Means and methods of enhancing delivery to biological systems

A nucleic acid

• (a) which is esterified at one or more of the following positions with a guanidinium alkanoic acid or a PEG substituted with a guanidinium group and a carboxyl group:
• 5′-terminal 5′ hydroxyl group;
• (ii) 3′-terminal 3′ hydroxyl group;
• (iii) 5′- or 3′-terminal 2′ hydroxyl group;
• and
• (iv) internal 2′ hydroxyl group;
• (b) which is esterified at one, more or all phosphates with a guanidinium alkanol or a PEG substituted with a guanidinium group and having a free hydroxyl group;
• and/or
• (c) which has a 2′ hydroxyl group converted into an acetal with a guanidinium alkanol or with a PEG substituted with a guanidinium group.

A method of enhancing the capability of a polymer to cross a biological barrier, the polymer having one or more carboxyl, hydroxyl, sulfhydryl, and/or phosphate groups, comprising the step of modifying at least one of said groups to give

• wherein independently for each occurrence of Formula VII
• (a) X is —(C═O);
• Y is O or S;
• (b) X is —O or —S;
• Y is (C═O) or (CHRa)—O;
• (c) X—Y is —S—S;
• or
• (d) X is —O—P(═O)ORp;
• Y is O or S;
• and
• each occurrence of J is independently selected from H;
• halogen;
• NH2;
• alkyl with 1 to 15 carbon atoms;
• and [CHR]o—NR′—CH(NHR″)—NH—R′″;
• each occurrence of R, R′, R″, R″′, Ra and Rp is independently selected from H;
• substituted or unsubstituted alkyl with 1 to 15 carbon atoms;
• and substituted or unsubstituted aryl;
• wherein R and R′;
• R′ and R″;
• and/or R″ and R″′ may together form a cyclic structure;
• m is an integer from 0 to 10;
• wherein if J is [CHR]o-NR′CH(NHR″)—NH—R″′, then m is 1;
• o is an integer from 1 to 15;
• and
• p is 0 or 1;
• wherein if p is 0, then the free valence of N bearing R′ is filled with H.

A method of enhancing the capability of a peptide or polypeptide to cross a biological barrier, comprising the steps of

• (a) formation of one or more esters or thioesters
• (i) at the carboxylate of the C-terminus with a guanidinium alkanol, a guanidinium alkanethiol, a PEG substituted with a guanidinium group and having a free hydroxyl group, or a PEG substituted with a guanidinium group and a sulfhydryl group;
• (ii) at a side-chain carboxylate of one or more Asp or Glu residues, if present, with a guanidinium alkanol, a guanidinium alkanethiol, a PEG substituted with a guanidinium group and having a free hydroxyl group, or a PEG substituted with a guanidinium group and a sulfhydryl group;
• (iii) at a hydroxyl group of one or more Ser, Thr or Tyr residues, if present, with a guanidinium alkanoic acid;
• and/or
• (iv) at a sulfhydryl group of one or more Cys residues, if present, with a guanidinium alkanoic acid or a PEG substituted with a guanidinium group and a carboxyl group;
• and/or
• (v) at the N-terminus with a guanidinium alkanoic acid or a PEG substituted with a guanidinium group and a carboxyl group, wherein said N-terminus is previously amidated with an alpha- or beta-hydroxy group of said alpha- or beta-hydroxy acid, and wherein the ester is formed between the carboxylic group of said guanidinium alkanoic acid or said PEG substituted with a guanidinium group and a carboxyl group;
• and/or
• (b) formation of one or more disulfides, the disulfide being formed between the sulfhydryl group of a Cys reside, if present, and a guanidinium alkanethiol or a PEG substituted with a guanidinium group and a sulfhydryl group.

A method of enhancing the capability of a nucleic acid to cross a biological barrier, comprising the steps of

• (a) forming an ester with a guanidinium alkanoic acid or a PEG substituted with a guanidinium group and a carboxyl group at one or more of the following positions:
• (i) 5′-terminal 5′ hydroxyl group;
• (ii) 3′-terminal 3′ hydroxyl group;
• (iii) 5′- or 3′-terminal 2′ hydroxyl group;
• and
• (iv) internal 2′ hydroxyl group;
• (b) forming an ester with a guanidinium alkanol or a PEG substituted with a guanidinium group and having a free hydroxyl group at one or more phosphates;
• and/or
• (c) forming an acetal between a 2′ hydroxyl group and a guanidinium alkanol or a PEG substituted with a guanidinium group.

A method of enhancing the capability of a liposome or micelle to cross a biological barrier, comprising the steps of

• (a) forming an ester with a guanidinium alkanoic acid or a PEG substituted with a guanidinium group and a carboxyl group at one or more hydroxyl groups of said liposome or micelle;
• and/or
• (b) forming an ester with a guanidinium alcohol, a guanidinium alkanethiol, a PEG substituted with a guanidinium group and having a free hydroxyl group, or a PEG substituted with a guanidinium group and a sulfhydryl group at one or more acidic groups;
• and/or
• (c) converting a primary amino group of said liposome or micelle into a guanidinium group.