The cellular uptake of PMOs (
phosphorodiamidate morpholino oligomers) can be enhanced by their conjugation to
arginine-rich CPPs (
cell-penetrating peptides). Here, we discuss our recent findings regarding (R-Ahx-R)(4)AhxB (Ahx is
6-aminohexanoic acid and B is
beta-alanine)
CPP-PMO conjugates in DMD (
Duchenne muscular dystrophy) and murine coronavirus research. An (R-Ahx-R)(4)AhxB-PMO conjugate was the most effective compound in inducing the correction of mutant
dystrophin transcripts in myoblasts derived from a canine model of DMD. Similarly, normal levels of
dystrophin expression were restored in the diaphragms of mdx mice, with treatment starting at the neonatal stage, and
protein was still detecTable 22 weeks after the last dose of an (R-Ahx-R)(4)AhxB-PMO conjugate. Effects of length, linkage and
carbohydrate modification of this
CPP on the delivery of a PMO were investigated in a coronavirus mouse model. An (R-Ahx-R)(4)AhxB-PMO conjugate effectively inhibited viral replication, in comparison with other
peptides conjugated to the same PMO. Shortening the
CPP length, modifying it with a mannosylated
serine moiety or replacing it with the R(9)F(2)
CPP significantly decreased the efficacy of the resulting PPMO (
CPP-PMO conjugate). We attribute the success of this
CPP to its stability in serum and its capacity to transport PMO to
RNA targets in a manner superior to that of poly-
arginine CPPs.