Improvements in drug delivery

Improvements are disclosed in the delivery and use of Cell Penetrating Agents (CPA's) or Cell Penetrating Peptides (CPP's). More particularly, there is provided a drug carrying cell penetrating molecule (DCCPM) comprising: a biologically active compound (BAC), and a cell penetrating agent (CPA), which BAC and CPA are linked directly or via a bi-functional linker (BFL). The CPA is a stabilized peptide (CPP) which has a conformation imposed upon it by stapling to form a stapled peptide (StaP) or stitching to form a stitched peptide (StiP). The StiP or StaP comprise a cross link or bridge between at least two amino acids of the peptide and the cross link or bridge provides a cyclisation between at least two amino acids which are not formed by an olefin metathesis. Cyclisation may be achieved by one or more of: condensation of an aldehyde or ketone with a hydrazine or protected hydrazine; a thiol-ene Michael addition: a di-sulfide formation; a Huisgen 1, 3 di-polar cycloaddition; a reaction between an amine and carboxylic acid; a singlet or triplet based carbine reaction; or a Suzuki or Sonogashira coupling. The BAC is a low electrical charge carrying phosphorodiamidate morpholino oligonucleotide (PMO) with a charge between -3 to +3 ay pH 7.5 and the CPP comprises less than 15 amino acids.