Business Description

. ​ Overview ​ We are a leader in the field of gene therapy, seeking to deliver to patients suffering from rare and other devastating diseases single treatments with potentially curative results. We are advancing a focused pipeline of innovative gene therapies, including our clinical candidates for the treatment of Huntington’s disease, refractory mesial temporal lobe epilepsy (“MTLE”), Fabry disease, and amyotrophic lateral sclerosis caused by mutations in superoxide dismutase 1 (“SOD1-ALS”). ​ Recent Product Candidate Developments ​ Huntington’s disease program (AMT-130) In September 2025, we announced p ositive topline data from the pivotal Phase I/II study of AMT-130 for the treatment of Huntington’s disease. We analyzed clinical outcomes for 29 patients treated with AMT-130 (n=17 high-dose; n=12 low-dose) of which 12 patients per dose group had attained 36 months of follow-up and were evaluated at that time point. Outcomes for each dose group were compared to a propensity score-matched external control drawn from the Enroll-HD natural history data set (n=940 for high-dose; n=626 for low-dose). Topline 36-month efficacy results for patients receiving high-dose AMT-130 were as follows (data cutoff as of June 30, 2025): ● A statistically significant 75% slowing of disease progression as measured by composite Unified Huntington’s Disease Rating Scale (“cUHDRS”) (p=0.003), which met the primary endpoint of the study. Treated patients had a mean change in cUHDRS from baseline of -0.38 compared to a change of -1.52 for patients in the propensity score-matched external control. ● A statistically significant 60% slowing of disease progression as measured by Total Function Capacity (“TFC”) (p=0.033), which met a key secondary endpoint of the study. Treated patients had a mean change in TFC from baseline of -0.36 compared to a change of -0.88 for patients in the propensity score-matched external control. ● Favorable trends in other secondary endpoint measures of motor and cognitive function, including Symbol Digit Modalities Test (“SDMT”), Stroop Word Reading Test (“SWRT”) and Total Motor Score (“TMS”). o An 88% slowing of disease progression as measured by SDMT (p=0.057), with a mean change in SDMT from baseline of -0.44 compared to a change of -3.73 for patients in the propensity score-matched external control. o A 113% slowing of disease progression as measured by SWRT (nominal p=0.002), with a mean change in SWRT from baseline of 0.88 compared to a change of -6.98 for patients in the propensity score-matched external control. o A 59% slowing of disease progression as measured by TMS (nominal p=0.174), with a mean change in TMS from baseline of 2.01 compared to a change of 4.88 for patients in the propensity score-matched external control. A mean reduction from baseline in cerebrospinal neurofilament light protein (“CSF NfL”) of -8.2% was observed at 36 months in the high-dose of AMT-130 of the Phase I/II studies. CSF NfL is a well-characterized, supportive biomarker of neurodegeneration. Elevation in CSF NfL has been shown to be strongly associated with greater clinical severity of Huntington’s disease. 6 ​ Table of Contents We believe that the consistently favorable results in functional, motor and cognitive endpoints at 36 months observed in the high-dose group, compared to the variable trends observed in the low-dose group, reflect a dose-dependent response to AMT-130. Various other supportive analyses of the results from the AMT-130 high-dose treatment group, including those using a propensity score-weighted external control and comparisons to the TRACK-HD and PREDICT-HD datasets, were consistent with the primary analysis. AMT-130 was generally well-tolerated in the Phase I/II studies, with a manageable safety profile at both doses with no new drug-related serious adverse events (“SAEs”) observed since December 2022. The most common adverse events in the treatment groups were related to the administration procedure. In 2025, we treated six patients with the high-dose of AMT-130 in a fourth cohort to evaluate the safety and efficacy of AMT-130 in patients with lower baseline striatal volumes compared to previous cohorts in the U.S. Phase I/II study. In April 2025, we announced that the FDA granted Breakthrough Therapy designation to AMT-130 for the treatment of Huntington’s disease.…