Taysha Gene Therapies has finished dosing the registrational Rett study and now sits on an unencumbered gene-transfer asset after the Astellas option lapsed last autumn. The investment debate is whether a single-arm, natural-history-controlled path to a biologics license can carry a late-stage construct that already shows deepening functional gains in the earlier cohort. Completing an overenrolled pivotal cohort of seventeen patients converts the equity from a dosing story into a waiting-for-data story.
The earlier twelve-patient Part A cohort is the evidence the market is extrapolating. Every treated patient gained or regained at least one developmental milestone by twelve months, and functional gains kept accumulating rather than fading. That pattern is what makes a six-month interim analysis a plausible filing basis rather than a hope. The counterweight is design. There is no concurrent placebo. The success bar is a response rate of 33% against a natural-history null near 7%. A rival MECP2 program is also advancing, with a different delivery route and a different overexpression-control design.
The June financing added $230 million of gross proceeds and lifted period-end cash above $455 million. Management frames that cash as enough to reach a potential approval window in the second half of 2028. Research spending nearly doubled as process-qualification batches and commercial-readiness work ramped. The question the next several quarters resolve is whether the six-month pivotal readout still looks like the earlier cohort, and whether regulators still treat that interim as enough to file.