Described herein are methods and compositions for intracellular delivery of therapeutic molecules. Disclosed herein are selective delivery conjugate comprising a targeting ligand conjugated to a selective delivery molecule (a) an acidic sequence (portion of A) which is effective to inhibit or prevent the uptake into cells or tissue retention, (b) a molecular transport or retention sequence (portion of B), and (c) a linker between portion of A and portion of B, and (d) at least one cargo moiety. Also, described are selective delivery molecules comprising a second linker comprising an intracellular cleavage site and optionally a self-immolative cleavage site.
