Branched synthetic peptide conjugate

A branched synthetic peptide conjugate intracellular vehicle having the formula I:

• ##STR7## where D is a domain which is a peptide or peptide mimic specific for binding to a target cell surface receptor, or for enabling the transport of the branched synthetic peptide conjugate across the plasma membrane of a cell, or for localization into a specific internal cell compartment;
• a cytotoxic group;
• or a diagnostic probe;
• J is linear and may be a junctional segment or spacer that may have a chemically active moiety or a marker, a carboxy-terminal structural unit which is an amino acid residue, or a short peptide;
• BP is a branched polymer comprising diaminocarboxylic acid residues which provide the branched synthetic peptide conjugate with a plurality of amino-terminal portions;
• where each of a, b, c, d, e, f, s, t, u, or v may be 0 or 1;
• and at least two of a, c, e, s and u is 1;
• n is an integer .gtoreq.2;
• and under physiological conditions
• one of D.sup.1, D.sup.2 or D.sup.3 is present and is a polycationic linear peptide or peptide mimic which enables the transport of the branched synthetic peptide conjugate across the plasma membrane of a cell.