23 | Preclinical evaluation of 3s-HMGB1 as a therapeutic strategy for Duchenne muscular dystrophy

Federica Esposito¹, E. Sbolli¹, S. Curtarello¹, E. Ruggieri^1|2, M. Patrone^1|2, M. Rodrigues³, V. Taglietti³, F. Relaix³, E. Vénéreau^1|2 | ¹Unit, Division of Genetics and Cellular Biology, IRCCS Ospedale San Raffaele, Milan, Italy; ²University Vita-Salute San Raffaele, Milan, Italy; ³Univ Paris-Est Créteil, INSERM, U955 IMRB, Créteil, France.

Duchenne muscular dystrophy (DMD) is a severe disorder caused by mutations in the dystrophin gene, leading to progressive muscle degeneration, chronic inflammation and death. Current therapies aim to reduce inflammation and boost regeneration. Corticosteroids remain the standard treatment due to their anti-inflammatory effects, but their long-term use is limited by modest efficacy and significant side effects. It is recognized that treatment for DMD requires a multifaceted approach that integrates anti-inflammatory and regenerative strategies. We identified the nuclear protein High Mobility Group Box 1 as a novel therapeutic target in DMD. When released extracellularly, HMGB1 promotes regeneration or exacerbates inflammation depending on its redox state. Our studies reveal that oxidative stress, a hallmark of DMD, shifts HMGB1 to its disulfide form (dsHMGB1), which drives inflammation and muscle damage. Glucocorticoids have been reported to interfere with the pro-inflammatory activities of HMGB1, indicating that their beneficial effects might be attributed to the targeting of the oxidized HMGB1 isoform. We engineered a redox-inactive mutant of HMGB1, 3S, which retains potent regenerative properties ameliorating the dystrophic phenotype. We are currently conducting preclinical studies to evaluate the safety, optimal dosage, and administration routes of 3S in wild-type and DMD mouse models. Our findings indicate that low-dose intravenous delivery is both effective and well-tolerated. We are advancing 3S therapy in collaboration with Extend and Evotec, while also assessing its potential synergy with glucocorticoids. Our data confirm the harmful effects of prolonged glucocorticoid use in DMD mice, underscoring the urgent need for new treatments like 3S that can reduce side effects while enhancing therapeutic efficacy. Our results support 3S as a promising candidate for clinical development, with potential to serve as both a stand-alone and adjunct therapy in DMD.