Improvements in drug delivery are brought about by Cell Penetrating Agents (CPA's) or Cell Penetrating Peptides (CPP's) which have been stabilized by, for example: stapling two amino acids to form Stapled CPP's (StaP's) or stitching three or more amino acids to form stitched CPP's (StiP'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.La présente invention concerne des améliorations de l'administration de médicament et l'utilisation d'agents de pénétration cellulaire (CPA) ou de peptides de pénétration cellulaire (CPP) qui ont été stabilisés par, par exemple : i) l'attachement de deux acides aminés pour former des CPP attachés (StaP) ou ii) la liaison de trois ou plus de trois acides aminés pour former des CPP liés (StiP). Plus particulièrement, l'invention concerne une molécule de pénétration cellulaire portant un médicament (DCCPM) comprenant : un composé biologiquement actif (BAC), et un agent de pénétration cellulaire (CPA), lequel BAC et CPA sont liés directement ou par l'intermédiaire d'un lieur bifonctionnel (BFL). Le CPA est u
