%, respectively.

●We suspect that TSHA's more rapid onset of action, coupled with

benefits observed in patients of a more diverse age group, could be

driven by the double-stranded construct, CNS-specific promoter, and

clear evidence that IT administration gets to the brain.

●We'd also point out the safety differences: nine patients reported 68

events on TEAEs related to NGN-401, whereas TSHA reported nine

patients with 37 events related to TSHA-102. TSHA has also not had

any serious TEAEs reported in its study.

●In a nutshell, we're encouraged that across-the-board, we have a great

dataset now supporting gene therapy. But overall, we think TSHA has

the more competitive package. Couple this in with favorable route of

administration and we're confident this will lead to a robust uptake.