A method for improving intracellular administration of a therapeutic agent is
provided
comprising: contacting cells with a compound comprising a charged derivative of
a therapeutic agent having a therapeutic activity, the charged derivative being
conjugated to a protein having a biological activity of being transported across
a cell membrane into a cell; and having the cell transport the compound into the
cell where the cell metabolizes at least a portion of the compound to form a charged
metabolite product that possesses the therapeutic activity of the therapeutic agent,
the charged metabolite product being less prone to being transported across the
cell membrane out of the cell relative to the compound and less prone to being
transported across the cell membrane out of the cell relative to the therapeutic agent.
