Novel eRF3a degrader enhances gentamicin-induced premature termination codon readthrough in epidermolysis bullosa

Recessive dystrophic epidermolysis bullosa (RDEB) and junctional epidermolysis bullosa (JEB) are severe blistering skin disorders caused by mutations in genes encoding type VII collagen (<i>COL7A1</i>) and laminin 332 (<i>LAMA3</i>, <i>LAMB3</i>, or <i>LAMC2</i>), respectively. In RDEB, 25% of patients carry nonsense mutations that result in premature termination codons (PTCs), while in JEB, the majority of mutations in <i>LAMB3</i> are nonsense mutations (80%). CC-90009, an eRF3a degrader, is effective in inducing PTC readthrough in various <i>in vitro</i> models of diseases caused by nonsense mutations. This study evaluated CC-90009's ability, in combination with gentamicin, to suppress PTCs and promote the expression of type VII collagen (C7) in primary RDEB keratinocytes and fibroblasts, as well as laminin 332 in primary JEB keratinocytes with nonsense mutations. While CC-90009 alone demonstrated limited efficacy, its combination with low-dose gentamicin led to a dose-dependent increase in C7 and laminin β3 production, surpassing the effects of high-dose gentamicin alone. Furthermore, CC-90009/gentamicin reversed the hypermotility and poor substratum attachment characteristic of EB cells. Finally, C7 and laminin 332 induced by CC-90009/gentamicin localized to the dermal-epidermal junction in RDEB and JEB skin equivalents. Therefore, CC-90009/gentamicin may present a novel and safe treatment option for RDEB, JEB, and other inherited skin diseases arising from nonsense mutations.