BB-301: a silence and replace AAV-based vector for the treatment of oculopharyngeal muscular dystrophy

Vanessa Strings-Ufombah; Alberto Malerba; Shih-Chu Kao; Sonal Harbaran; Fanny Roth; Ornella Cappellari; Ngoc Lu-Nguyen; Keiko Takahashi; Sophie Mukadam; Georgina Kilfoil; Claudia Kloth; Petrus Roelvink; George Dickson; Capucine Trollet; David Suhy

doi:10.1016/j.omtn.2021.02.017

BB-301: a silence and replace AAV-based vector for the treatment of oculopharyngeal muscular dystrophy

Mol Ther Nucleic Acids. 2021 Feb 18:24:67-78. doi: 10.1016/j.omtn.2021.02.017. eCollection 2021 Jun 4.

Authors

Affiliations

¹ Benitec Biopharma, Inc., Hayward, CA 94545, USA.
² Department of Biological Sciences, School of Life Sciences and the Environment, Royal Holloway University of London, Egham, Surrey TW20 0EX, UK.
³ Sorbonne Université, INSERM, Association Institut de Myologie, Centre de Recherche en Myologie, 75013 Paris, France.

Abstract

Oculopharyngeal muscular dystrophy (OPMD) is a rare autosomal dominant disease that results from an alanine expansion in the N-terminal domain of Poly-A Binding Protein Nuclear-1 (PABPN1). We have recently demonstrated that a two-vector gene therapy strategy significantly ameliorated the pathology in a mouse model of OPMD. This approach entailed intramuscular injection of two recombinant adeno-associated viruses (AAVs), one expressing three short hairpin RNAs (shRNAs) to silence both mutant and wild-type PABPN1 and one expressing a codon-optimized version of PABPN1 that is insensitive to RNA interference. Here we report the continued development of this therapeutic strategy by delivering "silence and replace" sequences in a single AAV vector named BB-301. This construct is composed of a modified AAV serotype 9 (AAV9) capsid that expresses a unique single bifunctional construct under the control of the muscle-specific Spc5-12 promoter for the co-expression of both the codon-optimized PABPN1 protein and two small inhibitory RNAs (siRNAs) against PABPN1 modeled into microRNA (miRNA) backbones. A single intramuscular injection of BB-301 results in robust inhibition of mutant PABPN1 and concomitant replacement of the codon-optimized PABPN1 protein. The treatment restores muscle strength and muscle weight to wild-type levels as well as improving other physiological hallmarks of the disease in a mouse model of OPMD.

Keywords: AAV; OPMD; PABPN1; gene therapy; oculopharyngeal muscular dystrophy; siRNA; silence and replace.