Early experience optimizing immunosuppressive use and monitoring in MyPEAK-1, a first-in-human study of TN-201, an AAV9 gene replacement therapy in MYBPC3-associated hypertrophic cardiomyopathy
M Y Desai, S F Nagueh, J O H N R Giudicessi, D Kellner, M Pollman, B Varfaj, N A T Paterson, W Harrison, R Pushkin, L T Tomlinson, B Mangal, G Argast, L Lombardi, K Ivey, W TingleyAbstract
Background
Immunosuppression (IS) is required in AAV-mediated gene therapy to maximize safety and efficacy, in part to mitigate potential hepatotoxicity and prevent immune-mediated loss of transgene expression. However, prolonged IS increases the risk of complications, including infections. MYBPC3-associated HCM patients have limited treatment options. MyPEAK-1 is a first-in-human trial to assess the safety and efficacy of TN-201, a gene replacement therapy, which was designed to address the underlying genetic cause of MYBPC3-associated HCM in symptomatic adults.
Objective
To describe the safety and refinement of the IS regimen and monitoring used during the dosing of Cohorts 1 and 2 in the MyPEAK-1 trial.
Methods
The dose-escalation study utilized two cohorts (n=3 each) receiving 3E13 vg/kg (Cohort 1) or 6E13 vg/kg (Cohort 2) of TN-201 as a single IV infusion. All patients received prophylactic prednisone (starting at 1 mg/kg, maximum 80 or 60 mg/day) and sirolimus (target trough level of 4–8 ng/mL). Prednisone was tapered over several weeks, with variable timing depending on safety laboratory results. The dose of prednisone and timing of sirolimus were adjusted to reduce IS burden in Cohort 2. Specifically, sirolimus was initiated earlier (Day -7 vs Day -3) and the maximum starting dose of prednisone was reduced (from 80 to 60 mg/day). Monitoring frequency was increased to weekly throughout the course of IS. An independent data safety monitoring board provided safety oversight.
Results
All six patients successfully completed the IS regimen. TN-201 was generally well-tolerated at both dose levels (follow-up >52 weeks and >12 weeks in Cohort 1 and 2, respectively). Adjustments to the IS regimen and monitoring during Cohort 1 facilitated a significantly shorter course of IS in Cohort 2, with a mean duration of prednisone use of 256 vs 81 days. Despite receiving a higher dose of TN-201, peak transaminase levels, reflecting liver inflammation, were lower in Cohort 2 than Cohort 1. There was no clinical TMA in either cohort. Mean sirolimus trough levels remained consistent between groups (7.2 vs 7.4 ng/mL). Increases in MyBP-C protein, decreases in circulating cardiac biomarkers, and a reduction in LV hypertrophy were observed during follow up.
Conclusion
Standardized adjustments to the prophylactic immunosuppressive regimen in the MyPEAK-1 trial successfully managed the immunogenicity of AAV9-based gene therapy. Cohort 2 patients required lower cumulative corticosteroid doses without compromising safety or cardiac transduction. These refinements enabled lower cumulative steroid exposure and shorter IS durations in the higher-dose cohort. These results suggest that individualized, protocol-driven IS is effective in controlling the immune response to TN-201 while supporting transgene expression, paving the way for continued investigation of this gene therapy clinical investigation in MYBPC3-associated HCM population.Corticosteroid duration and daily doseFor image description, please refer to the figure legend and surrounding text.