Polyquaternium-mediated delivery of morpholino oligonucleotides for exon-skipping <i>in vitro</i> and in <i>mdx</i> mice

<p>Antisense oligonucleotide therapy for Duchenne muscular dystrophy has shown great potential in preclinical and clinical trials, but its therapeutic applications are still limited due to inefficient delivery. In this study, we investigated a few polyquaterniums (PQs) with different size and composition for their potential to improve delivery performance of an antisense phosphorodiamidate morpholino oligomer (PMO) both <i>in vitro</i> and <i>in vivo</i>. The results showed that Luviquat<sup>TM</sup> series, especially PQ-1 and PQ-3, promoted the exon-skipping efficiency comparable to Endoporter-mediated PMO delivery <i>in vitro</i>. Significant enhancement in skipping dystrophin exon 23 has also been achieved with PQ-3 up to seven-fold when compared to PMO alone in <i>mdx</i> mice. Cytotoxicity of the PQs was lower than Endoporter and PEI 25 K <i>in vitro</i> and muscle damage not clearly detected <i>in vivo</i> under the tested concentrations. These results together demonstrate that the optimization of PQ in molecular size, composition and distribution of positive charges is the key factor to achieve enhanced PMO exon-skipping efficiency. The higher efficiency and lower toxicity endow polyquaternium series as AO delivery enhancing agents for treating muscular dystrophy and other diseases.</p>